Why does Propane make a engine go boom? Timing

[2500]

thanks for the link... that now proves diesel performance product propane controller delivers at a rate set by boost and goes up as boost goes up. very_controllable!

nice setup!

but does it have a method to vaporize liquid propane?
all vehicle mounted tanks will hit bumps... which will splash liquid into vapor pickup or dip tubes. ANY regulator setup for vapor will deliver too much propane if exposed to liquid.

Biodieselpower:


http://www.dieselperformanceproducts.com/videos/video_2.html

 

[Charles]

thanks for the link... that now proves diesel performance product propane controller delivers at a rate set by boost and goes up as boost goes up. very_controllable!

nice setup!

but does it have a method to vaporize liquid propane?
all vehicle mounted tanks will hit bumps... which will splash liquid into vapor pickup or dip tubes. ANY regulator setup for vapor will deliver too much propane if exposed to liquid.

This is what I used with it:

 

[BiodieselPower]

The FS2000 I was running did not. However, I don't think this was the cause of failure. I could audibly hear/feel what I described as advanced timing when it was on, even though everyone I talked to explained to me that the propane had no effect on timing..... When in fact that was true, it had no effect on injection timing for the actual diesel fuel, however, it was drastically effecting the timing of combustion in the cylinder. For me, the problem developed when towing. I was hauling ass pulling another truck down the interstate and in-cylinder temperatures exceeded the auto-ignition point for the propane farther and farther in advance of TDC until the subsequent burn, and the subsequent effect on diesel fuel injected into an environment already engulfed in flame resulted in cylinder pressures above and beyond what the headgasket could withstand. At a mere 340ish rwhp no less.

Ok i didn't realize the kit was adjustable-point proven. But thanks for explaining how you blew your motor. This helps make a lot more since of what happened. You pretty much summed it up yourself...you were hauling ass with a truck making pretty close to DOUBLE the stock hp at the wheels. Ok so you must be putting more fuel in there which creates heat-we both know that’s bad for propane. To complicate problems im assuming the chip you ran advanced timing (if so do you know how much?) i know your going to say it doesn’t matter because the propane is already burning, but it does matter the sooner the diesel gets in there to burn the more cylinder pressure you are going to have because the piston is still trying to go up-but your forcing it down too soon. Now look at the title of the topic again as i mentioned timing. What happens if you would reduce your diesel timing? It may not solve the problem but its definitely gonna help. Its though to say how much. You said earlier you didn’t know what the EGT's were cuz it was 5 years ago. Who hauls ass in a diesel truck making close to 2X the power it was designed to with out watching the EGT's?

Now i am back to explaining LEL again it is 2.2% at atmospheric pressure and 20 degrees Celsius for propane. So at those temps and pressures even a flame would not ignite the propane. But when you apply more pressure and temperature (just as you were doing) then the LEL will go down. You were not at 2.2% propane you may have only been at 1% but with the elevated temp. and pressure you lowered the LEL in your combustion camber to a point where it could preignite at this point making your engine live is a matter of backing off because as you said it keeps igniting further and further down the stroke. This is why propane should be used for milage but maybe not performance…the more timing/boost/heat the worse off you’ll be with propane. Unfortuantly for big HP we have all three of these things.

Also, is it possible that the propane was not burning until the diesel was injected but with the addition of propane it increases the speed of combustion? So much that peak cylinder pressures are before TDC? I know most propane advocates say it aint so…they claim it slows the burn.


I pummeled that engine to death with that propane. It was ignorant on my part. I should have trusted my better judgment and pulled that sh*t off of my truck after the first test drive.


Something I forgot about until now...

Even though it puked like crazy any time I was hard in the throttle after this point, and eventually had white smoke out the tailpipe at times, after removing the propane it STOPPED PUKING. I drove another 3 months with the propane proping the barn door open without issue until I popped a hpop and just decided to go ahead and yank my early 99 engine and swap in a late model engine with AD injectors, larger Garrett, larger hpop, ability to run a 38R, so on and so forth. Funny how it completely stopped lifting the heads once the propane was removed. Especially since the propane wasn't the problem and all...

Did you ever try to retourqe your head bolts? It still cracks me up about how defensive you get when I suggest and head gasket going bad at 240,000 miles. Maybe it stopped puking coolant because you were making 72 less HP. Do you really think that cylinder pressures would not go up by adding in enough diesel to create 72 extra HP? 268HP to 340 HP that is a 26% increase in power.


I have not once stated that I believe propane should be used to take a truck from 800 to 1200 HP. It should be used during low load conditions to maximize milage.
I wish some more people with broken motors would chime in and explain what the circumstances were when they had trouble.

 

[2500]

had a chance to speak with the very_knowledgeable folks at Diesel Performance Products.

evidently they are very aware of problems of liquid going forward. which will enrich mixture by 270x over vapor. according to Diesel Performance, for on road applications a tiny bit of liquid splashed into pickup tubes will not damage motor. it would take a steady liquid stream to blow your headgasket.

they offer a line preheater for their 4x4 applications. it really simple to construct a preheater by coiling a few loops of copper line on propane supply line in front of propane regulator, then connecting to engine coolant.

I asked about what net mpg gains from using propane. Their answer is none after mileage from propane is taken out. where you will realize gains is ... if costs of propane is less than diesel and more power while burning cleaner.

one could achieve the same mileage range increase by adding an extra 15 gallon or what ever size diesel tank.

also if your propane fuel cost is lower than diesel. than fuel costs savings will be realized. In my case, propane per gallon is higher than diesel in Tulsa.

 

[Charles]

Would it interest you to know that on the replacement engine that I towed FAR heavier, and FAR faster for oh, 3+ YEARS running fuel only with as much as 544rwhp?

And no, increased power does not equate to increased cylinder pressure. Power is torque @ rpm. Torque is effectively BMEP. BMEP can damn sure go up without raising the maximum cylinder pressure one pound. It happens every day.

Take the stock forged 7.3L engines running 600+rwhp as proof positive. Those engines are being subjected to similar, if not less cylinder pressure than a stock injectored truck that's making 400hp on propane. This is evidenced by the fact that the propaned engines pop regularly at that power level, yet of the handful of stock forged engines running 600, 700+hp with proper tuning, I know of not one that has popped in the last 3 years. And I can think of 4 or 5 off the top of my head at 600+hp. These trucks can do this due to extensive live in-cylinder pressure testing done during thorough testing and tuning. I know exactly what is happening to cylinder pressures when engines are happy, and keep running and running. I also know exactly what is happening to cylinder pressures when engines start coming apart.

I will preface the paragraph to follow by stating that I have never personally viewed in-cylinder data taken while running propane injection. Primarily due to the fact that by the time I was involved with any cylinder pressure testing, running a combustible through the intake track of a compression ignition engine hoping for good power was something I had gotten out of my system years beforehand.

However....

The combustion basics and the lifespan of the involved internal components remains the same. The fact is, while the BMEP for a 400hp propaned engine is much lower than that of a 600hp fuel only engine (as evidenced by the 200hp deficit) the maximum pressure value, and the pressure CURVE are FAR different, as evidenced by the incredible tendency for the 400ish hp propaned engine to undergo rapid self dissasembly without warning.

What happens is that the cylinder pressure for the propaned truck will almost certainly hit hard, quick, with a peak probably in the 2 to 4 degree ATDC range, and then, since all the fuel has rapidly flashed off, the cylinder pressure will fall on it's face and tail off quickly beyond that. A large "flash in the pot" and then not a whole lot of substance. Just a big connecting rod slam, and it's gone as fast as it came.

Compare this with the 600hp fuel only engine, and you will see cylinder pressures rise MUCH slower, with peak CP occuring ~7+ degrees ATDC, and then a nice, long push out to the right, where cylinder pressure maintains a nice, smooth slope down as crank angle increases beyond TDC, toward BDC.

The net effect is FAR more BMEP, with LESS maximum cylinder pressure, and possibly even more important, with a FAR less VIOLENT pressure onset curve.



This is just the way of the world. This is why you don't see any 600+hp stock injectored trucks running propane...

You can't time the sh*t.


And I missed your conclusive dyno data on the exact power output of your truck with and without the propane. You know, just to show me how much power you're making on the gas, and to show me how pathetic my 7.3 is.

For instance, if you're doing 2300hp on propane, then more power to you.

:hehe:

 

[roachie]

Ok, Im back in for just a min.

Explain how the hell LEL has any meaning in a compression ignition engine.







Get your thermal dynamics books our for that one.

 

[BiodieselPower]

Ok, Im back in for just a min.

Explain how the hell LEL has any meaning in a compression ignition engine.



Get your thermal dynamics books our for that one.

I will not spend too much time here because I don’t have my thermodynamic book here. LEL is the minimum amount of gas to air ratio necessary for a given substance to auto ignite. Propane is 2.2%-diesel is .3% that means it takes 2.2 pounds of propane for every 100 pounds oxygen…but I know this is at 20 degrees Celsius and 1 ATM. So when you raise pressure and temp there is a curve where the LEL becomes a lower ratio compaired to air.

It does not magically become ZERO as soon as we compress the air to 2 or even 3 ATM. It is on a curve where it becomes easier and easier to auto ignite. Hints as to why one would not really want to run very much at all on a high compression, EGT, or boost engine. But at lower boost, EGT, and compression engines(as diesels go) you will be fine because 2.2% is a lot of propane when you are running 4 gallons diesel to one gallon propane most of the time your running around .5%. This is low enough of a volume that it keeps it below the LEL for the given pressure/temp. I have said before watch EGTS/boost.

Does the last paragraph make since to nobody here at all? It’s a matter of chemistry as to when it will preignite. NOT EVERY GOD DAM TIME I PUT AN OUNCE IN THERE. Do the math.

 

[BiodieselPower]

Would it interest you to know that on the replacement engine that I towed FAR heavier, and FAR faster for oh, 3+ YEARS running fuel only with as much as 544rwhp?

Wow a fresh engine witch i assume/hope had HEADSTUDS has not blown a headgasket yet in three whole years!! How many years did the stocker have on it 7 plus 240,000 miles-without headstuds? I'm incredibly baffled.

And no, increased power does not equate to increased cylinder pressure. Power is torque @ rpm. Torque is effectively BMEP. BMEP can damn sure go up without raising the maximum cylinder pressure one pound. It happens every day.

Where in larger displacement engines? Otherwise please tell me how i can make 2500HP on my Cummins because without increased cylinder pressure the engine will hold no problem. Heck I won’t need headstuds/o rings/girdle/pistons/rods leave the internals stock they were designed to handle a certain amount of pressure which our mighty Charles will keep the same as stock.

Take the stock forged 7.3L engines running 600+rwhp as proof positive. Those engines are being subjected to similar, if not less cylinder pressure than a stock injectored truck that's making 400hp on propane. This is evidenced by the fact that the propaned engines pop regularly at that power level, yet of the handful of stock forged engines running 600, 700+hp with proper tuning, I know of not one that has popped in the last 3 years. And I can think of 4 or 5 off the top of my head at 600+hp. These trucks can do this due to extensive live in-cylinder pressure testing done during thorough testing and tuning. I know exactly what is happening to cylinder pressures when engines are happy, and keep running and running. I also know exactly what is happening to cylinder pressures when engines start coming apart.

Honestly please tell me how you increase power without increasing cylinder pressure I am a rookie fill me in on this concept.

Pretty bold to say ZERO 600-700HP stock rod powerstrokes have blown a headgasket in the past 3 YEARS!!! At least not that you know of. I would bet my truck that their has been more than one stock rod powerstroke blow a headgasket in the past three years. That is if there is any stock rods that last long enough to blow the gasket. By the way I ran propane on PMR rods for 2 years!!

I will preface the paragraph to follow by stating that I have never personally viewed in-cylinder data taken while running propane injection. Primarily due to the fact that by the time I was involved with any cylinder pressure testing, running a combustible through the intake track of a compression ignition engine hoping for good power was something I had gotten out of my system years beforehand.

Who can do this “extensive live testing” on cylinder pressures I would be willing to bring a motor to test if they offer their equipment to test cylinder pressures and are willing to work with me. Not because i wanna be right because i would like to know the FACTS.

However....

The combustion basics and the lifespan of the involved internal components remains the same. The fact is, while the BMEP for a 400hp propaned engine is much lower than that of a 600hp fuel only engine (as evidenced by the 200hp deficit) the maximum pressure value, and the pressure CURVE are FAR different, as evidenced by the incredible tendency for the 400ish hp propaned engine to undergo rapid self dissasembly without warning.

What happens is that the cylinder pressure for the propaned truck will almost certainly hit hard, quick, with a peak probably in the 2 to 4 degree ATDC range, and then, since all the fuel has rapidly flashed off, the cylinder pressure will fall on it's face and tail off quickly beyond that. A large "flash in the pot" and then not a whole lot of substance. Just a big connecting rod slam, and it's gone as fast as it came.

Compare this with the 600hp fuel only engine, and you will see cylinder pressures rise MUCH slower, with peak CP occuring ~7+ degrees ATDC, and then a nice, long push out to the right, where cylinder pressure maintains a nice, smooth slope down as crank angle increases beyond TDC, toward BDC.

The net effect is FAR more BMEP, with LESS maximum cylinder pressure, and possibly even more important, with a FAR less VIOLENT pressure onset curve.

Wait let me rephrase you when refering to cylinder pressures: "I will preface the paragraph to follow by stating that I have never personally viewed in-cylinder data taken while running propane injection."

So this is all a hopefully "educated guess” I guess it’s as good as mine until we can actually see some cylinder pressure data. I guess the argument is pretty much done until we can actually see some real data because to be honest neither of us knows for a “fact” what is happening.

This is just the way of the world. This is why you don't see any 600+hp stock injectored trucks running propane...

You can't time the sh*t.

How many times should i say it-you dont need to. inject a small enough amount so it doesn't preignite under the pressure/temperature.

And I missed your conclusive dyno data on the exact power output of your truck with and without the propane. You know, just to show me how much power you're making on the gas, and to show me how pathetic my 7.3 is.

I'm pretty sure i have said at least three times that i don't advocate using it for maximum HP-but for milage gains. Although i am willing to race your powerstroke or sledpull. Go ask sniperonhigh how much power the truck makes i bought the truck from him.

For instance, if you're doing 2300hp on propane, then more power to you.

:hehe:

I just want to know some real data so if you know anyone with access to cylinder pressure equipment and a dyno let me know.

 

[2500]

for those that are acronym challenged like me...

Lower Explosive Limit = (LEL): The explosive limit of a gas or a vapor is the limiting concentration(in air) that is needed for the gas to ignite and explode. The lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source(arch, flame, heat). At concentration in air below the LEL there is not fuel to continue an explosion. Concentrations lower than LEL are "too lean" to burn.... Each combustible gas has its own LEL concentration. Flammability limit

Temperature and pressure also influences flammability limits. Higher temperature results in lower LFL and higher UFL, while greater pressure increases both values.

assuming the 2.2% LEL number is correct and your engine is operating at 17:1 ratio. then if propane delivered is below 1/17 of 2.2% ... then pre-ignition cannot occur.... this is assuming LEL point has not changed from higher temps.

what can be assumed is factoring for higher temps and pressures. if propane mixture is leaned out enough... at some point mixture cannot detonate, even with ignition source.

on the flip side .... if enough propane is delivered, engine will certainly reach detonation stage with ignition source. over pressure results in damage to engine, more likely a blown headgasket.

safe to assume that point would be immediately reached if liquid propane gets by regulator. since liquid propane is 270x richer than vapor.

there would be NO way I'd run propane without a engine coolant preheater on fuel line to vaporize any liquid propane that gets forward anytime a bump splashes liquid propane in your tank's pickup tube.

since I don't have a source of propane cheaper than diesel and my goal is better fuel mileage. it'd be a waste of time for me to install propane on my 12v cummins.

 

[Charles]

Biodiesel:

You aren't reading very well at this point. For instance, I stated personally knowing of 4 or 5 stock forged 7.3's with proper tuning running in excess of 600rwhp, and that none of them had encountered any such failures in the last 2 or 3 years.

You then made some kind of rhetorical statement about how you're sure that plenty of 7.3's have blown head gaskets in the last 3 years.

Ah, okay. Well then maybe you wouldn't mind explaining how that fact in any way contradicts what I stated?


You also made a statement downplaying the fact that after lifting the heads on my original engine due to propane after ~1 yr with it on the truck, and the fact that the puking and tailpipe smoke stopped after the propane system was removed from the truck, and then the further evidence in the fact that I then went on with the replacement engine to run as high as 3 and a half TIMES the power increase I received from the propane on the original engine for 2, 3+ years. And it NEVER DID have a cylinder pressure related failure. The G'damn pistons were all cracked to hell and back from running OVER 1800 degrees for YEARS with that little 38R as a single.

And yes, I did stud the replacement engine, however, if you knew your sh*t, you would know that 9 times out of 10, the same cylinder pressure and pressure curve capable of wiping out a stock gasket is more than capable of also wiping out stock rods/main registers. Plenty of people have run in excess of 3+ Times the power I received from the propane on stock gaskets/bolts when running fuel only. This isn't saying, they ran the SAME power, but over 3 TIMES the power picked up from the propane.... Factors this large should be hitting you in the forehead pretty hard.

Honestly please tell me how you increase power without increasing cylinder pressure I am a rookie fill me in on this concept.

I already did just that in the very post where you inserted this text. The fact that you honestly can't imagine know how to increase power without increasing the cylinder pressure maximum and/or engine stress level again states the childlike way in which you view engines. I don't mean that necessarily as a "dig", more just a statement of fact.

Making SA comments like the one above when you're so clearly ignorant to the concepts involved does more to point out your own inadequacy on the subject than anyone else ever could. The fact that you cannot understand how BMEP can (and often does) go up without effecting max cylinder pressure for the cycle is appalling. Especially so after I took the time to explain how in the very post you made the statement in.

Are you serious in your assertion that BMEP cannot go up while holding maximum cylinder pressure constant? Or are you just arguing for sport? Because it's not even like this is a rare situation. It's very common to increase BMEP while holding maximum pressure constant, or LOWERING it. That's just good tuning.


Lastly, if you'll notice, you're right back to my own position, that the propane is worthless, because if you're injecting enough to make a worthwhile change in power, you're causing undue stress on the engine for no good reason, and if you're not injecting enough to cause the engine to be put under excessive stress, you're also not getting any damned power out of the sh*t.

It's a catch 22 my friend. If you could time it, it would be different. But when fumigating a compression ignition engine with it that's running 17.5:1 compression with 20+lbs of boost atop that, you're just asking for it. You're actually begging for it.



There is one thing I don't understand...

This whole notion that a fuel will not combust if it has access to too much oxygen...

Aside from citing coefficients for various flammable gasses/liquids, how is this conceptually possible?

Is this to say that a container of propane gas might combust in a room that is 10 x 10 x 10, but that if I remove the walls and allow the entire atmosphere of the earth have access to the tank that the percentage of propane to the available oxygen in the whole of the earth's atmosphere will not allow this same amount of propane to combust if ignited in the same way?

 

[roachie]

I will not spend too much time here because I don’t have my thermodynamic book here. LEL is the minimum amount of gas to air ratio necessary for a given substance to auto ignite. Propane is 2.2%-diesel is .3% that means it takes 2.2 pounds of propane for every 100 pounds oxygen…but I know this is at 20 degrees Celsius and 1 ATM. So when you raise pressure and temp there is a curve where the LEL becomes a lower ratio compaired to air.

It does not magically become ZERO as soon as we compress the air to 2 or even 3 ATM. It is on a curve where it becomes easier and easier to auto ignite. Hints as to why one would not really want to run very much at all on a high compression, EGT, or boost engine. But at lower boost, EGT, and compression engines(as diesels go) you will be fine because 2.2% is a lot of propane when you are running 4 gallons diesel to one gallon propane most of the time your running around .5%. This is low enough of a volume that it keeps it below the LEL for the given pressure/temp. I have said before watch EGTS/boost.

Does the last paragraph make since to nobody here at all? It’s a matter of chemistry as to when it will preignite. NOT EVERY GOD DAM TIME I PUT AN OUNCE IN THERE. Do the math.

17:1 is not what I would call low compression.

You have a decreasing LEL with increasing air temp, AIT of 150*, + cylinder heat. And you have a controller that increases the amount of propane that get injected as those temps increase.

Yea, I understand it perfectly.

Your chemistry is flawed in your thinking that it can be too lean to ignite. When dealing with auto ignition lean is not a word.

 

[BiodieselPower]

17:1 is not what I would call low compression.

You have a decreasing LEL with increasing air temp, AIT of 150*, + cylinder heat. And you have a controller that increases the amount of propane that get injected as those temps increase.

Yea, I understand it perfectly.

Your chemistry is flawed in your thinking that it can be too lean to ignite. When dealing with auto ignition lean is not a word.

Ok so the simple fact that the earths atmosphere contains 4 flammable gases means jack ****t to you guys? Ammonia, Carbon Monoxide, Hydrogen, Methane. Every diesel engine on earth should be experiencing preignition 24/7. We should also need a throttle body to keep the engine from “running away.” Like I said before it’s all about the amount you put in and YES you can lean out a diesel and it no longer runs on diesel or propane.

 

[BiodieselPower]

Biodiesel:

You aren't reading very well at this point. For instance, I stated personally knowing of 4 or 5 stock forged 7.3's with proper tuning running in excess of 600rwhp, and that none of them had encountered any such failures in the last 2 or 3 years.

You then made some kind of rhetorical statement about how you're sure that plenty of 7.3's have blown head gaskets in the last 3 years.

Ah, okay. Well then maybe you wouldn't mind explaining how that fact in any way contradicts what I stated?


You also made a statement downplaying the fact that after lifting the heads on my original engine due to propane after ~1 yr with it on the truck, and the fact that the puking and tailpipe smoke stopped after the propane system was removed from the truck, and then the further evidence in the fact that I then went on with the replacement engine to run as high as 3 and a half TIMES the power increase I received from the propane on the original engine for 2, 3+ years. And it NEVER DID have a cylinder pressure related failure. The G'damn pistons were all cracked to hell and back from running OVER 1800 degrees for YEARS with that little 38R as a single.

And yes, I did stud the replacement engine, however, if you knew your sh*t, you would know that 9 times out of 10, the same cylinder pressure and pressure curve capable of wiping out a stock gasket is more than capable of also wiping out stock rods/main registers. Plenty of people have run in excess of 3+ Times the power I received from the propane on stock gaskets/bolts when running fuel only. This isn't saying, they ran the SAME power, but over 3 TIMES the power picked up from the propane.... Factors this large should be hitting you in the forehead pretty hard.





I already did just that in the very post where you inserted this text. The fact that you honestly can't imagine know how to increase power without increasing the cylinder pressure maximum and/or engine stress level again states the childlike way in which you view engines. I don't mean that necessarily as a "dig", more just a statement of fact.

Making SA comments like the one above when you're so clearly ignorant to the concepts involved does more to point out your own inadequacy on the subject than anyone else ever could. The fact that you cannot understand how BMEP can (and often does) go up without effecting max cylinder pressure for the cycle is appalling. Especially so after I took the time to explain how in the very post you made the statement in.

Are you serious in your assertion that BMEP cannot go up while holding maximum cylinder pressure constant? Or are you just arguing for sport? Because it's not even like this is a rare situation. It's very common to increase BMEP while holding maximum pressure constant, or LOWERING it. That's just good tuning.


Lastly, if you'll notice, you're right back to my own position, that the propane is worthless, because if you're injecting enough to make a worthwhile change in power, you're causing undue stress on the engine for no good reason, and if you're not injecting enough to cause the engine to be put under excessive stress, you're also not getting any damned power out of the sh*t.

It's a catch 22 my friend. If you could time it, it would be different. But when fumigating a compression ignition engine with it that's running 17.5:1 compression with 20+lbs of boost atop that, you're just asking for it. You're actually begging for it.



There is one thing I don't understand...

This whole notion that a fuel will not combust if it has access to too much oxygen...

Aside from citing coefficients for various flammable gasses/liquids, how is this conceptually possible?

Is this to say that a container of propane gas might combust in a room that is 10 x 10 x 10, but that if I remove the walls and allow the entire atmosphere of the earth have access to the tank that the percentage of propane to the available oxygen in the whole of the earth's atmosphere will not allow this same amount of propane to combust if ignited in the same way?

Why do you keep bringing up 600hp engines anyway? I said I don’t advocate using it on them unless you could keep egts below 1000…good luck. Also, what is the reason we use headstuds? If the bottom end is going to let go anyways then why bother? Also, why would the bottom end let go you’re not running any extra cylinder pressures?
Do you not understand how an internal compression engine works? It explodes a fuel in a sealed chamber…then what happens we get a pressure spike. This is good it pushes the piston down and we have power. Yes pressure forces the piston down. I know we can even out the pressure without raising peak pressures but we can only do that for so long before we must increase peak cylinder pressures. You really think that engines running 5-10 times their original power levels are going to have the same cylinder peak pressures as stock. Here is a link to a stock motor running biofuels blends and they do peak pressure data and IMEP which is torque as you yourself stated. Guess what the biofuels have less energy, less IMEP, and less Cylinder pressure throughout the rpm range even at peak. Go to the bottom and look at graphs.

http://www.biodiesel.org/resources/reportsdatabase/reports/tra/19950801_tra-020.pdf

Pressure=Torque and Power

You said if you put propane in a room 10X10X10 it will explode. See your looking at it all wrong you have to let out the entire contents of the bottle and make sure they are homogenous through the room. This will actually make it too rich to burn and you could light a match inside the room if there was enough propane. On the other hand if I take it outside and let the entire contents out and they spread throughout the atmosphere they will not ignite either-yep they are too lean I wouldn’t even be afraid to start my diesel up and smoke a cigar at my house after you let out 500 gallons at your house. In the motor there are no rich and lean spots of propane. You inject it preturbo then through an innercooler then through the heads and at this point it is 100% homogenous.

 

[Charles]

Why do you keep bringing up 600hp engines anyway? I said I don’t advocate using it on them unless you could keep egts below 1000…good luck. Also, what is the reason we use headstuds? If the bottom end is going to let go anyways then why bother? Also, why would the bottom end let go you’re not running any extra cylinder pressures?

I keep bringing up 600hp engines because miraculously that's pushing on an engine similarly, if not less so than running stock injectors and propane making say 400rwhp. I keep bringing it up because it should be one hell of a reality check in the fact that you can make over 400 additional hp on fuel without floating heads bending rods and cracking blocks, yet an additional 100 or so hp on propane can and HAS done all of that, often. On propane you are quite literally abusing the engine for every additional hp it makes due to the propane. That is why I keep bringing it up. Disparities in failure points of this magnitude should kick a light on in your head to alert you to the fact that the propane is beating the sh*t out of the engines, so much so that when running propane the engine's are limited to an amount of additional power around 1/3 or less what is possible fuel only, or with nitrous oxide (which is obviously not a fuel).


Do you not understand how an internal compression engine works? It explodes a fuel in a sealed chamber…then what happens we get a pressure spike. This is good it pushes the piston down and we have power. Yes pressure forces the piston down. I know we can even out the pressure without raising peak pressures but we can only do that for so long before we must increase peak cylinder pressures. You really think that engines running 5-10 times their original power levels are going to have the same cylinder peak pressures as stock.

I thought I made it clear that I had been viewing live cylinder pressure data for some time now? I assumed you would then understand that to mean that I have viewed plenty of cylinder pressure graphs, and am fairly versed in how power and cylinder pressure are related. Especially given the fact that this was the testing that has allowed stock forged 7.3's to go 650+hp without fail, where plenty of others have consistently rodded blocks and blown gaskets in the 450ish hp region. Do you understand what the M stands for in MEP? It's MEAN. I'm sure you're aware of this, and fully aware of the fact that it is the "Average" pressure in general terms. This is why I can't understand why it seems so hard for you to wrap your head around the idea that a 400ish hp truck gaining it's power from the burning of propane could easily be incurring far greater maximum pressure values than one making 600ish hp on fuel even though the one making 600ish hp on fuel is obviously producing higher MEP. Propane "flashes" off very, very quickly compared to diesel fuel. Combine this with the inability to time it's combustion (you can agree on that or not, I'm done arguing it) and you get a fuel that combusts and is spent right at TDC, creating a LARGE rise in pressure, but no follow through. It's akin to slamming a 10lb hammer down on a bicycle pedal to power it. The force applied on the pedal near TDC is intense, but the torque produced at the sprocket over the course of the pedal's cycle from TDC to BDC is still minimal when compared to an average guy merely pushing down on one good stroke all the way from TDC to BDC with his leg. The force applied to the pedal, arm and sprocket are FAR less with the applied force from the man's leg, yet the MEP is much higher.

Obviously this is just another explanation as before, but I hope that if I keep saying the same thing in different ways you might get it. The ruins of thousands of broken engines running propane at power levels half or less those routinely attained with reliability by fuel only trucks provides all the substantiation needed for any sane individual.



Here is a link to a stock motor running biofuels blends and they do peak pressure data and IMEP which is torque as you yourself stated. Guess what the biofuels have less energy, less IMEP, and less Cylinder pressure throughout the rpm range even at peak. Go to the bottom and look at graphs.

http://www.biodiesel.org/resources/reportsdatabase/reports/tra/19950801_tra-020.pdf


I can't get the link to work. However, what does the fact that biofuels have a lower BTU/gal than diesel fuel have to do with propane auto-igniting in a compression ignition engine?

Pressure=Torque and Power


That's not true. It seems pretty simple, but let me spell it out again, pressure = instantaneous force (for any given piston surface area). And the AVERAGE pressure for the length of the stroke determines the torque. Farther removed from this still, the RATE at which this torque is applied is power. The detail might seem trivial to you, but it's in the detail that you'll find the flaws.



You said if you put propane in a room 10X10X10 it will explode. See your looking at it all wrong you have to let out the entire contents of the bottle and make sure they are homogenous through the room. This will actually make it too rich to burn and you could light a match inside the room if there was enough propane. On the other hand if I take it outside and let the entire contents out and they spread throughout the atmosphere they will not ignite either-yep they are too lean I wouldn’t even be afraid to start my diesel up and smoke a cigar at my house after you let out 500 gallons at your house. In the motor there are no rich and lean spots of propane. You inject it preturbo then through an innercooler then through the heads and at this point it is 100% homogenous.

Okay, I follow that. The whole LFL makes much more sense now. Unfortunately, this has sparked an entirely new problem for me conceptually...

If your goal is to operate the engine where the incoming propane quantity shall always be controlled such that the percentage of propane in the intake charge is always below this lower flammability limit, such that it cannot phycially burn, as it is not flammable..... then how does it ever burn? I mean, the percentage isn't going to go up once the intake valve has closed. The game is over at that point. You have a homogenous mixture, and it's not going to change..... one that's inflammable no less, as defined by the LFL for the particular substance in question.

Oh wait..... but environment effects the LFL, as you have said. And you don't find it possible, likely even, that by compressing the atmosphere over 17 times the 1 ATM the rating is given at that you'll be at or over the edge of the bubble here?

You already mentioned your truck running quieter on the propane. Can YOU account for that? I already gave my explanation.

 

[BiodieselPower]

Okay, I follow that. The whole LFL makes much more sense now. Unfortunately, this has sparked an entirely new problem for me conceptually...

If your goal is to operate the engine where the incoming propane quantity shall always be controlled such that the percentage of propane in the intake charge is always below this lower flammability limit, such that it cannot phycially burn, as it is not flammable..... then how does it ever burn? I mean, the percentage isn't going to go up once the intake valve has closed. The game is over at that point. You have a homogenous mixture, and it's not going to change..... one that's inflammable no less, as defined by the LFL for the particular substance in question.

Oh wait..... but environment effects the LFL, as you have said. And you don't find it possible, likely even, that by compressing the atmosphere over 17 times the 1 ATM the rating is given at that you'll be at or over the edge of the bubble here?

You already mentioned your truck running quieter on the propane. Can YOU account for that? I already gave my explanation.

I must have misread you earlier saying that you haven’t look at cylinder pressure data. Anyway im not arguing that when the propane is preigniting that it raises cyl. Pressure-I know that. I am saying that if ran at low enough level that it won’t. From what I have been told by many people who sell propane kits is that propane slows the burn which would in fact lower the peak pressure and give a more even power stroke like you said we WANT. But you say it causes a quick burn like hitting the piston with a hammer and igniting everything at once giving high peak pressures relative to the rest of the stroke. Basically a single spike. So I don’t know which to believe.

I understand that you are saying the propane is preigniting and lessening the diesel knock making it quieter. But on the other hand if its not preiginting you say it causes a quick burn and pressure a spike. What if the propane is causing the diesel to burn slower (like many believe) wont it reduces the knock. I have personally heard an engine go anywhere from quieter to knocking at idle from running too much propane I can do this easily on the kit I use (not that I like to do it).

Even though the propane is below its LEL it will still burn as soon as the diesel is shot in the cylinder because then the mixture becomes rich enough. The fuel “mix” and burn. Like if I mix gas and diesel they still burn on a fire.

Just throwing this out to help complicate matters: why does high cetane fuel quite the motor. Cetane is the ability of a fuel to light. Meaning high cetane fuels light better and burn FASTER-that’s why there used in high rpm applications. But then if its burning quicker why does it make the motor quieter?

So basically I think I have concluded with the noise issue that either:
A: it is preigniting like you said and softening the blow of when the diesel is injected or
B: it is slowing down the burn rate of the diesel charge lessening the sudden pressure spike like high cetane.


I honestly think B makes more logical since because preingiting the propane would cause a nasty knock before we even inject diesel. Also, Think of what happens to an overtimed engine-it knocks louder.

 

[Charles]

I must not have be clear before when I explained the "diesel" sound we hear from our engines.

That is the sound of detonation, directly due to ignition delay. What is happening is that you are injecting fuel into a cylinder faster than it can auto-ignite and burn and it subsequently "pools" and begins forming a pocket of unburned fuel where only the surface of the pocket is beginning to burn. Then as the piston continually approaches TDC, the cylinder environment keeps getting hotter and hotter and rapidly doing so, until the point comes where this pocket of fuel violently flashes off, producing the audible knock we hear through the head/block as "diesel rattle". Advance the timing (inject into an even colder cylinder) and the sound gets more and more crisp and harsh. Retard the timing, and it will continue to soften and soften until the sound is gone. The truck will usually be hazing and doggy at this point, but the ignition delay will be so small that the fuel doesn't build a pocket which obviously then doesn't detonate reporting the audible sound to our ears.

Now, say you had a pre-existing flame front in the cylinder prior to injecting the diesel fuel. The ignition delay would be minute, almost negligible. The fuel would combust almost immediately, and combustion would continue evenly and smoothly for the duration that the injector was held open (assuming a practical duration ATDC). The net effect would be a very, very smooth running engine. Which in itself is not a bad thing. However, idle and light throttle are not the only operating points for an engine. As more and more power is requested you begin getting higher and higher concentrations of the injection quantity burning BTDC, creating higher and higher cylinder pressures on the wrong side of the stroke. Effectively negating power production, yet still stressing the engine just the same. The real problem begins when you have a substantial quantity of fuel, that is timed such that with natural diesel fuel ignition delay, flame front propagation and rapid combustion will occur on a pace that places the highest cylinder pressure at 7+ degrees ATDC, with a good percentage of the burn continuing beyond that, pushing that MEP higher and higher. However, if this has been altered by another, untimed fuel residing in the cylinder, what would have timed out nicely, would when injected into a pre-existing flame result in nearly no ignition delay at all. And the diesel would almost immediately burn, shifting the burn window far more BTDC than ATDC, resulting in higher maximum cylinder pressures and simultaneously lower BMEP. Hence the situation I described to begin with. Lots of stress without the accompanying BMEP which ==> Torque which eventually ==> Power.

And the increased Cetane works in the exact same way. Decreasing the ignition delay decreases the amount of fuel that will form into an unburned pocket when approaching TDC, as the fuel will quite simply burn quicker, lessening this unburned fuel to flash off near TDC.

Fwiw, if you look at many cylinder pressure graphs, you will become accustomed to often times seeing a dip in cylinder pressure just as the injection event is initiated. This is because you are injecting cool (relative to the cylinder) diesel fuel with great mass. The fuel literally sucks so much heat out of the cylinder upon initial injection that you will often times see cylinder pressure fall even in the face of decreasing volume due to the rising piston approaching TDC. Although I will say that a dip such as this is usually an indication of overly advanced timing, or something I would expect on a mech pumped truck without the ability to reduce timing in the lower rpm range.

Something else that is keeping me from believing that the propane is slowing the burn is the fact that tailpipe smoke usually decreases substantially when propane is introduced. If the burn was taking longer (similar to say, running a smaller nozzle and increasing the injection duration) the smoke level would increase out the tailpipe as the fuel continued to try and burn in an ever colder cylinder as the piston dropped away from TDC. The introduction of propane cleaned my tailpipe smoke right up, just the same as advanced timing would.

I also believe seeing some value given for "flashpoint"? of propane, and it being far lower than that for diesel? Wouldn't that also point to the propane as a fuel that would in fact burn very, very rapidly once combustion had commenced? If so, I find it hard to see how that would slow the combustion event for the diesel fuel.

 

[roachie]

Ok so the simple fact that the earths atmosphere contains 4 flammable gases means jack ****t to you guys? Ammonia, Carbon Monoxide, Hydrogen, Methane. Every diesel engine on earth should be experiencing preignition 24/7. We should also need a throttle body to keep the engine from “running away.” Like I said before it’s all about the amount you put in and YES you can lean out a diesel and it no longer runs on diesel or propane.

No, it really doesn't.

Nitrogen 78.084%
Oxygen 20.947%
Argon 0.934%
Carbon Dioxide 0.033%
Neon 18.2 parts per million
Helium 5.2 parts per million
Krypton 1.1 parts per million
Sulfur dioxide 1.0 parts per million
Methane 2.0 parts per million
Hydrogen 0.5 parts per million
Nitrous Oxide 0.5 parts per million
Xenon 0.09 parts per million
Ozone 0.07 parts per million
Nitrogen dioxide 0.02 parts per million
Iodine 0.01 parts per million
Carbon monoxide trace
Ammonia trace​

http://mistupid.com/chemistry/aircomp.htm

manifold pressure x compression ratio = X x 4.79 = air temp after compression

14.7psi x 16.7 = 245.49 x 4.79 = 1,169F

At 15:1 CR you have 1056*F at TDC

At 13:1 CR you have 915*F at TDC

This is at idle, under no boost at sea level.

At 16.3cr and 7psi positive manivold pressure (on the gauge) = 1694*F at TDC

Thats 9.63*F per rotational degree of the crank, so at 90.54* BTDC you have the 842*F needed to autoigninte propane.

Lower Flammable Limit (LFL)
The lower explosive limit (LEL) or lower flammable limit (LFL) of a combustible gas is defined as the smallest amount of the gas that will support a self-propagating flame when mixed with air (or oxygen) and ignited. In gas-detection systems, the amount of gas present is specified in terms of % LEL: 0% LEL being a combustible gas-free atmosphere and 100% LEL being an atmosphere in which the gas is at its lower flammable limit. The relationship between % LEL and % by volume differs from gas to gas. For data on other gases, refer to the most recent edition of the Handbook of Chemistry and Physics published by the C.R.C. Press. Typical settings for the alarm circuit are 20% for the low alarm, 40% for the high alarm and 60% for the high-high alarm.
The LEL of a gas is affected by the temperature and pressure: as the temperature increases, the LEL decreases and hence the explosion hazard increases; the relationship between LEL and pressure is fairly complex, but at approximately one atmosphere a pressure increase usually lowers the LEL. The LEL of a gas is not significantly affected by the humidity fluctuations normally encountered in the operation of a gas-detecting system.

http://www.delphian.com/gloss.htm#Liquid

Im assuming 2.2% is at sea level and 70*F.


Start explaining....

 

[BiodieselPower]

I must not have be clear before when I explained the "diesel" sound we hear from our engines.

That is the sound of detonation, directly due to ignition delay. What is happening is that you are injecting fuel into a cylinder faster than it can auto-ignite and burn and it subsequently "pools" and begins forming a pocket of unburned fuel where only the surface of the pocket is beginning to burn. Then as the piston continually approaches TDC, the cylinder environment keeps getting hotter and hotter and rapidly doing so, until the point comes where this pocket of fuel violently flashes off, producing the audible knock we hear through the head/block as "diesel rattle". Advance the timing (inject into an even colder cylinder) and the sound gets more and more crisp and harsh. Retard the timing, and it will continue to soften and soften until the sound is gone. The truck will usually be hazing and doggy at this point, but the ignition delay will be so small that the fuel doesn't build a pocket which obviously then doesn't detonate reporting the audible sound to our ears.

Now, say you had a pre-existing flame front in the cylinder prior to injecting the diesel fuel. The ignition delay would be minute, almost negligible. The fuel would combust almost immediately, and combustion would continue evenly and smoothly for the duration that the injector was held open (assuming a practical duration ATDC). The net effect would be a very, very smooth running engine. Which in itself is not a bad thing. However, idle and light throttle are not the only operating points for an engine. As more and more power is requested you begin getting higher and higher concentrations of the injection quantity burning BTDC, creating higher and higher cylinder pressures on the wrong side of the stroke. Effectively negating power production, yet still stressing the engine just the same. The real problem begins when you have a substantial quantity of fuel, that is timed such that with natural diesel fuel ignition delay, flame front propagation and rapid combustion will occur on a pace that places the highest cylinder pressure at 7+ degrees ATDC, with a good percentage of the burn continuing beyond that, pushing that MEP higher and higher. However, if this has been altered by another, untimed fuel residing in the cylinder, what would have timed out nicely, would when injected into a pre-existing flame result in nearly no ignition delay at all. And the diesel would almost immediately burn, shifting the burn window far more BTDC than ATDC, resulting in higher maximum cylinder pressures and simultaneously lower BMEP. Hence the situation I described to begin with. Lots of stress without the accompanying BMEP which ==> Torque which eventually ==> Power.

And the increased Cetane works in the exact same way. Decreasing the ignition delay decreases the amount of fuel that will form into an unburned pocket when approaching TDC, as the fuel will quite simply burn quicker, lessening this unburned fuel to flash off near TDC.

Fwiw, if you look at many cylinder pressure graphs, you will become accustomed to often times seeing a dip in cylinder pressure just as the injection event is initiated. This is because you are injecting cool (relative to the cylinder) diesel fuel with great mass. The fuel literally sucks so much heat out of the cylinder upon initial injection that you will often times see cylinder pressure fall even in the face of decreasing volume due to the rising piston approaching TDC. Although I will say that a dip such as this is usually an indication of overly advanced timing, or something I would expect on a mech pumped truck without the ability to reduce timing in the lower rpm range.

Something else that is keeping me from believing that the propane is slowing the burn is the fact that tailpipe smoke usually decreases substantially when propane is introduced. If the burn was taking longer (similar to say, running a smaller nozzle and increasing the injection duration) the smoke level would increase out the tailpipe as the fuel continued to try and burn in an ever colder cylinder as the piston dropped away from TDC. The introduction of propane cleaned my tailpipe smoke right up, just the same as advanced timing would.

I also believe seeing some value given for "flashpoint"? of propane, and it being far lower than that for diesel? Wouldn't that also point to the propane as a fuel that would in fact burn very, very rapidly once combustion had commenced? If so, I find it hard to see how that would slow the combustion event for the diesel fuel.

That could be about the best definition of a diesel knocking that I have ever heard.

So your pretty much agreeing with the title of the tread that timing has a lot to do with a propane engine having problems. I inject the diesel later and it makes the peak pressure after TDC where it should be. This is saying you don’t inject so much propane as to cause cylinder pressure to go high before diesel is even injected. Forgetting about the propane for a minute at what point is the fuel injector finished injecting fuel-like it starts at say 15 degress when is it done? Also, when does this “pocket” of fuel typically begin to flash off? How long before its done burning? Degrees? I know it will very greatly with timing, compression, cylinder temps. But lets just say a typical STOCK engine running under load.

Wouldn’t high cetane reduce power unless you reduce timing accordingly? Your easily igniting the fuel then it burns quick. So it seems you would waste power/fuel during the compression stroke instead of the power stroke. This is where I was originally thinking of timing because you’re burning the diesel and propane on the wrong stroke. If timing was reduced then the diesel fuel would burn more on the powerstroke than the compression stroke.

I have a problem with thinking too much fuel is burning on the compression stroke because why with the propane does it take less total BTU’s to move the truck down the road? Typically when using propane I use 4 gallons diesel to 1 gallon propane. That’s 6 (5.66 gallons when ajusted for BTU's) total gallons to go 105 miles at 21 mpg compared to 6.5 gallons of regular diesel at 16mpg. These are the exact numbers I saw on my powerstroke. If it was lighting too soon wouldn’t I use more diesel fuel because I am wasting it on the wrong side of the stroke to raise cylinder pressures. Then the PCM injects more diesel to get the work done. Maybe fuel economy would be a good way to tell if you’re raising cylinder pressures on the wrong side of the piston.

I can see where your coming from on black smoke but think of this: Propane reduces smoke by simply injecting less diesel fuel to do the desired work because of the extra propane BTU’s and more complete burn. and the propane produces no black smoke and burns extremely clean(ever seen engine oil from a straight propane engine). Also, doesn’t this help validate the fact that the propane is increasing mileage? Less smoke is less wasted fuel.

I agree one would think a low flashpoint would burn quicker but I don’t know if having a low flashpoint means something will burn faster-it means one thing it flashes easier. Biodiesel has a higher flashpoint than diesel-but it has a higher cetane too causing it to burn more rapidly than regular diesel.

On my cummins motor i can see 20-23 MPG on a high cetane coconut biodiesel(70 cetane) That is actually better mileage than on diesel by approx. 2 MPGs impressive considering biodiesel contains 11% less energy. That is why i started the tread about timing i think i need to set mine back because i see no gains with propane and i suspect it is burning too much on the compression stroke since timing is already advanced to 16 degrees. On my powerstroke i would see noticeably better results when running my TS chip on the 100 setting as compared to any other setting. Not sure if it changes timing but I assume it did.

 

[BiodieselPower]

No, it really doesn't.

How does it not? You just listed them for us-Methane, Hydrogen, carbon monoxide, and ammonia are all flammable. i know its not much but it actually does contain 4 flammable gases. You are saying it does not matter on a compression engine what quantity of gas as long as it is hot enough then its going to ignite. If it were igniting we wouldn't be able to shutoff our trucks without closing a throttle plate. It is so insignificant that it is below the LEL, like when running propane.

Nitrogen 78.084%
Oxygen 20.947%
Argon 0.934%
Carbon Dioxide 0.033%
Neon 18.2 parts per million
Helium 5.2 parts per million
Krypton 1.1 parts per million
Sulfur dioxide 1.0 parts per million
Methane 2.0 parts per million
Hydrogen 0.5 parts per million
Nitrous Oxide 0.5 parts per million
Xenon 0.09 parts per million
Ozone 0.07 parts per million
Nitrogen dioxide 0.02 parts per million
Iodine 0.01 parts per million
Carbon monoxide trace
Ammonia trace​

http://mistupid.com/chemistry/aircomp.htm

manifold pressure x compression ratio = X x 4.79 = air temp after compression

14.7psi x 16.7 = 245.49 x 4.79 = 1,169F

At 15:1 CR you have 1056*F at TDC

At 13:1 CR you have 915*F at TDC

This is at idle, under no boost at sea level.

At 16.3cr and 7psi positive manivold pressure (on the gauge) = 1694*F at TDC

Thats 9.63*F per rotational degree of the crank, so at 90.54* BTDC you have the 842*F needed to autoigninte propane.

That is saying that you have reached the LFL. LFL will go down from 2.2% as the piston reaches TDC so at a certain point you reach LFL, but we don’t know what that point is. AT low enough propane percentages we don’t even reach the point before TDC. The problem is the point changes indefinitely as boost/egt/%propane all change.

http://www.delphian.com/gloss.htm#Liquid

Im assuming 2.2% is at sea level and 70*F.

Yes

Start explaining....

Did i miss anything?

 

[Charles]

That could be about the best definition of a diesel knocking that I have ever heard.

So your pretty much agreeing with the title of the tread that timing has a lot to do with a propane engine having problems. I inject the diesel later and it makes the peak pressure after TDC where it should be.

Peak pressure will always be ATDC unless you have a mechanical failure of a cylinder seal. This is because whatever pressure you record at __ degrees BTDC, the piston will still advance closer to the head as it reaches TDC, increasing this pressure. The only other way to have peak pressure BTDC would be if you rapidly cooled the cylinder after some point BTDC with say coolant, or a broken nozzle, or something similar. But for the sake of understanding, just be aware that peak cylinder pressure isn't going to continually occur BTDC on a functioning engine. The variance we are talking about will usually be the different between peaks that occur right at TDC, vs occuring at or beyond 5 to 10 or more degrees ATDC. And in terms of engine stress, the shape and onset of that pressure. Even the exact same maximum cylinder pressure value can be achieved in such a way with proper tuning that results in long component life when compared to having produced that same pressure, but in such a way that approaching TDC the pressure is reached VERY quickly, almost instantly as the fuel source detonates. The difference is akin to placing your shoe on the top of an empty coke can and pressing down slowly, and uniformly until you are applying 100lbs of force to that can, vs merely taking a 100lb plate and holding it in a fixture where it is barely touching the top of the can, and then releasing it onto the can. Even though the force will be 100lbs, the timeframe in which it was delivered makes all the difference. So even speaking in terms of maximum cylinder pressure isn't even addressing the route cause of engine failure, which is shock loading, and really anything that isn't smooth and uniform that results in forces acting within timeframes that exceed the mechanical strength of any components in such a way that the service life is drastically cut short, if not immediately in some cases.

This is saying you don’t inject so much propane as to cause cylinder pressure to go high before diesel is even injected. Forgetting about the propane for a minute at what point is the fuel injector finished injecting fuel-like it starts at say 15 degress when is it done?

That depends on the injection duration and engine rpm. Obviously longer durations and higher rpm will extend the crank angle over which the injection window takes place. If you say a timing advance of 15 degrees, injection delay of say, .5ms, and in injection duration of 2ms at 1656rpm (chosen for round numbers), you'd have an injection window that started at 10 degrees BTDC, lasting 20 degrees and ending at 10 degrees ATDC. That might represent a cruising situation. It's just an example, I didn't know if that's what you were looking for.

Also, when does this “pocket” of fuel typically begin to flash off? How long before its done burning? Degrees? I know it will very greatly with timing, compression, cylinder temps. But lets just say a typical STOCK engine running under load.

Say, ~5 degrees BTDC, with the spike hitting right at or slightly ATDC. That should be in the ballpark, although I haven't spent much time looking at part throttle cylinder pressures, so I can't say for sure.

Wouldn’t high cetane reduce power unless you reduce timing accordingly? Your easily igniting the fuel then it burns quick. So it seems you would waste power/fuel during the compression stroke instead of the power stroke. This is where I was originally thinking of timing because you’re burning the diesel and propane on the wrong stroke. If timing was reduced then the diesel fuel would burn more on the powerstroke than the compression stroke.

This is assuming the engine was properly timed to begin with. For instance, most people will pick up response and mileage by advancing their stock timing a bit, because that timing might not have been set specifically for maximum combustion efficiency by the OEM for various reasons, emissions often being the culprit here. In such a case (as if often found) a quicker burning fuel will be advantageous. And yes, state of tune and intended engine usage/rpm operating range directly effects whether or not cetane increases/decreases will be of benefit for the reasons you outlined above.

I have a problem with thinking too much fuel is burning on the compression stroke because why with the propane does it take less total BTU’s to move the truck down the road? Typically when using propane I use 4 gallons diesel to 1 gallon propane. That’s 6 (5.66 gallons when ajusted for BTU's) total gallons to go 105 miles at 21 mpg compared to 6.5 gallons of regular diesel at 16mpg. These are the exact numbers I saw on my powerstroke. If it was lighting too soon wouldn’t I use more diesel fuel because I am wasting it on the wrong side of the stroke to raise cylinder pressures. Then the PCM injects more diesel to get the work done. Maybe fuel economy would be a good way to tell if you’re raising cylinder pressures on the wrong side of the piston.

As above, in most cases, increasing timing over a stock calibration nets positive results, which is effectively what is occuring with the propane in many cases. Reading this paragraph I think by the end of it you have come to the same conclusion.

I can see where your coming from on black smoke but think of this: Propane reduces smoke by simply injecting less diesel fuel to do the desired work because of the extra propane BTU’s and more complete burn. and the propane produces no black smoke and burns extremely clean(ever seen engine oil from a straight propane engine). Also, doesn’t this help validate the fact that the propane is increasing mileage? Less smoke is less wasted fuel.

I was speaking in terms of WOT, where diesel fuel delivery would be constant, and the only variable would be with or without propane. In this case the addition of the propane decreased tailpipe smoke considerably, leading me to believe the burn must have occured quicker, started earlier or both.

I agree one would think a low flashpoint would burn quicker but I don’t know if having a low flashpoint means something will burn faster-it means one thing it flashes easier. Biodiesel has a higher flashpoint than diesel-but it has a higher cetane too causing it to burn more rapidly than regular diesel.

On my cummins motor i can see 20-23 MPG on a high cetane coconut biodiesel(70 cetane) That is actually better mileage than on diesel by approx. 2 MPGs impressive considering biodiesel contains 11% less energy. That is why i started the tread about timing i think i need to set mine back because i see no gains with propane and i suspect it is burning too much on the compression stroke since timing is already advanced to 16 degrees. On my powerstroke i would see noticeably better results when running my TS chip on the 100 setting as compared to any other setting. Not sure if it changes timing but I assume it did.