timing and nitrous

[BlackSkyRacing]

Charles, c16 is harder to light which is why it's higher octane. I still don't by it that it burns faster. With a bigger bang yes, faster I just don't see it.

I have to agree here... Without the compression to support higher octane fuel you will only kill an engine by running it since it burns slower at lower temps oke: At least that is always what I have been taught.

Not meaning to derail. But shouldn't something also be said about cetane when talking about rate of burn???

 

[morkable]

stock height gasket

 

[Joesixpack]

I agree, more oxygen in the cylinder net effect is more "average" timing.

I think what most miss is a diesel injection rate is over time, its not just a hot bang like a gasser, but a fueling over degrees of crank shaft rotation.

The net timing increase is due to the reduction of ignition lag.

 

[Jetpilot]

Charles, c16 is harder to light which is why it's higher octane. I still don't by it that it burns faster. With a bigger bang yes, faster I just don't see it. I could be wrong have been many times before but nobody can show me how it burns faster. They just say it does. I learning like most with these diesel's we play with and have run a bunch of nos in these things. I'm not a beginner with this stuff. Nitrous in a gas motor works different from what i'm finding I was just curious if others have found the same thing or if they just do what others say because it's the way it is. Thanks for the replies Jeff

What would you like as proof? Maybe I can supply the info.

Doug

 

[Stingpuller]

Track Times!

Nobody can fool a track time with a given weight. I like real world results. Thanks again Jeff

 

[Jetpilot]

Nobody can fool a track time with a given weight. I like real world results. Thanks again Jeff

There is a lot more to it than track times..... Even same day same conditions a faster/slower time wouldn't tell if the burn was faster or not. I am not trying to be a prick just trying to answer the question.

 

[John Robinson]

Maybe this will help.Lets go back to the command module fire in 1967. That killed the 3 astrounauts. In mere seconds it was all over. It was pure oxygen being pumped into the module....It couldnt have burned up that fast with regular old air could it. Oxygen burns faster. Kind of a poor analogy i know but it makes it clear to me. Hope this helps

 

[morkable]

So I guess I will continue to run on level 8 with no extra timing,,, lol

 

[Stingpuller]

Timing

Correct on the burn with Oxygen but thats my point. There is no extra oxygen until it breaks down which is over the flash point of diesel. I'm done I have hyjacked this tread enough. Sorry for that. Thanks Jeff

 

[XLR8R]

Good point - however, the heat from compression as the piston rises reaches the critical temp of NO2 (allowing the oxygen to free associate) before #2 is injected... so effective timing does increase with nitrous.

 

[paulb]

Good point - however, the heat from compression as the piston rises reaches the critical temp of NO2 (allowing the oxygen to free associate) before #2 is injected... so effective timing does increase with nitrous.

What does the temp of the air get to on the compression stroke, before the fuel is injected?

 

[John Robinson]

Good point - however, the heat from compression as the piston rises reaches the critical temp of NO2 (allowing the oxygen to free associate) before #2 is injected... so effective timing does increase with nitrous.

No but....We all agree cylinder psi rises with timeing right. Cylinder psi also rises when you use n20. Drive psi goes through the roof as well. :hehe: Good lord this thread is starting to make me dizzy.

 

[Charles]

Charles, c16 is harder to light which is why it's higher octane. I still don't by it that it burns faster. With a bigger bang yes, faster I just don't see it. I could be wrong have been many times before but nobody can show me how it burns faster. They just say it does. I learning like most with these diesel's we play with and have run a bunch of nos in these things. I'm not a beginner with this stuff. Nitrous in a gas motor works different from what i'm finding I was just curious if others have found the same thing or if they just do what others say because it's the way it is. Thanks for the replies Jeff

I'll try again:

Which burns faster.... dumping a cup of moonshine on a fire, or putting a swig in your mouth and spraying it on the fire in a well atomized state?

Same goes for injection pressures in these trucks. If you crank the rail, you atomize the fuel more, and it burns quicker. Sometimes to the point of creating audible cylinder pressure spikes that some people refer to as "rattling".

Well.....

What's happening when something is more "atomized"? It's nothing more than taking one large pocket of fuel, and turning it into many, many, many small drops of fuel. The difference is that the ratio of volume to surface area goes up DRASTICALLY as the droplet size decreases. The net effect is that the fuel per volume, has better access to the oxygen in the cylinder. The result? The fuel burns faster, and since the event is dependent on piston position and everything is happening with a time limit, it also burns more completely, because it burns the fuel FASTER. If it didn't burn it FASTER it wouldn't clean up when someone hits the spray. It would still be burning out the manifold like when they're on fuel only and unable to clean it with the chargers.

When you just add nitrous oxide you increase the oxygen and speed things up the same way as with better atomization. Only chemically, instead of physically. The fuel has more access to oxygen.

 

[Joesixpack]

What does the temp of the air get to on the compression stroke, before the fuel is injected?

Depending on the compression ratio, 900F to over 1000F, so the argument that the nos isn't available untill after the cylinder fires does not hold water.

Excess amounts of juice could cool to the point that they don't come available to well after TDC and the resultant cylinder wall blow outs.

Another reason why most find pre-CAC seems a good place to inject the lion share of the juice, your intercooler works in reverse, helping gas off before combustion.

 

[XLR8R]

the heat from compression as the piston rises reaches the critical temp of NO2 (allowing the oxygen to free associate) before #2 is injected...

What does the temp of the air get to on the compression stroke, before the fuel is injected?

Depending on the compression ratio, 900F to over 1000F

Excess amounts of juice could cool to the point that they don't come available to well after TDC.

Another reason why most find pre-CAC seems a good place to inject the lion share of the juice, your intercooler works in reverse, helping gas off before combustion.

Exactly - the oxgen in nitrous oxide is theoretically available for combustion prior to the advent of fuel injection.

Same reason why water injection won't normally be able to hydrolock a cylinder - there's generally no liquid phase water remaining in the chamber approaching TDC.

Obviously, shock-cooling of the intake charge & combustion chamber with excessive NO2 negates it's disassociation by the heat of compression, and too much fuel or water has a related effect on the cylinder charge's temperature rise.

In extreme cases, incompressible liquid water or fuel (especially in the case of nitro engines that run on the verge of hydrolock) can cause mechanical damage to the reciprocating assembly.

BTW - that's one of the better explanations why pre-CAC nitrous usually generates more power.

 

[Stingpuller]

Timing

Good debate! I guess I'll see everyone at the race track. Jeff

 

[morkable]

I understand exactly what everyone is saying,, but,, this dosent really help in how MUCH timing to use,,

 

[XLR8R]

For instance, if you run TNT-R #9 w/default timing as your best fuel-only tune, then back off #9's timing to level 3 for a shot of NO2 - or level 4 for two stages. Take out more for water/meth or added rail pressure.

Since SW#8 makes the same power as #9, but uses duration (& pressure IIRC) instead of timing to do so, it's conceivable that best safe power would be generated on #8 w/default timing, stacked RP, water/meth & 2 stages of NO2.

Really, for a particular engine you have to push timing until the onset of rattle, then back off a couple degrees... or just continue leaning on the motor regardless of warning signs like WOT timing rattle, knowing that carnage will eventually occur.

It's a personal decision based on risk analysis - CTDs can withstand amazing abuse, so it's tempting to squeeze them 'til they pop. :Cheer:

 

[full pull]

For instance, if you run TNT-R #9 w/default timing as your best fuel-only tune, then back off #9's timing to level 3 for a shot of NO2 - or level 4 for two stages. Take out more for water/meth or added rail pressure.

Since SW#8 makes the same power as #9, but uses duration (& pressure IIRC) instead of timing to do so, it's conceivable that best safe power would be generated on #8 w/default timing, stacked RP, water/meth & 2 stages of NO2.

Really, for a particular engine you have to push timing until the onset of rattle, then back off a couple degrees... or just continue leaning on the motor regardless of warning signs like WOT timing rattle, knowing that carnage will eventually occur.

It's a personal decision based on risk analysis - CTDs can withstand amazing abuse, so it's tempting to squeeze them 'til they pop. :Cheer:

Thats what I was saying...







What kind of timing can you run in a CR with out NO2?

I ran mine with all the timing I could throw at it this weekend, It ran great and never rattled.. Im guessing it was at 30*+

 

[Extreme Engines]

18-19* of static timing is the most i would go, because when you factor in the added 27,000+ psi RP you are "really" getting about 24-26* of timing. RP has alot to do with timing.

Something to think about.oke: