What's the minimum thickness you should allow from bowl edge to piston od?

[COMP461]

I believe that the fuel should never get a chance to reach the outer wall. The pressure of the CR system and the size of the injector, and timing should if all is optimal have the fuel burn 100 % of the fuel should burn , the smoke show is due to late fueling , and to big of a fuel delivery at the wrong time. You always hear, that “it cleaned up, when the turbo lit “well done right there should be very little to no smoke. The CR injection lends itself to giving the optimal timing to help spool a charger, this is not possible with a fixed timing P pump, so excessive fuel is delivered; this excessive fuel is the problem with the pistons getting fuel impingement.
With designing a optimal piston crown, I believe that you should look at the optimal injector pattern, and then fill any area in with aluminum that the injector is not fueling. A flat bottom to a piston bowl is having a dead area .

 

[COMP461]

You keep talking about this 2.6 engine program. What do you consider to be a competitive size turbo for the 2.6 class. Maybe instead of trying to make all these new products you should fix the problems and failures with your current ones.

Unless you can contribute to this thread with real knowledge, justified by facts and data, go play somewhere else

 

[RonA]

Unfortunately, in my particular case common rail is not an option, so all of my questions will have to be viewed from a mechanical injection perspective. I'm hoping to try this again in 3 or 4 years when stand alone technology improves and go with a common rail system.

Paulb.
If you could pm me what type of coating you had Swain do I would appreciate it. Also, did you have to coat the valve faces and cylinder head also?

 

[joefarmer]

At what point is it considered too thin? I would assume it becomes too hot and causes problems with the top ring, or starts to melt and round off if it is too thin in that area.

.200-.210

 

[Smokem]

Buy control the flame do you mean that you want the center point of the corner radius to be below the top of the piston.

I am talking about directing the angle of the fuel jet down the piston hat and having no re-entrant lip to contain it to the bowl. If you do not keep the flame in the bowl, you cannot control the consequences.

I believe that the fuel should never get a chance to reach the outer wall.

That is contrary to every design of a diesel injection system, good luck if that is the path you have chosen. Now if you are unable to do so, and the fuel reaches the wall, with the piston design you have, where do you think the flame will travel?

 

[BigDamnCummins]

So do you design the bowl, shallow , with a lip on the top of the bowl to keep the fuel in the bowl? As the 03-04 pistons are doing or a 24v piston.

 

[COMP461]

So do you design the bowl, shallow , with a lip on the top of the bowl to keep the fuel in the bowl? As the 03-04 pistons are doing or a 24v piston.

the bowl has to be so many CC , or the compression will go thru the roof.
so if the bowl is shallower , then it has to be wider

allready run the wide design and make good power , if you keep from overfueling it , its going to work fine.
remember in a CR there is no need for overfueling. moving the rig land down helps as well . also reving the engine up reduces cylinder pressure ,

 

[BigDamnCummins]

Yes i understand that i need "x" CCs' to make my compression "X". How much lip should you leave around the edge? .500'' or .625" The .625" looks a little better on paper?

 

[RonA]

Yes i understand that i need "x" CCs' to make my compression "X". How much lip should you leave around the edge? .500'' or .625" The .625" looks a little better on paper?

Mine are closer to the .5 mark. It will have to do. The rest of the set are due this week and when they show up I'm going to send them out for coating.(Thanks Paulb).

 

[promodracer]

piston dome design

But they were looking for emissions as well, and I believe that part of the closed bowl design was for a passive EGR . The third design is the best we have run so far the top piston is a extreme RPM design for my Dragster. This is a piston that will run from 4500 to 6000, and never be loaded under that.

There is a lot to share here, and we have a lot of development to achieve. Just think people were laughing at my wanting to port heads, and saying it didn't make a difference 5 years ago, and people are just now beginning to understand that a cam can be the best possible bang for your buck, of anything you can do to a diesel. I have ground over 700 cams in the last few years, and this is just the beginning

I was thinking the same thing. Stock design parameters are different. They are not trying to achieve the same results.
p.s I think you have done a great job with your research and testing.
j & e make great close tolerence pistons used in promods...
Keep up the great wk.
Best wishes

 

[BigDamnCummins]

I believe some of these piston manufactures require .013" tolerance.

 

[JOHNBOY]

I did also note what piston KPE used in their Z28 build.

The only reason that piston ended up in there was lead time. Simply not enough to get a better piston. Problem has been corrected.

It is apples and oranges Weston. Cummins and GM are focused on low rpm power and emissions. What Comp posted is for a higher RPM engine and all out power. Very much like the pistons used in Mike Woods Dmax. It seems to work just fine.

But what do I know?:bang

 

[Smokem]

Cummins and GM are focused on low rpm power and emissions. What Comp posted is for a higher RPM engine and all out power.

Well that's good to hear, someone is finally designing a piston for high RPM and all out power, because I don't think that it has been done before. Wait, no, it has. With no containment wall on the bowl, no matter what fuel injection type is used, you are asking for problems, just not sure why it is so hard to understand.

 

[mondtster]

With no containment wall on the bowl, no matter what fuel injection type is used, you are asking for problems, just not sure why it is so hard to understand.

You're referring to the "lip" at the outside top rim of the bowl here, correct?

 

[JOHNBOY]

Well that's good to hear, someone is finally designing a piston for high RPM and all out power, because I don't think that it has been done before. Wait, no, it has. With no containment wall on the bowl, no matter what fuel injection type is used, you are asking for problems, just not sure why it is so hard to understand.

Give up on putting my words in my mouth Weston. I never ever said it was not done before. It has been with great success and great failure.

I only jumped in because you tried to speak for Tommy. You did not know the full story so I filled you in.

So for us we are very pleased with the results. It is not just add these magic pistons. It is a package along with injectors, heads that work and a cam that have aggressive profiles.

Problem with the "containment wall" while it does a great job of spinning the mixture back over itself is that it small section width by nature lends itself to early fatigue and cracks. Once a crack starts it is a very small matter of time before that crack causes complete piston failure. With a piston like the monotherm and it's steel make up I could see going back to the containment wall. But not with the aluminum. It is a paradox. There is a good reason for it to be there but it can cause heartache.

Here is an example of the lip starting to fail.

 

[Smokem]

I'm not putting words in anyone's mouth. Trying to control the flame with a re-entrant lip on an aluminum piston is not new, it has everything to do with the cone angle, and point of contact for the jet. If the setup they are using is having failures on the lip, change the angle, do not remove the lip. Like I said before, if you let the flame run out of the bowl, how can you control the result?

 

[JOHNBOY]

I'm not putting words in anyone's mouth. Trying to control the flame with a re-entrant lip on an aluminum piston is not new, it has everything to do with the cone angle, and point of contact for the jet. If the setup they are using is having failures on the lip, change the angle, do not remove the lip. Like I said before, if you let the flame run out of the bowl, how can you control the result?

Sure. Agree to disagree on that one.

Making the bowl wider and shallower was done to help with keeping the flame in the bowl. If you think we have not done drawn things up to see where the spray patterns really are, we have. I even posted some of the pictures about a year ago.

You must have missed this part so I quoted so you could see it again.

Problem with the "containment wall" while it does a great job of spinning the mixture back over itself is that it small section width by nature lends itself to early fatigue and cracks. Once a crack starts it is a very small matter of time before that crack causes complete piston failure. With a piston like the monotherm and it's steel make up I could see going back to the containment wall. But not with the aluminum. It is a paradox. There is a good reason for it to be there but it can cause heartache.

With CR and its pilot injection your not always going to be able to keep the shot in the bowl. So you cant read the piston like a mech pump engine.

Now in the case of a Dmax you deactivate the Pilot and Post on those so equipped. And I do but not every where. Pilot has it usefulness. I tune the NX mustang, the Z28 Dmax and my own pulling truck. I have iges. files of the piston designs. I used my CAD skills to draw up the injection patterns and come up my a max timing number for each. The NX mustang is no where near it. It runs surprisingly hard with out the timing so I did step it up. The Z28 has all the potential to run harder. Same basic engine but with much more air from its twins. But unrelated gremlins have so far spoiled that. I will be back on the dyno soon with it.

I run the most aggressive tune up on my truck. So far the pistons have held up great.
Would I put these pistons in a Daily driver? No
Would I like to try a monoterm with the reentrant bowl? Hell yes. I was on the phone with Mahle several times this week. Trying like mad to get a set for myself to try.

 

[Smokem]

I've dealt with Mahle on the issue with the Cummins piston design, like I said, oddly enough they went back to a 146* pattern on the cone angle with a micro-blind nozzle with the 6.7l. I agree with a few ex-Bosch engineers about the cone angle issue with the wider bowl, they could not understand why it was designed that way. A perfect example to see if something doesn't work, is if a company after spending countless hours of design time and a large budget, abandons the idea to go back to what they were doing before. Ever notice how you can take the main event completely out of the bowl and have EGT's in excess of 1800*'s and have no failures, yet use the narrow cone angle and contain both events and have failures at much lower peak cylinder temperatures?

 

[COMP461]

Well that's good to hear, someone is finally designing a piston for high RPM and all out power, because I don't think that it has been done before. Wait, no, it has. With no containment wall on the bowl, no matter what fuel injection type is used, you are asking for problems, just not sure why it is so hard to understand.

The ideal situation that no fuel will reach the wall, this is only if the other parameters are correct. There is a lot more to doing ejectors then just bigger is better.
These parameters that are critical in diesels engine combustion efficiently are the size of the nozzle, the number of holes, the shape of the combustion chamber, and the reach of the plume, and the fuel pressure. If all are right the engine should be as clean. Clean is mean, when you have a over fueling condition the extra fuel will over reach, and cause piston wash. These parameters are only achievable is you have active control of timing, delivery rates.
The CR engine is making the most power when it’s lean and clean, and most people are just tossing bigger injectors in and making power that produces smoke, and high egts , and residual combustion chamber temps.
You should first read the ASE research papers on piston designs that Bosch published, might enlighten you, and then go thru a few sets of pistons, moving in the direction that the data tells you.

Piston bowl design from the OEM is designed for small hp, and a wide range of applications.

 

[Smokem]

You should first read the ASE research papers on piston designs that Bosch published, might enlighten you, and then go thru a few sets of pistons, moving in the direction that the data tells you.

Stop Greg, your killing me. Was this before or after they realized there was a problem?