3.2L twin turbo L28 stroker

[letitsnow]

Ok, that's probably what you'd need to do when building such a large, boosted engine, but if I can recall what was being said about such a situation in Corky Bells book, Maximum Boost, the 'squish' is all wrong and that can introduce all sorts of combustion problems. Is that true and does it apply here to some degree?

 

Your question is a little unclear, is Bell saying squish is good or bad? Personally, I'd unshroud the valves some and possibly run a reverse dome piston if I need the compression lower. I would not run a thick head gasket or sink the top of the piston down the cylinder.

[ozconnection]

............ Personally, I'd unshroud the valves some and possibly run a reverse dome piston if I need the compression lower. I would not run a thick head gasket or sink the top of the piston down the cylinder.

 

Yes, this is what Bell was suggesting in his book.

[B00STDZ]

I wonder if anyone is accually successfully running 90+mm pistons...

[Daeron]

What you do is machine a relief in the flat top of your piston that mirrors the combustion chamber in the head. It will be similar in shape, but probably much shallower and definitely much smaller in perimeter (a smaller peanut, as it were.)

 

Get your piston to kiss the quench pad as close as you want, (I always blow the clearance b/c I cannot remember whether its metric or standard) then from there determine the volume of a relief needed, and get to work carving out a smaller peanut centered over the same point as the CC in the head is centered (the little peanut is off-center, but you get my drift) and there you have your lowered compression, high quench P-90 setup.

[ozconnection]

Yes, that's it. Thanks for reminding us on that one Daeron.

 

Only thing is the piston crown would have to be fairly thick cause for a 3.2 litre engine, there would be substancial dish required. What would be the minimal crown thickness after machining? Also, can you do this at home or is it a machine shop operation? Expensive?

 

Or if it's easier, can you direct me to the thread that has this info in it please.

 

Thanks

[B00STDZ]

Kameari pistons might work...

 

www.zccjdm.com

[Daeron]

http://forums.hybridz.org/showthread.php?t=130872&highlight=quench

 

http://forums.hybridz.org/showthread.php?t=119151&highlight=quench

 

I take 1 fast Z at his word as my "quench and piston" expert, so his word is Holy Writ in this matter as far as I'm concerned.

 

You want to run about .025" piston to head clearence, for maximum quench.

....

 

Technically you should get your pistons to have a PERFECT mirror image of YOUR p90 head for maximum quench. This is done by assembling your engine for mockup, and inserting each piston in one at a time and then put your head on, and "bump" each piston to the head with prussian blue on it then scribe your combustion chamber and mill out ONLY that area and NEVER go outside that line, THEN you will have the MAXIMUM quench you can obtain. Most people skip this step and mess up, P90 heads are worthless without all of these steps.

[ozconnection]

http://forums.hybridz.org/showthread.php?t=130872&highlight=quench

 

http://forums.hybridz.org/showthread.php?t=119151&highlight=quench

 

I take 1 fast Z at his word as my "quench and piston" expert, so his word is Holy Writ in this matter as far as I'm concerned.

 

That's great Shawn, thank you for the links!

[Daeron]

That's great Shawn, thank you for the links!

 

There is alot more to be read, but it boils down to what I quoted earlier, and the other post provided his opinion on piston machining.

 

When I look at it in a practical light (IE, imagining myself with a box O' pistons needing to actually DO rather than just talking about it) I would be in touch with the machinist I plan on having do the work before purchasing my pistons, to get their opinion on the same topic. I'd hate to get pistons that I thought were thick ebnough and have my machinist refuse to mill them "that thin."

 

You can also ALWAYS remove all the material you want from the underside of the piston, but it is MUCH harder to add it back, right? (Another trick I picked up from 1 fast Z.)