Turbo pistons question

[createaaron]

What do you guys like to see for a compression height on the piston for a turbo application?

For arguments sake lets say a 4 inch bore with 20+ lbs of boost.

[cjperformance]

Top ring position and land thickness would be my first concern. Followed by keeping as much piston inside the bore at BDC. These 2 will then sort of govern comp height in a given application.

[Orr89rocz]

Really depends on design. If its custom made for boost it can be made somewhat short on height and still work and seal well. I have run the shelf je dish boost pistons in the 20+ psi range with a 1.125" height in a 4.125 bore. Worked well. But they werent designed for super high power and at 28-30 psi and 1400 hp, they eventually went out of round lol on tear down we found that out.

If its big power you want a full round skirt typically and definitely thick wall wrist pins.

General concensus is pick a crank and design a piston for the power, then find a rod to connect the two lol

[Mark O'Neal]

Depends on the engine....and the tuner.

[piston guy]

1.125 is my minimum for 20+psi. That leaves enough for acceptable ring land thicknesses.

[user-23911]

Just the same as a normal piston only with lower CR.
No dome, bigger dish.

[MELWAY]

1.125 is my minimum for 20+psi. That leaves enough for acceptable ring land thicknesses.

Is it more of a heat thing rather than load/force issue when trying to design boost Pistons ?

[user-23911]

It's all smoke and mirrors.

[createaaron]

So to go along with the thick top ring land, what do you like to use for a ring pack size wise?

[piston guy]

1.125 is my minimum for 20+psi. That leaves enough for acceptable ring land thicknesses.

Is it more of a heat thing rather than load/force issue when trying to design boost Pistons ?

Both have to be considered. Heat dissipation and land strength.

[createaaron]

If you guys had the option would you prefer a 1.125 ch with the longer stroke or stock stroke and a 1.25 ch piston? Obviously were talking Chevy now. 20 psi range, moderate street mostly strip mileage.

[Orr89rocz]

If you guys had the option would you prefer a 1.125 ch with the longer stroke or stock stroke and a 1.25 ch piston? Obviously were talking Chevy now. 20 psi range, moderate street mostly strip mileage.

Whats the rest of the combo look like? What bore and stroke are considered? What rod length? What turbo and planned power?
My gut tells me i would want the 1.25" but a 1.125" can be designed to work fine. I have used shelf je blower dish pistons to 30 psi at 1.125", despite piston going out of round and nearly ripping out the weak .150" wall wrist pins. Bigger power stuff you definitely want some thick wall pins. Tool steel ideal. But those pistons would live forever at the lower power i was making in the 20 psi range

[createaaron]

Whats the rest of the combo look like? What bore and stroke are considered? What rod length? What turbo and planned power?

3.48 stroke with 1.25 ch piston and 3.75 stroke and 1.125 piston, 6 in. rod, 4.030 bore, 78-80mm turbo, first goal is 600 and final goal is 800-900 on this engine. If i go with the stroker crank, It will require a dish piston, and at 1.125 i'd be getting worried of the deck thickness on the piston

I have used shelf je blower dish pistons to 30 psi at 1.125"

My plan is to get away with a shelf piston. Ive been eyeing the cp bullet series pistons.

[peejay]

1.125" is shorter than Subaru 2.5l pistons (bore size 3.9something, compression height a shade under 1.2) and they are reknowned for their ability to break ring lands because there isn't enough room for a good ring pack.

I wonder what people are doing differently.

[Orr89rocz]

1.125" is shorter than Subaru 2.5l pistons (bore size 3.9something, compression height a shade under 1.2) and they are reknowned for their ability to break ring lands because there isn't enough room for a good ring pack.

I wonder what people are doing differently.

Well a je blower designed piston is not a suburu stock piston lol

The top ring is down .280 on the shelf je piston with 1.125" ch. oil ring is into the wrist pin about .210" so requires oil rail supports. No big deal tho. They work fine

Since you are looking for 800-900 hp, the shelf pistons should cover that. There will be plenty of piston crown thickness on a shelf boost piston even if dished for that power. The stroker motor will spool sooner and have lower rpm power band for the most part. If its a s400 type turbo, with a 96mm turbine wheel the 348" motor will have more absolute max power potential due to not backing up the turbine. But that turbine will still feed 383 cubes to higher power than what you have planned.

So either way you go will work imo.