Civic TSI

What do you guys use ? For a turbo D16Z6 mainly street driven @ 15psi ? Track race @ 25+psi ?

For piston to wall, I thought about 0.004

For the upper ring, 0.006, lower .0045 per inch of bore, which come about .020mm and 0.015mm.

I'm not an engine builder, this is what my mecanic recommended me.
By doing some search, this sound about right. Just want to make sure.

turbodohcsi

the .015 sounds kinda small, but your pistons should of came with a chart, and calculations to help you figure out the gap

earl

Piston to wall should be .0035"
upper gap .018"
.020" middle

Civic TSI

Thank Earl. For piston to wall, we were debating between .0035 and .004. He's used to work with JE and he wanted to go with .005 at first. What makes CP pistons kind of use the same clearance between an N/A and FI ?

Did you revisited your rings clearance ? It's not what you were saying like a year ago ?

earl

I believe they use .003" for NA and .0035" for FI.
I have always used the .018" upper gap but have increased the middle gap (per the advice of CP) to .002-.004" larger than the upper gap.

fled

JE out of the box recommends piston to wall clearance to be 0.004. Earl, would you care to expand on why you prefer 0.0035? Does it really matter?

earl

I just do what CP calls for. I never try to out think them.
Both CP and JE build their desired clearance into the piston. You buy an 84mm piston and you bore your block to exact on 84mm. The clearance is into the piston. I think both CP and JE are smart enough to make that call. Now some of the other piston manufacturers......

fled

I did not know that JE built their clearances into the pistons, I thought only CP did that. I thought i had to overbore 81.5mm (piston spec) + 0.004mm (clearance spec)

Ok yeah i just read the spec sheet online carefully and it says that the clearances are built in, but for turbo and similar...additional clearance may be required.


Modified by fled at 9:58 AM 4/3/2005

earl

yeah, I guess that would depend on how lean you plan to run your tune-up as to extra clearance. That would be the only reason I could see to increase the specs.

Civic TSI

As I said, I'm not an engine builder, more like an engine blower LOL
Just a quick question, what is the difference between .0035 and .004 ? Better compression ? Rings longevity ?

Thanks again for the info.

earl

Just more room to expand. Probably no power difference. They could slap a litte on start-up with extra clearance.