so, i had inherited a set of Buschur/JE "drop in" pistons. i was told they were stock compression ratio, so i emailed BR with the number from the piston. i believe they told me they were stock, CR, but now i'm thinking maybe not.
my compression ratio, after a fresh build and break in, is 135psi across the board with 264 cams. each cylinder jumps right to 90psi, then peaks at 135psi. i'm pretty sure my OEM pistons were right around 140-145psi before they came out.

i'd guess these must be in the 8:1 range to have such a low CR?? i'm doing a leakdown tonight to make sure the machine shop didn't mess up something in the head.

all i know is my HKS 7460r is making 300whp at 25psi, tapering to 19psi and my STOCK turbo, with stock rods/pistons, and same cam made 330whp.

this sucks. any info would be appreciated. thanks!

 

Timing has been checked 100 times LOL.
Car also idles like crap, but drives fine.

 

do you have photo of piston top?

 

I do:

 

hmm. those do look like stock compression. may be as low as 8.5/1. but certainly not 8.0/1. I would suspect something else is going on here. poor idle, lower compression, and less power does suggest cam timing is off.

 

I think they are 8.5:1, judging by the catalogs.

I've checked timing 4 times. The only thing I haven't found a way to check is the MIVEC. My tuner says there is a way to log it, so I'm looking.

Another thing I'm going to check Is to be sure that MIVEC gear is lined up on the cam correctly . A friend of mine did that part for me and I warned him because I remember reading people sometimes get the dowel in the wrong spot. He said it was fine, but I don't know that he really checked. It's a longshot, but at this point I'm stumped.

 

Are you using 150mm rods, or 156mm rods with 2.3L pistons making it a 2.0LR?

I made this mistake in the past.
9.0 stroker pistons, 156mm rods and 88mm crank = ~8.2:1 CR.

 

stroker pistons would have the wrist pin coming trough the oil ring..

 

Standard-length rods and crank. Standard pistons.

 

If you remember the number on the piston, you can Email JE and get a spec sheet for them..

 

i am trying to find the email i sent to Buschur (they are supposedly their spec) that had the info from them. i seem to have possibly deleted it. fail.
still looking and have an email out to BR, in case they store their emails.

 

Let the engine get to operating temp then check compression. Forged piston have more clearance for expansion. Also what did you gap the rings to?

 

I've never done a cold compression test and .020-.022 top ring/ .022-.024 bottom (I can't remember off the to top my head) per Buschur. I know we only had to slightly file one ring. All others were perfect

 

I have a hunch that you may be on a wild goose chase. Slightly lower compression test results as compared to the factory pistons and rings isn't necessarily indicative of a problem. Have you performed a leakdown test with a good quality tester? Have you pressure tested the intake system?

 

This is interesting to me. I would have thought that a stroker piston would be what you use for a long rod build. What would the difference be?