I'm wondering if anyone knows or feels that the standard CP pistons are crappier or substandard in comparison to other pistons of similar quality and price range out there on the market...

I've spoken to a couple companies and race teams of which I am friendly with, and they pretty much told me not to go with the CP pistons available for the STi. Of course that was followed up by a recommendation to go with their sponsored piston manufacturers...however they were quite serious about ther recommendation.

I have used Ross Racing pistons, and Wiseco pistons in the past with no issues.

I'm not looking to be running crazy power, however if I do choose to build my block, I prefer to use pistons that will prove themselves to have quality and longevity.

What are the CP pistons users feelings here about them? Any piston issues in relation to longevity or performance?

Who else makes forged pistons that would fit the EJ257 block? I of course am not looking to spend $1,000,000 on pistons, however if a set of pistons for $800 are known on the average to be better thna a set of $400 pistons, then I'm going with them.

I'm not looking for a debate, just basically for solid info, before I choose my direct path.

I'd like to thank any members or vendors who respond here in advance. The more information I have the better. Thank you.

User tarmecel is building up a block using a set of Wiseco pistons and rings. IIRC the price was just north of $400.

http://forums.nasioc.com/forums/showthread.php?t=732024&page=3&pp=25

A lot of STI owners are running CP pistons (myself included - can't give you longevity report - 400 miles on the motor). Also two of the big motor builders here are running CP's (Crawford and Axis). tmarcel bought the Wiseco's and they look pretty good, but he doesn't have his car running. But he's one of the first people I've seen on here that is running the wiseco's. For the most part aftermarket pistons for the STI are around $500 no matter who you go with. PDXTuning is running 400+ WHP with just a set of CP's and I know they have some miles on their motors. I'd say do what you want to do. Wiseco makes good pistons and I think CP does to, so I think you'll be ok either way.

There are TONS of users running Cp pistons trouble free.

There are also people running them with problems.

There are also people running Wisecos, and every other piston,part, brand on the planet having tons fo problems.

If they told you not to go with them, and gave no specific, solid, real reasons, its 99% BS. This isnt just speaking of this case, this is speaking of almost all things.

I was given reasons not to use them...however as these are real people in the racing world, they also recommended that I did some reaserch for myself on the message boards and web to find out info myself.

It's nice talking to professionals about this stuff, however in their fields of racing their pistons alone are valued at more than my car is worth. In a streetable situation it's a tad different.

The major reasons, not specifically to subaru engines with standard CP pistons, had to do with their overall design of the piston, metal of choice (grade mainly), and forging techniques.

The never bad mouthed the product, however said, if I could get another product, then go for it...

So this is why now I'm doing some real world data gathering. I'm also looking into actual info on the metal chosen for the pistons (silicon content, etc), and forging procedures. Not all info is readily available of course...however most companies will talk about their metals and forging procedures.

And also specific real world data of these products actually used on the Subary EJ25X engines...

thanks for the responses so far.

I believe the CP's and Wiseco's are made of the same material.

There are TONS of users running Cp pistons trouble free.

There are also people running them with problems.

There are also people running Wisecos, and every other piston,part, brand on the planet having tons fo problems.

If they told you not to go with them, and gave no specific, solid, real reasons, its 99% BS. This isnt just speaking of this case, this is speaking of almost all things.


I hate when I agree with Davenow!
He's right.

Also keep in mind that a part that is FAR too low of quality for the INCREDIBLE abuse of a pro race application, may be WAY more than enough for serious street abuse. Pro racers can break ANYTHING, so maybe the Cp pistons break sooner in their experience (just guessing) but that doesnt 100% mean that for street use, you will ever break them.

100% agree davenow...hence the reason I figured I'd ask this here...

Forged piston use on an EJ motor pushing 400+ hp is all I really care about, and not my contact's 750hp 2.1L destroked MZR mazda I4.

Anyone else using CP or other pistons...I should probably check around the EJ20 owners too, since they'd have been running them for longer I'd assume.

Just ordered a set of CPs from Ron today, I even asked him about the wisecos since they come coated and with their own rings. Ron said he prefers CPs on street cars since they are made to run with a bit tighter tolerance for less noise and wear on startup, and also he didnt feel the need to run different rings since the failures he had seen were in the piston and not the factory rings.

I would still like to hear good things about the wisecos, keep in mind unless you get a custom CR their off the shelf piston for us is 8.5/1 cr

Wiseco comes coated.. that is nice.. The only thing i dont like a bout CP STI and WRX pistons is that you have to use the OEM rings, but i have to say they are very good quality. But i still would choose Arias, or Atomic pistons for the WRX anyday. If Arias was smart they would make a shelf piston for the STI, Ive used a set of custom Arias pistons in the past that I put in a STI .5mm OS. I havent seen Wiseco in person, but i do know Arias and CP are of the same quality except you get rings with the Arias pistons.

How would you measure such a thing? How many people in the world are capable of making that call? Most of the names mentioned are used by multiple racers.

Hey Invisiguard,

Are you doing the build yourself?