Piston question

Craz1000 · Post by **Craz1000** » Wed Apr 25, 2007 12:29 am

im rebuilding an '03 motor for a turbo, i know the rods are pretty weak, but what about the pistons, how much punishment or psi can they take

kc2005ptgt · Post by **kc2005ptgt** » Wed Apr 25, 2007 12:33 am

I have heard our bottom end is good for no more than 250 hp/tq, as well as most of our other parts, including tranny, clutch, axles. I would gather this would include the pistons. I know the rods need to be changed out - someone on here just blew up there turbo swap and spent all sorts of money but did not replace the rods.

but pistons, like I said, only what I have read, not from any personal experience or mechanical knowledge on the matter.

OB · Post by OB » Wed Apr 25, 2007 12:46 am

If you plan on running much more than 6-8 psi id highly suggest replacing the pistons and rods, just to be safe. They can probably handle a bit more but I wouldnt push it.

Kevin_GP · Post by **Kevin_GP** » Wed Apr 25, 2007 1:38 am

hmmm

Rods are the weak link, tranny and axles are good past 250, clutch will die shortly after a little bit of power past stock. People replace the pistons to because they are forged, have different ring seals (further away from the top of the piston), and most importantly they lower compression. PSI means nothing, ive been up to 8 psi on my 9.8:1 block and theres no holes in it. Compression is arguable, yes lower compression helps with a larger tuning window but thats not always the case. Working with 9.8:1 isnt that big of a deal, you just cant beat on it and need to know what you are doing.

OB · Post by OB » Wed Apr 25, 2007 2:40 am

Sure, PSI doesnt directly have anything to do with piston life, but the temperatures and conditions that come along with higher boost levels do. When someone uses a certain PSI to rate something, theyre usually not trying to say that that part cant take some extra air pressure. Its the other effects of turbocharging that the internals cant handle. The settings of a system with over 6-8 psi typically require forged, lower compression pistons and high octane fuel to prevent detonation and general meltdown in the bottom end. Of course this isnt a rule and many motors can safely boost higher than this, but its not a good idea.

Ryanm07 · Post by **Ryanm07** » Thu Apr 26, 2007 12:56 am

When I was doing my research 10psi seemed to be the magic number. I was told that as far as the motor goes, stock it will handle 10psi as long as it had a good tune. But I heard that was like the limit, anymore and your really risking blowing it. And that was the motor, not the tranny. I'm doing 7psi on stock motor and auto tranny on my 01. Motor is perfectly fine, but the trans is starting to have a slight slip when its cold. But its not too bad for a trans with 150k on it thats never been serviced

00element10 · Post by **00element10** » Thu Apr 26, 2007 9:10 am

even if you dont lean out your afr at 10psi, your motor still isnt going to last too long.

esteinmaier · Post by **esteinmaier** » Thu Apr 26, 2007 9:38 am

Hmm... Mine's seen 13psi and about 15k miles since turbo.

Craz1000 · Post by **Craz1000** » Thu Apr 26, 2007 11:15 am

well i just finished pulling the pistons off my '03 motor and the setup looks alot different from turbodudey's 02 rods/pistons so the rumer that they changed the rods also is true, maybe these rods are a little stronger

weber · Post by **weber** » Thu Apr 26, 2007 3:17 pm

Kevin_GP wrote:hmmm

Rods are the weak link, tranny and axles are good past 250, clutch will die shortly after a little bit of power past stock. People replace the pistons to because they are forged, have different ring seals (further away from the top of the piston), and most importantly they lower compression. PSI means nothing, ive been up to 8 psi on my 9.8:1 block and theres no holes in it. Compression is arguable, yes lower compression helps with a larger tuning window but thats not always the case. Working with 9.8:1 isnt that big of a deal, you just cant beat on it and need to know what you are doing.

As long as you prevent the dif pin from shotgun'n out , they are mint for high HP.