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roguetrip · **cryo treatment on pistons**

Ok, so i was wondering why no one cryo's pistons, would this be a cheaper way to go with low to moderate boost (equal or less than 12lbs). Most people here seem to go forged, but i think if cryo might be another (cheaper) route. Thoughts?

**mopar2ya** · 09-21-2006, 08:09 PM

We'd be glad to cryo them for you.

Ondonti · 09-21-2006, 09:18 PM

well no matter how much you cryo them, its still going to be a 3.0 mitsu piston, with an incredible amount of silicone in it.

**c2xejk** · 09-21-2006, 09:22 PM

based on what I have read in the past, ring gaps (or lack of ) are a bigger issue...

Ondonti · 09-21-2006, 09:48 PM

Im pretty sure the small ring gap helps coax the ring land to remove itself from the piston near the intake valve relief when the ring butts.

**mopar2ya** · 09-21-2006, 10:16 PM

But you can take a cheap piston and make it more durable, even with the high silicone. Its not as good as a forged piston, then again its alot less $$.

Boost_virgin · 09-21-2006, 10:37 PM

If you make the piston harder will it make it more likely to shatter or crack? I'm not sure about pistions, but if you over harden tool steel in a die it will shatter under too much pressure.

roguetrip · 09-21-2006, 10:57 PM

Quote:

Originally Posted by c2xejk

based on what I have read in the past, ring gaps (or lack of ) are a bigger issue...

I was wondering that you could probably have a larger gap machined in before cryo was to be done, i've seen bad ringland cracks as well from boosted motors.

My figuring is it would make it a better piston if under low/moderate boost, if Harvii can run 15psi on stock internals then to cryo the pistons might just give a better peace of mind.

I'd admit that my plans are far in the future and just gathering information, but my 3.0 won't be a strip demon, just a good reliable daily driver (more than i can say for my stealth), my figuring on maybe 220-250hp which should be enough to put down mid to low 14's on a G-body.

DustyR/T · 09-22-2006, 06:28 AM

hope you have enough fuel to feed that boost on these motors especially. If you're stock pistons, cryo or not, it probably won't take much predetonation to bust one or two. I myself went w/ forged for peace of mind. I don't want to have to worry period when It's all assembled. And BTW, everything in the shortblock will be cryo'd minus the rods.

**mopar2ya** · 09-22-2006, 09:23 AM

I dont think the best word it "harder" but more durable. It stress relieves parts and realigns the molecules to increase wear resistance and becomes stronger due to the molecules being aligned. I convinced Stephane to try it on some of his "normal wear" components, it reduced the wear dramatically and now heres cryos about everything.

**c2xejk** · 09-22-2006, 12:19 PM

Quote:

Originally Posted by roguetrip

I was wondering that you could probably have a larger gap machined in before cryo was to be done, i've seen bad ringland cracks as well from boosted motors.

My figuring is it would make it a better piston if under low/moderate boost, if Harvii can run 15psi on stock internals then to cryo the pistons might just give a better peace of mind.

I'd admit that my plans are far in the future and just gathering information, but my 3.0 won't be a strip demon, just a good reliable daily driver (more than i can say for my stealth), my figuring on maybe 220-250hp which should be enough to put down mid to low 14's on a G-body.

Ring gaps are set on the rings themselves. As the engine heats up, the rings expand. If there is insufficient gap, they go somewhere... ie break a piston ring land...

So EGT's are probably a bigger factor than hp...

Forged pistons are more resistent to detonation damage, but not immune to it... They are also not immune to ring gaps being too small...

Setting the ring gaps is a standard part of a rebuild. Mike can pipe in with what he set the gaps at in the engine he is building. I think he set that gap ~2x stock...

I think a completely stock engine can be boosted to low-14's easily... Stein was only traction limited from reaching low-14's (most of the cars at the track that day running 98MPH 1/4 were in the low-14's...) Brent hit high-13's on a relatively stock turbo'd engine, I believe...

Harvii · 09-22-2006, 01:55 PM

I had to gap my rings to almost 2X recommended when I rebuilt my motor. The machine shop I used to cut the block was real helpful and has built countless high HP big boost motors, so their word was good enough for me. The rings butting up is what killed my OE 120K motor(it probably would have ran forever if I hadn't added boost(to the tune of 15psi), but the extra heat caused the rings to kill the ringlands and smoke poured from the tail pipe.

roguetrip · 09-22-2006, 02:32 PM

cool info harvii, anyway you can get the actual spec on the gap they used on your rings?

So it looks like proper gapping + cryo would be the most benificial if going low boost. When looking at 800+ for forged pistons for such low power goals doesn't go very well with me.

Mopar2ya: how much is it to cryo 6 pistons btw? Thanks

Ondonti · 09-22-2006, 04:16 PM

Yeah, as long as you have proper ring gap I think 10-15 psi is not out of the question on pump gas depending on your setup.
Just dont get boost greedy and turn your brain off (SOOO EASY TO DO).

When i look at what happened to my engine, I really dont know if I had detonation. My plugs never showed any detonation, and the ONE piston that never broke a ringland looked pristine.

I ran 13.9@101.89 on 5 psi boost, but the engine was up around 10 psi when I broke ringlands. The last 2 ringlands I broke were at high elevation running 10-11 psi (9 psi on my absolute gauge). The car ran great in lower gears for short runs on the higher boost, but if I tried a 4th gear pull on the freeway, I think the rings got to hot and overexpanded, busting off the weak intake valve ringland. Engine was already junk so i wasnt worried. I did have the stock fuel pump fail to maintain fuel pressure at higher boost which IMO just meant runing leaner and hotter. I know what knock sounds like on the motor in the lower rpms, and I never had a single sound from the engine like that. Just a bump when a ringland would let go.

If that didnt make sense sorry, I just wrote and essay so Im not feeling too eloquent.

roguetrip · 09-22-2006, 04:51 PM

Quote:

Originally Posted by Ondonti

Yeah, as long as you have proper ring gap I think 10-15 psi is not out of the question on pump gas depending on your setup.
Just dont get boost greedy and turn your brain off (SOOO EASY TO DO).

When i look at what happened to my engine, I really dont know if I had detonation. My plugs never showed any detonation, and the ONE piston that never broke a ringland looked pristine.

I ran 13.9@101.89 on 5 psi boost, but the engine was up around 10 psi when I broke ringlands. The last 2 ringlands I broke were at high elevation running 10-11 psi (9 psi on my absolute gauge). The car ran great in lower gears for short runs on the higher boost, but if I tried a 4th gear pull on the freeway, I think the rings got to hot and overexpanded, busting off the weak intake valve ringland. Engine was already junk so i wasnt worried. I did have the stock fuel pump fail to maintain fuel pressure at higher boost which IMO just meant runing leaner and hotter. I know what knock sounds like on the motor in the lower rpms, and I never had a single sound from the engine like that. Just a bump when a ringland would let go.

If that didnt make sense sorry, I just wrote and essay so Im not feeling too eloquent.

Yeah, i'm not going to be boost crazy, but 13.9 @ 5psi sounds good, was that intercooled turbo? I also don't know what other mods you had done at the time.

My mods before boost seem like the most BPU's, flywheel, udp, 52mm tb, and 2.5" exhuast, maybe port and polished heads.