I just got my engine rebuild kit - finally. It came with Sealed Power hyperutectic pistons, and I was wondering if they'll be okay under boost conditions. I had originally ordered the kit when I was going to do an all-motor build but I'm not sure if I can use them now that I'm installing a turbo. I know they're supposed to be better than the stock pistons, but the thing I worry about is I've heard they're a bit less forgiving than even stock pistons in the event of detonation.
If I absolutely have to I'll shell out for a set of forged pistons, but I jsut want to know if these are okay. If it makes a difference, I'm limiting things to 8psi when it's all said and done.
Hypereutectic piston
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Hypereutectic pistons are cast internal combustion engine pistons made from aluminum with over 16% silicon content for strength and durability. The term 'hypereutectic' comes from eutectic. Special melting processes are necessary to ‘supersaturate’ the aluminum with additional silicon content. Special molds, casting and cooling techniques are required to obtain finely and uniformly dispersed silicon particles throughout the material. This produces pistons that are very hard, thus brittle. They have proven to be un-forgiving with engine knocking. For this reason they are great in naturally-aspirated engines, but should be used with caution for 'nitrous', super- or turbochargers. Generally speaking, forged pistons are a better choice for high boost.
Hypereutectic pistons are used in many original equipment engines. They are favored because of reduced scuffing, improved power, fuel economy and emissions. The reduced thermal expansion rate allows the piston to be run with reduced clearance, which reduces losses due to gases escaping past the sealing rings.
Retrieved from "http://en.wikipedia.org/wiki/Hypereutectic_piston"
"The FACTS are always subject to CHANGE once the TRUTH is applied"
"In the entire history of man the only stupid questions are the ones that don't get asked"
Hyperutectic is better than a stock piston but not quite as good as a forged one. Like JE or Arias. I think your only concern would be thermal expansion. If i remember right from school they expand at a different rate than a forged one would. That would play a role in your piston to wall clearance in hi temp turbo application. As far as actual strength of the piston you should be fine at 8 psi. I don't know how much further than that i would push it. Talk to your builder he should be able to give you specs and explain your situation a little better.
- 97 Z24 Racecar work in progress
- 04 WRX STi
ATR Crew Member
I don't have a builder. The only outsourcing I'm doing is to have the block prepped. The actual rebuild will be done by myself and a couple of friends. I've just never used this type piston before so I wanted t osee if anyone has. I did read that wikipedia thing, and it seems the only issue is with detonation being really bad for them. So I guess if the fuel and timing are where they need to be, and there's no detonation going on, then I can't see the harm. What the hey, I could always just put em in and see what happnens...
Nah. I'll see what some others think and go from there. But I have a feeling I'm buying forged and selling these.
If your going boost for sure thats what i would do. If your willing to spend few more bucks then you have nothing to worrie about. Better than taking the chance and spending a lot more on another motor.
- 97 Z24 Racecar work in progress
- 04 WRX STi
ATR Crew Member
Yeah especially on the chance if something happens that gets you lean... i wouldnt want to have to worry about breaking a ring land from slight detonation that could create more damage.. go with forged and be done with it
So where's the cheapest place to get them? I looked on ebay and didn't find any forged ones for the LN2.
www.importperformanceparts.com
horsepower is how hard you hit the wall, Torque is how far you push the wall with you
I like to use carcustoms.net good prices & awesome service
- 97 Z24 Racecar work in progress
- 04 WRX STi
ATR Crew Member
looks like you've already made your decision, but i'll throw in a little for ya'...
i've got hyperutectic pistons in my wagon, which is very-much based on an OE, boosted engine found in a late-80s/early-90s grand prix...which also came with hyperutectic pistons. owners of these grand prix have been known to run up to about 15psi on stock pistons. they just made sure that the fuel mix was nice 'n' rich.
once the wagon's computer is tuned, i won't be headed north of about 12psi. this isn't for any longevity or safety issues, but rather a simple, personal choice.
if you want to drop a few hundred more on forged, by all means do so! folks with boost know how addictive it can be. once you've got it, you soon want more, right?
if you plan to stick with 8psi, you'll be fine with what's already in your hands. if you bump up to 15 or 20psi, you'll be missing those forged units pretty damn quickly!
what are your goals with this engine? what's your budget like?
...and as Atomic mentioned, Karo is very good to work with and has great pricing! i've bought parts for three cars from him over the years. he's got my vote!
Have you seen the turbo wagon?
13.90 @ 105.46mph
street tires
rough tune
jux wrote:
what are your goals with this engine? what's your budget like?
My budget is pretty scarce. I really don't even ahve a budget, I'm jsut making due with what I can afford, which is why I'm using a lot of used and fabricated part. I've pillaged what's left of one of our VR4 parts cars for everything I can use, which was basically the turbo, downpipe, intercooler, BOV, and some vacuum lines. I'm also modifying a header I have for my motor and making brackets to support the turbo so it doesn't rip the header to pieces. I went to the junkyard and picked up a lower intake off another '97, and a fuel rail and injector parts off a 2200. And then I got some LT1 injectors that a friend of mine had from one of his projects. All of that will eventually be my topfeed conversion, along with a TB spacer I cut from a 1/2" thick piece of plastic. There's other stuff like the Cartech FMU and what not but you get the idea.
As far as the goals, I'm not looking to make a track monster. This is more of a fun project until I find another VR4. There's one here locally I've been trying to buy but the guy keeps going back and forth on the price so I doubt anthing happens there.
What engine are the pistons for and what compression ratio did you buy them at? I might be able to find a buyer for you if you want to go forged for the turbo and sell the hyperuretic ones. I know a couple people working on a couple cavvys here and they want pistons at about 11.5-13:1 compression.
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'96 Cavalier Good ol' Pushrod 2.2
-24X,000 miles on factory build
-Some oil loss between changes, me thinks it be rings.
These are nowhere near 11.5:1. These were part of a rebuild kit and the compression ratio is 8.5:1. For that high of a compression ratio, I'd seriously recommend against hypereutectic pistons. You run a greater risk of running lean and blowin sh#t up with that kind of setup than I ever would on 6psi of boost.
ln2johnny wrote:VR4 parts cars
that thing still have a full, straight body? I have a drivetrain
fortune cookie say:
better a delay than a disaster.
i didn't even notice the galant vr4 bit in your siggy. those things are damn cool! only seen one in person, and it was, frankly, not well maintained...but the idea behind these cars is so impressive...and a bit on the outlandish side. something about that combination just deserves attention. time to get yourself back into one!
...and dodge thought they had a sleeper with the spirit r/t...hehehe! the galant totally outdoes the spirit.
Have you seen the turbo wagon?
13.90 @ 105.46mph
street tires
rough tune
Hey, Johnny.
Anyone used Hyper pistons with boost? Yeah, me. And everyone else boosting a 94 or newer LN2. GM switched to Hypereutectic alloy in 94. Do they work? Well, ok. I'm with Jux on this. Keep the tune ok, and they'll work ok. Keep the boost mild and they'll be happy. Even the replacement speed pro 2.0L Pontiac pistons are hypers.
I know your pain when it comes to budget not equalling cost. I have not yet found a reasonable source for forged pistons, other than Adler's used parts (if he's still got them).
I've got my Speed Pro book here. If you could get some L2492F pistons for a 2.8L engine without the wrist pin holes machined, then you might be able to find a machinist willing to put the pin at the correct height and to machine off unnecessary portions of the skirt. Of course you'd have to look at ring position and thickness and pin boss areas, too, before planning this.
The problem isn't finding 89mm pistons. The problem is that no other OEM uses such a short piston pin height as GM, at least as far as I can tell.
-->Slow
slowolej wrote:other than Adler's used parts (if he's still got them).
Nope, I have them now
no idea what I'm going to do with them however, and they're 2200 pistons, so compression with a 2.2L head is through the roof.
My custom-made Ross pistons were something like $700 with pins, rings, locks, etc...ouch
fortune cookie say:
better a delay than a disaster.
OHV notec wrote:ln2johnny wrote:VR4 parts cars
that thing still have a full, straight body? I have a drivetrain
Unfortunately, no. It's pretty much down to the shell. Got a good trunk lid and rear doors, though.
jux wrote:i didn't even notice the galant vr4 bit in your siggy. those things are damn cool! only seen one in person, and it was, frankly, not well maintained...but the idea behind these cars is so impressive...and a bit on the outlandish side. something about that combination just deserves attention. time to get yourself back into one! ...and dodge thought they had a sleeper with the spirit r/t...hehehe! the galant totally outdoes the spirit.
Yeah I’m working on getting one. Or should I say another one. I miss my old VR4 to be honest. I hated it at times, you have to really love working on cars to actually own one and drive it every day lol. They can be a pain to own, I’ll admit, but they’re fun to drive and they take to power mods like nothing I’ve ever seen. There’s one here locally that needs a whole new driveline but the guy keeps going back and forth on the price so I doubt I ever buy it.
It’s too bad you’ve only seen one up close. We’ve got five of them right here in Des Moines, and one of them is a JDM model. Six if you count my buddy that moved from here to Las Vegas lol. I don’t count the parts car cuz it doesn’t even look like a GVR4 anymore.
And it’s a shame when people don’t maintain them at all or don’t know how to do it properly. They’re just like the DSMs in that they need constant maintenance to keep them in proper running order, and I’ve seen so many put up for sale because the owner just didn’t understand the car.
slowolej wrote:Hey, Johnny.
Anyone used Hyper pistons with boost? Yeah, me. And everyone else boosting a 94 or newer LN2. GM switched to Hypereutectic alloy in 94. Do they work? Well, ok. I'm with Jux on this. Keep the tune ok, and they'll work ok. Keep the boost mild and they'll be happy. Even the replacement speed pro 2.0L Pontiac pistons are hypers.
I know your pain when it comes to budget not equalling cost. I have not yet found a reasonable source for forged pistons, other than Adler's used parts (if he's still got them).
I've got my Speed Pro book here. If you could get some L2492F pistons for a 2.8L engine without the wrist pin holes machined, then you might be able to find a machinist willing to put the pin at the correct height and to machine off unnecessary portions of the skirt. Of course you'd have to look at ring position and thickness and pin boss areas, too, before planning this.
The problem isn't finding 89mm pistons. The problem is that no other OEM uses such a short piston pin height as GM, at least as far as I can tell.
-->Slow
I had no idea that the LN2s were switched to hypers. I knew GM had made the change in a lot of other cars but I thought the LN2 still had standard cast pistons. But I guess that answers it, I mean there are quite a few running stock bottom ends.
Notec, you're way too busy sucking up all the good parts these days.
How thick is the piston crown? Can ya machine it flat?
If I'm going to spend $$ on custom pistons, I'm likely to specify a "D" shaped dish. I mean, if I'm spending $$, why not get the piston I want? Keeps quench distance small and keeps compression low at the same time.
But right now, I'm not planning to spend money on pistons.
-->Slow
Well, at $400, I couldn't pass the set up, seeing as the rods cost almost that much by themselves
Here's some comparison shots:
It's very obvious that the 2200 design will be vastly superior to the 2.2L, just look at how much more meat there is above the rings...that should really help prevent this from happening again:
And here's what my high boost motor will be running:
These are 2200 pistons, but with an extra 1/8" of protection above the rings. If the same thing happens with these, well, I will have to concede victory
Oh yeah, I finally got some more precise equipment, so I'll hopefully be cc'ing both 2.2L and 2200 chambers and dishes around noon. Now, back to my neighbor's heater core replacement...
fortune cookie say:
better a delay than a disaster.
Is that piston in the last picture protruding above the deck?? Please tell me it's not attached to a rod.
Did you determine what caused that ring land to break? Binding rings? Detonation? I don't feel those pistons are as fragile as some people would have you believe.
-->Slow
slowolej wrote:Is that piston in the last picture protruding above the deck?? Please tell me it's not attached to a rod.
Did you determine what caused that ring land to break? Binding rings? Detonation? I don't feel those pistons are as fragile as some people would have you believe.
-->Slow
Haha, yes, that is attached to a rod, the block is assembled. The piston's position came as a shock to me, too. Protrudes almost .040".
The piston definitely went from detonation. I was only using an FMU on 9psi, and the FMU broke, leaning it WAAAYYY out.
My measuring setup isn't working as well as hoped, but it's closer than last time. So far I have the 2200 chamber as 52cc, and the 2200 piston dish as 5cc. I'll see if I can get the 2.2L stuff tonight as well.
fortune cookie say:
better a delay than a disaster.
Okay, so you're putting 2200 pistons in a 2.2 block? Am I reading this right?
