my views of pistons

hyper pistions are like the super model with std you know you want to put it in her but your affraid of the consequences.

forged pistions- the only reason why i like them is the tend to hold together better un like hyper that tend blast your engine with metal particals when they go.
hyper is not all that bad but I rather pay the few extra dollars, have a little extra weight (couple grams big whoop) and know i have a quailty part. Also when things go bad it keeps engine damage to a minium. But if you really want to hyper will work, but forged is good insurance.

overall I would not put any thing in my engine that im not 100% confidence Im I have a doubt or have a question of liabilty like your asking that part is not coming close to my engine bay.
If in doubt throw that **** out.

 

My personal and mostly unscientific rule of thumb is that anything above 1hp per cubic inch gets forged pistons.

 

Production LS6 (Z06/CTS-V) makes do with cast hypers @ 1.16-1.17 hp/cube. You ARE a conservative fellow.

 

SSTroker, what would you say is a practical upper limit for hypers? I have a 355 with hypers that would see nearly 575hp and 6,500rpm with a little bit of nitrous. I also have stock crank and rods, though it's balanced and with arp bolts. I'm afraid to spray the thing because I have a buyer for it as long as it's running

 

I'm not a fan of using nitrous with hyper-pistons, although plenty of people do. I'd probably get into the high 400's (flywheel) without spray on hypers with my own engine. I'm conservative (but maybe not as conservative as LRN), so if I thought I'd get over 500, I'd probably go forged.

I really like your idea of not spraying with a buyer in your back pocket.

 

I've turned the KB hypers to 7300 rpm with a dual stage (200hp) nitrous system on an older bracket car. Kb hypers, Scat I-beams, C&A taper wristpins, plasma moly rings.....
Goes without saying that the a/f mixture needs to be fat, but I never had any problems out of this motor until a broken lifter took it out.

Yeah, I'd try to keep it together if you're planning to sell and play with something else if you want to push things.

-Mindgame

 

Guilty as charged.

 

Anyone know the difference between JE and SRP forged pistons. Say you were to buy the same exact piston from both, say a nitrous/blower piston, 16cc dish, yada yada yada....they are made by the same company, both forged aluminum pistons. What makes the JE ~$200 or whatever it is more expensive?

 

Actually, the 2.4 turbo from DCX and the LS6 from GM both use a Mahle 142 alloy, which is eutectic. The 2.4 turbo has piston cooling jets though, which makes a huge difference to piston life. The 142 alloy pistons in these applications are cast, but the silicon content is lower than hypereutectic pistons. This makes the pistons more forgiving and less brittle. I'm doing a NA engine right now using Mahle's 124 alloy with piston cooling jets. The jets can easily reduce the piston crown temp by 20-30 deg. C.

Mahle has 2 alloys they generally use in the US - 124 and 142. They both are eutectic alloys, but the 142 has a higher copper content to help it's fatigue resistance in the higher temperature ranges, above 200 deg. C or so. The extra copper makes the piston heavier though. Since we are really going after mass on the engine we stayed with 124 and added cooling jets. Karl Schmidt has similar alloys to Mahle, and also does not use hypereutectic pistons. Ford uses a lot of KS pistons. Federal-Mogul has 413 and 425 alloys. 413 is just about dead in their line. Last I heard the GM 3.8L engine was the last one to use it. 413 is a eutectic alloy. 425 is used in all other US sourced pistons by Federal-Mogul. It's a hypereutectic alloy. Hypereutectic alloys got their start in the US to help eliminate top ring groove wear and microwelding. It's a whole lot cheaper than anodizing if your application has borderline microwelding or ring groove wear issues. The wear ratings I've seen from a hypereutectic piston vs. a eutectic seem to indicate a 10% reduction in wear with hypereutectic, which can make a difference over a long durability test if you have marginal top ring groove life.

I can tell you the new 500 HP 7 liter LS7 will be using 142 Mahle pistons, cast, unless things change before launch. I can also tell you a very high output supercharged Northstar engine should be coming to market soon with a 425 alloy F-M piston. You can use any good alloy for a piston design. You just have to make sure you design for the intended application. The problem with many aftermarket designs in this respect is they were almost certainly not designed for your specific application. As such, I'd tend to buy components that seem to be way overdesigned for my application, just in case.

 

Thanks for the correction.

Aren't most high(er) performance aftermarket pistons for US V8's either cast hypereutectic or forged? Mahle's Power Pak are forged 4032 or forged M138. Even if Mahle offered 124 cast as an economical high perf piston, the market would probably go for the forged 4032.

An NA engine with oil cooled pistons? Sounds "trucky" to me. Will it be constant cooling or load sensitive? If I recall, Lycoming aircraft engines only sprayed oil during boost conditions. That may not be true, however. I forget easily.

 

I don't know for sure about aftermarket pistons. There are so many different alloys it's hard to keep up. Since I haven't started building my engine yet I haven't really tried to do the research. That's one of the reasons I'm reading this board.

The Hemi engine has very hot pistons and quite high EGTs from the factory. Since our engine is higher output than the current Hemi we were concerned, so we added piston cooling jets from the beginning. It's lucky we did. We did a test plugging the squirters running 300 deg. F oil recently and promptly destroyed a piston. We didn't have the knock sensors active so hot spots did us in.

The squirters are pressure activated. IIRC, they come on at 25 psi. That may be raised soon depending on oil consumption testing results.

You guys have some interesting threads on this board. I'm home sick today and can't seem to sleep so I'm spending some time perusing the board.