Piston Weight Comparison

[racin17]

Got my new Ross pistons in today. Wow, I think I bought from the right company! Here is my weight comparison:

stock HO 559 grams
JE 532 grams
Ross 441 grams

(all weights are piston, pin, retaining rings, and piston rings)

WOW... so with Ross pistons and Eagle rods, I'm shaving over 200 grams off of each piston/rod combo. WOW. That'll require a lot of mass out of the crank to balance it. Reciprocating and rotating weight reduction is a good thing!

Pictures are attached.

Rod weight thread for reference: Quad4 Rods weights - A Community for the GM Quad 4 and Twin Cam Engines (http://www.quad4forums.com/forums/showthread.php?t=5846)

Jeff

[90BerettaGTZ]

ill be the first to add to this.

i too have Ross pistons with Eagle rods. going by your math, thats 1047g for the Ross/Eagle combo and 1296g for an oem setup per cylinder. converting to pounds, thats 2.3lbs each for the lightweight setup and 2.86lbs for oem. roughly 2lbs saving for all 4 cylinders.

add in a lightweight flywheel, which is 8.4lbs vs 15.2lbs stock. i do not know the weight of the Spec stage 3 clutch, but im guessing its slightly lighter by design [ 6 puck ] vs a full disc clutch.

total weight savings is roughly 8.8lbs over stock using Ross pistons, Eagle rods, and a lightweight flywheel from fidanza.

i dont know your piston specs, but mine are 11:1 flat tops. i would assume piston wights to be nearly equal with similar compressions ~1 point or so.

[racin17]

Well, mine are flat tops also (with 4 reliefs, remember -- same as yours I assume). Pat from Ross quoted close to 10:1, but I don't believe that number too strongly. I'd previously calculated about 10.6 or 10.7:1 with flat-top pistons (assuming 2 reliefs at the time). I'll do some calculating eventually for this particular engine (with measured head CC volume), to know what my CR is.

I assume my pistons are identical to yours (oh, mine are 0.020" over -- probably the size I'd bet money on that you have :) ).

90Beretta, did you get your rotating assembly balanced, also? (I'd HOPE so with pistons and rods that much lighter than stock! (although I'm no expert on how bad of a sin not doing that would be)) I expect that will take a few pounds out of the crank also.

Ok, pictures added above.
Jeff

[CuriousMind]

Wow, even rotating weight is easily underrated, and reciprocating weight has even more of an impact. Two pounds holy shit!

[CuriousMind]

Hey, and if anybody could get the weight from some similar Wiseco pistons
(including the pin, and rings) that'd be pretty cool too.

[90BerettaGTZ]

yes Racin, the entire engine was balanced of course. :)

this is what 11:1 pistons look like [ 4 valve reliefs ]:

[nukkinfuttz]

i just had mime balanced as well with the ross pistons and eagle rods. the balancer said the stock set up was already 23 grams out of balance from the factory. with the new equipment, he was able to balance with in a half gram!

[CuriousMind]

That's impressive. Gotta love attention to detail and the kind of quality control that simpley doesn't happen on an assembly line.

[BlindManDesigns]

I am eager to know how much more hp is gained bythe lighter rotating mass, Wouldn't the peak hp peak higher with a properly rotated mass since it wont be fighting against excessive vibration due to the unbalanced stock setup?

I hope to have a quad built up someday but mine done seem to want to die even with over 150,xxx on the bottom end on the 91 :)

[nukkinfuttz]

wow, you better knock on wood dude.

[nukkinfuttz]

That's impressive. Gotta love attention to detail and the kind of quality control that simpley doesn't happen on an assembly line.

yeah, well rather than correct the problem, you see GM would rather engineer a balance shaft assembly to counteract it and draw even more HP away from the wheels. i guess someone needs to justify their continued employment.

[CuriousMind]

I am eager to know how much more hp is gained bythe lighter rotating mass, Wouldn't the peak hp peak higher with a properly rotated mass since it wont be fighting against excessive vibration due to the unbalanced stock setup?

It's not too difficult to calculate. You figure how much weight is removed, and how far the weight has to move. The pistons are purely reciprocating, whereas the rods are mostly reciprocating, but with some angular accelleration involved as well. You can average the rods out to an appropriate level of simply reciprocationg motion, and still remain fairly accurate. Then you can calculate how much horsepower it takes to accellerate those parts back and forth. Compare that to your stock numbers and you can figure out net HP gain at given RPMs. I know that's pretty vague, but it's really not that hard.

It doesn't shift your power curve, just raises it. So your peak HP may occur at a higher RPM, but that's only because your HP kept climbing where it had previously started falling. The amount you gain will increase as your revs increase, since however much weight you removed was previously reducing horsepower as the RPMs raised.

You would obviously be removing weight from your crank as well, the concept remaining fairly similar. It seems to me that the amount removed from the crank should be identical to how much you've reduced the weight of the pistons and rods. Not necessarily in physical weight, but in angular momentum and such. That's just me hypothesizing though.

And of course this is still comparing a stock weighted balanced setup to a light weight balanced setup. Balancing will obviously help a lot, but I think it mostly affects the longetivity of parts, and your subsequent ability to rev higher. There is going to be power lost due to friction and distortion of parts, especially at higher RPMs, but it's easiest just to say "it will make your engine happier" than to try and predict any kind of actual numbers.