PacerX

<---- The point.



<--- Whale dung (which sinks...).



<---- Your head.

jg95z28

I disagree about the LS7 being more economical. Cost-wise its a wash, until you include the LS7's dry sump oil system. Furthermore, being a bigger engine that's fairly close to the limits of the bore-size the LS block can handle, there's a bigger potential for parts breakage. No doubt, I'd rather see a detuned LS9 than the LSA because of the forged internals, however the LS7 would need more internal mods to increase performance, whereas the LSA and LS9 would merely need a pulley swap. (See below.)
That's the primary reason I like the idea of a factory supercharged engine. The ability to do a simply pulley swap to improve performance. Performance minded buyers are going to be doing that simple and inexpensive mod as soon as its available. More reason to push for a detuned LS9 with forged internals over the standard LSA. (While I suspect some Cadillac CTS-V buyers will also tweak their cars, the overwhelming majority won't.) Heck if we don't want the Corvette guys to get upset about the Z/28 getting a detuned LS9, call it something else. My vote is for LSZ.

95redLT1

+1

Bob Cosby

LOL. I'll be chuckling for hours over this one....

rlchv70

What if all the hype over forged pistons is just that - hype? What if GM's cast piston is strong enough to take lots of abuse?'

The material properties of forged aluminum is greater than cast. However, it is possible to design a cast aluminum piston with extra material in the right places to make up for that deficiency.

Z284ever

The cast pistons are just fine at the power level GM will deliver it in. But they're fairly maxed out for reliability at anything higher. I've heard the same about the steel rods as well (vs expensive titanium in the LS9).

PacerX

Then the cast piston is too heavy.

GM wouldn't keep throwing material at the casting until they solved any issues. Well... if they are sane they won't...


Only partially. The distance between the the piston pin and the top surface of the piston is pretty well fixed unless you want to deal with other changes... like different con rods... or a different cylinder head...

The tops of pistons are carefully designed for both good power and emissions, particularly in the quench area. One cannot go *****-nilly making changes there without significant effect.

GM will have optimized that piston structurally, meaning that the right amount of material is in the right places. Merely throwing material at it would add mass that gives a proportionately lower return relative to strength.

Furthermore, that's a terrible business case where life cycle costs and other costs to the vehicle are concerned...

Heavier pistons mean lower fuel efficiency. From a life cycle perspective, the bazillionth of a gram of extra fuel used on every revolution of the crank (merely to swing the larger mass) adds up over time.

Other costs would be associated with the more expensive rods needed to keep those heavier pistons under control (all other things being equal).

Lastly, a heavier piston (AND con rod) would negatively influence power at every point on the curve. Obviously, that influence is greater at the top end.




That fastest, bestest, smartest thing for GM to do?

LS series cranks are pretty darned spiffy as is. Go with a forged piston and a strong set of con rods and leave more "breathing space" for the enthusiast. Like FORD did...

...and DO NOT repeat the "explode-o-rama" 10-bolt or the 1st Gen CTS-V "wheelhop your rear end into shrapnel" mistakes by going cheap on a flagship performance motor.





***Someday, I am gonna invent the automatic "Shut the F*CK UP" stick for engineers. If, during a meeting, a beancounter suggests that money needs to be saved by replacing... say...forged pistons with cast ones on a flagship performance motor... Well, then the "Shut the F*CK UP" stick would magically appear like a lightsaber in the hands of the nearest sane engineer, would then have a legal blank check to beat said beancounter's head right through the table Al Capone-style.***


***Oh yeah... and if the engineer happens to be the one who says something like: "We can't figure out how to make the pistons less noisy" -or- "We can't put a better rear end in this car because we can't find the mass anywhere to offset it"... Well then the automatic "Shut the F*CK UP" stick would magically appear and force him to beat HIS OWN head into the table, Al Capone-style.***

2010_5thgen

this thread is going right down with that whale dung.

2010_5thgen

are you planning on actually buying this mythical "z28" if they put forged in? are you planning on if they dont?

WhiteHawk

I think all of you guys are blowing this out of proportion. People are making in the 600's to the wheels with the blower and turbo kits for these cars already - and they are all stock compression without the high silicon pistons that come in GM's factory boosted LSx's. Are you saying that every one of these aftermarket kits is unreliable?

I don't think you are ever going to make a car idiot proof, but if the boosted motors are as capable as the NA motors, I don't see what the weakness is.

-Geoff

2010_5thgen

PacerX

Why in hades does that matter???? Everybody at GM isn't going to buy one either, does that mean that they should all agree to make boneheaded mistakes in the reliability department because of it?

"Well hell, I'm not buying one... let's go with 4-lug wheels."


I never bought a GMT-800, but does that mean I should have gone cheap on the seat frames I engineered for it???

"Awwww heck... Let's NOT use that super-spiffy and expensive ultra high strength steel and use some crappy HSLA instead... sure the frame will separate and send the driver rocketing through the windshield if he hits a brick wall at 40 mph... but everything is fine if he hits the brick wall at the Federally mandated 35!"



PS - My next car will probably be an old barge of a Cadillac. Late 60's/early 70's Coupe Deville... See... the cheapest way to go stupid fast is with a motorcycle, not a car, and I just love those old gigantic Cadillacs.

That being said, it'll probably be LS-series powered, and I sure as heck don't want to have to replace the pistons.

I still love cars, and still buy only Chevrolets for my DD's, but just can't justify spending $50,000 for an 11 second quarter mile when I can get a 9 for $13,000 and a super-nice classic Cadillac for the $37,000 I have left over.



---

JakeRobb

What is it that makes forged pistons more expensive than cast? Is it something that could be offset by economies of scale? It'd be awesome if GM (and everyone else, for that matter) stopped using cast pistons in any engine, ever. Reduced rotating mass is good for everyone, whether they know it or not. Most people would never know the difference, but the minuscule improvements in economy and longevity would be nice, and the enthusiast community would be forever grateful.

Prorac1

The sad fact is, is that hes probably right. Those of us who are REAL automotive enthusiasts wont buy the car. The same strokes who are into flash and "generally" by the z06, zr1, new z28, etc, will be the ones to buy it so they can brag to their buddies at the country club what their car "could" do if they had a "clue" as to how to drive it. Not trying to be a jerk, just stating my opinion. It kinda breaks my heart. But ill just stick with my standard model muscle/race cars, and take heart in the fact that I built it, I engineered it, and I designed it to be EXACTALLY what I want. Most buyers of the new Z28 (if theyre is one at all) probably couldnt do that, thats why they build cars like that. Jmho. Eric L

Z28Wilson

Oy vey.

I never thought such a simple point could be missed so many different ways and so many times in the course of a thread.



Ok, deep breath. Here's a simple little exercise for you.

What is the car more gearheads and serious drag racers are going to plunk their hard-earned $45,000+ on.

• Mustang GT500 with a motor capable of 800+ HP with no internal modifications.
• Camaro Z28 with a motor containing internals almost guaranteed to explode when approaching anywhere near said power levels.

Are you prepared to sit there in your right mind and tell me that Z28 will be the choice? Unless you're a Chevrolet cheerleader who won't accept anything other than the bowtie-cladded car, it's a no-brainer.