What GM should do to improve the 2009 CTS-V before final release

[atdeneve]

Originally Posted by CVP33

So somebody break it down for me. As an "old timer" I'm use to forged crank, rods, pistons being the strongest period. So what was the reason GM chose hypereutectic pistons? I understand that these cast pistons have more silicon, have reduced wear, minimal expansion and allow for the compression ring to move farther up the piston. Thus you can have a lighter, shorter piston reducing reciprocating weight and allowing for a faster rev-ing engine. The downside is detonation, which a cast piston will not tolerate for long.

The forged piston has expansion issues, which could make for a noisy engine when started cold. They are also heavier, more expensive, etc. So it the bottom line cost? Is the issue that a modern V8 with a stock PCM shouldn't be allowing detonation of any kind anyway so forged internals are overkill? I gotta know GM, I gotta know!

Originally Posted by Katshot

Sorry to single you out but this is what I've been talking about. You say "cast" but you're actually describing "hypereutectic".
A hypereutectic piston can be either cast or forged. People are bashing GM and they aren't even sure about the technologies involved. Check out the link I posted earlier in this thread. It's very informative on the subject.

I think he was referring specifically to the hypereutectic pistons in the Gen II V application, which are indeed cast. If you read the sentence preceding his first reference to "these cast pistons", you'll see he's referrring to the hypereutectic pistons.

Originally Posted by CVP33

So what was the reason GM chose hypereutectic pistons? I understand that these cast pistons ...

Regardless, more often than not, a hypereutectic piston is a cast piston, and vice versa, which may be why people might be using the two interchangeably (although, yes, technically they are distinct) - in fact, even the article you linked to indicates that, while "Hypereutectic pistons can be forged, [they are] typically are only cast."

In any case, I think the fact that Gm / Cadillac decided to use cast hypereutectic pistons throws a lot of people off. Why did they decide to go that route? On both counts: hypereutectic and cast. I mean, even you yourself acknowledged that hyper pistons can be forged. Why didn't they go with the forged pistons, or better yet, why not have gone with eutectic (not even hypoeutectic) forged pistons? That would have alleviated any smog concerns, piston slap / NVH issues, piston scuffing, thermal dissipation requirements (so any of those reasons for opting to go with hyper pistons is out). And we would have obtained decreased piston brittleness (by both decreasing excess silicon content and by high pressure forging).

Or take it one step further and use a plasma coating sprayed on the cylinder wall instead of a steel cylinder sleeve (simlar to that in the new Nissan GT-R VR38). Without the iron lining, the aluminum piston and the aluminum block would have a closer rate of expansion, thereby eliminating the need for hypereutectic pistons. You also get the advantages of better heat transfer, larger bore diameter for the same bore center, and decreased mass (all advantages recognized by the VR38). Ah, we could only hope, right?

In the VR38, the plasma coating is 0.15 mm / 0.006 in thick, replacing an iron liner 2.6 mm / 0.10 in thick for a increased diameter of [(2.6 mm - 0.15 mm) x2] = 4.9 mm (actual increase of 4.8 mm / 0.19 in). Any of you that have the specs on the LSA's cylinder sleeve could probably figure out the realized gain in displacement you might see with a plasma coating on the 6.2L.

Ultimately, it all comes down to the cost savings. That's the only way I can see it. I mean, if it's sufficient (for stock levels), fine. But, they know that at least a good portion of those who buy the V are buying it because of, not only the amenities provided for in the luxury class, but also the handling and the engine - an LS engine. Now, an LS engine, they know is gonna end up being modified. You can't tell me they don't know this. With that in mind, why not put in forged eutectic pistons? Money. There's really no mystery here. I think...

But, hey, maybe it was just a typo. Psh. Yeah right. (I do hope it is, though)

[Katshot]

I think you could drive yourself crazy trying to second-guess the OEM on this.

[FIVEOH!!!]

I think people just need to relax and just wait to drive one. It's amazing the knowledge that exist in this board regarding these motors. But wait to drive the car first and then talk about stuff like this. I can almost guarantee that the minute someone drives the 1st car sold, They will go nuts about it. Then they can start talking about what changes they would make. For now just let it be.

[atdeneve]

Originally Posted by Katshot

I think you could drive yourself crazy trying to second-guess the OEM on this.

I think you're right.

Originally Posted by FIVEOH!!!

I can almost guarantee that the minute someone drives the 1st car sold, They will go nuts about it.

Mos Definitively.

[Katshot]

It just amazes me that this place is so consumed with fears of engine failures. Has Cadillac ever had such problems? Ok, let me rephrase that. When has a non-Cadillac engine in a Cadillac had such problems? Ok, let me rephrase that too. When has a Chevy engine in a Cadillac had such problems?.......Ok, I think THAT one will fly.

[Albertan]

I'd be a bit circumspect of anything in Wikipedia. The sources can be anyone so the information could be correct or could be completely wrong. I'd feel happier if a piston manufacturer was quoted. I did look over the link and it looks like it could be correct but then I'm not an expert on pistons. I did use forged in a 2.4litre Sunfire motor but only because they were easier to get. So I guess my daughter could put a maggie on her car!

[Katshot]

Originally Posted by Albertan

I'd be a bit circumspect of anything in Wikipedia. The sources can be anyone so the information could be correct or could be completely wrong. I'd feel happier if a piston manufacturer was quoted. I did look over the link and it looks like it could be correct but then I'm not an expert on pistons. I did use forged in a 2.4litre Sunfire motor but only because they were easier to get. So I guess my daughter could put a maggie on her car!

I checked a few other sites too but you're right. To that end, I DID contact Wiseco but have not yet heard back from them. If I get a chance, I'll try another. I too, am no expert on pistons but am a retired (but w/30 years experience) professional mechanic with lapse ASE credentials, so I have at least SOME degree of experience with this stuff.

[jasaero]

I think the fact the LSA has cast hyper pistons is MOSTLY a recip weight and NVH reasoning. Seems LSA is all optimized for extra operating efficiency and refinement compared to the LS9. The SC is supposed to be more efficient than the 2.1L unit in the LS9 even. I actually think these will be good for some pretty robust low cost upgrades anyhow. Most are going to work the whole engine anyhow if they are going to do anything REALLY extreme. Unless they plan on taking a big risk anyhow. We'll see I guess.

[MauiV]

Not sure how many of you have actually driven an 08 but I have had the opportunity twice when mine was in for minor fixes (my dealer ALWAYS hooks me up with a new CTS or an Escalade, and I visit for the smallest tick tack things) and I love the look of the instrument cluster but it isnt functional at all. The long tubes force you to actually move your head to look down them at the 2 outer ones. It definatly needs to be opened up some, especially the tach.

[HiTechRV]

+1....

[wrazor1]

I'm still more concerned about weight than I am about pistons. Put the V on a diet! And not a Jenny Craig, lose a couple of pounds diet, I mean a full-on stomach staple. We need the Al Roker surgery on this car.

[Katshot]

Originally Posted by wrazor1

I'm still more concerned about weight than I am about pistons. Put the V on a diet! And not a Jenny Craig, lose a couple of pounds diet, I mean a full-on stomach staple. We need the Al Roker surgery on this car.

+1 for me too.

[ylwjacket]

I'd like them to have a performance driving school, like the M school, included in the purchase, similar to the M cars. You wouldn't be required to go to it, but since you paid for it as part of the car purchase, a lot of people might.

Also, I think that would add a little to the buying experience.

[anonfrank]

Originally Posted by ylwjacket

I'd like them to have a performance driving school, like the M school, included in the purchase, similar to the M cars. You wouldn't be required to go to it, but since you paid for it as part of the car purchase, a lot of people might.

Also, I think that would add a little to the buying experience.

I think that is an excellent idea. When I take possession of the car, it will be the most powerful I've ever owned. It would be nice to know how to drive it properly and SAFELY. I'm not worried about wrapping it around a tree, but I have only owned FWD and my current car is AWD, so learning some of the dynamics of RWD, especially in a car like this, would be very useful.

As far as the comments above about weight...If you read John Heinricy's live chat transcript, for Cadillac it's all about power to weight ratio, and despite the weight, it is better than the competition. I'm not at all worried considering my current car is a touch over 4k pounds.

[Seattle CTS-V]

Originally Posted by v84life

I thought our cars were about 3800lbs Still heavy at 4200 no doubt

3850lbs.