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Old 01-07-2011, 10:29 PM   #101
1st Civ. Div.
Drives: 2013 ZL1 Black, aka "Big SexZ"
Join Date: Dec 2007
Location: Savannah, Ga
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Originally Posted by radz28 View Post
Between 580-600 horse, IMO.

I don't really believe GM is going with power between SS and CTS-V. I see many photos with the GT500 in prototype testing, therefore I'm thinking that is the target. Having said that, in order to be competitive now, I believe Z28 has to at least match the GT500 where it currently is. However, I believe the GT500 is going to get a bump by 2012, so I think GM will try to look ahead, bump it closer to ZR1, so it's not going to see a huge spread, if any, should it be a significant increase from the serpent. It has to make up for the weight, which I believe will fall in between SS coupe and convert', so I'm a little torn on how to propose it will get there.

Since I've read CTS-V's exhaust is quite conservative, and it being a luxury car, I believe their are restrictions that can be relaxed for Z28, resulting in a small bump from LSA level. It appears the intake and exhaust systems might be a little less restrictive when the V6 goes from CTS to CAMARO, so that's another little bit of support to me. In addition, the quad tips suggest dual-mode exhaust, like those featured on the Y-Bodies; another opportunity for a bit more power. It certainly sounded better in those videos at the 'Ring!

A new upper intake plenum suggests to me there's a little more development between LSA and LS9. Because the upper plenum doesn't appear to be as flat as LS9, maybe there is a little less restriction, so perhap we could see a 2300 running 1900 psi levels (10.5 to 9.0, respectively) and make the power I'm suggesting.

It'd be nice to see an upgrade to the short block, for the pistongs and rods. I don't think Ti rods are necessary, but it'd be nice to see the forged slugs from LS9 carry over, and maybe some forged H-beam rods from the GMPP catalog. I'd like to see LS9's cam come over, too, since it doesn't have to be conservative, like one would expect in a luxury vehicle, like CTS-V. It'd be nice to be able to grow, safely, to 600-650 RWHP, like the GT500 can (and more...), but I can't complain, too much, knowing that if GM releases a 600 horse' Z28, it can't be pushed to 700 horse' with a little pulley, CAI, and exhaust upgrading/tuning.

I'm just crossing my fingers the chassis tuning will match the power in terms of performance. I'm sure we're going to be adding weight, so I hope GM can find a way to control it
I too believe that the Z/28's engine will be a hybrid of sorts between LSA and the LS9 as we know them currently. Remember that GM said the LSA was engineered for refinement for Cadillac and not for all out power and yes GM did have other supercharged engines in development prior to bankruptcy. The plenum cover on the prototype Z/28's engine is not like any we've yet to see by GM to date even though it say's LSA on the plastic cover, I think it could be for our amusement only and to downplay what's coming. This intercooler design is not like any so far from GM and it looks to have a much larger and pronounced intercooler compared to the CTS-V's. Note that the coolant lines on the prototype's intercooler is located on the front of the engine also.

GM also said at the introduction of the LSA and the LS9 engines was that the first big main difference from the two engines was the supercharger's size, 1.9L for LSA and 2.3L for the LS9.

The second big difference was that the LSA had a more efficient single brick intercooler compared to the LS9's dual brick intercooler on lowering the forced air temp. This was done on the LS9 to keep the hood design low which the camaro does not have an issue with since its cowl height is not as low as the corvette's.

The third is of course the forged pistons in the LS9 compared to the hypereutectic pistons in the LSA which was used because they are quieter and are much more tolerant on emissions especially start-up compared to the forged ones of the LS9. The hypereutectics in the LSA are pretty durable and can withstand a lot of punishment while producing high hp levels.

Hypereutectic Aluminum Pistons with Oil-Spray Cooling
Superior piston design sets the tone all of the 6.2L LSA's internal components. The engineering objective? Lighter, stronger and smoother.

The pistons themselves are aluminum-cast from a high-silicon alloy developed for its combination of strength and heat-management properties. Casting reduces noise-generating potential, compared to other high-performance piston materials such as forged aluminum, and is specified when NVH control is a priority. The hypereutectic pistons are also lighter than conventional steel, which translates to less reciprocating mass inside the engine. Less mass means greater efficiency, high-rpm capability and a feeling of immediate response as the engine builds revs. The LS9s pistons are made of forged aluminum. The key difference in material choice here, is the desire for refinement in the Cadillac application.

The combustion surface of the LSA pistons, or the top land, lacks the valve-relief pockets typical on high-performance engines with relatively high-lift valves. Rather, the LSA top lands are sumped, with a saucer-shaped indent that dips gradually from the outer edge of the piston. This design promotes a thorough mixing of air and fuel, and along with other durability enhancing features, allows a 9.1:1 compression ratio: higher than a conventional supercharged or turbocharged engine, for improved combustion efficiency.

The durability enhancements include an anodized top land, which reduces wear and helps deflect heat generated during combustion away from the LSA's bottom end. To further reduce wear, the piston skirt is coated with a polymer material, which limits bore scuffing, or abrasion of the cylinder wall over time from the piston's up-down motion. The polymer coating also dampens noise generated by the piston's movement. The wrist pins, which attach the piston to the connecting rod, were developed for maximum durability, with a large outer diameter and a tapered inner diameter. These pins "float" inside the rod bushing and pin bores in the piston barrel. Compared to a conventional fixed pin assembly, in which the connecting rod is fixed to the piston's wrist pin while the pin rotates in the pin bore, the floating pins reduce stress on the pin. They allow tighter pin to pin-bore tolerances and reduce noise generated as the piston moves through the cylinder. The benefit is less engine wear, improved durability and quieter operation.

Valves are among the most heat-stressed parts in an engine, and their wear resistance is crucial to long-term durability. Those in the LSA are manufactured from a high-chromium steel alloy called SilChrome 1 (The only difference between the LSA's exhaust valves, and the LS9s is that the LS9's are filled with sodium for the extra heat protection -- the LS9s intake valves are made of titanium.), with thicker heads than most other Gen IV V-8s. They promote heat transfer away from the valve face and valve guide to the cooler end of the stem, where it more readily dissipates. This maintains a lower, more uniform valve temperature, reducing wear on the valve guide for better alignment and a consistent seal between the valve seat and valve face over the life of the engine.

Finally, the 6.2L LSA represents the first line of small block V-8s equipped with oil-spray piston cooling. Eight oil-squirting jets in the engine block drench the underside of each piston and the surrounding cylinder wall with an extra layer of cooling, friction-reducing oil. The oil spray reduces piston temperature, promoting extreme output and long-term durability. The extra layer of oil on the cylinder walls and wristpin also dampens noise emanating from the pistons.

I don't think the Z will get the titanium connecting rods or sodium filled valves from the LS9 but you never know.

Stock for stock the LSA is a more durable engine test wise compared to the LS9 as was stated by GM at the debut. Regarding quality and durability, the 6.2L Supercharged LSA has been validated beyond 100,000 miles and accumulated more the 6,400 hours of dynamometer testing. It has run over 270 consecutive hours at wide-open throttle without a failure. (The LS9 has only accomplished 100 hours of this sort of testing!!!) It's been road tested in the world's extreme climates and track-tested under racing g loads on some the world's most demanding circuits. It has completed actual and simulated 24-hour track tests.

And just because the LS9 is rated at 638 now does not mean that it would not be bumped up a little to provide the Z/28's engine a little breathing room for it's hp rating.
The prototype Z/28 pic below looks to have a much taller intercooler cover with well defined twin riser to maybe house a taller version of the LS9 intercooler twin bricks for better combustion inlet temps.

The stock LSA as installed in the CTS-V has a rev limiter @ 6200 rpm yet it was shown to make more power well past 6600 rpm and was still climbing from this post from another site: I think the Z/28 engine will not have a rev limiter of 6200 rpm but of one much higher. It showed 451 hp @ 6200 and 485 hp @ 6600 with rev limiter raised or removed, thats a 34 hp difference. The gm performance parts crate LSA has a recommended 6600 rpm fuel cutoff.

Pics below are of the prototype Z/28 engine, then uncle Robin Lawrence's LSA stuffed camaro bottom left, and last but not least an LS9 stuffed camaro bottom right for comparison plus some side by side parts pics.
Attached Images

Last edited by RLHMARINES; 01-09-2011 at 06:53 PM.
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