Quote:
Originally Posted by radz28
OOOOOO!!! A tech' post!!!! 
As far as those rods - I think GM went with the Ti rods in LS9 for their weight, perhaps, more than because of their strength. They wanted lighter weight to get the revs' higher, and lighter rods enabled that, along with the other tricks they used to control the valvetrain. Isn't Ti more briddle than steel? That's not entirely desirable in all automotive applications, is it? I believe aluminum is desirable because they take the shock from N20 better, no (for example)?
Pistons - people seem very quick to take away any qualities of these hyper' pistons. It's like many automatically think they're the same as the "standard" LS3/L99 pistons, and they're not. In addition - the oil squirters are also going to assist those stay together more effectively. But don't both LS9 and LSA pistons have the coatings on the skirts?
SC - would it be possible that the 10.5 psi in the 2300 is necessary to produce the 80 more horse' and overcome inefficiencies in the packaging for LS9 in ZR1's body? I know they had to go to great lengths to keep the hood height low enough for visibility through the windshield which meant they really had to squish the SC and plenum down. Looking at the intercooler bricks on LS9, it's easy to see air is forced to change direction and shape to conform to the passages, IMVHO. Do you think this could have an effect on boost, since it is a reflection of restriction? |
The biggest problem with hypereutectic pistons is their hardness. They are actually "harder" than most forged applications,
but with hardness comes brittleness and susceptibility to breakage from deformation. Knock kills hypereutectic pistons, KILLS them, so in a factory application the tune will have to be much more conservative than a forged set would allow, which is necessary to accommodate varying weather and altitudes. That doesn't mean that the LSA can't make some fantastic power and run for years at that level, it just means that in comparison to the 5.4 tuning is going to have to be far more conservative on pump and equivalent fuels. That gives a big advantage to ford when it comes to factory outputs. The 5.4 could potentially put out (and has with the supersnake packages) over 700hp without touching the reciprocating assembly or any other internal engine component for that matter. Tuned for the crappy west coast 91, I highly, highly doubt the LSA is capable of numbers at that level while maintaining reliability with a factory tune. With a good dyno tune, it probably is. Anyway, this may not even be an issue as the cars may not move to those power levels for a long time, but it is still one thing that I'm sure Ford is aware of and Chevy as well. I have hypereutectic pistons in my car and have yet to break anything, but I also have a set of forged pistons waiting to go in for the day I get a tank of bad gas LOL.
Anyway, this just means that GM is going to have to pay a lot of attention to cooling, not only with squirters, but the intake charge and that is what you are going to want to take care of FIRST in the modding path. Cooling, cooling, cooling, a great tune, and consistent fuel delivery to battle knock.