Not too happy looking at the dyno's posted.

My LS1 was rated at 305 and made 330whp (in an auto). I was hopeing for the same situation on the LS4. That is, looking at the rating on this engine (303/323) and knowing GM ususally underrates, and some are running decent times suggests under rated,.. but the dynos dont jive...

I just saw ~253hp,285ft# from a dyno post...
What gives? 12% tq loss, and 17% hp loss. Makes me wonder if the converter isnt too loose and slipping, loosing some HP?

any thoughts..

 

I had originally thought it was probably underated like the LS1. However GM seems to be dead on with the factory numbers... and the loss is pretty normal for an automatic. The torque convertor could probably be a little better, but considering the drivetrain was originally built for a V6... it transmits the power pretty good. IMO

Most of the LS1s were over 350 HP at the crank... GM just underated them so Corvette owners didn't feel shortchanged.

Edit: The somewhat tall gearing and broad torque curve of the engine is a good combination on the LS4... which is why it runs very quick. Running in 2nd gear all the way to 100 mph helps.

 

Not sure if they were using SAE ratings or not before with the LS1's, but the current SAE 303 HP is supposed to be right on where before it was a good chance they picked a number out of a hat as long as it wasnt exaggerated (Mustang SVT anyone? ). I am also wondering about the stock dyno pulls on the internet, specifically if they are turning on the fans earlier or monitoring what the IAT is. At a standstill idleling the car runs at a temperature that correlates to a -3 degrees retard coolant temp point. Intake temps really pull timing out as well. Unless these were run with a cool motor?

 

The ls7 only produces 130-160 more hp than the average ls1, the ls2 is 20 or 30 hp more than the ls1, so the ls1 is not really a good engine to gauge this car against. My WS6 was producing 334 at the wheels with an airbox lid.