W88fixer

In general, the rear wheel dyno numbers posted here for C7s have been in the range of say 400HP/410 torque to maybe 415/420.

I find it interesting that the April 2015 issue of Car & Driver has two articles that address a 2015 Chevy SS which has a 6 liter LS series engine rated at 415HP/x? torque. C&D said that the car had 299HP/299 ft lbs at the rear wheels.

Of course I don’t know what type of dyno was used but being 100+ down on HP compared to the C7 is interesting. Don

theanswriz42

That doesn't sound reasonable to me. I'd expect something around 360 HP to the wheels on a 415 HP car.

Crabbers

Sounds like something's messed up. 299 at the wheels on a 415 hp car doesn't sound right at all.

W88fixer

I agree with you but I’m only reporting exactly what the magazine printed. Those numbers also don’t correspond with a 1/4 time of 12.9 in a 4000# car. Don

C7Joy

Their dyno needs a lube job!

Motohead279

They need to take the parking brake off.

sTz

Driveline loss is "generally" between 14-17%. The claimed numbers are definitely pretty low. The article is either not reporting accurate information, or there is significant parasitic drain somewhere. I suspect the former.

11B250

here is a stock SS dynoing for a baseline... made 359whp

thrilled

I had always heard subtract about 10% for wheel HP.

jovette

Funny, I've always heard and read that as a general rule, 15% is the number most frequently used and recognized as appropriate....perhaps 1or 2% higher for some automatic transmission vehicles, and 1 or 2% lower for some with manual transmissions.

dovervold

This is 13% drive line loss which I would say is a good bench mark. For the LT1, I would say 12% is a good ball park: 460 hp x .88 = 405 hp at the wheel with M7...

stevebz06

Dyno numbers tend to be all over the place. I think the usual correction factor is 15% for a manual transmission and more for an automatic.

The only real value for these tests is for when you are making changes to the car so that you can see if it is helping or not. But even that is suspect, since it is not unusual to see gains over the first run on subsequent runs without making any changes. Is that the car "learning" its' tune, lubricants warming up, or the dyno itself?

Maybe that Chevy SS cited was grossly out of tune, like some people suspected that the Z06 was when compared to the GTR at Willow Springs.

If you can always count on dyno numbers, then I have one of the world's most powerful stock LS6's.

davidtcpa

That seems to be the numbers I am hearing.

C7pimp

11-12%

M7 C7's average 410whp

W88fixer

I don’t know why I didn’t think of it before but that 299 HP number sounds just about right taking 17% off of the 361 HP rating of the G8GT with the 6 speed auto, the only transmission available that year, our second car.

Sounds like perhaps C&D grabbed the wrong dyno number? Don

tail_lights

Dynos vary a lot as well. That is a big gap though.

11B250

yeah... I've seen them dyno anywhere between 400 and 415