Just trying to make a bit of sense of the actual hp and torque of the Cobalt SS/SC. GM specs say 205hp and 200tq, right. Are those specs crank(bhp + btq) specs or whp + wtq specs? I assume that they are crank specs(bhp and btq). Since our cars seem to all be dynoing at 205-225 at the wheels for hp and most are at 190-200 tq at the wheels can we effectively say that our cars are in actuality more like 240-260 bhp and 220-230 btq(crank values). This would also assume a 17% loss from crank to wheels. Like I said I'm not 100% sure about my reasoning and numbers. Perhaps somebody could verify my reasoning/numbers or clarify things for me.

If GM specs are crank specs, then I assume all other manufacturers specs are the same, correct?

 

GM Under-rated the HP/Torque.

 

OK, yeah I know that they underrated the tq and hp. That's not the question. What I want to know is if I'm right in the numbers that I got in my first post as to crank and wheel hp and tq numbers. I believe I am correct, I just wanted clarification from others as to whether the numbers I used/got are close. Ie 17% loss from crank to wheels, etc.

 

How do you get 17% loss on a FWD car with almost no driveshaft?? The max loss s/b around 10-11%. Therefore, if you multiply dyno whp of 205 by 11% you get 225 bhp. The SS/SC actually dyno's closer to 196 at the wheels - this confirmed by GM Performance Division on Street Tuner Challenge aired on Speed TV. Therefore GM has underated the bhp by about 10

 

GM Performance has consistantly dyno'd within .5 hp ~190 or so. don't quote the exact number, but it's per the speed channel's tuner challenge cobalt baseline.

 

Hmmmm, you guys comments don't quite add up to what everyone else around here is saying about the underrating of the HP and TQ on the SS and their dyno results. As far as the loss goes, I was only going by what some other cars are, but I guess to really know the exact loss I'll have to ask GM.

 

Since there is no direct 1:1 gear on the CSS, even if a dyno was 100% accurate, you cannot get the true wheel power. So starting with a bad number, then applying, essentially, a guess as a correction factor and your results are to be taken with a grain of salt. The rate of error could be (my estimate) between 0 and 15 horsepower. That is a 30 horsepower margin of error. 15 in each direction from your starting point.

Hardly seems worth worrying about the accuracy of a flywheel estimate.

 

Everyone's dyno results are wrong because GM mis-quoted the gear ratios, if you look at the 2006 specs you'll see what everyone was using on the dyno (.98 in 4th) is/was the SS ratios and the SS/SC ratios are now different, and I would assume always were what they are now. I just noticed this the other day I could also be wrong however.

 

That's it!!!! I'm taking my engine out tomorrow and putting it on an engine dyno

 

We know that the GM US site is wrong and the GM Canada site is right

I thought the dynojet figured out the final gear ratio by doing RPM per MPH.

I should mention I did 2 dyno pulls back to back one in 3rd and one in 4th.
3rd Gear was 213 HP and 4th Gear was 203 HP

 

Yes, 3rd is lower than 1:1 and gives an optimistic reading, 4th is higher than 1:1 and gives a pessimistic reading. Your true power should be between the two.

 

Ok, so just for laughs, if we take zinner's dyno results and average the two, we should get 208, right. Now what I want to know is, let's say 208 which is at the wheels, is correct, what would be the crank hp. I don't need somebody to come on and say you're numbers are sh$t, you're retarded or whatever. I've already stated I'm not sure of the loss, that's why I'm asking. All I want is a hard % of loss from the crank to the wheels for the SS/SC cobalt. Does anyone know what that loss is? And also, I don't want somebody coming on and saying it depends on this, blah, and that, blah, blah.....it should be a fixed/known figure. So the questions stands what is that known figure?

One other thing I asked was, are the hp and tq ratings that GM advertises from the crank or at the wheels?

So two questions only, I hope these are clear enough:

1. Are the hp and tq ratings that GM advertises from the crank or at the wheels?
2. What is the power loss % from the crank to the wheels?

 

Well I'd like to tell you an exact number, but its impossible to figure out without pulling out the engine and putting in on an engine dyno

However, the most common numbers are between 15% and 20%. A FWD manual car (Cobalt SS) should be about 15%, while a RWD automatic car would be about 20%. 4 wheel drive and AWD vehicles experience significantly more loss through the drivetrain, usually in excess of 25%. So figure on 15% drivetrain loss for a Cobalt SS.

The numbers that GM (and every other manufacturer advertise) are taken from the flywheel (crank). So with something like the Cobalt SS putting down 210HP at the wheels, one can conclude its grossly underrated

Hope that helps

 

Thanks wesman, that's pretty much what I originally figured in my first post. So taking zinner's 208 hp dyno at the wheels would equate to 208*1.15=240hp at the crank. That's all I wanted to know. Thanks again wesman.