Makes you wonder...

 

Optimistic dyno

Then again, LPE just dynoed a stock ZL1 Camaro and came away with 518HP/513TQ .....and last month's GMHTP dynoed a stock CTS-V at 524HP/521TQ.

Uhh...ok.

 

Articles like that is why I have absolutely no faith in chassis dyno readings, as they are not run using any form of a standard testing protocol. The engine dyno testing that GM uses has a very strict protocol for their testing. The GS engine has 436 brake horsepower, period. No way does that car only have 5% driveline loss. Unheard of. Normal is 10-12% driveline loss on a C6 manual transmission and more like 15% on a A6.

 

GM testing of engine output of their Corvette motors are SAE certified 400,436,505 and 638 hp respectively. Why would GM conservatively list HP with all the surrounding competition currently out there?

 

Exactly

Even using an engine dyno (the most reliable means of getting a true and realistic number), you can get a different measurement based on correction factors.

The excerpt below is from a test/cam install on a stock crate LS7 motor, minus the front accessories, back in 2/2006......

"
One other important factor accounts for its seemingly tame rating as well. The 505hp rating is generated under SAE J-1349 testing conditions, which correct measured power output to more real-world temperature and atmospheric pressure conditions than the familiar Standard Temperature and Pressure factor used by racers and magazines that corrects to a generous 60 degrees F and denser air conditions. SAE numbers are generally about 5 percent lower than STP. Indeed, the tests we conducted with an as-delivered GMPP LS7 crate engine on a Super Flow 901 dyno at Thompson Racing Engines in Redford, Michigan, generated 546 hp at 6,100rpm and 514 lb-ft of torque at 4,900 rpm with stock LS7 manifolds but without catalytic converters or stock mufflers and exhaust using the STP factor. That translates to 522 hp and 492 lb-ft using the SAE factor. So in "magazine numbers," the LS7 is really making 1.27 hp/ci, which is decent for a mildly cammed pump-gas engine. And as you'll see, with more cam and better headers, it gets a whole lot more decent."

You can read the entire article, where they installed the GM Stage 2 and Stage 3 "hot-cams" into a stock LS7 crate motor at Katech, then presented the final SAE corrected engine dyno numbers.

You can draw your own conclusions and weigh the chassis dyno numbers you see and read about accordingly. I won't pooh-pooh on anyone's chassis dyno numbers, but sometimes a bit of common sense can go a long way in interpeting the recorded numbers

http://www.hotrod.com/techarticles/h...ls7_dyno_test/

 

we seem to go through this discussion with almost every generation of Corvette Same thing would happen back in the C5 days... and there have been threads on the same topic with regard to the LS7.... hence where the term "factory freak" gets coined

Katech pretty much debunked the LS7 factory freaks by confirming they (100's that they have dynoed) all produce within 1HP of each other give or take.

The same is true with the LS3, 2, 6, 1 etc etc.... GM would not just dyno a couple and throw out 436HP as the advertised power of the motor. There's a bit more involved than just doing a random test one day with 1 or 2 motors.

 

Yep, these discussions come up everytime there's a questionable chassis dyno reading...even more so when it comes from a performance magazine.

People should accept that there's no such thing as a factory freak anymore. The certification of power output using the SAE J-1349 testing conditions says the measurements are certified to within 1% variation. Now, could a factory submit a "ringer" vehicle that has a modified engine? Sure, but at what expense and consequence ?

Wasn't there a class action law suit way back when when the Cobra Mustangs didn't produced the "advertised" (non-certified, mind you) horsepower ?

Now, keep in mind that the new ZL1 Camaro I referenced in one of my post above has not been released for sale yet....so could GM "tweak" the powertrain on that package to get a bit more than 580 BHP it originally advertised before it hits the market ? I guess that's possible....but not on a current production LS3/LS7/LS9/LSA motor, not without advertising the boost in SAE numbers....no reason to withhold that info.

 

I thought the allowed variation was 5%? No?

 

Someone posted the actual SAE paper (or an excerpt from the paper) sometime back, and IIRC the allowed variation to meet the certification was no greater than 1% variation.

So, an SAE certified LS7 could make as much as 510 HP, or as little as 500.

Furthermore, The SAE organizations says this...

"J1349 was updated last year to eliminate some ambiguities that allowed engine makers to cite power and torque ratings higher than the engine's actual capabilities. Engine makers are free to cite power and torque figures drived from testing conducted outside the scope of the SAE standards, but they may not claim the figures are SAE-certifed. "

By the way, that would also be inclusive of UNDER RATING the horsepower and torque as well.

So.........GM says the LS3 as it's used in the C6 Corvette chassis is

"430 hp (321 kW) at 5900 rpm
and 424 lb·ft (575 N·m) at 4600 rpm
(both parameters certified to SAE J1349).
An additional 6 hp (4.5 kW) is available
with the ’08 Corvette’s optional “active”
exhaust system"

But the kicker is, is the engine in question an SAE Certified engine ? For an off the showroom floor "production vehicle", if the powertrain has "SAE Certified" in it's advertised power numbers...you better believe those numbers are valid.

If the "advertised" power numbers are not "SAE Certified", the manufacture can claim whatever power output they want, within reason.
I'm guessing that could be true for a vehicle that is advertised , but hasn't reached production and availability yet.

Right now, GM advertises the ZL1 Camaro's engine as "580 HP, SAE Certified".....but could that be revised before the actual production units arrives in showroom floors ? I don't think so, IMHO.

And, just to reiterate...the SAE Certified numbers are ENGINE DYNO numbers, not chassis dyno numbers. Each different chassis combination will yield different RWHP on a chassis dyno, dependent on driveline parasitic losses (which are just educated guesses).

 

But wasn't this 4 years ago or do you need an SAE cert every year? I guess what I'm trying to get at is, that the cert could be in 08, rated at 430hp given the application that was presented to them. So, couldnt you get away with bumping the hp and still have a SAE cert just as long as 2008 was in the details?

 

I seem to remember the same magazine did dyno pulls on at least one new 1999 Camaro Z/28 and found it to be significantly better than the advertised HP (which was 305 for 1999). The same engine as installed in the 'vette was rated higher.

It may have been the same issue where Evan Smith drove a '99 Z/28 through several quarter mile runs and obtained a best number of 12.896 @ 109.18 MPH. The same "press car" that the writers from some other magazines couldn't break 13.5 in.

He was/is known for exceptional ability on the dragstrip

 

I'm not an SAE engineer or expert, but my bet would be that IF the engine ratings were going to deviate anywhere outside of what the "Advertised SAE J1349" certification is for the LS3 engine, as supplied in the C6 Corvette chassis, it would have to show this power change to maintain the SAE J1349 certification as GM presents it in it's literture......and I'm very confident GM would have reflected this power bump in their advertisements and specifications for the Corvette.

As an FYI...Ford's new 5.8 supercharged motor for the 2012 Mustang GT500 is not SAE Certified. And Ford specifically states they reserve the right to make changes.....

"There's the Shelby GT500™ with the most powerfuel production V8 engine in the world – the 650-hp 5.8L supercharged V8 capable ..... Ford reserves the right to change product specifications at any time without incurring obligations."

 

 

The LS1's were never SAE J1349 certified, so the "advertised" horsepower could be anything GM wanted to say, within reason of course.

Also, keep in mind that SAE power output does not directly translate to the actual power production of the engine when superior environmental conditions exist.

My LS7 running in 35 degree air, 0 degree dew point, and 30.30 inhg baramoter, would put down considerably more power than the SAE cert.....10% or more. That 505 now swells to 555+ ....tack on another 5% if you use standard correction numbers, or 580+ crank HP. Pull off all the accessories and run dyno headers and no exhaust or cats and you could tack on another 20 crank HP to make it an even 600 crank HP.