biskitman

I have an 08' Coupe with LS3 and NPP, supposed to be 436 hp. I have seen others say its 10-15 more actually and some says its 10-15 less. I know that a dyno would tell me but they are subjective also and I dont want to go to the expense, wear, etc. My car is bone stock MN6 Is the 436 advertised pretty accurate? I know the gear heads will chime in with accurate answers.

talon90

I hate to disappoint the others but the LS3 is not underrated. The car's horsepower is certified to an SAE standard which have very little tolerance for underrating and overrating. As such, it is what it is. The reason that everyone things they have more power is that they are applying outdated "guesstimates" for drive line loss and attempting to back calculate flywheel horse power from rear wheel dyno results. The former assumptions on loss don't work with the LS3 and T6060 as the transmission and drive line is a more efficient package. If you apply the old routine you end up with some outlandish claims of crank horsepower.

budgreen3564

somebody correct me if i'm wrong, but i think the regular C6 LS3 is 430. Z51, 436

BetterMostC6

Its the dual mode exhaust "NPP" thats rated at 436hp. The suspension option Z51 has nothing to do with HP unless it also has the NPP option. NPP can also be ordered without Z51.

AORoads

Yes, I believe it to be accurate. There is absolutely no reason for GM to low- or high-ball it. None that I can think of. I say, take it as it is.

talon90

LS2 400
LS3 430
LS3 with NPP exhaust option 436

Z51 has no impact on horsepower.

keg

Right on the HP spec's.

JJC5

LS2 with aftermarket exhaust 406

talon90

Yep, I guess that would be the case.

RACN1320

I've heard some speculation that the LS2 may have been slightly over rated and thats why GM never got it SAE certified. However, the LS3 is SAE certified. This means that the engine power can't be more than +/- 1% of rated. Consequently a 430 HP LS3 couldn't have less than 425.7 HP or more than 434.3.

Vasta

Does anyone remember the percentage of horsepower loss from the crank to the rear wheels?

talon90

Michael,

Two part answer. Part one:

MN6 15%
A6 18%

In terms of what folks like to use for calculating RWHP from BHP.

Part Two:

(I've posted this previously)

I don't believe that a "15%" assumption is correct for the LS3. I believe that the LS3 is closer to 10 or 11% (if expressed in percentages, which I don't believe in that either). It appears that the LS3 drivetrain is loosing between 40 and 45 hp to the wheels.

The problem always comes down to the tolerances and differences vehicle to vehicle. There is no way to accurately predict crank horse power from rear wheel horse power. The only legitimate means of approximating driveline loss is if you have a baseline number for the crank on that vehicle and then can get an accurate rear wheel measurement on a dyno.

Driveline loss should not change on a given vehicle once established. What I mean by that is the same components should keep the same loss (allowing for wear) over the entire horsepower curve as modifications are made. If you use a divisor such as .85 (15% loss) you are taking more from the drivetrain as horsepower increases and that just shouldn't happen. For example:

baseline
400-60 (15%) = 340 on a stock C6 manual.

add intake and exhaust (gross about 15hp)
415-60 = 355 as the driveline didn't change so all the same friction and slop is present.

but using the conventional 15% it would show:

415-62.25(15%)= 352.75

Not too significant at lower hp ratings but think about as you begin to add a supercharger (150hp)

550-82.5 (15%)= 467.5 Why would the very same driveline now all of a sudden create a 82.5hp loss? No increased friction, so it should not.

C6LSx

Interestingly; the frictional losses from the flywheel to the rear wheels on the Nissan GTR are an absolute 10% due infact to high end component build materials in the drivetrain.

With regard to the stock LS3 with the stock GM ECU calibration; both with and without NPP, the Flowjet Dynomometer has consistently shown the following drivetrain frictional losses with:

Automatic A6: approximately 15%

Manual MN6: approximately 12.5%

Vasta

Thanks Paul.

C6LSx

[QUOTE=talon90;1566449512] Michael,

Two part answer. Part one:

MN6 15%
A6 18%

In terms of what folks like to use for calculating RWHP from BHP.

Part Two:

(I've posted this previously)

I don't believe that a "15%" assumption is correct for the LS3. I believe that the LS3 is closer to 10 or 11% (if expressed in percentages, which I don't believe in that either). It appears that the LS3 drivetrain is loosing between 40 and 45 hp to the wheels.

The problem always comes down to the tolerances and differences vehicle to vehicle. There is no way to accurately predict crank horse power from rear wheel horse power. The only legitimate means of approximating driveline loss is if you have a baseline number for the crank on that vehicle and then can get an accurate rear wheel measurement on a dyno.

Driveline loss should not change on a given vehicle once established. What I mean by that is the same components should keep the same loss (allowing for wear) over the entire horsepower curve as modifications are made. If you use a divisor such as .85 (15% loss) you are taking more from the drivetrain as horsepower increases and that just shouldn't happen. For example:

baseline
400-60 (15%) = 340 on a stock C6 manual.

add intake and exhaust (gross about 15hp)
415-60 = 355 as the driveline didn't change so all the same friction and slop is present.

but using the conventional 15% it would show:

415-62.25(15%)= 352.75

Not too significant at lower hp ratings but think about as you begin to add a supercharger (150hp)

550-82.5 (15%)= 467.5 Why would the very same driveline now all of a sudden create a 82.5hp loss? No increased friction, so it should not.[/QUOTE]

You are correct with regard to this statement. A preview of the Magnuson Supercharger advertising literature always makes references to the fact that the Maggie supercharger adds xxxRWHP and xxxRWTQ.

One of the few company's that always makes their increased performance numbers in terms of rwhp and rwtq number claims.

Fricitional loss is fixed which is why it's important to have a baseline.

Frictional loss however can be reduced with higher end micropolished gear sets and lowering unsprung weight as well.

Pocket Aces

But it does have impact on acceleration with slightly gripper tires and different gear ratios.

dvilin

sranger

Thanks for the SAE info. I know that non-SAE engine rating were usually allowed a more lienent +- 10% from the stated values...

jschindler

What if it has a badge?

HarleyB

That is ALWAYS good for 12 - 15 HP!!!