Too Much Horsepower For What It Is? Stock L99 @ 499HP

[Moto-Mojo]

Sound familiar? LOL. But seriously, check this simple formula from 'Chevy Hardcore' for estimating flywheel horsepower. Now math is not my strong suit but I double checked it:

Simply stated, it's a torque per cubic inch factor of 1.25 x cubic inches. That result x a 10% loss factor. That result x peak RPM. That result / by factor 5,252.

Thus:

1.25* x 376 CI = 470 LB FT

470 x .90 loss = 423 LB FT

423 x 6200 RPM = 2,622,600

2,622,600 / 5,252 = 499.3 Peak HP

*based on 10:1 compression ratio. If you use 1.3 for the higher LS3 engine, it comes out to 519 peak HP.

So...is this article full of it? Did GM UNDER estimate or did I fail yet another math test.

https://www.chevyhardcore.com/news/j...use-right-now/

[gtstorey]

So our engines don't make the 1.25 Lb ft per cubic inch. More like 1 - 1.1 in stock form. Aftermarket heads, cam and LT headers are more in the 1.25-1.3 range.

[SlingShot]

Those numbers are right, back in 09 one of the tv hot rod shows ran a LS3 on an engine dyno and they got just over the 500 mark. The numbers Chevy gives us a certified net and not gross.

[qcman]

If you look at the L99 which Dyno's about 330 RWHP and assuming 18-20% drivetrain loss that would put the L99 pretty close to the 400 HP Chevy claims. On the 2013 and later cars with the Electric Power Steering ( I don't think 2012's had it yet?) there should be a bit more crank horsepower as the motor is no longer turning the old hydraulic power steering pump.

I love the title of the thread BTW LOL.

[SlingShot]

Originally Posted by qcman

If you look at the L99 which Dyno's about 330 RWHP and assuming 18-20% drivetrain loss that would put the L99 pretty close to the 400 HP Chevy claims. On the 2013 and later cars with the Electric Power Steering ( I don't think 2012's had it yet?) there should be a bit more crank horsepower as the motor is no longer turning the old hydraulic power steering pump.

I love the title of the thread BTW LOL.

It would be more net, then gross would stay the same. The net is with all belts and accessories.

[qcman]

Originally Posted by SlingShot

It would be more net, then gross would stay the same. The net is with all belts and accessories.

Right that was what I was trying to say. You said it better

[Moto-Mojo]

So is it really more than the claimed 400HP? Not completely understanding net v gross...

[qcman]

Originally Posted by Moto-Mojo

So is it really more than the claimed 400HP? Not completely understanding net v gross...

I would say no in the sense the 400 HP includes the belts etc. (net) which is what they report but the HP on just the block (gross)would be higher than 400 though I don't know by how much.

I believe back in the 60's when they claimed HP on motors they were reporting gross which was a little misleading. I'm not sure thats what they did though.

[PepeLePew]

Cool article Moto-Mojo. I think the math works. I wonder what this line in the article means with regards to the heads and cam:

"Brule’ likes to use 1.25 lb-ft per cubic inch for a 10:1 compression street engine with good cylinder heads and a decent camshaft."

We know that the L99 and LS3 heads are awesome to begin with, but I wonder if they consider the stock cam as a decent camshaft. It seems like based on the results of your calculations, they probably do.

What I'd love to see if anyone has done it, is a test where they run the engine without accessories on the dyno and compare it to with accessories and then put the engine in the car and run it on the chassis dyno. Do this for the L99 and the LS3. That would give us an excellent idea of how much loss is associated with accessories and drive trains (auto and manual). That would take a lot of the guess work out of estimating flywheel/flexplate numbers. Just fun to know stuff!!!

Oh and funny topic title too. I wonder if we'll get any interest on this thread from our favorite troll.

[Moto-Mojo]

Originally Posted by gtstorey

So our engines don't make the 1.25 Lb ft per cubic inch. More like 1 - 1.1 in stock form. Aftermarket heads, cam and LT headers are more in the 1.25-1.3 range.

Ok, so that’s still 488HP. (1.1) Seems I have new bragging rights.

[Moto-Mojo]

Originally Posted by PepeLePew

Cool article Moto-Mojo. I think the math works. I wonder what this line in the article means with regards to the heads and cam:

"Brule’ likes to use 1.25 lb-ft per cubic inch for a 10:1 compression street engine with good cylinder heads and a decent camshaft."

We know that the L99 and LS3 heads are awesome to begin with, but I wonder if they consider the stock cam as a decent camshaft. It seems like based on the results of your calculations, they probably do.

What I'd love to see if anyone has done it, is a test where they run the engine without accessories on the dyno and compare it to with accessories and then put the engine in the car and run it on the chassis dyno. Do this for the L99 and the LS3. That would give us an excellent idea of how much loss is associated with accessories and drive trains (auto and manual). That would take a lot of the guess work out of estimating flywheel/flexplate numbers. Just fun to know stuff!!!

Oh and funny topic title too. I wonder if we'll get any interest on this thread from our favorite troll.

Yeah, I borrowed his tag line as bait!

[qcman]

Originally Posted by Moto-Mojo

Yeah, I borrowed his tag line as bait!

Be ready to set the hook!

[SlingShot]

Back in 09 the V6 was not certified and Chevy just did a guestiment on the power. The said it was 304hp, sometime in 10 they did a certification at 323hp.

[qcman]

Originally Posted by SlingShot

Back in 09 the V6 was not certified and Chevy just did a guestiment on the power. The said it was 304hp, sometime in 10 they did a certification at 323hp.

I think they went from 304 to 312 for the LLT and then to 323 when it changed to being the LFX in 2012 iirc.