Chevy SS/LS3 299 RWHP?

**Whamhammer** · 03-08-2015, 04:50 PM

Hi all,

Just got my April 2015 Car and Driver. An article in there features an automatic equipped 2015 SS sedan getting a supercharger installed atop its 415 hp LS3. They said the baseline rwhp and rwtq was 299 each. When new, werent stock F-body LS1's dynoing around that power level off of the showroom floor? Why is this SS sedan running that low at the rear wheels, despite a 70 hp/ tq rating over the late 4th gen' Firebirds and Camaro's?

**Whamhammer** · 03-09-2015, 11:14 AM

Originally Posted by Whamhammer

Hi all,

Just got my April 2015 Car and Driver. An article in there features an automatic equipped 2015 SS sedan getting a supercharger installed atop its 415 hp LS3. They said the baseline rwhp and rwtq was 299 each. When new, werent stock F-body LS1's dynoing around that power level off of the showroom floor? Why is this SS sedan running that low at the rear wheels, despite a 70 hp/ tq rating over the late 4th gen' Firebirds and Camaro's?

Bumped to emphasize correction of typos (darned smartphones and their small buttons)

***SMWS6TA*** · 03-09-2015, 11:31 AM

GM loves to detune or give out adjusted numbers showing lower HP numbers. It's also the HP at the crank vs HP at the wheel game. Some articles show the crank numbers while others show the wheel numbers. I feel they do it deliberately.

It could also be from drive train lost. What transmission is in the SS?

**Whamhammer** · 03-09-2015, 05:24 PM

Originally Posted by SMWS6TA

GM loves to detune or give out adjusted numbers showing lower HP numbers. It's also the HP at the crank vs HP at the wheel game. Some articles show the crank numbers while others show the wheel numbers. I feel they do it deliberately.

It could also be from drive train lost. What transmission is in the SS?

It was an automatic. The test was done by an indi' shop.

299 hp at the wheel is a 116hp and 28% loss from the crank rating. Even if the 4th gen F cars really had 340hp thats still a pretty wide difference at the wheels, been hearing 280-295hp at the wheels for them. The SS sedan just seems like a lot off drivetrain loss. Does the F5's have a similar percantage loss?

**Naaman** · 03-09-2015, 07:36 PM

299 at the wheels... that's weak.

I wonder if this one is a factory freak (but a weak freak, rather than a strong freak)...

**Firebirdjones** · 03-10-2015, 06:17 AM

For starters, these new autos suck some power. They are big and heavy with these new 6, 7, and even 8 speed autos coming out now. I would tend to think they aren't as efficient at transferring the power. Plus as these cars get newer they have bigger and bigger wheels and tires, bigger brakes, etc... that zap power. Lots of other reasons.

The other factor is that these 4th gens were very under rated when new. The advertised HP of 300-305-320 or what ever they were, was very conservative. If you've ever seen a stock LS1 on an engine dyno with no accessories (gross rating, the old fassion way) they routinely make right at 400 flywheel HP. Several magazines were doing this with brand new LS1 crate engines about 10-15 years ago.
So it's no surprise the LS1, strapped into the car with all accessories, exhaust, drivetrain loss, can still put down ~300-ish RWHP.

It's perfectly acceptable to see 100+ HP differences between an engine dyno with gross ratings, and then a chassis dyno once installed in the car. I've done this with my own cars.
Air cleaner, exhaust, alternator, water pump, fuel pump, mechanical fan, exhaust system, transmission, driveshaft, rearend, wheels.....all this stuff once installed in the car saps the power. You don't have these power robbing parts on an engine dyno (hence the gross ratings)

**Whamhammer** · 03-10-2015, 06:35 AM

Originally Posted by Firebirdjones

For starters, these new autos suck some power. They are big and heavy with these new 6, 7, and even 8 speed autos coming out now. I would tend to think they aren't as efficient at transferring the power. Plus as these cars get newer they have bigger and bigger wheels and tires, bigger brakes, etc... that zap power. Lots of other reasons.

The other factor is that these 4th gens were very under rated when new. The advertised HP of 300-305-320 or what ever they were, was very conservative. If you've ever seen a stock LS1 on an engine dyno with no accessories (gross rating, the old fassion way) they routinely make right at 400 flywheel HP. Several magazines were doing this with brand new LS1 crate engines about 10-15 years ago.
So it's no surprise the LS1, strapped into the car with all accessories, exhaust, drivetrain loss, can still put down ~300-ish RWHP.

It's perfectly acceptable to see 100+ HP differences between an engine dyno with gross ratings, and then a chassis dyno once installed in the car. I've done this with my own cars.
Air cleaner, exhaust, alternator, water pump, fuel pump, mechanical fan, exhaust system, transmission, driveshaft, rearend, wheels.....all this stuff once installed in the car saps the power. You don't have these power robbing parts on an engine dyno (hence the gross ratings)

I understand about the difference between the gross and net ratings. I am still surprised that even with the automatics ( I thought the 6 speed it has was a fairly effecient tranny, guess not) and the additional unsprung weight of the larger wheels, and the under rating of the LS1 Fcars (I heard it was more like 340 hp at the crank with accesories was realistic) how close an engine that is half a liter larger, ten years newer, and a higher spread in hp rating ( even taking into account LS1s under rating).

What are Camaro SS 6 speed autos showing on the dyno's, something similar to the SS sedan? It just sounds all kinda off to me.

**Firebirdjones** · 03-10-2015, 07:33 AM

I read the review, didn't see mention of it but I'd bet that car also has IRS, which is going to zap some RWHP too.

I can't believe those idiots were complaining about having chrome on the outside of the car

I've complained for years about cars having a lack of it. Whatever....

Anyway, I don't see much issue with the HP differences. Hard to say where GM pulled the 415 rating from, and the differences between dynos used at various facilities can be dramatic. I wouldn't read too much into it.

What I saw that I thought was terrible was the gas mileage ratings they are giving it. I thought these new cars were supposed to be better, not worse. They rate that thing at 15 city and 21 highway. That just flat sucks for a family sedan considering full size 3/4 ton trucks are doing better than that. Hell I have classics cars with carbs and no overdrive that will do that, lol.

**Whamhammer** · 03-10-2015, 09:58 AM

Originally Posted by Firebirdjones

I read the review, didn't see mention of it but I'd bet that car also has IRS, which is going to zap some RWHP too.

I can't believe those idiots were complaining about having chrome on the outside of the car

I've complained for years about cars having a lack of it. Whatever....

Anyway, I don't see much issue with the HP differences. Hard to say where GM pulled the 415 rating from, and the differences between dynos used at various facilities can be dramatic. I wouldn't read too much into it.

What I saw that I thought was terrible was the gas mileage ratings they are giving it. I thought these new cars were supposed to be better, not worse. They rate that thing at 15 city and 21 highway. That just flat sucks for a family sedan considering full size 3/4 ton trucks are doing better than that. Hell I have classics cars with carbs and no overdrive that will do that, lol.

The car does have IRS, its a reskin of the Holden Commodore/Pontiac G8 (with a LS3). It wasnt a very well written article and jumbled talking about the car and shine running too much. The Car and Driver article mentions the dyno run on the page 87 (rh side) about midway through. It also mentions the RWHP for stock and with supercharger in the stats section at the end (blue text).

**chuckie669** · 03-10-2015, 10:35 AM

I don't know if they kept this through 2015 model but when the camaro came back out it was the same block but technically classified as a ls3 in the standard and l99 auto i believe. Was like 20-30hp difference.

Think it had the same heads as my l76 g8

**67CamaroRSSS** · 03-16-2015, 02:46 PM

My bone stock 02 Z28 with 20,xxx miles on it put down 308 rwhp and 323 rwt on a DynoJet back in 2005. that was the 1st dyno for a base line before I started modding it. Sig shows the end result.

**KW Baraka** · 04-19-2017, 07:49 PM

My stock 2014 SS dyno'ed 356hp / 348tq to the wheels. It was dyno'ed the day before the 5200 mile LS3 was swapped out for a 329ci LS3.

On the SS forum, most guys who dyno their stock SS are pulling between 345 and 360 hp to the wheels.

Jus' sayin'.......

**Whamhammer** · 04-25-2017, 05:26 PM

Originally Posted by KW Baraka

My stock 2014 SS dyno'ed 356hp / 348tq to the wheels. It was dyno'ed the day before the 5200 mile LS3 was swapped out for a 329ci LS3.

On the SS forum, most guys who dyno their stock SS are pulling between 345 and 360 hp to the wheels.

Jus' sayin'.......

That's just so surprising that the LS1 Fbodies dyno so much closer to the Chevy SS's than they should. Are the days of GM under rating power over or something?

It almost sounds like there really wasn't much of a difference between the G8 GTs and the SS's, performance wise.