2017 Duramax Dyno Numbers

larry barnhart wrote:
To think we are very happy with our 05 for our towing needs. Happy is good so Merry Christmas and Happy towing fellas and ladies.

chevman PS hard to be happy at this time watching the snow fall in Wa st.

Grit dog wrote:
And one can pick apart dynos as well. 2 dynos, different conditions, etc, etc,etc.
Either way, we all know there's more than a 4% loss from crank to pavement.
So either, it's a rigged test ( we can open the popcorn bar up on that one) or GM was/is conservative in their ratings and that Dmax is a powerhouse!

fly-boy wrote:
It would be nice to see the magazines put all three trucks on a dyno and then go up the big hill!

My only thought is that the GM truck has always faired pretty well in the tests over the last three years- all while rated much lower in the HP/torque categories. So GM must have significantly less drive line loss or is very conservative in rating the trucks numbers- or both.

Huntindog wrote:

fly-boy wrote:
It would be nice to see the magazines put all three trucks on a dyno and then go up the big hill!

My only thought is that the GM truck has always faired pretty well in the tests over the last three years- all while rated much lower in the HP/torque categories. So GM must have significantly less drive line loss or is very conservative in rating the trucks numbers- or both.

This talk is all very famaliar. In 2011, GM released their power numbers after Ford... They were higher than Fords. Ford quickly released a reflash program to beat GMs numbers... But then Ford got beat badly by GM in towing hillclimb test after test.... Then everyone started the debate as to why GM was able to do that with lower numbers.

Many of the same theories that are being bandied about here were discussed then.

I followed that pretty close back then. The one thing that I thought made the most sense was that GM was (and I believe still is) the only one of the big 3 to use the strict SAE Dyno protocol.

It is my guess that is what is happening now.

Oh and there was a fella on one of the Dmax forums that ran his truck on his Dyno. IIRC, that 2011 rated at 397 HP put about 360 to the rear wheels.

His last name is one that many might recognize:
Granatelli.

4x4ord wrote:

Grit dog wrote:
And one can pick apart dynos as well. 2 dynos, different conditions, etc, etc,etc.
Either way, we all know there's more than a 4% loss from crank to pavement.
So either, it's a rigged test ( we can open the popcorn bar up on that one) or GM was/is conservative in their ratings and that Dmax is a powerhouse!

I take it you come up with the 4% drive loss by using the 880 lb ft mentioned in the video and the 910 lbft that GM rates the truck at. So if we agree 4% is impossible and assuming an unlikely driveline loss of only 12%, then either the new Duramax is making at least 1000 lbft of torque and GM has decided to be conservative on their numbers and rate the new engine at 910 lbft or the test is rigged.

I think there is a most likely third option: That the 880 lb ft of torque is not meant to represent the engine torque less driveline loss but rather it is the torque measured on the dyno rollers.

jfritz_drfritz wrote:

4x4ord wrote:

Grit dog wrote:
And one can pick apart dynos as well. 2 dynos, different conditions, etc, etc,etc.
Either way, we all know there's more than a 4% loss from crank to pavement.
So either, it's a rigged test ( we can open the popcorn bar up on that one) or GM was/is conservative in their ratings and that Dmax is a powerhouse!

I take it you come up with the 4% drive loss by using the 880 lb ft mentioned in the video and the 910 lbft that GM rates the truck at. So if we agree 4% is impossible and assuming an unlikely driveline loss of only 12%, then either the new Duramax is making at least 1000 lbft of torque and GM has decided to be conservative on their numbers and rate the new engine at 910 lbft or the test is rigged.

I think there is a most likely third option: That the 880 lb ft of torque is not meant to represent the engine torque less driveline loss but rather it is the torque measured on the dyno rollers.

I think you probably know this. A chassis Dyno measures the rate of acceleration of a known rotating mass. The torque and horsepower therefore are mathematical calculations. The raw results then are a measure of rear wheel horsepower. Correction factors for altitude and temperature are applied afterwards. Generally on inertial (not a load step dyno) you try to get as close to 1:1 gear ratio as possible (most efficient). An operator can manipulate the data several ways (gear ratio, correction factors, engine temp, standards). Back to back tests on the SAME dyno can be meaningful, tests on different dynos much less so.