Anyone measured the drive train loss?

I think everyone figures about 17% or 18% loss due to the drive train on the LX SRT8s? Is this the right number?

Is there something called a "coast down" test on a dyno to actually measure this? Has anyone done it?

 

Advertised crank HP = 425
Stock DynoJet = 360 RWHP(average)
Drive train loss = 15.3%

To do it any more accurately than this, you'd need to engine dyno the motor to get a true crank HP and then chasis dyno it to see the driveline loss. The driveline on the LXs is a bit more efficient than most automatics, so that 15% sounds about right to me.

 

if thats the case the neon has only 3.9%
crank=230
stock whp=221
drivetrain loss=3.9%

 

This all has to do with someone's claim that the SRT8s (and 5.7L) are underrated.

 

One an engine dyno, our first 426 with stock cam made 560hp. Once we put it in the car, we made 463rwhp. Thats 17.32% drivetrain loss. That changes with different converters/wheels/tires also.

 

Almost 3 years ago we had a stock 6.1L on the engine dyno and on the chassis dyno.

17.5% loss.

 

17% sounds about right no?...aren't the numbers usually between 14% and 21% (generally speaking) loss depending on all the different driveline configurations for most cars?

 

With JMatt's numbers from a few years ago, that makes the 6.1L about 440 at the crank from the factory.

440*.825 = 363 RWHP

 

Do we know of a few people who have done totally stock dynos?

I feel like 363 is a pretty normal "stock" dyno pull...no?

 

I'd say yes, seems that's what most are reporting stock, 360.

 

Excellent! This is what I was looking for. Thanks.

 

So that means our motors are not underrated then right Dave? 360rwhp dyno x 17.5% loss = 63 horse. 360 + 63 = 423 hp. Right??

 

Its 17.5% lost off the crank, not rear wheel HP.

So 425 at the crank - 17.5% (74hp) = 351 RWHP.

 

Thanx Adam, math never was one of my strong points, lol!

 

You were probably sleeping through that part...

 

I seem to remember when I first bought my SRT a couple years ago someone finding out that all the factory tests were done on heat-soaked motors. Especially the smog tests.
So 425 crank HP on a heat soaked 6.1L sounds about right. Cool it down and you get 10-15 more.

But then again my memory sucks.

 

Not as bad as my math! Lol!

 

adam, i think you are pretty much on the mark with this one. i recall talking to my tech at the dealer and he said pretty much the same. i then had the conversation with a srt guy and he was on the same page as well. something about "real world" scenario.......

 

I have heard 15% on lx cars and 25% on a 4 wheel dyno with the JEEPS. I called dyno jet and they told me that temp + DA and cars weight has a lot to do with it on any car. I think we will never no.