Driveline loss %

[Performin Norman]

Just curious what most people here use for driveline loss. I was using 12% and have noticed that most Viper and Vette owners say it is closer to 15%. I know this is very subjective but want some consistency here. Had a guy over at another board tell me it is more like 9%. I kinda laughed to myself thinking that I have never heard of a tranny that can transfer more then 90% to the rear wheels. I could be wrong, it has happened once before. LOL

Thanks for your input.

 

[Rich Detert]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Performin Norman:
I could be wrong, it has happened once before. LOL <HR></BLOCKQUOTE>

Now that's funny!

 

[GTS Dean]

Use 12.5% to 13%. Sean Roe confirmed this with a dyno'd engine slipped into his T1 racecar, then chassis dyno'd.

 

[Bill/APEX Motorsports]

There are SO many variables to take into account that it's really hard to put an exact number on it. However, if you use 15%, it should be somewhat close.
Dynoing the engine first then dynoing on a chassis dyno would certainly give you the most accurate percentage, but it's really not practical for most people. $$$

 

[MES]

There was a thread some time ago regarding this subject and I think it was 13% this was done by pulling the engine out of the car to dyno it, then dynoed again with it in the car. Considering most stock Vipers dyno right around 400 to the wheels the loss of 50 HP would give a drive line loss of only 11% This shows the engines are under rated. With the typical stock car dynoing at 400rwhp and taking into account the 13% loss you would have 460 HP at the crank (460HP X .87=400rwhp) seems close enough for government work to me

 

[joe117]

So where does the 50hp go? It must go to heat right? Is there any other way that it can be lost? That's quite a bit of heat. I'm not sure but it seems like nothing in the drivetrain is getting hot enough to account for it.

 

[Jack B]

When Dynojet collaborated with the Viper race effort the average loss was 15% for a new car and for a worn car it was 17-18%. The only way it is going to be in the 9-12% range is for a solid axle.

 

[jcaspar1]

For 12.5% loss, multiply RWHP by 1.14
For 13% loss, multiply RWHP by 1.15
For 15% loss, multiply RWHP by 1.176

The formula is HP=RWHP/(100%-%loss)
so 400RWHP with 13% drive train loss is 400/(100-13%)=400/.87= 460hp
400 RWHP with 15% loss is 471 at the crank

Multiply by 1.12 for 10.7% loss

 

[RockyTop]

As GTS Dean said above, Sean Roe did this on his Gen II by using an engine dyno and then a chassis dyno (or vice versa). To ascertain your flywheel number, I am pretty sure that Sean instructed us to multiply the rear wheel number times 1.12.

 

[Brad Manhattan Beach]

I talked to Todd at Arrow Racing about my engine this afternoon (which has just been dyno'd and shipped). According to Todd, the driveline loss factor that they have always used is 10% (5% loss at the transmission and 5% loss at the differential).

Being that they are the people that perform all of the warranty engine rebuilds for DC, I would tend trust their driveline loss factor more than anyone else's out there.

Is there anything that would cause this factor to change (to a higher number) that you guys are talking about?

I hope that this clarifies this debate.

Brad

 

[jcaspar1]

Well, a 10% loss would eliminate the idea that stock Vipers are under rated on horse power. 405 RWHP= 450 at the engine.

From my understanding, 10% is an extremely efficient drivetrain.

 

[genXgts]

Could be even worse SS, some AWD camps claim 30-35% loss when running all 4!

can not recall the source, pulled from some thread reading.....

 

[Wide Open Throttle]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Could be even worse SS, some AWD camps claim 30-35% loss when running all 4!
<HR></BLOCKQUOTE>

Be happy it's not that.

Vettes with a six speed see from 15%-17%

 

[jamie furman]

I don't think it is that cut and dry, besides driveline loss there is also exhaust questions. Most engine dyno's use tuned headers and no exhaust or extremely large diameter tubing off the headers that is usually alot better than the exhaust and mufflers on the car the engine is going in.And if it is a carbureted engine then the jetting might be different installed.I have had 2 engines done in the last year and there was about a 20 percent drop to the rear wheels after tuning due to driveline and exhaust system.