[s-cars] FW: Re; RS2+

[Mihnea Cotet]

Hap, I fully agree on the repetabilty of dyno runs with similar figures, 
however I'm not with you on the driveline losses part.

Quoting 22% driveline loss for all AWD cars is too simplistic IMO.... on 
quattros, the measurements we've done with "unreliable" dynos that measure 
driveline losses (dynos which are made by Bosch, whom I trust because they 
also make the ECUs that run our cars and because of a dozen of other 
reasons), the measured driveline losses on cars equipped with wheels and 
tires have always been between 22 and 27%, and they've been quite 
consistent for the same car dynoed at different times in similar ambient 
temp/pressure conditions.

I would really like to have an engine dyno/rig in my garage to be able to 
measure the HP an engine really has, then go on several types of dynos in 
order to see what the differences are and where the losses are, and I am 
fully convinced that power measured at the hubs+22% would be higher than 
what an engine alone has.

Car vs. car measurements make not much sense to me really, because each car 
and each engine is different, I've found it the hard way and ever since I 
have been a fan of individual and real-time tuning, so for me dyno runs are 
more meant to measure the relative increase a certain upgrade provides, 
rather than knowing that x's car is more powerful than y's. This all gets 
down to who has the biggest one somehow IMHO...


Mihnea, not trying to say anything about "real and unreal" dyno figures C.

At 22:58 9/01/2004 -0500, CaptMagu at aol.com wrote:
>Mihnea
>
>The correct name of the hub driven dyno is the DynoPack.The Dynojet is a 
>roller type that does in fact use the tires in contact with a roller. Both 
>of these can be used for 2 wheel drive as well as all wheel drive 
>vehicles. I won't argue with you on the losses being less for the DynoPack 
>because they are. Without the weight of tires and wheels there is less 
>mass to turn. There is also the lack of friction loss between the contact 
>surface of the tire and the roller once again in favor of the DynoPack. I 
>will argue however that this does not make up the biggest drivline losses.
>
>I just had along conversation with Scott Lampkin concerning his HRSB 
>installation. He owns a heavily modified urS4 and he is also the North 
>American distributor for DynoPack. He mentioned 22% as their given all 
>wheel drive driveline loss. I'd also make the point that the, as you put 
>it "real", chassis dynos that use rollers do a relatively poor job in car 
>vs car analysis. With the differences in wheel weights, vehicle weights, 
>tire compounds, and such things as suspension camber, you can come up with 
>significant performance differences from car to car that make side by side 
>analysis difficult. With an "unreal" Dynopack, all those diffrences are 
>thrown out the window and you end up with a very consistent appraisal of 
>"real" performance. Sport Compact Car ran a dyno comparison of DynoPack 
>dynos and found that with the same car and ambient atmospheric conditions 
>as near as possible they were within 1 horsepower between 6 dynos. Now 
>that's what I'd call a consistent tool for tuning.
>
>I sure hope this clears up any confusion you might be having about the 
>dynos we use here in the good ole USofA. Cheers.
>
>Hap, fumblin along with "unreal" dyno numbers in Everboost, Maguire