Rolling Road on 24/11/2007

[55JWB]

I am booked in on 4th December, I will let you know

[t_urbo]

Oh i see - so I guess the figures can be easily massaged depending on what criteria you use for the drivetrain losses.

Is 20% drivetrain loss about right for the RS4 then????

Surely power at wheels is the only figure that actually means anything meaningful?

The dyno (most of them)calculate the losses itself and a good dyno will be near enough to what it should be.

Its common that Dynos overstate the power output by a small amout but with the RS4 it seems that all of them are showing low figures.

It does seem that the RS4 B7 engine just does not produce the claimed figures of 414hp/420bhp.

[DavidT]

Or that the dynos don't cope well calculating flywheel figures for rear biased TorSen cars.

[mrdeli]

Surely it's a bit far fetched to think that Audi would overstate the output of their cars - they must surely test all engines within strict guidelines?

[GrahamS4]

Or that the dynos don't cope well calculating flywheel figures for rear biased TorSen cars.

Fair point.

I think what we need is a dyno operator friendly enough, perhaps with an interst in the marque to contact their dyno vendor for support on this.

I bet dyno dynamics have some expereince on this. Their website has FAQs for instance on dynoing a Skyline GTR etc which must have a fancy awd system, perhaps they would be more than happy to advise how the dyno should be setup for this vehicle or could at least research it given all the reports of them underreading?

[t_urbo]

Or that the dynos don't cope well calculating flywheel figures for rear biased TorSen cars.

If thats the case then how do dynos calculate the hp of a 996 turbo?

The split on the 996 turbo varies dependant on load with a max split that is the same as the RS4 B7.

Owners and tuners are reporting low figures the world over with this car.
It should produce the claimed output under reasonable conditions for a good portion of the time and it just doesnt.

I think the B7 at 414hp is stretched to its limit and the conditions have to be almost lab type to achieve them.

[VARSITY]

Alledgedly Audi's own RS4 experience cars, after they stopped them from blowing themselves to pieces, only produce between 360 and 380bhp.

Funny that!!!

Its amazing what you hear when you open your ears.

[t_urbo]

Alledgedly Audi's own RS4 experience cars, after they stopped them from blowing themselves to pieces, only produce between 360 and 380bhp.

Funny that!!!

Its amazing what you hear when you open your ears.

Problem is at £ 50-55,000 no one likes to hear.

It seems every B7 on the RR is falling short of the claimed figures yet people still want to believe theirs is pushing the full 414hp.

This topic will not go away and i think as time goes on more and more people are going to want to RR their cars to see if they are making the claimed, or rather to see how short their's are of the claimed!

[mrdeli]

Well i'm gonna cause a right sink with Audi UK if my car doesn't give out the advertised outputs (or near to). I spent a long time reading the hard backed brochure before I committed to the car - i'll be furious if it turns out i've been reading nonsence! Saturday will be very interesting. My brothers car will be dyno'd to, so it will be interesting to see if there is any differnce between the two under the same test conditions.

[sykotoy]

mine just got 227kW @ rear wheels..........Calculators please?

[audijohn]

mine just got 227kW @ rear wheels..........Calculators please?

Answer 304.41196 HP.................... well down.

[audijohn]

Oh i see - so I guess the figures can be easily massaged depending on what criteria you use for the drivetrain losses.

Is 20% drivetrain loss about right for the RS4 then????

Surely power at wheels is the only figure that actually means anything meaningful?

The dyno (most of them)calculate the losses itself and a good dyno will be near enough to what it should be.

Its common that Dynos overstate the power output by a small amout but with the RS4 it seems that all of them are showing low figures.

It does seem that the RS4 B7 engine just does not produce the claimed figures of 414hp/420bhp.

Surely 414BHP - 20% = 331bhp @ the wheels no?.

[audijohn]

I am going back in two weeks time, my mapped car running V-power only managed 323 bhp!

If this was @ the wheels, IMO it's not far short, 331BHP @the wheels = 414bhp claimed.

[mrdeli]

Agreed - just not sure whether the 20% is an actual recognised loss for the drivetrain or a casual figure banded about.?

[audijohn]

Agreed - just not sure whether the 20% is an actual recognised loss for the drivetrain or a casual figure banded about.?

From what I have read on the subject, BHP Trans losses are not "exact" to a specific model (car), as every car has different wear on components which make up the trans, some evo's have been measured 20% loss and others 24%, same cars and BHP (supposed) engines just different levels of "Losses".
On race gearboxs it depends on the "Cut" of the gears as to how much trans losses are generated, if you want to be technical, if you up the BHP of the engine it "May" stress bearing/shafts/gears ect and cause "More" losses rather than "overcome" them!! confused.................... me too.