RS246.com Forum :: The World's #1 Audi R, S and RS Enthusiast Community

I have spoken at some length with Audi in Germany about the lack of power from a STANDARD B7, they have asked me to send the dyno plot from my car to them, but I think and hope that if we send as many as possible it might make them actually do something about this. If you have a dyno plot from you car please send me a pm and I will get you my email so we can send them in bulk, on the dyno plot it would help if your chassis number was on it somewhere. It seams that the average power form a standard B7 is around 370bhp, not what we expected when we ordered/purchased these cars.
Let me know.
Mike.

I know what your saying dude, but can you give us more of a heads up as I'm a little bit clueless!

I do agree that the 415bhp does not feel like 415bhp, but i think its been mentioned here a lot, something to do with the 4WD system etc etc, I will be interested to read/hear about the out come of this!

For anyone interested in this and who do not have a plot for there car, I have spoken to Kim Collins from QST and below is his reply;
If any RS246 people want to come down with there RS4 B7's for this case I'll offer them a special price of £60.00+VAT instead of our usual £90.00+VAT for 2 dyno runs as long as we have 5 or more cars.
Please contact him directly if this is of any help or interest. Or anyone else you know who has a dyno

MikeD wrote:It seams that the average power form a standard B7 is around 370bhp, not what we expected when we ordered/purchased these cars.

Sounds like the cars made by a "sports car" manufacturer I used to work for. The press cars were all specially prepared so not only did they meet the claimed figures but usually exceeded them by quite a large margin. Customer cars were a different story ...

PetrolDave wrote: The press cars were all specially prepared so not only did they meet the claimed figures but usually exceeded them by quite a large margin.

I would love mine to be part of that group....

This will be interesting....

I'll volunteer my car...enroute to JD Engineering for a remap...which they ought to pay for if I get anything less than 414bhp - 5%!

Mike, as you probably already know, the 414/420hp figure is quoted in PS or, metric hp. This means that it's taken at the flywheel, rather than at the wheels. AWD systems in general can absorb between 20%-30% in drivetrain loss, which means that one could reasonably expect to see around 330hp at the wheels, assuming the Quattro system is at the efficient end of that range. (Whether it is or not I have no idea).

As an aside, some years ago while touring Porsche at Zuffenhausen we were escorted past the engine test cells where all engines were tested prior to fitment. When I asked why some engines were being stripped down close by I was told that they had been found to develop too much power! Besides checking that all functions were ok, the purpose of the run-ups were to check that each engine developed exactly the specified amount of power. No more, no less. Apparently, with the USA being a large export market, the lawyers insisted. In these increasingly litigious times I feel sure that Audi check each RS4 unit the same way.

I'd certainly be interested to hear Audi's response to your dyno plots!

Nib,

I suggest you check http://www.rs246.com/index.php?name=PNp ... ic&t=65055...

The "Audi takes car back because its under-powered" precedent has already been set....

First answer from Audi was;
1) The air box in an RS4 has an extra flap in it that will open at times of high demand and when the car is on a dyno there is not enough cold air flow so the motor will breath warm air and therefore be down on power, What if you live south of the boarder?
2) The AWD system in the RS4 will detect that there is a difference in speed from the front to rear wheels and therefore the system will cut power down.

I doubt that anybody who has spent the money to buy and install a dyno was born LAST NIGHT. I could be wrong but..........

@ Nib = Even if we allow for loss in the drive train and back calculate flywheel Bhp, still short on the numbers. Anyway we will see, any and all dyno plots could help

How about one run for £35, do you really need two runs ??

To be honest, despite what has been said on here, why not hire a Racelogic box and test 0-100 times..

We all know the weight of the cars ..

Funny mine was an ex press car and dynoed against another RS4 20kw more at the wheels. Mind you do a rough guestimate with a 30% drivetrain loss It would show around the correct rated horsepower.

MikeD wrote:First answer from Audi was;
1) The air box in an RS4 has an extra flap in it that will open at times of high demand and when the car is on a dyno there is not enough cold air flow so the motor will breath warm air and therefore be down on power, What if you live south of the boarder?
2) The AWD system in the RS4 will detect that there is a difference in speed from the front to rear wheels and therefore the system will cut power down.

I doubt that anybody who has spent the money to buy and install a dyno was born LAST NIGHT. I could be wrong but..........

@ Nib = Even if we allow for loss in the drive train and back calculate flywheel Bhp, still short on the numbers. Anyway we will see, any and all dyno plots could help

Mike, what they are saying is probably correct.
JD Eng dyno runs always show that a luke warm engine develops more power than a hot engine and it is a fact that unless you have F1 type wind tunnels no dyno fan will ever produce the same air flow as a car travelling at high speed.
This is why the DMS dyno day was in my opinion a joke, S4INT's car produced its highest output after it had been on the rollers for HOURS and after 10's of runs.
In perfect conditions the RS4 engine will just about produce the stated output. As for Simple's car claim, well how much do we really know about what went on there? Not alot!

Rule of thumb add or subtract 10% off a chassis dyno results. Lots of things can vary the result.

Mike, feel free to use my dyno plots taken from the following thread which I posted a while back. P_G's plots are in the thread as well:

http://www.rs246.com/index.php?name=PNp ... t=rs4+dyno

My flywheel power was calculated using a 22% transmission loss. Others use more, some use less in terms of percentage of loss. For example, if we used a 25% transmission loss, my car's flywheel figure would have been 411bhp. If we used 30%, flywheel power would be 439bhp...and so on. What matters, in my opinion, is power at the wheels...which was shown to be 308 bhp...which is about right for a car claiming to have 400bhp+

For what its worth, I don't believe there is a general issue with underpowered RS4s. I think the cars are being dynoed incorrectly by dyno operators who don't know what they're doing (using incorrect dyno modes), with very substandard cooling. In addition, everyone seems to focus on flywheel figures whilst using different transmission loss calculations. All this just makes the results impossible to compare. Because noone will be able to go through the hassle of using an engine dyno, at best what you want is cars dynoed in similar conditions, in the same mode, by the same operator/dyno and to compare power AT THE WHEELS.

Lastly, heat makes a huge difference to the results as per my 4th graph.

Good luck.

Alex

shall we make a air conditioned wind tunnel then, this will solve a lot of arguments lol