Dyno Bullshit!!

[P_G]

As said Jim it is a factor even if it were 5bhp, 50 bhp or 0.5 bhp. IIRC your car was pretty cool when it went on its first run or so I was told on the day, so Rob's second run was more interesting if this were the case. Factor into the temperature equation ambient as well which no one would have been able to control given you had 20 RS4's on the rollers in short succession it all adds up.

[Contigo]

Heatsoak I'd imagine is far more of a factor on forced induction system that rely more on cooled air.

[RI_RS4]

using the same calculator with 4200 and 108 yeilds 413 HP...

sounds like you found your problem, the intake flap..
dosn't that set a check light or code?

for reference mine comes up with 370 HP using 4220 and 104

The Intake Flap is not the problem. It is the symptom. The Bosch ECU is a load control system, and measures torque quite accuracy. (several of us have found that the torque, which is passed on to the traction control system, correlates to what is seen on the dyno. If the "power hump" between 5000 and 6000 rpm, when the flap opens, occurs on the dyno, it also occurs in VAGCOM torque log.)

You'll find that whenever the flap does not open under full throttle at 5000 rpm, the torque curve is down, and timing in one or both banks has been retarded. The problem is that something is causing the ECU to <beep> timing, which reduces the measured torque output of the engine, which keeps the ECU from opening the power flap ... because the extra air mass is not needed.

[Oli]

But the flap can seize in operation, so could well be the problem, and this has been found on a few cars......

[W8PMC]

Dunno how much it was down, how do we prove it as you simply rubbish dyno's! It's bullshit apparently. I'm talking real world driving after having had other cars to compare and in the real world it didn't feel like a 420bhp car.

Well i must just be very lucky then & 75% of other RS4 owners are very unlucky, as my car is every bit a 400+BHP motor & proves to be every time i drive it.

I've in no way rubbished dynos, just made the point that they do not give a genuine reflection of a cars true power & the plots should be seen as at best indicators if wild claims either way are seen (very high or very low) & of course for pissing contests.

I will one day stick my RS4 on a dyno out of idle curiosity, but i certainly would not react to whatever the Plot stated.

A simple test would be to take evey car that attended this event across to another DD RR & see what outputs are pulled. I guarantee you the orders & outputs would differ by a margin enough to substantiate my points regarding RR's. They do have their uses, but as an accurate measuring tool of power they're not as too much is based on human input & transmission loss formula, plus alterations in ambient temp & if true perhaps also tyre pressure.

I've also heard many times that Quattro cars are the hardest to get right due to their drivetrain set-up.

[ArthurPE]

The Intake Flap is not the problem. It is the symptom. The Bosch ECU is a load control system, and measures torque quite accuracy. (several of us have found that the torque, which is passed on to the traction control system, correlates to what is seen on the dyno. If the "power hump" between 5000 and 6000 rpm, when the flap opens, occurs on the dyno, it also occurs in VAGCOM torque log.)

You'll find that whenever the flap does not open under full throttle at 5000 rpm, the torque curve is down, and timing in one or both banks has been retarded. The problem is that something is causing the ECU to <beep> timing, which reduces the measured torque output of the engine, which keeps the ECU from opening the power flap ... because the extra air mass is not needed.

are you saying the flap is controlled by engine load not rpm?

how does it measure torque? rpm and throttle position? fuel flow?
accelerometer, strain gauge, etc?

the intro doc text does state rpm AND load...

honestly, that thing may be more of a gimmick and for sound than function...does the flap open with the Sport button?

my guess is at 50+ mph there is always positive pressure on the airbox, meaning the engine is never starved...

[S2tuner]

The ECU does NOT measure torque, it only calculates it...

[SR71]

Mihnea,

Bit of thread creep but I'm sure this torque sensing is what makes the car such a bitch to launch...

If you release the clutch aggressively, the car seems to modulate the clutch position by itself such that revs will drop and rise without one even touching the clutch pedal again....

Its infuriating...even if it is trying to save my clutch...

Could that be the case?

[RI_RS4]

I believe the torque that the ECU reports is based on all of the data it receives from it's sensors (MAF, O2, humidity, relative pressure ... etc), and was correlated to dyno runs during engine development. Since the load reported is passed to the traction control system, it has been adjusted for engine and transmission parasitic losses. The documents I've seen are not clear on whether it has been corrected for driveline losses.

The flap is actuated by an open loop control system, that has no feedback, except to detect that the vacuum solenoid has faulted. Inputs to the actuation signal are load, rpm and vehicle speed.

If you look at an RS4 factor dyno plot you will see a well-defined "bump" as the engine transitions from 5000 rpm to 6000 rpm. This is the point at which the power flap is opened, the throttle body is full open, and the short manifold runner flap is open, giving the intake slight positive boost. When everything is working as it should, you can feel the kick in the seat of your pants, especially on days with low ambient temperature. At the same time, timing logs will show little if any timing <beep>.

When the engine is not working at it's full potential, you will not feel as strong a kick, the intake power flap will not open, timing logs will show a significant amount of timing <beep>, and the torque/power hump will be depressed. I've measured this on a mustang chassis dyno and somewhere around 4400 RPM the torque curve starts to go south as timing is being pulled. Others have seen the same thing occur. When it happens, measured peak torque at the wheels is down by 16 lb-ft, and measured peak HP is down by 18 HP.

Interestingly enough, when I had Milltek non-res exhaust and downpipes installed, there was a 15 to 20 lb-ft torque increase between 3000 and 4500 rpm. By 5000 rpm that torque advantage was gone, because so much timing was being pulled above 4500 rpm.

[Gazzer68]

Okay weighed the car today.....4180lbs with me in it !
Just under 1/2 tank of fuel

So calculate horsepower
13.3 1/4 mile time
104 trap speed
4180lbs
= 359.07 hp

[Julesm]

Interesting thread.

There does appear to be a variance among the B7 RS4's. I ran against 3 at one of the previous Vmax events, one was std and we were neck and neck all the way, the other 2 were tuned / exhaust one of them being W8PMC and was definitely quicker. However this doesn't explain what sort of power the respective cars were/are running. I think the std one ran about 165mph to the tuned cars 172mph, which is a fair gap.

I was at VMax on Sunday and ran a Vmax of 167mph, my previous runs were 154mph due to the limiter being in place. Interestingly an R8 turned up (via Ecurie) and managed a best of 162mph?!!? Not sure how hard he was trying but again it's triggered the question are these engines underpowered?

One of the replies on PH is from a well known Dyno Tester / Owner who states that he has seen a variance from 330-390bhp and that the cars suffer from clogged valves, plus that cleaning the intake system can have a very positive effect, as well as de-catting and remap (MRC etc).

Jules.

ps my car is a BMW so not comparable.

[SR71]

Gazzer,

How many runs have you done to suggest 13.3 is about as quick as the car is going to go?

I refer you to what SilverRS4 wrote:

At 8,000 miles, the buildup on my valves was approximately 70% of what you see on the 2.0TFSI photo. After the dealer cleaned my valves, my mass airflow improved upwards of 10% (you've referred to that graph yourself PetrolDave!) and my 1/4 mile trap speed increased 4 mph. So I believe crudded up valves does impact performance.

That'd bring your car back up to ~400hp.

[Gazzer68]

Gazzer,

How many runs have you done to suggest 13.3 is about as quick as the car is going to go?

I refer you to what SilverRS4 wrote:

At 8,000 miles, the buildup on my valves was approximately 70% of what you see on the 2.0TFSI photo. After the dealer cleaned my valves, my mass airflow improved upwards of 10% (you've referred to that graph yourself PetrolDave!) and my 1/4 mile trap speed increased 4 mph. So I believe crudded up valves does impact performance.

That'd bring your car back up to ~400hp.

Best out of 3 so far, but it's difficult to get a good start.
My cars at 34k, so the valve build up may be immense !
How do i get audi to look at it though?

[Oli]

That is the million dollar question.......

[ArthurPE]

if you are not getting a good launch, use only trap speed...using the 3 best calculators and 104/4200
376
369
388
avg 377

using 414/4200 to estimate et/trap speed, same calculators
13.4/107
12.6/108 (flyer)
13.6/106
avg 13.2/107
tossing the flyer: 13.5/106.5

same for HP from ET of 13.3/4200 lbs
421
353 (flyer)
440
avg 405...
tossing the flyer: 430 HP

I would say your car is making 400+ crank HP