My RS4 dyno numbers...

[ArthurPE]

Day 3 - 11:40 AM update
I've been out with the car a couple times now.

I was a little skeptical at first. Drove the car back to work from the dealership and still didn't feel the 6K+ power I was hoping for. Only the valves were cleaned for carbon. No vacuum leak or flap issues were found.
Major thing noticed was ease of rev-matching on down shifts. Definitely less effort to "blip" the throttle.

Took the car out last night. Started to feel a bit better. WOT seemed to pull pretty hard through the range. Wondering if the computer had to adapt to the less restricted air flow?

I have another dyno appointment scheduled for next Thursday (a week from today). Obviously hoping to see improved numbers, along with a change in the charts from 6K+.

Side notes -
1. A little disappointed "after cleaning" photos weren't taken. I tried calling mid-clean to gather some details. I didn't hear back from them until the car was "done".
2. SA said levels of carbon buildup wasn't "that bad". Pictures look pretty nasty to me. Thoughts?!

honestly imo, not that bad...

if the dyno is accurate and repeatable, I'd be surprised if you saw a difference...
have you timed the car 3k to 8k 3rd gear?

[RS4Jay]

It looks bad enough that I would want it cleaned, but probably not bad enough to cause much of a performance degradation. I too will be surprised if you see more than a few percent difference on the dyno.

[zzzzzeke]

have you timed the car 3k to 8k 3rd gear?

I haven't yet (and actually I've never used the timer before).
I'll try and do a few runs tonight.

[silverRS4]

I see the dealer logged the actual torque, (like you can with Vagcom) and got a peak of 382 Nm after the clean. Its true, the advertised peak torque is 430 Nm, and I can log that repeatably in my car with 92 octane fuel....but only when its colder than 40F. In "normal" 70-80F temps at 985 millibar of atmospheric pressure (roughly 1000 ft above sea level), you would be hard pressed to break 400 Nm with an RS4 with 92 octane and I think 385-390 would be the norm. So as much as it sucks, your car is performing like most RS4's do in warmer temps. There is nothing wrong with it besides the fact that 5 months out of the year for an RS4 in Minnesota, it makes no where near 420 corrected hp. I highly doubt the dealer logged torque all the way up to 7800 rpm, but if they did, I'd bet the actual torque was 325 Nm or less, which equates to about 355 engine Hp. Your follow-up dyno pull will probably show some improvement, but the shape of the curve probably hasn't changed a whole lot. In 30-40F temps, an RS4 will trap over 111mph easily. In 70-80F temps its more like 107-108mph. That's just the way it is I'm afraid. I still love the car though.

[zzzzzeke]

The SA said they saw 388 Nm, but couldn't capture the screen in time.
Thanks for the info silverRS4.

[RS4Jay]

silverRS4 - What you are describing is common with all engines, especially high compression engines (or forced induction). There has been significant power differences between cool/dry weather and hot/humid weather (dyno, drag strip, and butt) in every car performance oriented car I've owned.

[ArthurPE]

the ecu torque is not the actual measured torque...it's a calculated value...of dubious accuracy
afaik there is no torque sensor in the car
now as to the algorithm, who knows: probably air temp, intake temp, throttle position, timing, vacuum, rpm (for vol eff) etc.

T = Pme x V/4Pi
Pme ~ mean effective cyclinder pressure ~ comp ratio x vol eff
V = displacement
4 = number after 3 and before 5 :D (2 for a 2 stroke)
Pi = Circumference/Diameter = I prefer warmed apple with a scoop of ice cream = 3.141596....

[Most-Wanted]

If you lower it on Stasis Coilovers it will feel much faster:) LOL... Inside joke...

Glad they did some cleaning for you.

[silverRS4]

silverRS4 - What you are describing is common with all engines, especially high compression engines (or forced induction). There has been significant power differences between cool/dry weather and hot/humid weather (dyno, drag strip, and butt) in every car performance oriented car I've owned.

The effect of variable inlet air density (due to temp, humidity, barometric pressure) is no mystery to me. The RS4 is no different from any other vehicle in this regard as you've pointed out. I've been in dyno rooms with OEM engines on engine stands and they typically make advertised HP without any fuss. Somewhere I read (Arthur, you'll know) that the acceptable variation from advertised is 10%, which means and RS4 could be putting out as little as 378 corrected hp and still be 'ok'. I'd bet a fair chunk of change that if you stuck a random RS4 engine on a stand at 990 mb of inlet air pressure and 70F temperature that it would just that...about 380 corrected. Now if the engine room was at 30F and the numbers were uncorrected, then its a whole different story. Fact: in cool temps, the B7 RS4 is an asphalt-ripping machine. In 70-80F temps, its just a fast car. In 90-100 temps with California 91 octane, its a huge waste of money. I'm just glad I live in the upper midwest. My next post should shed light.

[silverRS4]

So here are some plots showing the difference that cool temps have on the RS4, as well as the relative accuracy of logging Vagcom actual torque for the purpose of identifying particular trends. THE KEY THING TO REMEBER, is that its not just increased inlet air density that improves the RS4's power output. It is extremely knock sensitive and cooler inlet air temps all but eliminate the knock correction seen at higher ambient temps. The car that generated these plots (mine) is completely healthy with relatively clean valves and operative flaps. Yet during the dyno pull, the torque nose-dives after 5500 rpm and the horsepower curve (not shown) is relatively flat from 6000 rpm upward (yet peaking at 7250). Doesn't appear to be all that good. But then I take the car out into the January air, data-log much better numbers and can pull off a 112mph trap in the quarter with a granny launch (again, using Vagcom, but using its acceleration test feature, not data-logging). I will say it again...that's just the way the car is.

[Ill 3.0]

Fantastic information

I will say it again...that's just the way the car is.

Presumably the 12.5:1 compression and the OEM tuning necessary to achieve 100bhp/L are largely responsible?

[silverRS4]

I would say that has alot to do with it. Its twin-ECU set up , full-time lambda control make it a very effective and accurate air pump. Its perfectly capable of generating incredible power with cold dense air, but will obviously suffer when the air density is crap and the engine load gets nowhere near 100%. For instance, the engine load% during the dyno pull peaked at 89% while during the highway data-log a few days later in the cold air it was 95%. Lets not forget I'm at an elevation (1480 ft) where my inlet barometric pressure never gets above 975 mb. What I wouldn't give to drive my RS4 on a cool day at sea-level. This is one reason why all of the RS246 guys in England can't seem to figure out why American RS4's are so 'slow', not to mention they consistently use 98 RON (93 octane US). I've seen numerous data logs from UK RS4's and their ignition timing is far more consistent than ours. At full throttle with their 98 RON, their timing had no knock correction and is a very steady 33.5 (IIRC) while my timing with 93 octane my reach 33.5, it is sporadic and still knock corrected.

[Tweety-s-]

Very interesting Silver.... thanks for sharing.

[WinterRunner]

Thank you again Silver, that is great info.

Quick Q though, theoretically if we use 93 octane (98 RON), and are at sea level, then we (USA) should be just as fast and have the same degree of knock correction as the lads over the pond. Or am I not understanding something?

[ArthurPE]

the acceptable variation is 2.5% for type rating and 5% for production rating...
to make sure no engine is out side this boundry you would need to shoot for >rating (maybe +1%) or so, so if you did loose 5% you'ld still be in tolerance
having said this the average engine will make rated power...some a bit more, some a bit less, but with todays tolerances, probably spot on...or least as accurate as it can be measured...
the engine is also run at iirc 70F, 40%, 1000 mb (0' ASL), controlled, no correction factor allowed....
so if you are at 80F, 50%, 990 mb, 1000' ASL, yes, you will make less power...

I would be surprised if the torque 'measurement' is within +/- 10%

[silverRS4]

Quick Q though, theoretically if we use 93 octane (98 RON), and are at sea level, then we (USA) should be just as fast and have the same degree of knock correction as the lads over the pond. Or am I not understanding something?

Well then USA cars probably are as fast and the comparison is reaching the splitting hairs region. But I always found it curious that their data logs consistently show very little retardation, if any at all, even at high engine loads. To match their actual ignition timing levels (lack of retardation), I have to have 93 octane with IAT temps about 30 degrees cooler than theirs (for example 30F versus 60F), or I have to blend in race fuel up to about 95 octane to achieve their ignition levels at the same IAT. I really don't have a good explanation.

[WinterRunner]

That's very curious indeed. Would it be safe to say they have a slightly different ECU setup? It gets quite hot in England in the summer, not as bad as New England(where I reside), so I really do find it interesting that we (America) need an extra cold charge of -30 degrees to achieve the same results....... I would think that if you took 2 cars, one euro, one US, same temp out, same air density/humidity/sea level that they in theory should make the exact same numbers, unless in fact they do have different ECU tuning.

[zzzzzeke]

Back from the dyno. Reclaimed 21.6HP.

[zzzzzeke]

and here is Shootout mode - 24.8 HP gain

[silverRS4]

That looks better. How are the cold starts? Too bad actual ignition timing wasn't logged before and after as I'm pretty sure that's where most of the improvement was from. The mechanism of just how all the carbon particles effects idle, cold starts and ignition timing is difficult to comprehend, but it does. The people that have cleaned the valves themselves can testify that there are some large chunks that flake off easily. Thanks for taking the time to post the comparison.

[Espen W]

and here is Shootout mode - 24.8 HP gain

Looks like a nice and solid gain from cleaning the valves and intake. While some carbon buildup can actually be beneficial, if it gets excessive, it will cost power. Same reason why one sees gains from things like smaller diameter valve stems / undercut valve stems, multiangle valve jobs, etc. In really bad cases, it can prevent the valves from closing completely, reducing compression.
Did they do anything else than cleaning, like update the software?

[Espen W]

Quickest way to evaluate gains from valve cleaning and other changes is to log channel 120 with Vagcom, just make sure altitude/baro/humidity and temp are similar for both tests. Just a calculated value, but will yield values very close to claimed factory numbers and repeatability seems excellent

Quattro GmbH has issued the following guidelines for evaulating RS4 engine power via acceleration tests. Needless to say, must be measured with vbox/pbox or accurate accelerometer:

In gear acceleration from 60km/h in 4th:
080km/h 2,4sek.
100km/h 4,7sek.
120km/h 7,1sek.
140km/h 9,6sek.
160km/h 12,1sek.



Beschleunigung ab 60km/h im 5. Gang bis
080km/h 3,4sek.
100km/h 6,4sek.

120km/h 9,4sek.

140km/h 12,7sek.

160km/h 16,1sek.



Beschleunigung ab 60km/h im 6. Gang bis

080km/h 4,2sek.

100km/h 8,1sek.

120km/h 11,8sek.

140km/h 15,7sek.

160km/h 19,9sek.



Optimale Beschleunigung von 0km/h bis (in Klammern die von mir ermittelten Werte mit Winterreifen und Schlupf bei nass-rutschiger Fahrbahn)

040km/h 1,4sek. (2,0sek. / +0,6)

060km/h 2,3sek. (2,9sek. / +0,6)

080km/h 3,5sek. (4,4sek. / +0,9)

100km/h 4,8sek. (5,9sek. / +1,1)

120km/h 6,4sek. (8,0sek. / +1,6)

140km/h 8,3sek. (10,2sek./+2,1)

160km/h 10,7sek.

180km/h 13,5sek.

[Espen W]

Very interesting graph. The torque values from block 120 are surprisingly accurate, but only with stock software. Little doubt that the Dynojet shows more than real road hp, especially below 6K rpm, after that the rolling lossed add up.
Of course very easy to generate power cuves as well:
http://www.s2forum.com/forum/showthr...ight=block+120
On the VAG turbo engines, block 120 values will usually be well above factory numbers. For example, I have logged 260nm peak and 250nm steady on the BFB 1.8T that is rated at 225nm. This most likely has to do with how the dyno test is performed when establishing factory numbers vs. real power on the road, rather than the engines being underrated.

[ArthurPE]

this is very useful information, thanks

so in 4th 60-160 km/h (~36 to 100) should take 12.1 sec, with speedo error figure 39-40 to 105-106 mph

Quickest way to evaluate gains from valve cleaning and other changes is to log channel 120 with Vagcom, just make sure altitude/baro/humidity and temp are similar for both tests. Just a calculated value, but will yield values very close to claimed factory numbers and repeatability seems excellent

Quattro GmbH has issued the following guidelines for evaulating RS4 engine power via acceleration tests. Needless to say, must be measured with vbox/pbox or accurate accelerometer:

In gear acceleration from 60km/h in 4th:
080km/h 2,4sek.
100km/h 4,7sek.
120km/h 7,1sek.
140km/h 9,6sek.
160km/h 12,1sek.



Beschleunigung ab 60km/h im 5. Gang bis
080km/h 3,4sek.
100km/h 6,4sek.

120km/h 9,4sek.

140km/h 12,7sek.

160km/h 16,1sek.



Beschleunigung ab 60km/h im 6. Gang bis

080km/h 4,2sek.

100km/h 8,1sek.

120km/h 11,8sek.

140km/h 15,7sek.

160km/h 19,9sek.



Optimale Beschleunigung von 0km/h bis (in Klammern die von mir ermittelten Werte mit Winterreifen und Schlupf bei nass-rutschiger Fahrbahn)

040km/h 1,4sek. (2,0sek. / +0,6)

060km/h 2,3sek. (2,9sek. / +0,6)

080km/h 3,5sek. (4,4sek. / +0,9)

100km/h 4,8sek. (5,9sek. / +1,1)

120km/h 6,4sek. (8,0sek. / +1,6)

140km/h 8,3sek. (10,2sek./+2,1)

160km/h 10,7sek.

180km/h 13,5sek.

[ArthurPE]

I do find it amusing after all the hoopla Audi comes down to evaluating absolute performace by using an in gear accel test
what other dimwit has been proposing that? ;) too bad they didn't do it in 3rd, lol

[Espen W]

That should be pretty close. One thing to keep in mind is needle lag on the speedo, in addition to the speedo error, so I would recommend a GPS or accelerometer based timing system.
Lots of folks are having great results with the Racechrono software., using an old Nokia phone and a $50 GPS receiver: http://www.racechrono.com/
Supposed to yield numbers practically identical to the Racelogic Pbox for a lot less money.
It is possible to log speed with Vagcom too (the $12 Ebay cables will do this), but from my experience, the speed signal is less than accurate, as it depends on a preprogrammed rolling diameter, etc. Might be OK with the stock tires.

[Espen W]

I have seen references for the above acceleration tests dating back to 2007, so Quattro has been aware of the issue for a while, but probably wanting to keep things quiet.
The prescribed numbers match test data from mags like Sport Auto (but note that they test two up with a full tank of gas). I have seen G-Tech and Pbox data from well running RS4's and they also match the Quattro acceleration numbers, so the test should be quite valid.
The RS4 power issue is a mystery, really, but I suspect it has at least something to do with the 60:40 split messing up results on the dyno. A healthy B7 RS4 will stay next to a E90 M3 to high speed, despite the M3 being more than 200lbs lighter and 2wd

[ArthurPE]

that is exactly what I think also...the diffs, electronics, etc., see slightly differently wheels speeds, etc., and reduce torque/timing, whatever...

the 5th gear test 40 to 105 mph should take ~16 sec, so if it's anywhere near there, especially with an OAT of 95F, I'll be happy...I'm looking for order of magnitude 1 sec or less, not precision, 1/10th's...
I'll do <40 and 105+, ie, needle before 40 and after 105, this way I'll have the worse case, eg, longest time...
and with the time being so long, 16 sec, a small delay with timer operation isn't going to be significant, an in reality, only make the times longer, not shorter
my car is running like a champ, 35k miles, never cleaned...pulls like a train
I do wish they had some 3rd gear numbers, but since they are close to the magazine published results for 4/5/6, I'm guessing the 3rd gear stuff I have is close for 3rd gear 3k to 8k (36 to 96mph) of ~8.5 sec

I have seen references for the above acceleration tests dating back to 2007, so Quattro has been aware of the issue for a while, but probably wanting to keep things quiet.
The prescribed numbers match test data from mags like Sport Auto (but note that they test two up with a full tank of gas). I have seen G-Tech and Pbox data from well running RS4's and they also match the Quattro acceleration numbers, so the test should be quite valid.
The RS4 power issue is a mystery, really, but I suspect it has at least something to do with the 60:40 split messing up results on the dyno. A healthy B7 RS4 will stay next to a E90 M3 to high speed, despite the M3 being more than 200lbs lighter.

[Espen W]

Should be possible to find a suitable 3rd gear test interval from the 0-180km/h test.
At what rpm does the rev limiter kick in?
I assume that one would shift into 3rd before 120km/h (74.5mph), and one should be able to reach 160km/h (99.5mph) in 3rd.
Prescribed time from 74.5-99.5 (75-100) is 4.3s.
120-140km/h in 1.9s and 140-160km/h in 2.4s

[Ill 3.0]

that is exactly what I think also...the diffs, electronics, etc., see slightly differently wheels speeds, etc., and reduce torque/timing, whatever...

According to 034, the mechanical center diff split should not affect the dyno results, but I've never seen an explanation one way or the other. Too bad there isn't a center diff available with a 50:50 split that could bolt up easily to test. Not clear to me how the car would behave differently on rollers than the street to alter the car ECU calibrations. Assuming of course the front and rear rollers are locked and cannot move independently, which may not be true. I'd be really curious to find this out and if there is a way to record the roller speeds separately front and rear.

[ArthurPE]

According to 034, the mechanical center diff split should not affect the dyno results, but I've never seen an explanation one way or the other. Too bad there isn't a center diff available with a 50:50 split that could bolt up easily to test. Not clear to me how the car would behave differently on rollers than the street to alter the car ECU calibrations. Assuming of course the front and rear rollers are locked and cannot move independently, which may not be true. I'd be really curious to find this out and if there is a way to record the roller speeds separately front and rear.

on the street the surface is continuous/connected
the rollers could be at different speeds

I've seen dyno's same dyno, one car 250 HP, the other 330 HP, yet their in gear times are identical, sometimes the 250 car is faster...

[ArthurPE]

Should be possible to find a suitable 3rd gear test interval from the 0-180km/h test.
At what rpm does the rev limiter kick in?
I assume that one would shift into 3rd before 120km/h (74.5mph), and one should be able to reach 160km/h (99.5mph) in 3rd.
Prescribed time from 74.5-99.5 (75-100) is 4.3s.
120-140km/h in 1.9s and 140-160km/h in 2.4s

I've got several reference that put 3k-8k at ~8.5 sec
I've got a bunch that put the same speed interval (36 to 96 mph) using all gears at 8 flat...
I'm guessing the 8.5 is a good number...

I've also got >50 cars and >100 runs logged, and the avg is, you guessed it, ~8.5 sec when adjusted for temp and load (passenger, etc.)
I've never seen a car > 9 sec other than one running in 120F+ temps, and yet his avg was still only 8.8 or so...when corrected...<8.5 sec...
and the difference between cleaned/uncleaned deposits is indiscernable...

[Ill 3.0]

on the street the surface is continuous/connected
the rollers could be at different speeds

Right, hence my comment about is there a way to measure the individual roller speeds, via existing dyno software or other. Further, are some AWD dynos setup to have independently moving roller front and rear, while others may have rollers which cannot move independently. This might be illuminating.

[koolade9]

Right, hence my comment about is there a way to measure the individual roller speeds, via existing dyno software or other. Further, are some AWD dynos setup to have independently moving roller front and rear, while others may have rollers which cannot move independently. This might be illuminating.

I recall this being an issue with dynoing e46 M3s (perhaps Arthur can speak to that) where the car needed to be on an awd dyno and have the front/rear rollers connected so all 4 wheels could rotate at the same speed. I know gmg's dyno cell is setup like that... I think dynopacks would be the offender in this scenario...

[ArthurPE]

I recall this being an issue with dynoing e46 M3s (perhaps Arthur can speak to that) where the car needed to be on an awd dyno and have the front/rear rollers connected so all 4 wheels could rotate at the same speed. I know gmg's dyno cell is setup like that... I think dynopacks would be the offender in this scenario...

iirc that is correct...the earlier cars could have the systems (ASC, etc.) disabled by holding the off button longer, so they could be dyno'ed, otherwise the cut torque or went into limp mode
the later cars could not...so dyno'ing them was a bit more complicated...

does the RS4 ECU have a parameter that can be set for a 'dyno mode'?

[koolade9]

does the RS4 ECU have a parameter that can be set for a 'dyno mode'?

and that could be the $100k question...

[ArthurPE]

just did some runs:
3/4 tank fuel

3 in 5th, 37 to 100 (indicated ~40 to 105 for speedo error, I know my error, stopwatch, GPS verified)
16.7
16.3
16.9
avg 16.6
sounds like 'slow' vs the 16.1 benchmark
first, I was conservative in my timing...start early, stop late

but more significant:
OAT 92F
RH 42%
atm P 30.04 mm HG
Elev 1125' ASL

cf ~ 94.5% ... ~ 1 sec

more than content...

side note:
the revs only hit ~5500
I'll try in 4th, but 3rd would be better, takes it to redline/power peak

[silverRS4]

This (anti-decent-dyno-number-ECM-trickery theory), IMO, is a needless rabbit trail. The green line on the graph (Vagcom actual engine torque) and the red line (Dynojet torque) are fairly normal RS4 results at 70F; about 315-320 whp. The Vagcom torque plots for an ambient temp of 70-80F are all very similar to the green line. I have dozens of them. The green line is not lower than the blue line due to the blue line being logged while the car was on the road instead of a dyno. Its lower than the blue line because it had intake air temps 45F degrees higher. I have dozens of Vagcom road logs with the car making 430 Nm as well (317 ft-lb), but they were all at temps below 40F. If you could somehow feed 32F air into the engine while an RS4 was on an AWD dyno, I'm sure there wouldn't be some fuzzy logic restricting the output. You would more than likely see uncorrected numbers that support the ability of the same 3950lb car to trap 113mph in the same temps. Its like this:

70F, about 320 whp, 107mph trap, 3000-8000 rpm (3rd gear) in 8.3-8.5 sec, slightly lower than advertised power, will keep up with E92 M3 up to about 80mph
32F, about ?? whp, 113mph trap, 3000-8000 rpm (3rd gear) in 7.8-8.0 probably higher than advertised power, has no problems with E92 M3

I have lots and lots of timed data from a healthy RS4 over the course of two years to support this general trend. Due to its knock sensitivity, its incredibly fickle when it comes to ambient temps. The ECM's are not doing anything strange when the car is on a dyno. Especially when you consider that I logged several parameters while on the dyno, including ignition timing and throttle valve position, and nothing was out of order compared to doing the same log at 70F on the road.

[ArthurPE]

the engine is rated by EC standards at 20C (68F)

same day, same dyno...one car 350 (cf crank) another 400 (cf crank)
same times 3k-8k...
temperature has an influence, but there is more at play here...
I don't think it's as much timing as mass density...

[silverRS4]

Of course inlet mass density is the primary issue. Do temps that are 40 degrees cooler explain a 60+ hp difference? If so, that all it is. If not, then the decreased ignition correction seen numerous times at cooler temps is also playing a part.