A disappointing day at the drags

[JAXRS6]

Disappointing for two reasons, but first I need to set the stage.

I went to Bradenton Motorsports dragway and conditions could hardly have been better for Florida: a cool sunny day, temps in low 60s, even a tail wind of 15 mph or so. When I went there a year ago in my chipped 2000 S4, on a warmer day IIRC, I scored a 13.775 quarter -- not great but a record for me and a full .45 seconds better than I had been able to do at Moroso, another Florida track, or at Milan in Michigan; I never got below 14.2 at either of those tracks, despite multiple visits to each. But at Bradenton, I broke below 14 in the S4 on my first run -- with a missed shift! I was so surprised I even asked around to make sure the locals weren't getting unexpectedly fast times, too; they weren't. So, bottom line, I had several reasons to be optimistic today about the prospect of substantially lowering my RS6 times compared to Michigan.

It didn't happen. Eventually it got much WORSE than Michigan, where my best in the RS6 is 13.674.

I did a LITTLE better than that at first, but not much -- with runs of 13.650 and 13.604. All my best RS6 runs, MI and FL, were with ESP off, the tranny in S and about 1/3 tank of Amoco 93 octane. Best RS6 runs also included torque braking, if that's what it's called, tho the beast allows no more than 2500 rpm for that. So, QUESTION NO. 1 is: Why is the improvement with the RS6 only .07, compared to .45 for the 6-spd S4?

On my third run today at Bradenton, I accidentally left the AC on -- and ran 15.126! I can't imagine AC alone would add 1.52 seconds, but that was my time & I could feel the slowness. Who wouldn't?!

Later I kept the AC off, of course, but I still couldn't come close to breaking under 14. The best I got was 14.536 (5th run), still almost a full second slower than what I was getting less than an hour beforehand.

Obviously something went wrong. 60 ft. times for the RS6 were 2.132 on my best Michigan run (13.674), 1.990 on my best Bradenton run (13.604), then 2.019 on the 14.536 5th run at Bradenton -- so my faster 5th launch at Bradenton still resulted in almost a second slower ET compared to Michigan.

Of the six or so racers I talked to today at Bradenton, none had worsening times to compare with mine; in fact most were improving.

So, I thought of these OTHER QUESTIONS:

2. Could having the AC on under stress cause something else to fail?

3. Is it possible that my ESP switch went bad, indicating it's on when it's off -- and off when it's on? (Even if that's the case, tho, having the ESP on in Michigan cost me half a second -- not a second.)

4. Could the tranny somehow get "switched," so that I'm in S when I want D and D when I want S? (On the way home, tho, S held the engine to higher RPMs before shifting, just like it's supposed to do.)

5. Can anyone out there think of anything else that might have cause such a big performance decline?

BTW there was some fun today when a semi truck got to the line, fired up his JET engine & made noise like -- well, a jet engine accelerating at close range! It quit just before he finished. Someone said he burned 100 gallons on each run, so maybe he prepped a little too long. But he still finished under 9 seconds!

[TheBrit]

The joys of combining a turbo engine and an automatic gearbox!

Launching the RS 6 is like rolling for sixes on a dice, sometimes you get lucky and oftentimes you don't. There are so many factors that can contribute to a good or a poor performance, but at the end of the day, the RS 6 is a fast luxury car - I'm sure Pobst and Galati's RS 6s are more consistent in performance, but probably wouldn't be much fun for hauling 4 adults and luggage several hundred miles!

You might be getting slower on repeated runs due to heat soak - did the intercoolers (they are more like heat sinks actually) have sufficient chance to lose stored heat between runs? Sitting idling in a little "hotspot" of your own heat won't help. If possible, the car should be run at a steady speed with low amounts of throttle to keep airflow over the intercoolers without generating much extra turbo heat.

When you turned the AC off, did you leave it off all the time? The AC might sap power and produce extra heat in the engine bay around the heat exchanger, but the infamous "siren" fan that is linked to the AC pushes a lot of that excess heat out (too near the brakes IMHO, which don't really need the extra heat). Wouldn't leaving the AC off all the time just mean the extra engine bay heat from the runs isn't being pushed out either?

Fuel grade might also be causing problems. Regardless of octane rating, if you get a slightly contaminated tank of fuel causing detonation or knock, the ECU will retard the timing and will only advance it slowly again. Of course, muiltiple hard runs will only increase the cylinder's residual heat level and the likelyhood of detonation if the fuel is dirty, and cause the ECU to retard the timing even further.

I'm sure there's a whole load of other things that could affect the car on a particular run, day or whatever.

There's also the consideration that in frustration you may have been trying too hard to improve your times - sometimes the best performance catches you by surprise when you're not really expecting it and you find yourself thinking "She's fast today!" or something like that.

[AvusRS6]

You need a CHIP!

Sorry to hear, but I'm not surprised as the RS6 in stock form to me did not feel much faster than my Dinan5 540. The RS6 does not feel like a 450HP car to me and frankly with the Chip, I still believe that best numbers I would achieve is about high 12's. I ran with a S4 buddy of mine and believe me the RS6 isn't much faster than a chipped S4 IMO.

[Erik]

Originally posted by JAXRS6
5. Can anyone out there think of anything else that might have cause such a big performance decline?

Temperature!

Many modern turbo cars have a power limiter if the intercooler / air intake gets to varm.

I know from my own experience that standing on idle and waiting for the run can be devastating.

[andyp]

Have all the hoses checked for tightness ... the place where I got my chip said that many of the RS6's that they have worked on have had loose hoses that can cause loss of pressure. This is something that can get worse with repeated use at full boost.

[Erik]

Originally posted by andyp
Have all the hoses checked for tightness ...

There must be a reason why Champion is using something different than latex(?) hoses.

[JAXRS6]

Some make a lot of sense & I will respond accordingly.

My speeds dropped in Michigan, too, after my first run, altho I was able to come close later (11th run). To counter the heat build-up, I will drive the car between runs next time.

I've heard no knocking or anything else unusual. Please explain "detonation" and how it can be detected. (The remedy, I presume, is fuel free of contaminants; right?)

I wasn't "standing on idle" to any great extent, if by that you mean revving the engine. I did pump up to the allowed 2500 RPM just before launch, with the brake depressed, for about 1-2 seconds. Would that be enough to cause "devastating" results?

I just checked hoses & the ones I could get to were tight. I suspect there are others beneath the carbon fiber cover that I can't see, tho, so if the problem continues I may ask the dealer to take a look. Also plan to be in Pompano Beach sometime soon, so I may stop there & ask Champion about alternatives to latex that will be warranty-friendly.

One more question category: How do the car mag guys get times that are so much faster? With a 6-spd I'll grant them better talent in shifting, but with an automatic ... I just don't understand. Especially since the apparent heat build-up degrades performance with each subsequent run. Are they getting sub-13 times on the first try? Seems unlikely, don't you think? And if they are, how come I'm so much slower than them with my best (early) runs? A foot to the floor is a foot to the floor, isn't it? Granted launch is important, but even with 60' under 2 seconds for my best run, I'm still a half second or more off their mark.

And if it's so difficult to get good times, why didn't at least one of the mags mention that?

[gjg]

MTM's reinforced hoses are IMHO the best bet if you want stronger ones.

gg

[J.Moss]

Hi Jax,

A few questions:

What was your MPH? This will show if your power is well below the level expected.

How was the car shifted? Was it is "Tip" mode? At what RPM shifted? If it was in "D" some of my 2.7 Tip clients found that if you held the pedal down into the "Down-shift detent" the car held the gear longer than optimal.

Someone mentioned the sitting still and heatsoak factor. This has been an issue to some of us before. Just idling or sitting still will heat soak the IC's and take away some power.

Good luck.

Jeff

[JAXRS6]

Originally posted by J.Moss
What was your MPH? This will show if your power is well below the level expected. How was the car shifted? Was it is "Tip" mode? At what RPM shifted?

Speed at the end of my fastest run at Bradenton yesterday (13.604) was 103.43. At the end of my fastest run after the AC incident (14.536), the speed was 94.62 mph.

I kept the car in S, which, after a dozen runs one day at the dragway in Michigan, seems best. D was slower and shifting the tip "manually" twice resulted in no improvement over S.

As for RPM, I wasn't paying a lot of attention yesterday & probably should have, I guess. But now that you mention it, the shift point was around 6500 in Michigan; yesterday, the one time I looked (which I think was 2nd-to-3rd gear in the fastest run after the AC incident), it shifted around 6200-6300.

Re idling -- guess I'll try to avoid that, although a certain amount is required to wait in line for the run. It brings up a point I've been meaning to ask about, however: On another S4 forum, numerous Audiphiles recommend waiting until the oil is WARM before running the engine hard ... but at an Audi event at Moroso, some were pushing their turbo cars to keep them COOL before the run. Can anyone explain this apparent conflict of opinion?

I don't know what "down-shift detent" means.

BTW what's the line drawing on your sig?

[J.Moss]

Originally posted by JAXRS6
Speed at the end of my fastest run at Bradenton yesterday (13.604) was 103.43. At the end of my fastest run after the AC incident (14.536), the speed was 94.62 mph.

Some more information would be nice. Temperature and elavation play a role also.

Re idling -- guess I'll try to avoid that, although a certain amount is required to wait in line for the run. It brings up a point I've been meaning to ask about, however: On another S4 forum, numerous Audiphiles recommend waiting until the oil is WARM before running the engine hard ... but at an Audi event at Moroso, some were pushing their turbo cars to keep them COOL before the run. Can anyone explain this apparent conflict of opinion?

When you are idling or have run the car and shut it down the Ic's will heatsoak. IMO the engine should have a little bit of temp with cool IC's. You can try to leave the hood up between runs. This will allow the Ic's to get more ambiant air, in place of air from just the underhood.

I don't know what "down-shift detent" means.

I have not driven an RS6 yet. But every other automatic trans Audi I have driven has a normal range of accelerator travel and just after that a small detent or click at the very bottom.

BTW what's the line drawing on your sig?

Nurburgring.

Good Luck to you.

[JAXRS6]

First, thanks for all your help!

Originally posted by J.Moss
Some more information would be nice. Temperature and elavation play a role also.

Temp was in the low 60s, as mentioned in the opening post. And this being Florida, i.e. flat, elevation was probably 30 ft, give or take a few.

FYI I already raise my hood while waiting between runs. But I'm still unsure -- should I try for cool, warm or hot at launch?

[J.Moss]

Originally posted by JAXRS6
First, thanks for all your help!



Temp was in the low 60s, as mentioned in the opening post. And this being Florida, i.e. flat, elevation was probably 30 ft, give or take a few.

FYI I already raise my hood while waiting between runs. But I'm still unsure -- should I try for cool, warm or hot at launch?

Try it all ways. Have used cool many times. IMO as long as it is not cold it should be A-OK.

It is disturbing that your speed is only 103-104. I would try another time and see if they remain at that speed. We have seen 5 mph gained by changing winds.


Jeff

[Erik]

Originally posted by JAXRS6
Re idling -- guess I'll try to avoid that, although a certain amount is required to wait in line for the run. It brings up a point I've been meaning to ask about, however: On another S4 forum, numerous Audiphiles recommend waiting until the oil is WARM before running the engine hard ... but at an Audi event at Moroso, some were pushing their turbo cars to keep them COOL before the run. Can anyone explain this apparent conflict of opinion?

I guess the trick is to keep the oil warm enough not to damage the car (i.e. no cold starts) and the air/engine intake as cool as possible.

It's not easy, but you should not be on idle a very long time before the run.

I'm not sure about the RS6 but I know for a fact that the new Volvo S60R/V70R has a feature that significantly drops the power when the engine gets too much heat.

[TheBrit]

Originally posted by JAXRS6
I've heard no knocking or anything else unusual. Please explain "detonation" and how it can be detected. (The remedy, I presume, is fuel free of contaminants; right?)

You are unlikely to ever really hear knock or detonation, at least not if the ECU is doing it's job properly!

Pre-ignition occurs when the temperatures and pressures in the cylinder cause the air/fuel mix to bearn before the spark. The edges of the valve recesses in the piston crown can cause this as they get very hot under heavy engine loads.

Detonation is an explosive burn of the remaining fuel/air and exhaust gas mix after ignition, and can seriously damage an engine. Detonation causes the engine to vibrate.

The ECU has sensors that detect the characteristic vibration caused, and retard the spark timing. By retarding the timing, power is reduced.

IMHO, the ignition retarding in the RS 6 might be quite agressive, the UK model's manual states that 98 RON fuel should be used and warns that engine damage can occur with 95 RON fuel - this leads me to believe that hot-spotting may be a problem with this engine, and the only way I can think to reliably reduce the risk is to perform timing retarding quite aggressively at the first signs of abnormal burning.

Higher octane fuel is more resistant, but impurities in the fuel (which could be from manufacture, or dirty handling etc) can lead to knock or detonation that the particular octane rating of fuel shouldn't be suffering from in those conditions if it were clean. I'm not sure of the technical reasons, but I think it's something to do with (chemical?) acceleration of the combustion caused by the impurities.

Use of quality branded fuels is about the only advice I can give with regard to knock, but of course any fuel could become contaminated. Normally, the ECU takes care of it, but you will suffer a loss of power to a greater or lesser extent.

[Fast One]

HI JAXRS6,my dad ran the rs6 on the first run 13.4@105.5,next two runs 13.7.we didnt launch perfectly because we brake torqued for a few seconds and rpm dropped to about 1800.I know turbocharged cars have alot of heatsoak,so just driving to the track and running within a few minutes will cause a loss in power.If you have the time just let the car cool off before the first run.We should be going to the track soon to run the car for the first time with chip and exhaust P.S anyone that has run their car please post numbers

[andyp]

One other thing I thought of:

Most of the tuning companies recommend swapping out the diverter valves on the turbos. The OEM ones are some kind of plastic I believe so they might be susceptible to sticking and leaking boost. You might want to change yours even if you don't do any other mods.

[Graeme]

Interesting one this.
For loss of power and subsequent bad times there really can be a million answers that I'm aware of. Although the opinions raised in this forum are very valid, there really is no substitute for getting your car to a tuning outfit with a rolling road or even to an approved Audi RS dealer with the requisite Diagnosis tools.
Although the Air con will cause a loss of power through resistance caused by the operation of the mechanism, you’re not talking about a big difference. Cool air is of course more volatile because of the mass of oxygen increasing with the decrease in temperature, but at 60 degrees and an engine that isn’t practically overheating on the gauge, you should be seeing a good power level on a healthy car.
Keeping your engine cool is all well and good, but the most important thing is to keep the oil hot and at a high viscosity, otherwise you'll just be damaging your engine through increased friction.
I'd recommend taking your car to a tuning outfit or a dealer before you start throwing your money at uprated hoses or other suchlike potential wastes.
If your dealers in the US are anything like the English ones, then make sure they know what they're doing with an RS6 and not just reading it out a manual to work on a car they've never dealt with before. We have designated RS specialists in the UK and not sure if you have the same in America.