RS4 Quick Launch

[gareth_oau]

here's a quick in-car video of my RS4 launching.

It also highlights the benefit of the JHM shortshifter

http://www.youtube.com/watch?v=hJyF7vjYiQg

[Brooner]

Thank feck that's not my gearbox

[sonny]

Did you have TC turned off?

[sakimano]

good shifting!

what RPM are you leaving at? Sounds a tad high, and then you caught it on the downswing which cause the bog. Try a steady hold at 3500 rpm next time.

[gareth_oau]

you're right sakimano, I did manage to catch myself on the downswing on launch, so will avoid that next time.

Sonny, TC was fully off. I find that necessary otherwise the the car bogs down horribly between gear chagnes.

[sakimano]

I did a couple of 0-60mph pulls tonight using my GTECH RR on GPS and terrain map verified flat road. 3500 rpm launch gives a good amount of tire spin and a full bore launch with no bog. Nice and cool out here (55 fahrenheit/12 celsius) so good temps for making power.

4.4 and 4.5 seconds were the results. 60 foot times were a lacklustre 1.9 both times though. Too much tire spin.

p.s: ^^^lame how the forum inserts hotlinks to advertisers and butchers your post so you look like you don't know how to write.

[gareth_oau]

ahhh you guys are heading into northern winter, I'm envious.

Its forecast to be 35deg C/95F today here in Perth.

I'm not planning to do too many launches in my RS4, I like my clutch too much, and they are rediculously expensive to replace here!

[adsgreen]

3500 too low.
Try nearly doubling it.

The problem you're possibly having with wheel spin is that by having the revs too low the engine will want to bog so you have to apply more throttle quicker after dropping the clutch which makes for a tricky start.

With higher revs you use the inertia of the engine to launch and minimise wheelspin as you don't need to add any throttle initially. The revs will naturally drop as you snap engage the clutch then quickly stabilise after minimal wheelspin then you an floor it.

You do want an element of wheelspin as a rule of thumb number is that tyres offer peak longitudinal traction when moving 15% faster than the road (similar for braking).

[PetrolDave]

You do want an element of wheelspin as a rule of thumb number is that tyres offer peak longitudinal traction when moving 15% faster than the road (similar for braking).

+1

Same rule applies when braking as accelerating, the best calibration for an ABS system is to allow about 15% slip as it generates maximum grip between tyres and road.

[sakimano]

3500 too low.
Try nearly doubling it.

The problem you're possibly having with wheel spin is that by having the revs too low the engine will want to bog so you have to apply more throttle quicker after dropping the clutch which makes for a tricky start.

With higher revs you use the inertia of the engine to launch and minimise wheelspin as you don't need to add any throttle initially. The revs will naturally drop as you snap engage the clutch then quickly stabilise after minimal wheelspin then you an floor it.

You do want an element of wheelspin as a rule of thumb number is that tyres offer peak longitudinal traction when moving 15% faster than the road (similar for braking).

No offense mate but I've got about 100 dragstrip passes in 4.2 V8 powered S4s and RS4s and everything you just said is counter to what the fastest S4s and RS4s in the world do (and should lead to the demolition of stock clutches if followed).

quattro traction is significant, and the stock clutch's ability to grab at 6000-7000 rpm from a dead stop is suspect at best...in all likelihood you'll glaze or destroy your clutch. Read the story below from mickf29 if you want a preview of what will happen when someone launches from the RPMs you're suggesting.

My B7 S4 launched from 3500 RPM was able to cut 1.8 60' times with ease, and with tune and exhaust I was running 12.9-13.0 @ 107 mph. I bet there aren't many NA RS4s on earth that can match that time...and the ones that do are definitely not launching from 6000-7000 rpm.


http://forums.quattroworld.com/rs4b7/msgs/11271.phtml

Story on track night at PIR [warning: graphic, may cause convulsions]
Posted by: Mickf29 (2524) on 2009-08-12 16:43:08
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Last Friday I went to the drag strip to try one more time with the weather cooler to get some decent times. Joining me was a friend of mine who has done some track time in Alfa Romeo's in the past.

I setup for my first run, and had a really good start, decent time. I posted a few days ago, 1.884 60', 13.403 1/4 time.

Anyways I decided to let my friend try it out, he said he had done it before. I can sense some of you cringing already. Yeah, it is bad. Lets just say last time I let anyone drive this car. Period.

I told him "3500-4000 is where you want to rev to, when the last yellow light goes, drop the clutch from the floor all the way out. A split second after you feel it engage, give it gas and go. Rev to 7800 or so, shift, and so on".

I went up to the stands to take pics, and watched. He got to the line, hit the gas, sounded about right. The light tree went down, and I hear the engine wind up. But the car moves only a few feet at first. then he shifts to 2nd, and I hear the engine whine up, and he moves past me really slow, like 30mph. Then I see smoke and am just sinking in my stomach. Then to my disbelief, I hear him shift to 3rd and wind it up again. All I am thinking is "F me, F me, F me!"
He didn't stop, went all the way down the track like that. I was completely crapping myself. i ran to the other end where he was sitting with the flashers on, in the grass outside the track.

I got in the car, all I smell is toasted clutch. Car won't go in gear, pedal is completely loose. I knew the clutch was totally shredded. Hoped nothing else was wrong.

Dropped it off via tow truck at the dealer, and they are putting the parts in now. here are some pics of the old clutch. Totally nuked. Guys said they have never seen this bad on an RS4. good news is the rear seal, the slave rubber pieces all look good. No heat out of the case. Flywheel is damaged though.

Day at the track: $25
Burger and Fries: $11
Full Tank of Gas: $45
New Clutch and Flywheel: $3200Telling all your friends that the driver who did this is a moron: Priceless!

Good news is my friend is a very standup guy, and he has been in contact with the dealer to pay for it himself. Otherwise, my wife would have my nuts.

[adsgreen]

To be fair drag strip is completely different as the surface is grippy beyond anything you'll find on the road or even a decent race track.

I don't know if stock clutch but this illustrates what I was meaning. 6k launch from standstill with 125bhp nitrous kit.
http://www.youtube.com/watch?v=DlqR9_SxEik
The key to launching with high revs is to not mash the throttle soon after dropping the clutch - the clip shows this really well. clutch is released with the throttle constant, revs drop and a split second after stabilising throttle is down full.

Don't get me wrong - no full power start is going to be easy on any transmission esp a 4wd.

[bam_bam]

...I told him "3500-4000 is where you want to rev to...
I went up to the stands to take pics, and watched. He got to the line, hit the gas, sounded about right...

@ sakimano - so did he launch at 3500-4000? It sounds as though he did but the clutch still gave out, it doesn't really support your post.

[adsgreen]

Probably fed the clutch in too slowly and once it starts to slip and overheat doesn't matter after that.

I do agree with sakimano that you can very easily break a clutch at a drag strip by overdoing it.

[Jules]

To be fair drag strip is completely different as the surface is grippy beyond anything you'll find on the road or even a decent race track.

I don't know if stock clutch but this illustrates what I was meaning. 6k launch from standstill with 125bhp nitrous kit.
http://www.youtube.com/watch?v=DlqR9_SxEik
The key to launching with high revs is to not mash the throttle soon after dropping the clutch - the clip shows this really well. clutch is released with the throttle constant, revs drop and a split second after stabilising throttle is down full.

Don't get me wrong - no full power start is going to be easy on any transmission esp a 4wd.

Wow that does look quick,a little brutal but i would like to have a go one day just to experience it.

The best times people are quoting dont seem that quick though but i suppose without a charger there not going to be

[rs4m3e46]

i want to start saying that i am a little lucky = i am working for the biggest spare parts in romania and the parts are easy to find for me.The relevance for that is that a stock clutch for me is 200 euro (and we have 120 garages) and last year after i smell for the first time the burn clutch i was thinging - ok - now i will launch hard to kill the clutch and to replaceit.After that i think i was hard launching the car for maybe 60-70 times and the clutch is in very good shape(one of may friends was responsable for that little clutch burn).
For me the best way to do it is with 4500 rpm,sidestep the clutch and sinchronyse gas with the moment the clutch is engaged.Launching with lower rpm is consistent lower but not tu much,only with 0,1 - 0,15 seconds to 100 km/h,
I think the best times you will see will be with 5,000 rpm in that way - keep your foot to the clutch go from iddle full gas to 5000 rpm and then release the clutch( sidestep).Dont do that if you love your car!!!!!!!! it is brutal and is posible to damage the car.I was tryed that method but my clutch is a little to old for that and it was a liitle slip and the times was equal to 4500 method.
i posted 2 graphics from dynolicius(*very accurate as tested in magazines and sites).12.89 S TO 1/4 MILE AND 4,63 0-100 KM/H WAS THE BEST FOR ME.Is true that was with new michelin tyres,new air filter,new oil and all vacuums fixed in 15 Celsius(60 fahrenheit).In two days i was making 10 tests with times from 12,89 to 13,02.
In that 15 C the range was 12,89 to 12,92.
My car is 72,000 miles, stock beside off Miltek,100 cels cats but stock map.
This week i will clean the valves(never cleaned and i will remapes with Revo stage 2.After that i will post hopefully some 12,6 times...