RS4 Quick Launch

[sakimano]

...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.

no, he launched at high rpms

maybe mick will chime in.

[bam_bam]

Pretty sticky ground to be doing a high rev launch, as said. Traction has been known to lunch many a drivetrain componet. Better the clutch go, rather than something more expensive before the wheels.

[HYFR]

lol
i 6k launched in my courtesy Nissan Note today .... fair to say it didnt really move

[sakimano]

here's a 3500 rpm launch...fairly effective I'd say.

http://www.youtube.com/watch?v=BoV0lB3g3kE

[gareth_oau]

cheers sakimano, just got added to my YouTube faves

[sakimano]

cheers sakimano, just got added to my youtube faves

thanks

hey do you work in finance by any chance? Saw an email chain from Australia the other day, and there was a Gareth on there. Some tit at Citi emailed the entire iBanking group and analyst group an article about how great he was with the ladies...on his first day...and one of the recipients was someone named Gareth who forwarded it on and started one of the funniest flame-fest email chains I've seen in a while. Was hoping it was you so I could say thanks lol.

[adsgreen]

That is a good launch - no doubt there.

I'm not saying you can't get a good launch at 3.5k rpm or you have to launch at 6l rpm just the the methods are different and have different outcomes.
Launching from 3.5k means are using the torque of the engine to break tractions and launch. You can test this by holding revs at 3.5k and dropping the clutch. Chances are you'll bog significantly and be lucky not to stall. So you have to feed the power on as you lift the clutch - it too easy to be too early on the clutch and bog or too early on the power and wheelspin.
Granted - get it right and it works very very well.

Launching from higher rpm means you use the rotational kinectic energy of the engine already spinning to break traction - this is more constant as there's nothing really to balance in terms of clutch and throttle control. You won't bog as the revs will be high enough that by the time the clutch is fully disengaged the wheels would still be slipping slightly and you're free to mash the throttle down.
This has the advantage of being able to accommodate a wide number of road conditions relatively easily - slightly wet then just use lower launch rpm but the process is the same.

I used to do this racing and found that the massive reduction in the chance of bogging down useful when you have another fast car also launching fast only a few meters behind you. Also the the workload on the driver is much less and I'd much rather be looking around at whats going on than distracted with balancing the clutch and throttle.

Interesting seeing the launch systems of various cars.
The Audi R8 v10 Launch Control Operation (per owner's manual):
Manual Transmission:
•With the engine running, press the "ESP OFF" button one time. The ESP indicator light in the driver information system display illuminates and the message "ESP sport" APPEARS.
•Press the clutch and hold it down.
•Engage the first gear.
•Press the accelerator pedal all the way down until the engine speed remains steady at 6500 rpm.
•Release clutch carefully.

[P_G]

Good launch there saki but get those exhaust valves lubed up mate.

[sakimano]

Good launch there saki but get those exhaust valves lubed up mate.

lol sounds like a haunted house doesn't it?

Canadian winters mean squeaky valves . I'll throw some WD40 or Penetrating Lube on it though...never really thought about it.

Thanks.

[sakimano]

Interesting seeing the launch systems of various cars.
The Audi R8 v10 Launch Control Operation (per owner's manual):
Manual Transmission:
•With the engine running, press the "ESP OFF" button one time. The ESP indicator light in the driver information system display illuminates and the message "ESP sport" APPEARS.
•Press the clutch and hold it down.
•Engage the first gear.
•Press the accelerator pedal all the way down until the engine speed remains steady at 6500 rpm.
•Release clutch carefully.

You do know that there is programming in the R8 ECU the when you activate launch control it modulates the throttle, and eases the launch off of about 4000 RPM right???

The R8 process you describe doesn't launch at 6500 RPM. Revving to 6500 RPM is to engage the launch control program. That's it. Once you release the clutch, it drops RPMs and modulates throttle, resulting in a launch at around 4000-4500 RPM.

My JHM Tuned B7 S4 had JHM LAUNCH ASSIST on it and it did the same thing. Rev to 5500 RPM as the 'on switch' and hold, then release clutch...same process...release clutch and BANG! you're flying. (see videos below)

Knowing the tuner from JHM I asked him if this was 'dangerous' for the clutch/transmission and he explained the '5600 RPM' level was just to trigger Launch Assist to turn the system on...but it immediately drops and modulates the throttle to launch you from around 3500 rpm (on the S4). It's in fact much safer than launching on your own because it's all controlled to protect the clutch.

You're spreading dangerous mis-information sir. I would like to see some videos from you, with your prescribed 6500 RPM launch technique. If only videos could carry 'smell'.

For further education, here are a few videos of my car with JHM's Launch Assist (they also have this on their RS4 flash...included free with the tune. I'll definitely be looking at their tune when the time comes for me to map my car).

http://www.youtube.com/watch?v=AxMkC7F4SyI

http://www.youtube.com/watch?v=aoAxXcM2nN8

Using this at the dragstrip allowed me to cut a 1.82 60 foot time (my previous best was 1.89) and run 12.9 seconds @ 107.8 MPH. That's the 4th fastest all motor B6/7 S4 time ever.

http://www.youtube.com/watch?v=c8G9bgOr_NY

JHM has programmed Launch Control (they call it JHM Launch Assist) into their B7 RS4 flash/tune/map as well guys. You can see them demo it in this video

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

[adsgreen]

You seem to be missing my point. You seem to think I'm launching the same as you from 6k rpm... it doesn't work like that. I'm sayin the saying thing as you... when the clutch comes up the revs drop (probably to about 3-4k). It's not like I'm launching from 6.5k then mashing the throttle causing a huge amount of clutch slip. The video you posted on the other decarboniser thread shows this as that definatly is at 5.5k ish when the clutch is released.

Refer you back to the nitrous rs5 launch and thats with another 150 bhp ontop of stock.

My other car has launch control and it most certainly does launch from 7k+ with no problems although.

[gareth_oau]

cheers sakimano, just got added to my youtube faves

thanks

hey do you work in finance by any chance? Saw an email chain from Australia the other day, and there was a Gareth on there. Some tit at Citi emailed the entire iBanking group and analyst group an article about how great he was with the ladies...on his first day...and one of the recipients was someone named Gareth who forwarded it on and started one of the funniest flame-fest email chains I've seen in a while. Was hoping it was you so I could say thanks lol.

LOL no, I think there must be 2 Gareths in Australia. I work in Oil and Gas

[ArthurPE]

I've seen good launches with TC on and 2000 rpm and bads one with it off and 4000 rpm...
an engine is a variable torque machine, if the wheels are spinning it's making less power than hooked up, so less motive force/thrust... the key is balance...
a car just driving down the road at 60 mph has 3% tire slip
15% slip sounds like a lot but if a car is doing 20 mph (30 ft/sec) the wheel is spinning ~4.4 rps, 15% slip is 5 rps or another 54 deg per rev or the road is moving 30 ft/sec and the tire 34.5, it's difficult to observe

up to a few years ago F1 cars had launch control...when they took off they looked slow, low rpm, no spin, looked slow, but applied torque ~ to traction and picked up speed fast, now they have none and are slower to 100 mph: wheel spin, bogging, etc.

my preference is 2000-2500 or so, this allows more first gear to be used and the associated higher torque multiplication, which yeilds a higher driven wheel thrust...
once rolling give it the throttle the surface can take...a car wi;; accelerate faster squeezing the throttle rather than 'flooring it'
it's smoother, easier on the drivetrain, a few 1/10'ths on the street mean little to me...

[sakimano]

my preference is 2000-2500 or so, this allows more first gear to be used and the associated higher torque multiplication, which yeilds a higher driven wheel thrust...
once rolling give it the throttle the surface can take...a car wi;; accelerate faster squeezing the throttle rather than 'flooring it'
it's smoother, easier on the drivetrain, a few 1/10'ths on the street mean little to me...

interesting

I was at the drag strip today and a more smoothe surface, despite traction stickiness applied, meant that my 3500 rpm launch that is succesful on teh road was a disaster at the strip. Car spun the tires mercilessly.

I didn't get many runs in, but the ones I did manage were all around 13.1 @ 107 mph with 2.0 sixty foot times (not bad for a 30,000 mile 'carboned up' RS4 eh?). On the road my 60' times were more like 1.90...and that 1 tenth turned into about 1.5 tenths in the full length of the run. You could actually see it on my 330' times that it was already 0.15 seconds slower than on the street.

So I may need to try your technique next time I go (in a couple of weeks). I've only had the car a month so I'm still learning. Got any videos of you launching it your way?

[ArthurPE]

the launch point can be determined from the torque curve and gearing
for example, if you want to maintain 15-20% slip max (with quattro imo lower is better, maybe 10-15 max)
1st gear ~5 mph/1000 rpm
if you launch at say 4k...wheel speed is 20 mph, 15% slip is 17 mph, so until you are moving 17 mph slip>15%
so you won't apply max force from 0-17 and you'll be shifting to a lower gear in 4k rpm, if you increase revs before 17mph it only gets worse

if you launch at say 2k, wheel speed is 10, slip >15% until 8.5 mph, you get caught up quickly and can give it throttle trying to stay at 15% slip and you have 5.5k (37% more) time in 1st gear with it's higher torque multiplication...
obviously this is all done by 'feel'

there is a 'sweet spot' and it is the lowest rpm that you can produce max torque while maintaining traction (slip <15%) while giving it good throttle
since the RS4 produces ~the same torque at 2k-2.5k vs 3.5-4k (~85% of max) no need to go >2.5 so you can use 1st longer
at 2.5 you are on the rising part of the curve and hit max at 3k and hold it to 6k or so
so if you can hook up by 3k (after a 2.5k launch) and feed it throttle you still have the meat of the curve in front of you
if you launch at 3.5 and hook at 4+ you have lost a good portion of the curve...basically 1/3 of it in 1st gear
catching it on the rising portion also gives you an 'shove' or impulse as it rises

that's the beauty of this engine, good torque down low with great traction...you can hole shot pretty well from 2-2.5k
and is easier on the clutch