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Getting off the line quickly... BOG DOWN!!!

gents,

A question that has probably been asked and discussed here many times before, however i cannot find much using the searches available on here... soo...

What is the best/most mechanically minded way of getting a impreza off the line quickly? I have a 2005 sti type UK, with an andy forrest remap to 350bhp, and try as i might i cannot get the thing off the line quickly, and i really dont want to resort to full bore launches, unless this is fine for the clutch!!! i have also heard that if you feed the clutch in this is also harmful for the clutch, so i am a bit lost as to what to do!!

Speaking to someone who has a lot of experience with scoobies ( ;) ) he has told me to be brutal with the car, step the revs up and dump the clutch is the only way to get the car off fast! now, i would of thought this would not be good for the longevity of the clutch, however he says not, now without starting a big arguement, anyone any evidence to suggest which can be true?

also as my sti has the DCCD, will setting this up a certain way help with the launch? also i do find the biting point on the clutch very high up, does anyone else find this? i have heard this is adjustable but is a bit of a **** to do, or is this just a sign that my clutch is bolloccks anyway?? :luxhello::luxhello:

Thanks in advance for any ideas,

Craig :)

There is no way of doing it that is completely "kind" to the car, but what you want to avoid if you are concerned with mechanical symapthy is anything that produces a sudden big jolt on the transmission i.e. just dropping the clutch. If you dial up 4000rpm find the biting point then release the clutch quickly (not drop it) and floor the accelerator you'll get a slingshot effect off the line that'll make you grin from ear to ear without the wince inducing bang of a dumped clutch!! The downside is that it's harder on the clutch wear, but clutches are cheaper than gearboxes! :D

You just have to grit your teeth and go for it. There's nothing particularly subtle about a good launch! :D

This has been my experiance in a MY05 STi, and it might make you wince, it certainly did me.
I had tried being mechanically sympathetic and 'driving' the car off the line (as suggested by NS04) with modest rpm (4k to 4.5k) and feeding the clutch. Most of the time it just bogged down and once or twice just span the (stock) clutch quite badly.
After having my car mapped by Dynamix and having launch control set up, I have since found that even 5k rpm wasn't enough to get a clean run.
The last time out I was using L/C at 6k rpm and dropping the clutch. I also had the DCCD in manual and set on the first orange down from Locked on the dash display.
It's a lot less dramatic than you might think, and it took off like a dog shot up the ar5e! 1.64 second 60ft. :D

this was one of my other questions, as i bought my car as it sits, with an andy forrest stage 2 remap to 350bhp, on the advert with the car the previous owner mentioned that it had launch control fitted, now being stupid at the time of buying it i never found out whether it did or it didnt! how can i tell if it is fitted? newbie alert!

full foot down in neautral.. shoouldnt red line

Got to agree and say theres no way to do it thats 'nice' to the car

I also let the clutch take most of the beating, as already said its cheaper than a new transmission

I usually rev between 4.5 and 5.5 to keep it in boost while waiting to go, then upto biting point and as the light go quickly (but not step) lift of the clutch and floor it, usually gets me around 1.8 60 feet

right update...

the car does have launch control, and holds it at around 5.5k for a few seconds before then going on to redline, so i tried it, dumped the clutch and it certainly takes off when you do that! tried it a second time and dont think i timed it right as i think the clutch burnt a bit as i could smell it for the next 10 minutes or so! wont be doing it that often, but its nice to know its there if needed! :)

As already stated here by Eggy :-

Quote:

Originally Posted by eggy790 (Post 9590732)

full foot down in neautral.. shoouldnt red line

Doesn't sound like L/C as I know it. Should hold a pre-set rpm regardless whilst stationary as far as I know. Have to say I've not held mine longer than necessary, say 3 to 5 seconds, but never yet seen it redline in the way you describe.

The whole idea of L/C is that it doesn't involve you in any timing with regard to engine rpm, other than of course your reaction to start lights.

hmm, i may ring andy forrest for clarification then as its his map on the car...

Yeah definitely worth speaking to Andy first.
There may well be more than one format for L/C, although I can't imagine why.:thumb:

my launch control works like this..

in first gear, full throttle, the revs wont go over approx 5.5k, then as you start to move, say approx 3/4mph the limter is removed, and then allows full power. this was the same on a different car, and im sure its how most L/C works when mapped to the car.

if your drag racing, or want a slingshot effect, its more about timing, i pulled of a few perfect launchs with no clutch smell etc, i also let the car roll about 1/2mph and then piled on the power, and that was the nuts, its just that initial movement that causes me to bog down sometimes (found it might easier to do with no weight in the car)

Clutches are cheaper than gearboxes.

Therfore give a little bit of slip, but plenty of revs. Use rapid full throttle blips to obtain the desired RPM and get the turbo up to speed before launching.

Bog down = need more slip or more revs
Too much slip = need less revs or be a bit faster with the clutch

There is no exact science, its just down to feel and timing; In terms of how long to slip the clutch, its just a case of holding it at just a shade higher than its normal biting point for half a second or so whilst mashing the throttle pedal then let it out completely.

Quote:

Originally Posted by eggy790 (Post 9590732)

full foot down in neautral.. shoouldnt red line

Oh yes it will ;) Launch Control engages when it's out of neutral :D

Just go for a 4 pad unsprung disc & you will launch like a slag! Those clutches bite hard!

There's a bit more to it than just clutch choice.
What RPM is best, what tyres, what tyre pressures etc.

I can see a long affair thread lol. Im now subscribed as im going to be likely changing the clutch this year, as some of you know my car didnt launch well at all in the 1st round grudgement nor on the 1.4's offering up 0-60ft in 1.8 (slippage).

Previously my car had a push type carbon pro spec clutch with 4.3KG flywheel. It was a unsprung disc & had alot of chatter. Launching wise it was brutal. Low revs such as 4k & a little side step would give a hard launch.

Now i have the ACT extreme street disc. It is a full face sprung disc with a extreme pressure plate. As stock, it is a pull type clutch & honestly speaking it needs alot more revs to launch properly whereas the push type needed less revs.

Hmm- I have our hill climb tomorrow, and am a complete wuss off the line! 3k, bog down then go, mainly as Im fearful of the gearbox going.

You guys all running 6 speeds? If so the above makes more sense to me- Im not sure I would try in my 5 speed, even with only 330lbs.

Quote:

Originally Posted by Grant74 (Post 10029676)

Good luck tomorrow mate, and your no wuss, your just thinking long term, or even short term if you shred the box....

My 5 Speed went on me in my last car, and one thing you can rest your mind with is, if you do shat the 5 Speed, your likely to get change out of £500 fitted for a replacement :thumb:

Tell us more about your car and hill climb?

Rob :D

Oh and nursing off the line is what I would recommend too ;)

Its a 98 WR edition, with a cage, seats, harness, fire system etc, but still with full interior! Flocked interior :)

Its running a VF37 twin scroll with Spec C headers, and full 3' turbo back system, with a Hybrid FMIC.

It has a pretty flash baffled sump from API, and an oil cooler, with relocated filter.

Fueling is a Walbro 255, with FPR and flow matched injectors- cant remember the size but only running 70% flat out!

ECU is a Simtek, and brakes are Brembos off a later car, Bobs Kevlar blue pads (they heat up very quickly) with grooved discs, braided lines, and 5.1 fluid

Car is fully pollybushed, with BC suspension, and uprated ARB's, running 2' of camber on Yoko Advan AD08's, as incredibly Im still running in Production class- a lot of the above mods fall into breathing and exhaust, and suspension is still the same configuration etc.

Im in Jersey, so its Bouley Bay- lined with trees that dont move, and very tight corners! Only been at it a few years, but love it- held the record last year, holding off another Impreza, a GT3RS, M3, and Renault Megane Cup (very quick), but lost it to an Evo a few weeks back- very well driven, but on super soft R888's, as was the M3 which also beat me this year.

I cant afford to change tyres, and Im not taking anything away from those guys who drover very well, but next year I will- the yokos are very good, but no where near as good as the toyos.

You still have to drive them though! Dont think I drove that well last time to be honest, so looking forward to tomorrow.

Sorry- epic post as cant sleep! must go to bed.

Quote:

Originally Posted by Grant74 (Post 10029750)

That sounds great, and to say your running it all on a standard? 5 Speed :eek: If you could harass it off the line and gain a second would that help your times? I mean the 6 speeds over the 5 speeds are mch heavier, but they can take the brutality to punch a launch at huge rpm in some big powered cars, I think Daz Davies, Big Arf, Steve and many others are running a 6 Speed and I have winessed there launches:cool:

Let us know how you get on mate :thumb:

I know what yoiur saying about £££ though. My First job was in jeporady over the last week or so and we fell into administration, but that still didnt stop me from spending, but it did make me think more about trying to cut costs with comprimising on quality, One of which is tyres, Im running on Eagle F1's atm, and they arent good for Tarmac/Concrete sprints, or at least not with my current spec *Note, I must spend money on decent ARB's:cuckoo:* I have a set of Proxes in the Shed that (if my car is ready) I will try at the SSO this month. However my clutch will not permit me to launch, as such Im thinking of fitting a 6 paddle clutch to give me that extra advantage, not that I would recommend a paddle for a standard 5 speeds.

Anyway I best some work done....

Rob :thumb:

I dont rate proxes around corners as the sidewall folds, but will be fine for sprints.

Still nursed it off the line, but beat my PB by 0.03 of a second so happy! The 64ft times were poor at 3s, and one 2.8, although that is a standing start up a hill.

6 speed is 60kg heavier I though with diffs, which is a lot, but could be offset by some other weight saving measures- I have a steel bonnet for example.

I think the advice on here is spot on for launches, and some of the big power guys run them very succesfuly it seems, so I think the secret is just being brave, with a little mechanical sympathy with the clutch.

6 speed, super soft 888's, and a large pair of gonads FTW