1/4 Mile Launch

[CptnVortex]

I am about to attend my first ever Street legal drag racing event. It is a 1/4 mile track, so I expect it to be quite grippy....

I am wondering from the r3v community, about tips for a good launch. I dont want to be sunday driving it, but I also dont want to break much....

The car in question is a 4dr 2.7l stroker, with about 200-220lbs stripped from stock trim. Tires are a decently grippy street tire 195/50/15.

So what say you, r3v? Any tips welcome!

[Adrian_Visser]

You will be disappointed and will return home thinking of turbos and engine swaps.

Here is a quote from a quote from another thread:

Since you asked so nicely, here are my thoughts. I've assumed the following:

+ Street radial tyres
+ Pump fuel

Setup For Drag Racing - Weight Reduction
First setup you car before going to the strip.

Your first task is weight reduction. Ensure you get to the strip with 1/8th tank of fuel. That means allowing enough fuel to get there with 1/8th left. Better to arrive with too little fuel and then topping it up a tad from your jerry can, which is of course filled with the same 98 RON fuel you have in your tank. A properly mixed slug of octane booster will give you some peace of mind too. Remember to put the booster in first to allow the petrol to mix with it properly in the tank.

Every 1 litre of fuel weighs 640 g.

Next drain all the water out of your washer botle. My M Coupe takes 5 litres in the washer bottle which is 5 kgs you don't need.

Then remove the spare tyre, toolkits and anything else from your boot and from inside your car. Anything that can be eaily removed should go (CD Stackers, carpets, lose stuff, etc).

Now decide if you want to go to the trouble of removing your rear seats and passenger seat. Believe me when I tell you it will make a big difference. On average they say every 100 lbs (~45 kgs) is a tenth (0.1 off your ET).


Setup At The Strip - Tyre Pressures
Now you've driven to the strip and been through scrutineering, get out your trusty pass journal and tyre pressure gauge.

Ensure you've got 1/8th tank of fuel - you don't want to starve for fuel during a pass. Now hook up your compressor and increase your front tyres to 55 psi. If you don't have access to a compressor then swing by the closest servo to your drag strip and do this before you lob at the strip.

You increase the pressure in your front tyres to minimise rolling resistance. If you happened to have an alternate set of narrower wheels/tyres then you'd fit the narrowest practical set for race day.

The rear tyre pressure is more involved, because you've got to try a range of pressures and see what results in the best 60' times. The optimum setting changes as the weather conditions change, so this is a bit of a black art. That's what your Pass Journal is all about. This is where you record your car setup and the results after each run. That way you can make changes one at a time and make some sort of analysis in order to optimise your setup.

Generally speaking you should drop your rear tyre pressure 4 psi from standard and then work your way down by half a psi at a time until your 60' times get worse.

Remember that fine adjustments on street radials is less of a factor than when you graduate to drag radials or slicks. However it is still well worth your while to get close to the optimium.

Your Pass Journal will have an entry for every pass you do, including the following information as a minimum:

+ Tyre pressure
+ Launch RPM
+ 60' result
+ My comments

More on how to use your Pass Journal seek the optimum setup in a later post.


The Burnout - How Long?
If you are a beginner or feel a bit nervous about the upcoming pass, then simply drive around or through the water box and don't worry about a burnout. You can add the burnout to your later passes as you become more comfortable.

Remember that street cars using street radials are very different to a Top Doorslammer. You're not going to do a half track burnout and wow the crowd. Street cars that do long pointless burnouts are basically wasting everyone's time. Don't be one of them!

Now street radials like a touch of heat in them to get optimum traction. But too much heat and their traction is reduced. However if you don't spin the tyres at all then you've still got some water and grit on your tyres from the water box (unless you managed to drive around it).

My advice for street radials is to drive through the water box and come to a halt. When signalled by the official, dial up the revs and drop the clutch. Wait until your tyres smoke a tad and then button off. We're talking less than a 2 second burnout here. More than that and you risk cooking the rubber (ie reducing traction until they cool).

Realise that drag radials and slicks are made totally differently to street radials. These special tyres require a lot more heat to work. Street radials don't.


The Burnout - How To Do One?
Now you know how long to let the burnout go for, exactly how do you perform a decent burnout?

Let's start from standstill, waiting for the official to motion you to start your burnout. Select the appropriate gear (1st, 2nd or 3rd depending on your horsepower, the higher the gear the more power required to turn the tyres over). When the official signals to start your burnout, dial in some revs and drop the clutch. You can dance your left foot over to touch the brake a tad and balance the revs via throttle with forward movement via brake (takes a bit of practice).

Now if you continue to creep forward and start to contact your tyres with dry sticky track then you're obviously going to put more strain on your driveline.

When you've got some heat into the tyres, just let off the brake and /or drop revs a tad and your car will creep forward. Get off the gas and allow the car to roll gently towards the staging lights.


How To Pre-Stage
You're rolling gently towards the staging lights. Keep your eyes on the Christmas Tree and look for the White Pre-Stage light to blink on. The instant you see this light come on you nail the brakes and come to a total halt. You're not yet fully staged - just pre-staged. The second Full Stage light is still unlit.

I recommend you now wait until your opponent is at least Pre-Staged or even on Full Stage before you bump in to Full Stage. Once either compeitor is on Full Stage, the other racer has only 20 seconds to fully stage or the starter may disqualify you. In practice at a street meet the starter will rarely disqualify you, but they may come over and bang on your side window to hint that you're holding things up!

Once you are pre-staged you must now focus on that Full Stage light with all your concentration. Because as soon as you fully stage, the starter can trigger the Christmas Tree at any time.


How To Bump On To Full Stage
You're at a halt with the Pre-Stage light up and your competitor is fully staged.

Now apply your handbrake gently and dial up your pre-determined launch RPMs. You've already thought about what RPM you're going to launch at before you lined up. If this is your first pass, then just choose whatever starting point you think appropriate.

Your clutch is in, your RPMs are steady at your launch point and your handbrake is slightly on. Now you ever so gently tease your clutch out - looking for the friction point where the RPMs start to dip showing you the clutch is dragging you your engine just slightly.

With your left hand you are holding the handbrake just slightly on. This is a delicate balancing act, ensuring your engine is at launch RPMs, your car rolls forward ever so slightly and your rear brakes are just slightly on to ensure you move very very slowly on to Full Stage.

This is called bumping on to Full Stage and is not easy to do. If you roll forward too far you will Redlight by crossing over the start beam. No big deal, it's all practice and you'll do better next time.

Once you bump on to Full Stage you pull your handbrake up firm so your car comes to a dead stop. But you don't allow the handbrake to ratchet on lock, you keep it on but not locked by pressing the button as you hold it.

If you get it right you will find yourself fully staged, motionless on the start line and most importantly, you are solidly locked on your launch RPMs with your clutch just at friction point, dragging against your handbrake.

You are not looking at your tacho to check your RPMs. You are not looking at your handbrake. You are not looking at anything other than the Christmas tree.


The Launch
It's been covered in detail in many other places so I'll just state it here. Because of human reaction time and because of the vehicle reaction time of your car's suspension and drivetrain, you do not launch when you see the Green light on the Christmas Tree. You launch the instant you see the last of the three Amber lights come on.

You're at steady launch RPMs with the clutch at friction point and the handbrake held on but not locked. As you see the last Amber come on, you release the handbrake fully (holding the button in), progressively mash the throttle and modulate your drivetrain using your clutch.

This is not easy to do and takes many repetitions to get a good result. This is where it's all at - your reaction time versus your opponent and how well you can launch your car without wheelspinning.

You must slip your clutch mercilessly to get an optimum launch. Sometimes you may find you have not let the clutch out fully before it is time to change up a gear. This is OK.

Wheelspin on launch or upshift will cost you precious time. The optimum launch is at 10% wheelspin. This is very difficult to achieve and again comes only with much practice and experience. It's all good!

Yes, you will punish your clutch. Yes, it will give off that awful smell of tortured components. Yes - it is the only way to optimise your launch.

Clutches are consumables and are meant to be replaced. Regular drag racing will severely shorten the life of your clutch, but so what? You replace the clutch and go on your way. Just like tyres.


Getting A Better Time
Your reaction time (RT) is all about how quickly you react on the start line. It does not factor into your ET at all. However the winner of each race is very much affected by the RT. So once you are comfortable with the process of doing the burnout, launching and shifting up through the gears I recommend you treat each pass like it's a race. The only way to get better is to practice like you race.

Drag racing is all in the launch. Every tenth (0.1 second) reduction in your 60' time is .15 to .25 reduction in your ET.

You can beat an opponent with a much more powerful car by getting a sharp RT and by getting a sweet launch.


That will do for now, happy to answer any specific questions or prate on about any area in more detail if desired.

[CptnVortex]

Lol! Thanks! Yes, I know... I'm already planning the Turbo..... MAF/WAR chip soon, and Injectors in the mail already..... Just looking to attend my first event, see if I catch the bug!

[nando]

I'd be really surprised if you broke something with a 2.7 M20.

is this at mission raceway?

[CptnVortex]

Yup, Mission. And yea.... I'm hoping nothing will break, but she is a little tired that's for sure... Lots of upcoming maintenance that I want/should to do this summer...

[ForcedFirebird]

I'd be really surprised if you broke something with a 2.7 M20.

is this at mission raceway?

I bent a drive-shaft with my stock eta and a hard launch lol. Could only get a 2.2 60' using bald 195/60's lowered to 20psi.

[CptnVortex]

Wooo rain cancelled the event.... nothing broke yet! Lol

[Kershaw]

I bent a drive-shaft with my stock eta and a hard launch lol. Could only get a 2.2 60' using bald 195/60's lowered to 20psi.

i managed a 2.15 60' on a stock IS. came out to 15.9 i think. .2 seconds off new is not bad for a 25 year old car i think.

used 32psi on whateverthefucktirescameonthecar. i didnt try to burn out or do anything ridiculous. went around the waterbox. didnt even drop the clutch. just punched it from idle.

[CptnVortex]

Wow, impressive. Short gears? I've got a 2.93 rear end, LSD I THINK. Could just be welded... definitely leaves 2 lines of rubber though!

[Nsquared97]

^You would know if your diff is welded.

[Rsully70sev]

You will be disappointed and will return home thinking of turbos and engine swaps.

[CptnVortex]

Finally attended the event, wow that was a blast! My first run was my best, as I got greedy with the revs and couldnt control my wheelspin. 1st run was from idle as I didnt know what was going on with the lights lol! I had a .933 reaction time, and managed a 15.69! Quite pleased with that!

[FLG]

Finally attended the event, wow that was a blast! My first run was my best, as I got greedy with the revs and couldnt control my wheelspin. 1st run was from idle as I didnt know what was going on with the lights lol! I had a .933 reaction time, and managed a 15.69! Quite pleased with that!

Only person that ive heard "pleased" with a 15s run :D

Congrats tho, you didnt break anything and you didnt wreck.

[nando]

Finally attended the event, wow that was a blast! My first run was my best, as I got greedy with the revs and couldnt control my wheelspin. 1st run was from idle as I didnt know what was going on with the lights lol! I had a .933 reaction time, and managed a 15.69! Quite pleased with that!

what was your trap speed?

this must have been at mission? :) I had the same problem. first time, I rolled right through the lights and got no time. LOL

[CptnVortex]

Trap was 91.8mph. Yup, Mission. It was a great sunny day so I was pleased to be under 16s and yea, didnt blow anything up!