Launch Tips for Drag Racing- 1/4 mile
Quotes taken from BMW/other make Drag Fans (racing that is ):
"I do think lowering the psi in your rear tires will make a difference. I don't know what size tires you have, but if you have the stock 245/40-17's in the rear, you want more tires on the road, not less when it comes to the 1/4 mile drag strip for launching.
Now the standard mfgr recommended psi for 245/40-17's is 32 psi. Here's the key, you gotta play with it some. If you go too low you could have cupping, and that doesn't help either.
I'm guessing at 245/40-17's for you, but that is my OEM size too for my car and I have run it at the track with those OEM Dunlops before (I usually run my drag radials at the track...). Anyhow, you're safe dropping them to 28 psi, no problem. You might even be able to go as low as 26 psi, maybe 25 psi, depends on the weather and the track surface temps.
Also, for less friction/rolling resistance, take the front tires up to 45-55 psi.
Also, for weight savings, take as much out of your car as you can. The spare tire and mounting apparatus can weigh as much as 30-40 lbs.
Back seat, passenger seat (my passenger seat weighs like 60 lbs), any excess weight. Take the gas tank down to 1/8th a tank of gas, 1 gallon of gas can weigh like 5 lbs, run a 13-16 gallon tank down to 1/8th a tank, another 50-70 lbs, etc...
You can shave 150-200 lbs with that kind of prep work.
Also, try launching higher. You need to find the sweet spot, between bogging and wheelspin, and that will takes lots of practice and change from day to day, track to track, etc...
The more traction you get from the tires, the higher you can launch your car, and you generally want to launch above torque peak so that when the tires grab, the tach drops, and if you can work the clutch right, avoid major wheelspin, you'll launch like a rocket.
With my DR's I launch at 5500 rpm. On my OEM Dunlops more like 4500-4800 rpm at 26 psi.
Gotta get the throttle steady when staging, an even rpm, clutch half in, half out, just about to grab, the tach dipping ever so slightly.
When the green hits, don't slam your foot down on the gas to the floor, quickly and steadily squeeze it to the floor, and gradually but quickly let out the clutch, sense too much throttle, keep it steadily continually going down and adjust the power to the wheels with the clutch, not the gas.
Now, if when you're shifting you're chirping your tires on every shift, you're losing maybe a tenth. In my car if I'm not careful I could get sideways on every shift, but this method can help anyone chirping on shifts too much:
Find the appropriate amount of throttle to stab back down, then squeeze it to the floor. For me, it's about halfway, then just like on the launch, I quickly squeeze the gas pedal down. I stab halfway (versus all the way back to the floor) and quickly squeeze the pedal back down to the floor. Makes for more uneventful shifts and buys me a couple tenths in the 1/4 mile (I have to shift 3 times, I finish in 4th gear).
Your car may work best with a 2/3rd stab then squeeze, or 3/4th throttle then the quick squeeze, all these techniques require practice and could change given the weather or the track. I take notes on all these items and then tape the timeslip next to it on a notebook page and save it for the future track visits.
Also, if you feel like you're destroying your clutch, you're launching properly if you feel like you preserved some of it, you're not launching right... "
base text sourced from bimmerforums.com