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Senior Member
Car: 2006 Chrysler 300c AWD
Join Date: Jun 2006
Member Number: 6238
Posts: 790
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2005 Big Body...Here is a thread that covers the subject pretty well.
http://www.300cforums.com/forums/general-discussion/25123-first-night-track.html?highlight=launch+technique.
Post 13 of this thread by Meister leaves very little to chance.
Quote:
"I know there are some threads someplace where guys have pooled their knowledge and will cover a lot more ground that I will attemp to here. I'd strongly encourage you to do word searches for "launch technique", etc., etc. And if one of our other members can come up with some references to where those lists are, please post that info here to help everyone out.
Fan mod: The best first step is to get a cockpit-selectable fan mod and run your radiator fan from the point you start your car at home until racing is over. Don't run the fan for more than 30 minutes without starting your car for two or three minutes or you'll be looking for a jump start. Have jumper cables in your trunk handy. Barring a fancy fan mod make the nickel fan mod. Do a word search. Avoiding heat soak is the key to multiple competitive runs. Along that line a cooler tstat helps greatly as well.
Tire pressure: Front. The only practical variable here is tire pressure. The goal is reduced rolling resistance. Hence the 20" bicycle tires inflated to 140 psi on rail dragsters. All *we* can easily vary is the pressure, so how high does one go? As high as you're comfortable with.
Our stock Contis had 51 psi stamped in them. I'm sure my GYs are at least that high. And I know there's a sizeable safety factor built into that conservative 51 psi. So I inflate to something beyond that myself. I do this at the last service station enroute to the track that has free air.
Rear: The variables you can control here are two-fold: pressure and tread temperature. The goal here is max traction to minimize wheel spin.
Pressure: A pressure less than you'd use on the road is desired here. Experiment. Start with 28 psi and work down. The size of the increment depends on how many passes you realistically expect to make. The more the runs the less the increment. You'll probably find something between 28 and 22 psi to be best. Go too low with street tires and you not only increase rolling resistance but you deform the contact patch and the tire's center isn't contacting well and you lose traction. If I had street tires, a mostly stock engine and was only going to get one pass I'd probably go with 25 psi.
Tread temperature:
Passenger tires: Unlike racing tires, passenger car tires are designed to grip effectively at low to moderate temperatures. Doing a full burnout, if one could do one, would usually be a negative factor and you'd spin more coming off the line. I recommend bypassing the water box, aligning, then backing to a point short of the wet surface. Then do a brake hold, and when signalled do a very brief burnout of no more than a second or so to clean rocks & debris from your tires. Your brief "burnout" is to clean your tread, not to heat it.
Drag radials/racing slicks: Here you must do an extended burnout to realize the full potential of these tires, whose tread compound is forumulated to give the most traction when heated considerably. This is one place where the GSM mod is essential - partial, even 2nd stage, disengagement of ESP won't allow a true burnout with both tires. At least with my car. Only with the GSM mod switch thrown (BAS/ESP light on) and the ESP button pushed (skid icon showing) can I do the full 3- to 4-second burnout required to really roast the tires to bring the tread temperatures up to full grip-tion. The other option is pulling fuse 17, which, unlike the GSM switch, also deactivates ABS braking. Following this serious burnout I'll shallow stage.
Launch: Consistency is important. I can be much more consistent from a dumb launch - brakes on, engine at idle, throttle foot poised on the pedal - than I can from a torque hold, where it's a challenge to be at exactly the desired rpm at launch cue. So dumb launch is the technique I use. At the appropriate light cue, simultaneously smoothly go full throttle and release brakes. The throttle goes to full very rapidly but I refrain from doing a "panic stab". For me the difference is hard to describe but the results are night & day. If I stab the throttle to the carpet I'll spin excessively. If I begin application of throttle just as quickly, but take nanoseconds longer to reach full throttle I'll hook and go. Practice this and find what works best for your particular combination of track conditions, tires and power on any given day.
When to launch: Don't wait for the green light. You'll be looking at disappearing tail lights if you do. There are two delays in play here. The first is you. From the time your brain registers the stimulus that is your launch cue until you've told your foot to rapidly but smoothly go full throttle, until you foot actually does it takes a while. Several hundredths of a second anyway.
The second is the drivetrain. From the time the gas pedal begins moving till the PCM registers it and opens the throttle, till all the slack is taken out of the drivetrain and the wheels are driven takes a short while also.
Thus we have to lead the green light, and by just enough that the car is just beginning to move as the light turns green, thus breaking the beam nearly immediately with the light going green For me that lead point for some time has been just as the second amber light has fully bloomed - when I'm sure I'm seeing the entire face illuminated, not just the center of it. But since the cam/heads/headers install my car begins moving ever so little earlier. Using my old cues I'll now red light by about -.015 or so. If I delay minutely I'll cut a good clean green. (Added note, 10/1/06: The production prototype air intake system I've just installed increases throttle response dramatically, necessitating a further delay. I did, indeed, red light first run post-install - by -.012.)
Well, hope you're still awake, xxxx. We've barely scatched the surface - there's much more to learn - shallow stage vs. deep stage, the advantages of each, etc., etc. Again, I've seen some excellent collections of drag racing tips. Hopefully you'll find them or other forum mates will point them out.
All the best as you venture out, and remember to relax and enjoy it - it's a great deal of fun, especially when you're out with your fellow LXers."
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275/40/20 Pirelli P Zero Rosso tires; Detata Double D 20x9 chrome wheels; S&B CAI; KW VII coilovers; Dynatech LT Headers; CORSA Exhaust; 180 Tstat; DR Heads; FRI Littleboy Cam; 6.1 forged crank & dampener; RR forged 8.6:1 pistons; forged rods; Pillar PSI & AFR meter; Predator.
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05-17-2007, 12:44 AM
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