DRAG RACING QUESTIONS - NEED EXPERTS HELP

[onerareviper]

Viperholics,

I have a 1998 Viper GTS with smooth tubes, filters, 2.5' Corsa, Sean Roe high-flow cats, 18' Purner Street Wheels (A bit lighter than stock), and 3.73 gears (430-440 RWHP). I have driven a stock viper with 3.07 gears, and it seemed much slower than mine, especially out of the hole. I have not done any 1/4 mile runs, but have practiced my launch technique on the street (Ride the clutch out while applying more throttle with no or little wheel spin). I usually shift around 5,500 RPM's. I keep my tire pressure at 29 (18' pilot sports). Can you experts give me some tips if I ever go to the strip: Tire pressure, RPM shift points, launch techniques, burnout technique, etc... I hoping for 11's at 120+ (top of 4'th gear). Thanks for any tips/advice.

Steve

P.S. - I realize any more HP/Torque, and I will probably have to change the gear. But for now, I love the 3.73's.

 

[Craig 201 MPH]

Go to www.btrviper.com Tom has a "How to Drag race you Viper" video in both VHS and DVD format, I beleive it's for sale on his site. I havn't seen it but there has been much praise for it on the board.

Craig

 

[onerareviper]

Craig,

I am aware of this video, and plan to order it. Although, I would like other racer's opinions. There is more than one way to skin a cat (or a vette)...

 

[Venom Lover]

You can pull 11's at 120 mph on street tires. It will all depend on the launch. Personally, my best on street tires was 12.0 at 122 mph in my '97 (see signature for mods), but I don't claim to know how to launch really well on street tires. Best short time was 1.9 sec. I find it more fun to run on ET streets and run in the mid 11's.

I agree, get Welch's video. It'll tell you everything you need to know.

Once concern I have is, I don't know if you will need 5th or not with the 3.73 gear. Probably not, given your mods, but I'm curious what the top speed is in 4th on your car. Any ideas?

 

[Venom Lover]

Well, if you want opinions other than Welch's, here goes.

(1) Buy Purner's slick and skinny set-up. You already know John, obviously. If you want to do any serious drag racing, it's more fun to be able to do a big smokey burnout and have a really good launch every time.
(2) With slicks, drive through the water box, rev to 4500 rpm, dump the clutch and stand on the brake. Bring the revs to 5500 rpm and let 'em roast until you feel the tires start to bite a little. Ease off the gas and roll out. Don't do a dry hop.
(3) Stage and bring the revs to 4000 rpm. Dump the clutch fast. Depending on track conditions, you will probably be able to increase revs on subsequent runs, so long as you're not spinning. Short times of 1.6 will be yours every time unless the track is terrible.

If you must run on street tires, avoid the water, do a little dry hop to get the rocks off your tires, and use whatever technique seems to work for you on the street to launch. Of course the track should be stickier, so you can probably be a bit more aggressive. It sounds like you're on the right track with your technique. You should be able to get 1.8 sec short times on Pilot Sports.

 

[SteveBCloud9]

I'm far from an expert but I hear shifting at the top of your HP curve is the way to go. Have your car Dyno'd and look to see where you make peak HP.

 

[meggleto]

Shifting should occur at the point when you will be making equal power at the wheels in the higher gear. You'll need to know your gear ratios and have a dyno printout to do the calculations.

Your hp curve peaks and then drops off. You'll want to shift at the point after the peak where in the next gear you'll have the same rwhp but at the rpm that is before the hp peak.

There's a rule of thumb to use 10% past the peak hp rpm. For example if your hp peak is at 5000rpm then shift at 5500rpm. The rule of thumb is usually a decent estimate for going into gears 3 to 6. The shift point for 1st to 2nd is usually redline or close to it.

If you have the dyno numbers and gear ratios then you can make a spreadsheet and figure out the shift points pretty easily.

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I'm far from an expert but I hear shifting at the top of your HP curve is the way to go. Have your car Dyno'd and look to see where you make peak HP.

 

[Tom Welch]

Steve,

Im not going to get long winded here because of all of the very good posts from other board visitors, but one thing that is not helping you is the 3.73 gear.

Lower numerical gears are harder to initially spin your tires, but once spinning they don't want to stop. Higher numerical gears will initially spin your tires much, much easier but they will not spin as long.

There are lots of methods for launching on stock tires. First you need to establish your dragstrip tire pressure for the wheel/tire combination that you are using. This is done by launching on a clean concrete surface and reading the tread marks left behind. They are the best indication of your contact patch under acceleration. Pressure too high will leave darker marks near the center of the patch and pressure too low will leave darker "streaks" of rubber on the outer edges of the contact patch. You are looking for the pressure that will give even colored tread marks across the contact patch. Note that pressure and use it at the track.

NEVER, get water on your stock type tires and never do a water burnout. Like Venomlover said, just clean the rocks and debris from them before entering the racing surface.

E.T. streets will net the best elapsed times from your viper. Unfortunately they are expensive as rims for all four wheels must be purchased.

With stock tires I launch at around 2500 rpm slipping the clutch slightly as the car tries to lunge ahead. It takes practice to get the feel for it.

Take care, and good luck,

OH, BTW, if you don't intend on roadcoarse racing anytime soon you can take loose your front swaybar. This will help drastically with weight transfer.

Tom

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