New to Viper: Performance Driving Questions

[lilviv]

Hi guys, I am new to the Viper, got my first one last week or so. I've had fun driving it, put around 300 miles or so on it, so far. But, I had a couple questions I was hoping you veterans could help me with!

I have a '99 GTS with Corsa Exhaust and K&N's, Cold Air Box . . . so basically stock. Stock wheels and stock Pilot Sports.

1) What is the optimal shift point?
2) I noticed there is a yellow line and a red line. Is it safe to run all the way through the yellow into (or right at) the red?
3) If you are into the yellow, is that somehow detrimental to the car?
4) Is there a rev. limiter on the car (didn't want to try to find it by over-revving)?
5) Also, what RPM in near stock form (like mine) is best to launch the car at to get the optimal 60' time from zero?

Thanks guys, and sorry for the stupid questions! I'm a newbie and want to learn and get this down!

 

[plumcrazy]

if those are original tires...get rid of them.

i like to shift at around what looks like 5500 rpm's (probably higher by the time it happens)

the rev limiter is like 7000 rpm's i think. if you hit it, you'll know it. the car sputters and stammers.

dont ask me as i cant launch a viper on a track to save my life...lol

 

[Chuck 98 RT/10]

1. Optimal for what? 5200-5400 for performance. 2000-3000 for mileage.
2. Yes, although why you would I don't know.
3. Only as much as the wear caused by the extra rpms.
4. Yes. 6200.
5. Depends on your style.

 

[Detlef]

I am no expert, but when I dynoed my GTS, I noticed the torque curve to drop off after around 5,200 RPM, so may make sense to shift around that speed.

 

[RobZ]

Well I had some free time soooooo............

Here is a dyno of my stockish '97 GTS (K&N's and smooth tubes) at 3000 ft on a Mustang AWD Dyno. Same setup did 422 RWHP and 466 RWTQ on a Dynojet.

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Stock gear ratios with stock rearend with 335/35/17's.

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Shifting at 6000 RPM will yield the following RPM in the next higher gear.

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My dyno numbers, Blue = over 400RWTQ. Red = over 300RWHP. It is ideal for me to shift between 5000 to 5200 RPM to maintain the highest posible rate of acceleration.

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Hope this helps.

 

[lilviv]

1. Yeah, I wanted to know for performance, not mileage.
2. I am just used to another car, where highest revs seem to be best . . . but yeap, optimal shift point appears to be before yellow line, so you are right . . . no reason to go through the yellow/red line.
5. I will play with the car at the track and see.

And RobZ, the graphs did help, thank you.

Thanks for the replies, guys! Thanks for helping a newbie get started.

 

[SidewinderGTS]

My mag says to launch at 2400 RPM,dump the clutch gas to the floor and your off.If under 2400 engine bogs,over 2400rpm your smooking the tires.
This might work on the street,at the track I had no luck.Had old tires.

 

[TexasPettey]

I believe that the shift point discussion is not complete without looking at the rear wheel thrust and gear ratios. The peak engine torque range is only part of the equation. You should shift to stay in the peak rear wheel thrust range. Given the torque graph shown for illustration, the shift points should be at 5700, basically the redline. Here's why.

In 2nd gear, the ratio is 1.78:1. In 3rd gear the ratio is 1.3:1. You should shift from 2nd to 3rd when the torque curve is 75% of the peak or max RPM, whichever comes first. This is because 2nd gear as about 25% more gearing amplification of the torque to the rear wheels.

As an example, the relative RW torque in 2nd gear at 5700 RPM would be ~325 * 1.78 = 578. Peak torque in 3rd gear yields 436 * 1.3 = 566. In this scenario, it is faster to be anywhere in the range of 2K RPM to 5.7K RPM in 2nd gear than it is to be at the peak power range in 3rd gear.

4th gear is 1:1. So, 3rd gear redline is 325 * 1.3 = 422. Slightly less than the peak of 436. In that case, it may be worth while to shift slightly before the redline. If you shifted at 5500 RPM, it looks like you would be 350 * 1.3 = 455. so, somewhere between 5500 and 5700 is the optimal point.

This is somewhat simplified, but is close enough to illustrate the mechanics.

 

[Chuck 98 RT/10]

The math might look good on paper but in practice with stock tires and maybe 20hp of bolt-ons 5700 is waaaaaaaaaay too high for optimum 1/4 times. I've done a gazillion runs in my stocker and as much fun at those high rpms are they result in slower dragstrip times.

Maybe with some sticky Kumhos or another 80hp the shift point might move up. Dunno. But stock is pretty much at the 5400 mark.