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Penetration before detonation
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Discussion Starter · #1 ·
That's right- I'm finally putting Darlene on the strip tomorrow. I'm nervous, but really, really excited and even more hopeful. Here's a few things I'd like to know before I get to the track:

1. With the 315 Sumis I have in the back, what suggested tire pressure should I run?

2. I have my two-step set at 3300 launch RPM- is this a good RPM to launch at, with the 3.27:1 gearing and the Sumis, or should I set it higher or lower?

3. Along with the first-step RPM, what are the best shift points?

And, finally,

4. Should I powershift, or just shift really quickly?

Guys, ya'll are the best. Wish me luck!
 

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youll have to play around with the right launch speed, you want the tires to spin a little but not blow them away. as for pressure i wouldnt really run them any lower that dd pressure. street tires dont respond to this.
 

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youll have to play around with the right launch speed, you want the tires to spin a little but not blow them away. as for pressure i wouldnt really run them any lower that dd pressure. street tires dont respond to this.
if your proficient at power shiofting then do that, if not do whats best for you.

youll have to play around with the shift points to see what works the best for your car
 

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dont powershift get used to the track first. when your comfortable try a few powershifts out. i shift at about 5600 (not powershifting).
 

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I would lower the tire pressure, but not as low as a drag radial. I have always had good results with that. Probably about 20psi.

Do a few passes at dd pressure, and then lower it, see if it helps.
 

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Manual transmission shifting help.

I'll pass along what I have learned over a few years.

Before 10 people say it after I post this, let me say as a warning that all these methods are for racing, not day to day driving, and yes, they are hard on your car. It's hard on the clutch, the transmission, the rear end, U joints, and the engine. And that's assuming you don't blow a shift, which can be catastrophic.

Launching.

Okay. The first thing in racing is the launch. This depends greatly on your car & how much power it makes, what gears you have, what tires you have, and how sticky the track is. Atmospheric conditions also play a part in how your car runs. So even when you find your car's sweet spot, what worked one week for you may need adjusting another week or at another track.

The best launch is one where there is no wheel spin. Wheel spin = less forward movement. Try dropping your clutch at 2500 rpm. If the engine bogs down, you need a higher rpm launch. If you light the tires up, you need a lower rpm launch. Work your way up and down in 100 rpm increments until you find your car's sweet spot.
Sometimes, particularly in cars with lots of power, or in cars with an open differential (non-posi), or on a shitty track surface, you find that no matter where you dump the clutch, you spin the tires too much. In this case, sometimes you have to sidestep, or slip the clutch on the launch. This means slowly letting the clutch out as you roll on to the throttle to launch as hard as you can but without spinning the tires.

Shifting.

The best result for racing is power shifting. It sounds easy in principle, but it takes concentration, as a blown shift can be disastrous, especially if you are running a car with no rev limiter.

To perform a power shift, you keep your right foot on the accelerator pedal during the shift. When it's time to shift, keep the accelerator wide open. With your left foot, you stab the clutch in one quick motion, down and up, moving the shifter to the next gear as your leg is descending & disengaging the clutch. The clutch is only disengaged for a split second, just enough for you to ram it in to the next gear.

How do you know at what rpm to make the power shift? Again, this depends on the car. The reason you power shift is the quicker shift helps keep the rpm up higher where the power is. So this is also a trial & error thing, and takes you getting to know your car. If you are driving a typical Mustang GT that makes it's peak horsepower around 5700 rpm, stab the clutch right at 5700 rpm. Pay attention. If you do it right, the rpm should jump up just shy of your rev limiter, and then when the clutch re-engages, your rpm will still be right where all the horsepower is. Sometimes you're better off making the shift a little sooner in the rpm range, sometimes a little higher. If you bounce it off the rev limiter, you've made the shift too late, or at too high an rpm. You have to work at it until you get the best result for your car.


p.s. breaking **** is cool. :D
 

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pretty much the only advice anybody can give you is just try different things each pass, and decide what works best for you and your driving style.
 

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Penetration before detonation
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Discussion Starter · #13 ·
Alright, so I went up, had the tires at the stock pressure, and came away with a decent enough mph but a really shitty time! My tires don't grip, not even in third, so at about 60-65 mph, the car wanted to go into the wall (UGH!) Saved it though, and I'm goin back this weekend. I don't have the slip on me, but this is what I remember;

R/T: .225
60': 2.5
1/4: 14.7
MPH: 100.31

I KNOW there are better times to be had, but it's gonna take a good while of experimenting with shifts and launching to get that elusive low-14 or even high-13 second timeslip. Thanks for the help guys, you rock!
 

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Penetration before detonation
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Discussion Starter · #14 ·
Goin up there tomorrow, too- I'll be nailing that 1-2 shift
 

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Penetration before detonation
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Discussion Starter · #16 ·
Damn. Got the traction issue under control- lowered the rears to 23 psi- now the shifting is where I gotta improve. Ran a 14.40 @ 98.3 mph and beat the living dogpiss out of an old riced-up Accord. It's all about practice...
 

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sumi's are very wallet-friendly. but they dont hook, i ran them for about a year.

dont powershift until you know can fork up enough cash when stuff breaks. cuz it will when you powershift.

dont know what elevation you are, but im pretty sure you can hit 13.9s all night long.

oh and make sure traction control is off lol.
 
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