Your guide to drag strip success w/pics.
- Thread starter outofstep
- Start date
this takes a bit more practice, but you can prespool the turbo in your manual by holding the ebrake up (preloading the drivetrain, i think someone mentioned it). a little more wear on your clutch but its easier on the tranny itself since it eliminates the slack between gears/shock when you launch.
also I if youre new to drag racing, you may think your reaction time is related to e.t. or 60ft and jump the gun. ITS NOT. the time doesnt start until you trip the sensor so take your time and concentrate on what your doing.
also I if youre new to drag racing, you may think your reaction time is related to e.t. or 60ft and jump the gun. ITS NOT. the time doesnt start until you trip the sensor so take your time and concentrate on what your doing.
Err... this depends on what kind of racing you are doing. I've never seen a street legal style race that uses reaction time... but it's there for a reason, lots of race types do.diy guy said:
Optimum shift points can be calculated if you have a current dyno graph that shows horsepower numbers all the way up to redline.
Combine this with the shift point calculator at http://www.bgsoflex.com/shifter.html and the "MKIII gear ratios" thread in the FAQ: http://www.supramania.com/forums/showthread.php?t=1084
More general info here: http://www.allpar.com/eek/hp-vs-torque.html
Combine this with the shift point calculator at http://www.bgsoflex.com/shifter.html and the "MKIII gear ratios" thread in the FAQ: http://www.supramania.com/forums/showthread.php?t=1084
More general info here: http://www.allpar.com/eek/hp-vs-torque.html
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Optimum shift points are almost always redline. Every time you shift, you are no longer accelerating. I'll take a slight decline from peak horsepower over ZERO horepower while shifting and then subsequent respool and then eventual climb back up to peak horsepower.
You want to maintain acceleration as long as you can, you do this by staying in gear as long as you can. The instant you disengage you begin decelerating. Keep that to a minumum by staying in gear as long as possible.
The only times you need to calculate shift points is if you have a car that drops off just a retarded amount of horsepower before redline. Our cars don't do that even stock. If you've got any upgraded or larger turbo, you shouldnt drop off much at all before redline.
You want to maintain acceleration as long as you can, you do this by staying in gear as long as you can. The instant you disengage you begin decelerating. Keep that to a minumum by staying in gear as long as possible.
The only times you need to calculate shift points is if you have a car that drops off just a retarded amount of horsepower before redline. Our cars don't do that even stock. If you've got any upgraded or larger turbo, you shouldnt drop off much at all before redline.
JustAnotherVictim
Supramania Contributor
outofstep said:
commented on the sf thread, but got to argue this point, i shift at 55xxprm, why? because when i dynoed the car it was falling off so bad and i could feel it fall off that it was killing my MPH and times, now i just got a cutout so ill see how it feels but with a 3in exaust all the way back with a working cat, 8psi and intake the power fell off like a mofo
im gonna redyno it with the cutout off, so maybe that will change the curve
graph link: el linko
<l><l>
Me and outofstep PM'd on this subject. Here are my current thoughts:
The number of times you have to shift while going down the strip will likely remain the same, whether you shift at redline, or slightly before. If you can avoid a shift by going to redline, then by all means do this!
However, if you cannot save a shift, then the amount of time spent with zero power (in the middle of the shift) remains constant, and so it makes sense to calculate your optimum shift points for "maxiumum power under the curve".
For most of our cars that have been upgraded, the optimum shift point will be above redline for all gear shifts. But I maintain that it is still a good idea to get your dyno graph out and plug in the numbers.
Jim
The number of times you have to shift while going down the strip will likely remain the same, whether you shift at redline, or slightly before. If you can avoid a shift by going to redline, then by all means do this!
However, if you cannot save a shift, then the amount of time spent with zero power (in the middle of the shift) remains constant, and so it makes sense to calculate your optimum shift points for "maxiumum power under the curve".
For most of our cars that have been upgraded, the optimum shift point will be above redline for all gear shifts. But I maintain that it is still a good idea to get your dyno graph out and plug in the numbers.
Jim
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Maybe I didn't get it across well the first time.
It's an integration problem for dH/dT over total rpm. Maximising total area under the curve. So unless you have crazy retarded drop off before redline, optimum shiftpoint will always be redline.
This becomes even more so the case with anything larger than stock.
Very few turbo cars need to shift before redline, it's the nature of the beast; it's turbo. I have seen many NA cars where you actualy would want to shift before redline. But it's going to be so rare a case on our cars, that's it's pretty much not even worth worrying about. If you actualy do have a situation that would cause for shifting before redline with a turbo 7M, something is wrong with your engine...
It's an integration problem for dH/dT over total rpm. Maximising total area under the curve. So unless you have crazy retarded drop off before redline, optimum shiftpoint will always be redline.
This becomes even more so the case with anything larger than stock.
Very few turbo cars need to shift before redline, it's the nature of the beast; it's turbo. I have seen many NA cars where you actualy would want to shift before redline. But it's going to be so rare a case on our cars, that's it's pretty much not even worth worrying about. If you actualy do have a situation that would cause for shifting before redline with a turbo 7M, something is wrong with your engine...
Heckler said:
Like outofstep said, it's about area under the curve, not the time spent at zero power. If you spend a second at zero power at 60 mph this hurts your time more than if you were at 80 mph. You can graph this if you want. Figure out how far you'll go in a fixed amount of time with a shift at one speed as opposed to a shift at a higher speed. You'll find that you'll cover more distance in the same time if you shift at a higher speed with the same number of shifts. This is just a simple calculus concept.
True, but our dyno graph does fall off, because we're producing 460 ft-lbs of torque at 2800 rpm from a stock ct-26, this leads to a massive heap of midrange power, but typical, ct-26 top end. Consequently, by the time the engine gets to 5250, power has peaked, due to the surge of midrange torque, and power is on it's way down.
This is not a problem with the engine, it is getting the most midrange power from an undersized turbo. Short shifting at 5500 allows the engine to maximize the power under the curve, and helpped out a ton.
In a stock car, this would be non-sense, but the CT gives a ton of midrange power, and staying in the high revs would negate this power, as it behaves very much like a typicle, 300 hp mkiii above 5K.
Below 5K, it owns.
This is not a problem with the engine, it is getting the most midrange power from an undersized turbo. Short shifting at 5500 allows the engine to maximize the power under the curve, and helpped out a ton.
In a stock car, this would be non-sense, but the CT gives a ton of midrange power, and staying in the high revs would negate this power, as it behaves very much like a typicle, 300 hp mkiii above 5K.
Below 5K, it owns.
just a little comment on the higher stall converters. they usually go for about 450, not ~200. ive called around to a few places and its all in the mid 4 range. i called hughes, pro-torque, IPT and another place i dont remember the name and they all wanted around 450 to rework the stock converter to around a 3k stall.
I will be building an upgraded CT car this winter, my goal is to beat MKIIISupraGuy's record on the upgraded CT in the 1/4th. This thread along with loads of practice at Great Lakes Dragaway ( Same place he got the record, 12.1 ), will hopefully help me out.
IHI-RHC7;250730 said:True, but our dyno graph does fall off, because we're producing 460 ft-lbs of torque at 2800 rpm from a stock ct-26, this leads to a massive heap of midrange power, but typical, ct-26 top end. Consequently, by the time the engine gets to 5250, power has peaked, due to the surge of midrange torque, and power is on it's way down.
This is not a problem with the engine, it is getting the most midrange power from an undersized turbo. Short shifting at 5500 allows the engine to maximize the power under the curve, and helpped out a ton.
In a stock car, this would be non-sense, but the CT gives a ton of midrange power, and staying in the high revs would negate this power, as it behaves very much like a typicle, 300 hp mkiii above 5K.
Below 5K, it owns.
I have to say that the torque you're putting out isn't going to be a big deal after you've started moving already. If we're talking shift points here we want to think about staying in the HP band as much as possible when shifting from 2 to 3 and from 3 to 4. You may have to shift 4 to 5, but it's unlikely if you have a good gear set. If you have your HP graph this is an easy thing to think about, or if you're mostly stock I'm sure somewhere you can find the graph online. What we're looking for is the HP peak. We want to have a target shift point just after power starts to drop off. This is because of one thing, none of us is going to shift faster than about 1/2 a second unless power shifting which I agree isn't worth a blown tranny. If you have a shift light, set it at the peak of your HP RPM, only because again, none of us are machines and it will take a 1/2 second to realize the light is on, which puts us at a perfect shift point to shift above the HP peak, lose that 1/2 second shifting, and probably 1500 RPM and put us right back near peak HP keeping us in the band as long as possible. Another thing to think about is shifting before crossing the line. If you can hit your rev limiter before getting too close to the line, shift. If you're just about to hit it, or bounce once, I wouldn't worry about losing that time shifting, the limiter is there for a reason...to save your engine and turbo. In a perfect world you'd be across the line, full throttle, in 4th gear just over your HP peak or at redline.
I agree totally. If you can't do better than 14 seconds with BPU your a friggin embarrassment to the supra community. For shame!
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