Any idea of the magnitude of the improvement in ET from powershifting? In my case I a running right around 11sec. I know that a shift takes in the range of 0.2sec. If a power shift cut this in half, to 0.1sec I would gain 0.3sec and be running in the 10.7s. Is this possible? If so, I going to try it this weekend, since I having the T56 rebuilt/upgraded this winter anyway!

Rich Krause

 

Well, I would say your theory is not exactly correct. I have done it in previous cars and like most will say...you can shift just as fast by letting off. I usually keep my foot about 1/2 on the throttle when I shift.
You aren't really going to be looking at any realistic gains unless your normal shifting is slow. The key here is that you said you will be rebuilding your tranny anyways so I guess your not really thinking about the after effects

 

Rich, want me to make a pass in your car for ya? j/k of course

I usually ran .2 sec and .75-1 mph faster back when I powershifted (compared to a regular shift). I dont really do it anymore due to the fact that my college butt cant afford rebuilds that often. I since have learned that proper speed shifting is easier on the tranny, and is just as fast (based on my times) in the 1/4 as powershifting. I lift on the throttle ~25% between shifts....just right in my opinion for my car and driving style. That is how I have ran my fastest times.

Jason

 

This would only hold true if the car actually stopped moving forward between shifts but the time continued. While you shift, the car is still moving forward...thus the speed at which you shift would only affect how quickly the car begins accelerating after the start of the shift. This isn't directly proportional to the 1/4 mile ET. This makes sense to me, but I don't know if I know how to relay it. I'd think 1-2 tenths over the 1/4 could be picked up by power shifting.

 

I can attest. When I was brand new to the track, my first two runs were without powershifting my 99 T/A. Both were 14.2's @ 105. Third run, all out powershifts, I clicked a 13.6@105, same 60' times. You be the judge.

 

where is the T/A now? i dont know about that...

 

Well, I guess I need to try it to find out. I'll make sure it's the last day I plan to run the car this year though

I do want to see 10.xxx before the year is out and if speed shifting is what it takes, I will do it! Don't they say "drive it like 'ya stole it"?

Rich Krause

 

Lemon Law two years ago. I actually took that thing to a 13.51@106.9 bone stock, 16X8 RSA's, paper filter even. The huge improvement was the fact that was my first time at the track, and even though I knew how to powershift, I did'nt know the car too well. I just let it rip on that third run. 100% honesty though.

 

Rich I can't be the first one to tell you this but put a bigger n2o jet in it to go faster and if that is the biggest one take a drill bit out and drill it bigger j/k on the last part. But really why don't you add a little more n2o and fuel to that car?

 

The thought has certainly crossed my mind!

Rich Krause

 

my mph went up a good bit by powershifting 3rd. i just run 1/8mi.
jeremy

 

I have never been a believer of powershifting. Power shifting does not increase the speed of shifting. Basically you can put the car in the next gear at the same speed weather at WOT, Idle or engine off. The only theoritacial benefit of powershifting would be high engine RPM's when releasing the clutch.
Assuming you press the clutch peddle enough to release the clutch when shifting you will actually waste energy compressing the suspension and upsetting the chassis instead of creating forward movement.

I am a firm believer of speed shifting. You don't need to release the clutch, just open the synchros to shift. That plus matching the RPM/Load with the MPH of the shift will net lower ET's.

Basically, spend the time to learn to drive the car.

Not saying you can't drive Rich, you may be getting all you can from the car now if you are shifting correctly.

 

red, what kinda 1/8 times do you run with that 383? just wondrin'...
jeremy

 

The only way to get maximum ET out of a manually-shifted car is to powershift. As such, I will respectfully disagree with a couple of folks here..

I suppose you can go through the basic motions at about the same speed, but you will lose ET by letting off the gas. More on this below...

Correct, and thus less "bog" on the motor due to a LOT more momentum. Instead of the motor loosing rpm as you let off the gas, it actually gains it. When the clutch is again released, and assuming this can be done very quickly, the motor keeps a lot more of its kinetic energy, and thus transfers more of this energy to the transmission/driveshaft/rearend/etc.

Obviously a poorly-gripping clutch or lack of traction will hurt, and in this case, powershifting might hurt ET.

You're going to waste energy anyways. You will waste less, and upset the chassis less by powershifting than by lift-throttle shifting, IMHO. The chassis will unload a lot more by lifting the throttle, thus when you get back on the throttle, it will go through the motions of loading back up again.

Once again though, if you are traction limited, powershifting will tend to make this situation worse....especially the 1/2 shift.

I could not disagree more with this statement. The only way to shift a street-style transmission w/o using the clutch is to allow the engine rpm to drop down enough to match the speed of the tranny in the next lower gear. This will absolutely kill ET.

With this I agree 100%.

With all that said, make no mistake - powershifting is VERY hard on the transmission, and as mentioned earlier, if you are traction-limited, it can actually hurt vice help. Also, if you have a slipping clutch, powershifting will worsent that condition.

However, for ultimate ET, ask anybody that races heads-up in a class that requires a street-style transmission and they will all tell you the same thing - powershifting is the only way to get the ultimate ET out of a car.

If you're curious on what powershifting sounds like, you are invited to download a video of my car from a bit over a year ago. Except for the spinning of the tires early in the video, the noise is all of my car, so you can hear what is going on...

460k wmv

3 mb MPEG

 

A buddy of mine w/ his heads/cam/S-trimmed Z28 has shown me time and again he gains about .3 in the 1/4 by powershifting.

Do I do it?? Nope.....I abuse my tranny enough without powershifting. I'm still waiting for the day I finally destroy it (sadly, I have a feeling my ceramic clutch is gonna go first ). Of course, I'm the same guy who refuses to ice his intake; guess I'm just not desperate enough to shave a couple of tenths.

But hell, if you are rebuilding it, why not?? AND add some juice while you are at it. AND launch the **** out of the car.