How long are you guys staying in 3rd on the strip..6300?...6500?....redline?...:eek:

Took the car out to work on my technique for the first time today and DAYUM...this is Fun!:D

Thanks in advance!

David In Indy
03Z-ripper
12.6/112/2.0

 

If you hit the limiter, you loose time. But, I hold 3rd until the very last second. Its not gaining RPM quickly, so when you get almost to the redline (I'm actually on it in my car), pull 4th.

 

Thanks J-

One quick question. How high does the tach usually go when you push in the clutch...mojo told me to expect aprox. 100 rpm but he's driving a c4 and is lightning fast with his mechanics.

TIA
:cheers:

 

That's gonna depend on how fast you are with the clutch and the shifter. Obviously the goal is to NOT hit the limiter, because you'll be losing power, so you probably ought to plan on shifting around 6300-6400. The shift light on the HUD lights at 6300, so that's not a bad place to start.

 

in my car as soon as the physical tack in the dash touches red, the rev limiter kicks in.

experiment to make sure your car is the same, or find out where.

hold 3rd as long as possible. same with the other gears.

especially 3rd though.

 

I hold each gear until approx 200 RPM before redline and complete the shift without hitting the rev limiter. Hope this helps.

Les

 

If you plan to do much powershifting, you really need a plan as to how you are going to get the transmission rebuilt. C5 trannies - M6 or M12's, really don't like to be powershifted. Trust me on this.

Having said that, before I quit powershifting my last C5 on a regular basis, I allowed 100 rpm before redline and never hit the rev limiter.

 

I suggest you consider a Hypertech computer upgrade. It will allow you to move the shift point up to 7,100 RPMs. You can then feel the slight fall off in power at about 6,600-6,700 RPMs and shift. The motor will easily pull to 7,100 but it starts to lose power and you can feel it with practice. You never want to be on the revlimiter when driving for time or speed.

If you decide to install a 160 degree thermostat be sure to get your oil temp up to at least 150 degrees before you hammer it. I recommend 160 degrees if at all possible. You don't want to smear any bearings.

Good luck!

 

I have actually gotten my best times by shifting around 6000. Just look for the factory shift light to come on in the HUD (which comes on at like 5800) and by the time you have reacted to it you are at 6000.

If you look at the dyno chart of a stock motor (see below) it stops making HP around 5800-5900 RPM and just runs level to the 6700 rev limiter (which is why I would assume the shift light comes on at this point). What I have found is not to power shift in the sense of leaving it floored while you jam the clutch in and out to shift, but my technique is to actually be moving the shifter out of gear in unison with my pushing down on the clutch pedal, that way by the time I am about halfway to the floor I am starting to head into the next gear. You don't need to push the clutch all the way to shift the gears. I have found this to be a very fast way to shift without tearing up the tranny by basically doing a neutral drop in every gear if you power shift. You also will lose time if you spin when shifting and power shifting can do just that.

:cheers:


Click here for dyno chart

Edited because for some reason I couldn't direct post my image. :mad


[Modified by **** Finger, 1:19 AM 10/16/2003]

 

Excellent post,

I had the same questions. Do you also get the "lugging" effect of the car when trying to powershift. What am I doing wrong? I hate when that happens to me. It usually happens when I'm excited. I thought of putting a shift light in my car for that same reason. Thanks :steering:

 

If you are lugging the car at shift either traction controls are not off, you are hitting the rev limiter, are shifting WAY too low on RPM, or are shifting so slow you are on the low side of the power curve after the shift (that is why you want to shift around 6000 to 6100 IMO). Hope one of these makes sense to you.

Les :cheers:

 

What's all this nonsense about shifting below redline? Obviously the people who recommend shifting below redline haven't seen a stock z06 dyno chart. for those, let me post one (mine) here:



Now, it is a fact that you will get the best acceleration by being in the gear that puts you at the highest HP point. Now, the first three shifts (1-2, 2-3, and 3-4) in a z06 drop the revs by ~30%, which at 6500RPM brings you to 4500RPM. 4500!! So the moment I shift, my 365rwhp car becomes a 295rwhp car until the HP builds back up again, because Chevy chose to not give us a close-ratio transmission.

Anyways.. look what happens if you shift earlier.. let's say you shift at 6k. 6k*.7=4200RPM, which lands us at 260rwhp after the shift. Obviously worse. The hp peak is so close to the rev limiter that for the highest performance you want to shift as close as possible to the rev limiter, to spend as much time as possible at the peak and as little time as possible building back up to the peak again in the next gear. Remember, it's all about area under the HP curve throughout the race.

Andi

 

Andi,

Please also post your 1/4 mile times. Dyno's don't mean anything, other than tuning and relative power at different points on the curve. The top Z06 drag racers here shift between 6K and 6200, if you have a result that says holding longer is better I'd like to learn how.

Not a flame, just asking.

Les :cheers:

 

Andi,

I beg to differ here and also ask you to look at your dyno chart versus mine. The curves are identical and if you actually LOOK at yours you will see that you stop making power around 6000 and it just levels off to 6700. So you are wasting time continuing to rev the motor without making more power. If you shift at 6000 you are putting yourself back down in the fat part of the power range and you will go faster at the track.

Try it once and you will see. I have been drag racing for about 18 years now and have had the Z out on the track enough times to prove this over and over. :cool: :cheers:

 

I'm sorry but your understanding of physics is a bit lacking obviously. Just because your power is no longer increasing doesn't mean you're not "making power". As you can see from my dyno graph, the 365rwhp hp plateau extends from 5700RPM to 6500RPM. This means that I'm "making power", and in this context, making maximum power, all the way from 5700RPM to 6500RPM. And you get your best acceleration where you're making the most power. The goal here is to spend as little time as possible at lower power producing RPMs.

You say "if you shift at 6000 you are putting yourself back in the fat part of the power range." How can you say this with a straight face unless you have no physics understanding? Shifting at 6000 lands you at 4200RPM, which if you look at the curve, is NOT anywhere CLOSE to the power peak. 4200RPM is 270rwhp!! That's down almost 100hp from peak power!! Whereas shifting at 6500 throws you down to 4500RPM where you've at laest got 300rwhp to work with. Still sucks but it's better than 270... Remember, the name of the game is to always be in the gear that would put you at the highest hp point from your dyno curve.

Physics is physics...

Edit: **** Finger: i think your misunderstanding here stems from a misreading of the dyno chart. I think you're under the (wrong) impression taht you want your power to constantly be increasing, and you should shift when it stops increasing because you're not "making" more power anymore. This is wrong. It doesn't matter if your hp is decreasing or increasing, what matters is how much hp there is -- which you read directly from the dyno chart as the y value. Optimally you want a long wide, FLAT horsepower plateau, that is at least as wide as your gear spacing, so you don't fall off the hp plateau during shifts. We don't have that -- we have a pretty narrow horsepower peak, exacerbated by a rev limiter that cuts in too early and doesn't let us enjoy the other "side" of the horsepwoer plateau to maximize area under the curve.

Oh, and in response to Z06Les, for your acquaintances that shift at 6000-6200, that must be a 1st to 2nd shift where the tach is lagging far enough behind that they merely THINK they're shifting that low. Trust me, you can't bend the rule of physics, your car is not faster making 270rwhp than it is making 300rwhp.

Andi



[Modified by Andi, 12:13 PM 10/16/2003]

 

Reference this page on Andi's excellent web site for an even more thorough explanation: http://www.boostaholic.com/hptq.html

Andi is right. The end.

Jordan

 

He may actually be feeling torque management. I honestly do not think that powershifting is all that it is cracked up to be. If you learn to speedshift properly you are not gaining much by powershifting. Powershifting is extremely hard on all of the drivetrain, and with torque management you are not really doing much to get a better time by powershifting.

All IMHO

 

These cars pull like a freight train all the way until the rev-limiter kicks in. The power never falls off! :D Go take my old cobra for a test drive if you want to feel the power fall off. That car had a 6800 rpm redline,but was only good from 4000-6100, after that it ran out of breath. Tack that biznatch out as far as possible!! :yesnod:

 

I can tell you exactly how much difference powershifting makes. I had an 01 coupe that I got extremely consistent with. Due to transmission synchro problems, I reduced my powershifting to a minimum.

One night at the track, I made five runs without powershifting, then one last run powershifting. Here are the times for my last three runs - only the last was powershifted: (the first number is my 60" time) This is a 01 MN6 with 317 rwhp (stock + cold air intake and B&B PRT's),

2.10 12.89 110.4
2.07 12.88 109.8
2.07 12.77 111.3

Looking at the identical 60" times, this gives you a good idea of the effect of powershifting. BTW, even when I don't powershift, I shift extremely fast.

 

If you want to go slower, don't power shift or peak the engine. Changing the rev limiter up will allow you to shift at a higher RPM and be at a higher HP when you shift.

Physics is Physics. It does not change. Try it!