Help me stay off the Rev limiter

[svxhunter]

Before anyone says anything, this is not a street racing thread. I'm trying to improve my driving style and car for a track driven car.

OK, so we've had some successes, but I'm still a little baffled by this car. When the computers are making all the decisions, it's a little hard to control things.

The biggest problem seems to be that I can't get the car to accelerate and shift consistantly. WOT offers some interesting things, like the power mode shifting, but it creates other problems. My shift from 2-3 happens too early and too mushy, and it's almost impossible to keep the car from bouncing off the rev limiter. The only way to avoid the limiter is to back off the accelerator significantly and let it upshift gently, loosing lots of speed. I get similar results at hard acceleration that is a little short of WOT.

The car has been driven on a dragstrip (and will be again), but is mostly going to be autocrossed right now.

I can't describe all the details of the driving patterns in the autocross (I'm still watching cones). But I know exactly how we launch at the drags.

While power braking, we raise the rpm's to about 2100. At the light, we accelerate to WOT. This engages both the tranny power mode, and our nitrous shot. It's a great take-off.

After that, the car will do what it chooses. Sometimes the shifts are smooth and strong and at good rpms. Sometimes it jumps gears too early and dogs. If allowed to, 7100 rpms can arrive without a shift and bounce all over the rev limiter.

I figure, I'm either driving poorly, need to learn how to get the shifts I want, or deal with the limiter.

Any ideas would be appreciated.

Thanks!!

[SubaSteevo]

Maybe try making a power mode switch, there was a recent thread about it

[UberRoo]

Is your transmission slipping? "My shift from 2-3 happens too early and too mushy, and it's almost impossible to keep the car from bouncing off the rev limiter." That sounds like the classic 2nd to 3rd "flair" that precedes typical transmission failure of the third gear clutch. Of course, using NOS might have something to do with it!

As far as the retarded TCU, I think that's just a fact of life. Automatic transmissions do stupid things, especially since they have no way to tell the difference between the track and the street. I have to "outsmart" mine by driving like an idiot. Your symptoms however, may be related to a sensor. The TPS, MAP, or any number or other sensors may be buggy, giving you equally buggy shifting.

I'd check all the sensors you can. (Unfortunately that's no small task.) I'd also learn to use the gear selector. If it's shifting too early and "dogging," using the gear selector will eliminate that problem. Pull the resistor if you haven't already.

[svxhunter]

BurgundyBeast:

I will probably be trying a power mode switch

UberRoo:

I'm not sure "slipping" is the right word. Indecisive is more like it. I've had a tranny die starting with the classic 2nd to 3rd "flair"- this is a bit different.

Generally when we hit the rev limiter, it is because we have accelerated to that point hard, and the car has not upshifted. It doesn't slip to the red line.

"Using NOS might have something to do with it!"- Agreed. But we only use NOS on the dragstrip, and that was only once in April.

"retarded TCU"-

I find auto trannies to be fairly predictable. This is the first computer controlled auto tranny I've had- quite a different animal.

In what ways do you "outsmart" yours by "driving like an idiot"?

Yes, I'm going through the sensors.

What do you mean by "use the gear selector"? I've tried several things. Just can't get consistant results.

[drivemusicnow]

something you can do thats i'm SURE not good at all for your tranny, is to press or not press the manual button, and put it in first.. then when YOU want to shift, push the gear selector into 2... this (1/4-1/2 pause inbetween when you do it and when it shifts) then lets you also choose when you want to shift from 2 to 3. like i said.. i'm sure this isn't bad for a tranny, however, you might try it at the dragstrip and see how it works fo ryou. when i first got my car i messed with this a little (have since learned) and it pretty much gives you full control of when it shifts.. i don't think it shifts for you either, at least i know i bounced off the redline when i was in "1" way back when

Try driving it around in manual in 2nd not D...
See if that gets you anything..i use this gear selection when hitting corners so it wont shift prematurely and ruin my fun..

[SVX-FF]

The best solution I think would be to but a 5 speed in. It has good clean shift and better control of speed.

If you are keeping the auto tranny then do this.
1. change the fluid and add Lucas
2. tighten up the 2nd gear band
3. ad a stage 1 ECU kit. (will raise limit to 7400rpms along with a lot better low end torque)

Good luck bro

Steve

[rmjjensen]

Yes - try a manual trans and ditch the automatic. I've found that manually shifting the 4EAT is definitely much more fun and proves for better response. To get a quick shift hold the engine at a certain RPM before upshifting .....it'll chose the next gear in a microsecond.

I thought that even if the gear selector is in 1st, once the rev limit is hit the TCU will goto 2nd???

[svxhunter]

Originally posted by SVX-FF
The best solution I think would be to but a 5 speed in. It has good clean shift and better control of speed.

If you are keeping the auto tranny then do this.
1. change the fluid and add Lucas
2. tighten up the 2nd gear band
3. ad a stage 1 ECU kit. (will raise limit to 7400rpms along with a lot better low end torque)

Good luck bro

Steve

We are installing a 5-spd, but not in this car. In order to enter the car in the GRM challenge next year, we have to freeze the budget. 5-spd and the stage 1 ECU chip are both beyond the budget until after the 2005 Challenge.

Fluids have been changed. We're running Red Line high temp. I'm scared of Lucas (ruined a tranny once putting it in).

I did try the band adjustment, but didn't get as large results as I'd hoped. Maybe I need to try again with a little more patience.

Thanks!

[svxhunter]

Originally posted by rmjjensen
... manually shifting the 4EAT is definitely much more fun and proves for better response. To get a quick shift hold the engine at a certain RPM before upshifting .....it'll chose the next gear in a microsecond.

Are you suggesting on hard acceleration if I pause at a certain rpm (say 6500, for example) that it will choose the next gear? I need to play with this a bit more. I thought I had tried it with successful results, but as soon as I resumed acceleration it again downshifted and bounced off the rev limiter.

I'll do some more experimenting.

[svxhunter]

Do any of the rest of you find it fairly easy to hit the rev limiter? I don't remember ever hitting it in any other car, but in the SVX if I accelerate hard and don't let up it's sure to find the limiter. I especially want to learn to avoid it for when we hit the drags again. Since the rev limiter is a fuel cutoff, I hate the idea of it cutting my fuel supply when I'm running nitrous through it.

[SVXRide]

For straight autocrossing I'd suggest just putting the trans in 1st and leaving it there (NEWSVX taught me this trick) - the trans will shift up into second if you hit the red line.

As far the the drag strip goes - have you tried disconnecting the resistor behind the battery? Smallcar's shift kit is another alternative.

-Bill

[UberRoo]

Originally posted by svxhunter BurgundyBeast:
Generally when we hit the rev limiter, it is because we have accelerated to that point hard, and the car has not upshifted. It doesn't slip to the red line.

Sounds like it's just not shifting fast of firmly enough. Aside from cracking open the transmission, the only solution is to pull the resistor. ...unless it really can't figure out when to shift - which may be the case, because the rest of us don't have this problem. Is the use of NOS the only thing unique to you?

I find auto trannies to be fairly predictable. This is the first computer controlled auto tranny I've had- quite a different animal.

In what ways do you "outsmart" yours by "driving like an idiot"?

I agree that the mechanical ones are generally quite consistent and predictable. These electronic ones are kinda tricky. I "outsmart" mine by easing off the throttle before a shift to soften the shift. I'll accelerate a little bit more than normal to keep it from shifting before I'm ready. I'll blip the throttle to get power mode slightly before I need it. I'll modulate the throttle excessively to keep the torque converter from locking up. All these things make me appear to be an idiot, but do keep the TCU under control.

What do you mean by "use the gear selector"? I've tried several things. Just can't get consistent results.

I meant to use it specifically to prevent the transmission from upshifting prematurely. Otherwise it's not the greatest way of controlling things, but it's what we've got. Just leaving it in first, as some folks suggest, may be your best bet.

[svxhunter]

Thanks guys! These were the kind of tips I was looking for.