Help with T-brake launch (vids)
Thread Starter
Joined: Jan 2003
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From: Fort Worth, TX
Help with T-brake launch (vids) Could ya'll look at the videos below and see if you can help me out with hooking? This is a cam-only car leaving off 5100 TB with 28 stiff wall ET Drags @ 14psi. The front shocks are set at 1 and the rears are comp engineering set at 50/50. It's only pulling 1.49-1.50's on the brake and footbraking it to 3000 rpm. I figured off the brake it would be pulling low 1.4's or possibly high 1.3's 
These are off the 5100 TB
These are off the 5100 TB
Didn't spin? Looked like you came out and that was all you had. My white z was 1.48 on motor with 4800 and 1.38 on 150 shot. I at the time did not have enough converter/gear to get that combo to come out harder on motor.
It looks like the car is making a move off the line and is rolling over a little bit. Do you have a drag bar in the car? If not, get one. That will keep it level, and should help the issue. I'd probably try tighening the front shocks up one click, the rears if you can get a set of 12 way's on it will also help your cause too I'm sure. The comp 3 way's are a good starting shock, and can for some people work really well, but alot of cars need the 12 way adjustability to get the most out of it.
I'd try airing the tires down a lb too, I tried mine up that high, and never seemed to have the consistancey I did at 12 to 13 before the burnout.
I'd try airing the tires down a lb too, I tried mine up that high, and never seemed to have the consistancey I did at 12 to 13 before the burnout.
Thread Starter
Joined: Jan 2003
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From: Fort Worth, TX
PTC loosened up the converter before because it was too tight and I wasn't happy. The problem is this bastard transmission 4STB (Race built 4 speed AOD w/ GM bellhousing). I wanted an OD and at the time I bought it the 4l80e's hadn't been worked out in an FBody. There is only one company that makes a converter for it and I can't for the life of me make them understand the converter is still too tight 
In looking at the logs, not only does it not 60' well the shift extension goes back to 5600 rpm after the 7000rpm shift. With the cam's powerband (6000-7200) it looses 30 hp between shifts falling back to 5600 rather than say 6000 rpm. Atleast this makes since to me, but I may be totally off. What do you think?
In looking at the logs, not only does it not 60' well the shift extension goes back to 5600 rpm after the 7000rpm shift. With the cam's powerband (6000-7200) it looses 30 hp between shifts falling back to 5600 rather than say 6000 rpm. Atleast this makes since to me, but I may be totally off. What do you think?
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Verdad Gallardo Thread Starter
Joined: Jan 2003
Posts: 1,455
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From: Fort Worth, TX
It looks like the car is making a move off the line and is rolling over a little bit. Do you have a drag bar in the car? If not, get one. That will keep it level, and should help the issue. I'd probably try tighening the front shocks up one click, the rears if you can get a set of 12 way's on it will also help your cause too I'm sure. The comp 3 way's are a good starting shock, and can for some people work really well, but alot of cars need the 12 way adjustability to get the most out of it.
I'd try airing the tires down a lb too, I tried mine up that high, and never seemed to have the consistancey I did at 12 to 13 before the burnout.
I'd try airing the tires down a lb too, I tried mine up that high, and never seemed to have the consistancey I did at 12 to 13 before the burnout.
I got aroung to editing a slow motion launch so you can see what the car/tires are doing. I wish it was a little clearer, but maybe someone can see something a little better now and make more suggestions.
It looks to me that there is a good instant snap, but the rest of the 60' suffers from lack of power. I run a 1.506' leaving from Idle in my 4l60e 3600 stall. I'd bet that your 30' is quicker, but my 30-60 gets out from the power I have.
Just watched you launch, your car is nosing over after the car comes down from the launch. The power it not following through after the launch. Also something has to be wrong with your converter if you are dropping from 7000 to 5600. 500-600 rpm drop, yes, but over a 1400??
David
David
Thread Starter
Joined: Jan 2003
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From: Fort Worth, TX
Just watched you launch, your car is nosing over after the car comes down from the launch. The power it not following through after the launch. Also something has to be wrong with your converter if you are dropping from 7000 to 5600. 500-600 rpm drop, yes, but over a 1400??
David
David
I have been searching and reading all kind of threads on shift extension and can't seem to find a definate answer on how it should be calculated. One person said you want SE to be 300rpm before peak and shift 500rpm after peak for best performance, but nobody else has backed that up.
So If my cam peaks @ 6500-6600 and I shift @ 7000-7100 then I should match it with a converter with a shift extension of 6200 rpm?
Thread Starter
Joined: Jan 2003
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From: Fort Worth, TX
I think I found 1 issue. The pinon angle was either -5 or +5 (DS was -1 & Pinion was -4). Does adding 2 negitives create a positive or do you just add the negatives together?
Either way the Pinion angle is set to -1 now due to the rod end suspension as suggested in the stickies.
Either way the Pinion angle is set to -1 now due to the rod end suspension as suggested in the stickies.
Thread Starter
Joined: Jan 2003
Posts: 1,455
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From: Fort Worth, TX
I could easilly change to a TH350 with an ATI 5500 stall, but the $5000 dollars I spent on the tranny and converter I have now would be for nothing. I'm going to give the converter builder 1 more try at getting it right. That's why I have been asking the questions on what shift extension I would need for the most out of my setup.
You have a tranny setup that may be a very easy sell though... that would most likly cover a good part of a Th350 and the good ati converter........ I'd give the converter guy another shot, but if it doesn't pan out, that setup has to go if you want the car to run 100%
Is 500-600rpm drop what I need for the best results? If that's what you are saying then I would need a converter with a SE of 6400 rpm?
I have been searching and reading all kind of threads on shift extension and can't seem to find a definate answer on how it should be calculated. One person said you want SE to be 300rpm before peak and shift 500rpm after peak for best performance, but nobody else has backed that up.
So If my cam peaks @ 6500-6600 and I shift @ 7000-7100 then I should match it with a converter with a shift extension of 6200 rpm?
I have been searching and reading all kind of threads on shift extension and can't seem to find a definate answer on how it should be calculated. One person said you want SE to be 300rpm before peak and shift 500rpm after peak for best performance, but nobody else has backed that up.
So If my cam peaks @ 6500-6600 and I shift @ 7000-7100 then I should match it with a converter with a shift extension of 6200 rpm?
Call your converter shop. Explain the problem. If they are worth a crap, they should be able fix it. A 500-700 rpm drop is 'normal' where as 1400 is not.
David
