a friend of mine is having problems leaving off the transbreak!!!!! if we take the 2step off and let it go off the converter(4700rpm) it just shuts the car off. if we leave off the foot break everything is fine? for timing its locked out at 40deg total then ramps down to 34 total starting @10lbs of boost. box is a 7531 and fuel is c-16. max boost is set at 15lbs. what am i missing? my first guess would be the converter, just looking for more ideas.

combo is
331 8.2 to 1
afr205
vic jr
csu 850 72 84
3.73
26 qtp
mp t-70
3138 race weight.

oh yeah afr at wot is 11.9 and on the break is 11.7

 

https://www.theturboforums.com/smf/index.php?topic=96666.0

 

He's asking about a carburetor bogging on the trans-brake + 2-step, isn't this were it belongs? I am having almost the same problem and would like to hear some theories as well.

 

actually it comes up on boost on the transbreak as soon as u release it the car stalls!!!!!!!

 

Are you logging the A/F when it bogs? Sounds to me like it would be a good candidate for a BRPV.

 

we have a brpv set at 12LBS

 

mustang-junky, thanks for looking out man which is what I hope we all do. This one is good enuff to stay as it is carb related on the trans-brake and causing the car to bog/shut off.

 

Might seem stupid, but do you have jet extensions ?

 

WHAT is it stalling from........are you datalogging any of this.....does it stall because it runs out of fuel or does it stall because it gets too much fuel?

On the 'brake, im at about 13-1 AFR & i leave clean......have you tried leaving at more RPM? How much boost is it making on the brake?

-Carm

 

think i found the problem will post later after i try it

 

I have the exact same problem and have been on the phone with kevin on the dyno and at the track (2 times). No luck at all, but it will leave on the foot brake...I was attributing it to my recent smash into the wall and figured its in the trans. or converter. I tried to leave at 10psi at 12.0a/f on the lm1.. my car is dyno tuned at 11.8-12.0 clean out the whole pass.....brpv and jet extensions

 

Did you try and take the extensions out just to see if that would have made a difference?

 

Can someone explain why brpv's are need for a transbrake launch?

My issue is that I can't get the footbrake to hold the car long enought to build boost (the skinnys just skid) , and when it goes from the foot to the transbrake the motor just bogs and goes from low 12's afr down to high 9's afr. Once the car gets moving the afr goes back to the mid 11's for the pass. I have a homade carb with vent extensions and no brpv's.

 

Would benefit the thread starter if you didn't hijack

 

The reason guys use the brpv with a turbo setup and transbrake is when you go WOT on the transbrake your engine goes to 0 vaccum. At this point a standard pv is open dumping fuel out the boosters causing you to go pig rich and not build revs on the brake. With a brpv it only opens at a preset boost level, ideally when you have enough air moving from the turbo to compensate for the enrichment of the pv. With a blower car this is less of an issue because the blower moves much more air volume at low rpms then the turbo does before it spools up. So if you are going to 9:1 on the transbrake, you may want to think about sending your carb to a carb specialist for a brpv. Or you could talk to guys on here like Brent and build your own. Either way, 9:1 on the transbrake is not helping you and you should consider it.

 

Thanks for the info, I had planned on getting the carb upgraded over the winter.

To the original poster, sorry for the hijack. I just thought it would be better to get an answer here then starting another thread.

 

well it wasnt what i thought it was, but i did find another problem, my friend had an old fms boost gauge that was reading 15lbs. well we go testing last nite and i have the laptop open with msd prodatata software and i tell him to hit the gas from a roll. WHAT A SHOCKER WERE ONLY AT 5LBS !!!!! it was late so we called it a night. when he gets home we are going to open the wastegate(tial38) and see what spring he has in there!!!! anyway my theory is kevin set it up for 15lbs and were only at 5lbs and its just dumping fuel on the break.

 

Nope, but I'll give it a try sunday at the track.....