Building Boost on the Trans Brake
Building Boost on the Trans Brake I went to the track last weekend and had some good results, but was a little disappointed that it took so long for the car to get up on the converter while on the trans brake. It just seems like it takes forever to get the motor to make boost and get the rpm up. Right now it takes about 4 seconds from the time I go 100% throttle to when it builds 10 psi and 3 of those seconds are just getting the car to 5 psi according to the data log. I would think if I could shorten the time that it takes to get the car to 5 psi that would be a huge help.
I am wondering if I add timing to the cells that were hit during trans brake use if it would help spool the turbo quicker. I've done searching, but figured I'd start a new thread since none of the threads I found gave me the answer I thought I was looking for.
This is what my timing looks like right now.
and this is how I modified the table this morning (still haven't tested this out)
I followed the histogram to see which cell it was in when at X rpm and X kpa and added timing in those cells then smoothed it out. Can someone tell me if I am on the right track? Or if you think that might be a little much? Just looking for some feedback.
Since I know some people will ask: I do have a 2 step, but no 3 step. I'd like to cut the time to build boost on the brake down by at least half if I could.
I am wondering if I add timing to the cells that were hit during trans brake use if it would help spool the turbo quicker. I've done searching, but figured I'd start a new thread since none of the threads I found gave me the answer I thought I was looking for.
This is what my timing looks like right now.
and this is how I modified the table this morning (still haven't tested this out)
I followed the histogram to see which cell it was in when at X rpm and X kpa and added timing in those cells then smoothed it out. Can someone tell me if I am on the right track? Or if you think that might be a little much? Just looking for some feedback.
Since I know some people will ask: I do have a 2 step, but no 3 step. I'd like to cut the time to build boost on the brake down by at least half if I could.
Did you happen to stumble upon this thread while searching?
https://ls1tech.com/forums/forced-in...pool-time.html
https://ls1tech.com/forums/forced-in...pool-time.html
Did you happen to stumble upon this thread while searching?
https://ls1tech.com/forums/forced-in...pool-time.html
https://ls1tech.com/forums/forced-in...pool-time.html
I found out from experience that having it to rich in the areas coming up to boost and in the lower boost areas will make it not want to make boost on the brake. Figured it out in the driveway after I got home from the track with a friends suggestion.
Add some timing, lean it out, and try it again. I'm still working on mine, but from the times that I've been at the track I was on the brake for 1.8 seconds and had 8lbs. Where you added the timing you is the right idea. I'd try it until you don't get an increase in boost and then back it off instead of going straight to where yours is at now.
Add some timing, lean it out, and try it again. I'm still working on mine, but from the times that I've been at the track I was on the brake for 1.8 seconds and had 8lbs. Where you added the timing you is the right idea. I'd try it until you don't get an increase in boost and then back it off instead of going straight to where yours is at now.
I was just going to jump to that much timing because what read said 32-35° would be safe to have in the cells it hits below ~135 kpa and quickly ramp it down from there. I believe it was a post from phill99vette that I saw that info in.
What size turbo? A/R? Cubic inches? I'm running a 347 with a 76mm and a 1.58 exhaust and it takes me about 4 seconds to build 8 psi on the brake. Your converter will play a part in this as well.
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Converter is a huge part! I got a friend who had a car who took 7-8 seconds to comeup on the 2 step. He bought a new PTC and the time time was cut down to 3-4 seconds to be on the limiter and at full boost
I would like to see a reflash on that converter i had the same issues with my ATI it took 5-6 seconds on the brake to build 8psi now with this PTC i can go without footbraking and build 8 in about 2.5 seconds. and on the foobrake to TB less than 2
What converter setup?
Here was my 370 with a pt88. It took nothing on the brake to bring it on
370 lsx, PT88 turbo transbrake tuning - YouTube
Here was my 370 with a pt88. It took nothing on the brake to bring it on
370 lsx, PT88 turbo transbrake tuning - YouTube
Thanks for confirming. I tried the timing table above and leaned it out a little. It comes in to PE (100kpa) at 12.9 and 34.5°. Tapers to 12.0 and 30° by 132 kpa. 11.9 and 22° by 138 kpa. Just doing that knocked 1.25 seconds off spool time to 138 kpa. I'll lean it out some more and see where it gets me.
FormerVendor
Joined: Jan 2014
Posts: 323
Likes: 3
We can revisit the converter to help with your spool time.
Also, we have some guys experimenting with the third gear spool mod with good results. It may be worth looking into.
Shoot me a PM if you would like to discuss your options.
-Brian
Also, we have some guys experimenting with the third gear spool mod with good results. It may be worth looking into.
Shoot me a PM if you would like to discuss your options.
-Brian
Converter is a circle D 1b 258mm. I need to get mine down to that time.
I know what I have is probably effecting spool time quite a bit but for now I'd like to work around it.
Thanks for confirming. I tried the timing table above and leaned it out a little. It comes in to PE (100kpa) at 12.9 and 34.5°. Tapers to 12.0 and 30° by 132 kpa. 11.9 and 22° by 138 kpa. Just doing that knocked 1.25 seconds off spool time to 138 kpa. I'll lean it out some more and see where it gets me.
I know what I have is probably effecting spool time quite a bit but for now I'd like to work around it.
Thanks for confirming. I tried the timing table above and leaned it out a little. It comes in to PE (100kpa) at 12.9 and 34.5°. Tapers to 12.0 and 30° by 132 kpa. 11.9 and 22° by 138 kpa. Just doing that knocked 1.25 seconds off spool time to 138 kpa. I'll lean it out some more and see where it gets me.
It's nearly if not impossible to hurt a motor with timing on the footbrake or transbrake. That doesn't mean put 40-50 degrees in it at 10psi on the brake. N/A timing up to 5-6psi on the brake is very beneficial for spool.
Not disagreeing at all… But if adding timing is the way to go these days, why do all antilag setups I see retard the crap out of the timing to build boost on the line?
For example on 3500rpm 2-step on the brake my antilag settings were at -15* to -17* of timing. THe AEM woudl actually cycle timing very quickly between base timing and -17* or so. This would make 24lbs in 2-3seconds. When TB was released it would it would ramp timing back in very quickly. I launched a JY motor a good 20 times this way and did blow it up on the line on the 2 step at the end of the year. So I’m by no means suggesting this to anyone, just throwing it out there.
For example on 3500rpm 2-step on the brake my antilag settings were at -15* to -17* of timing. THe AEM woudl actually cycle timing very quickly between base timing and -17* or so. This would make 24lbs in 2-3seconds. When TB was released it would it would ramp timing back in very quickly. I launched a JY motor a good 20 times this way and did blow it up on the line on the 2 step at the end of the year. So I’m by no means suggesting this to anyone, just throwing it out there.
From what i researched the anti lag worked but was detrimental to longevity due to bringing the combustion into the exhaust instead of leaving it in the combustion chamber.
Martins the one that got me back on track.
Martins the one that got me back on track.
Or you could try this tricky trick here..........
Pull up and turn on your first bulb with the car in second, hit the transbrake button and floor it with your foot on the brake pedal holding it firmly. The boost will come up way faster because of the different gear ratio and your 2 step will still work because the button is pushed. Easy off the brake pedal to turn on your second bulb, once you are where you want to be pull it down to first and you are ready to ride.
Pull up and turn on your first bulb with the car in second, hit the transbrake button and floor it with your foot on the brake pedal holding it firmly. The boost will come up way faster because of the different gear ratio and your 2 step will still work because the button is pushed. Easy off the brake pedal to turn on your second bulb, once you are where you want to be pull it down to first and you are ready to ride.