Building Boost on the Trans Brake
#1
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.
#2
TECH Enthusiast
iTrader: (59)
Join Date: Jan 2007
Location: Layton, UT
Posts: 548
Likes: 0
Received 0 Likes
on
0 Posts
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
#3
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
#5
11 Second Club
iTrader: (43)
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.
#6
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.
#7
8 Second Club
iTrader: (12)
Join Date: Nov 2010
Location: Durham
Posts: 747
Likes: 0
Received 0 Likes
on
0 Posts
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.
Trending Topics
#8
T4 PT88 .96 a/r 370 ci. The converter is a little tighter than I expected it to be on the brake. The car drives nice and I don't think I would like it any looser as far as street driving goes, but it only stalls to ~2600 on the trans brake before getting into boost. Just seems low. Still haven't had a chance to do any testing. I'll try to do something with the car today.
#11
11 Second Club
iTrader: (1)
Join Date: Apr 2004
Location: F' Reno I live in Sparks
Posts: 590
Likes: 0
Received 1 Like
on
1 Post
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
#13
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.
#14
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
#15
Thanks Brian. To be honest with you I'm quite happy with the converter! Like I said above, I would like to see if I can work around this issue through the tune to get spool time up. Im sure another factor that is playing a large part here (something i just thought of) is the compression ratio of 8.7:1.
#16
FormerVendor
iTrader: (3)
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.
#17
8 Second Club
iTrader: (4)
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.
#20
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.