lurching on and off throttle with vafc / 440s
10-15-2003, 05:51 PM
#1
1.0 BAR
Thread Starter
Join Date: Sep 2003
Posts: 453
lurching on and off throttle with vafc / 440s
Know what happens in a manual when you are rolling at 15mph in 1st and you let off the car? Then what happens when you get right back on it? The car lurches forward, then back. I just installed a set of RC440 injectors (had the VAFC installed for about a week) and set it at -40 across the board and my car started doing that whenever I let on or off the gas. If the throttle goes all the way down to zero, and the pressure goes to a full vacuum it lurches a little bit, then when I press the gas, no matter how gently, from around 0%throttle and approx -12.0 psi it lurches the other way. This is not affected by speed or rpm, altho when the engine isn't producing much torque it isn't as noticeable. I didn't have this problem before I installed the injectors. Has anyone else experienced this? Know a fix? It is annoying!
10-15-2003, 07:02 PM
#2
3.0 BAR
Join Date: Mar 2003
Posts: 21,479
Re:hesitation from -12psi / 0%throttle
Check the injectors? Are you sure they are good?
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10-15-2003, 08:07 PM
#3
1.0 BAR
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Re:hesitation from -12psi / 0%throttle
I'm not sure how to tell - check them how? They seem fine. If they weren't putting out enough fuel, it seems like I'd have problems at higher rpms as well and not just when first pressing the throttle pedal. I've thought about running injector cleaner thru it, this just feels like an electronics problem more than anything, but I really can't rule anything out. That is why I was wondering if anyone else running an afc experienced anything similar.
10-15-2003, 11:11 PM
#5
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Join Date: Sep 2003
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Re:hesitation from -12psi / 0%throttle
I tried it for awhile at -45 and it didn't seem to make a difference. I didn't keep it there long since I haven't messed with the timing any, and it was making some uncomfortable noises. I'll try it again tomorrow when I have time to mess with it some more.
10-16-2003, 01:14 AM
#7
1.0 BAR
Join Date: Jan 2003
Posts: 438
Re:hesitation from -12psi / 0%throttle
no dude everybody is steering you wrong. It's only real bad when you lean it out TOO much.
set your crossover to 70%/71%, set your low throttle settings a -36 across the board, and set your high throttle to -38 across the board.
It's a great baseline, used it on three different cars. I've fucked around for hours. It's one of the better one's i've come up with. Too much fuel will cause a bog, too little fuel causes the jerk. -36 is jusssst right!
set your crossover to 70%/71%, set your low throttle settings a -36 across the board, and set your high throttle to -38 across the board.
It's a great baseline, used it on three different cars. I've fucked around for hours. It's one of the better one's i've come up with. Too much fuel will cause a bog, too little fuel causes the jerk. -36 is jusssst right!
10-16-2003, 05:51 PM
#8
1.5 BAR
Join Date: Jun 2003
Posts: 1,145
Re:hesitation from -12psi / 0%throttle
no dude everybody is steering you wrong. It's only real bad when you lean it out TOO much.
set your crossover to 70%/71%, set your low throttle settings a -36 across the board, and set your high throttle to -38 across the board.
It's a great baseline, used it on three different cars. I've fucked around for hours. It's one of the better one's i've come up with. Too much fuel will cause a bog, too little fuel causes the jerk. -36 is jusssst right!
Is this for N/A? or Boosted?
set your crossover to 70%/71%, set your low throttle settings a -36 across the board, and set your high throttle to -38 across the board.
It's a great baseline, used it on three different cars. I've fucked around for hours. It's one of the better one's i've come up with. Too much fuel will cause a bog, too little fuel causes the jerk. -36 is jusssst right!
Is this for N/A? or Boosted?
10-17-2003, 12:27 AM
#9
1.0 BAR
Thread Starter
Join Date: Sep 2003
Posts: 453
Re:hesitation from -12psi / 0%throttle
NA for now. I haven't got my piping, and I'm not totally comfortable installing the turbo until I've got the kinks worked out anyway.
So you are saying to set the low throttle to 70% and high to 71% (right now they are at factory 10 and 50%) and set the fuel subtract to 36 and 38? I should be rich already, that seems REALLY rich NA, but I guess it is worth a try. Unless of course you were assuming I was boosted already... I'll still try it since it would always occur off boost and so it shouldn't matter.
BTW, I was messing around today and discovered that the throttle doesn't have to go all the way down to 0% and the pressure doesn't have to go all the way down to -12psi. About -11psi and 3-5% will do it to if there is no load on the engine whatsoever. I sure hope I can figure out for sure what is causing it!
So you are saying to set the low throttle to 70% and high to 71% (right now they are at factory 10 and 50%) and set the fuel subtract to 36 and 38? I should be rich already, that seems REALLY rich NA, but I guess it is worth a try. Unless of course you were assuming I was boosted already... I'll still try it since it would always occur off boost and so it shouldn't matter.
BTW, I was messing around today and discovered that the throttle doesn't have to go all the way down to 0% and the pressure doesn't have to go all the way down to -12psi. About -11psi and 3-5% will do it to if there is no load on the engine whatsoever. I sure hope I can figure out for sure what is causing it!
