Haltech 80% fix to hesitation when accelerating from cruise
04-23-17, 10:49 AM
#1
80% fix to hesitation when accelerating from cruise
I had that weird hesitation when accelerating from cruise--fraction of second of lack of response after pushing throttle followed by a jerky movement forward. I tried the best I can with transient throttle but it was always there.
I think I fixed it. It's about 80% better, not as good as my daily driver but good enough not to lose traction while accelerating in a corner with >4k rpm in vacuum.
If you pay real close attention to the wideband while you're trying to induce the forementioned hesitation, you'll notice that the AFR becomes super lean for a fraction of a second. Transient throttle setting alone can't fix this in my experience. You have to give the high vacuum cells at <20% throttle at the problem rpm range some increase in the injector duty. Then more importantly, you need to play with "zero demand" fuel settings. I had mine turned off, and there was a world of difference when I turned it on. It's basically a fuel map when your MAP is lower than a set point. I set mine to -7psi. Tuning this is super easy. I just cruised around town and increased the numbers at problem rpm range until it got better. Again it isn't 100% but it's whole lot better than what it used to be. The transition is much smoother after I tuned the zero demand fuel map.
I think I fixed it. It's about 80% better, not as good as my daily driver but good enough not to lose traction while accelerating in a corner with >4k rpm in vacuum.
If you pay real close attention to the wideband while you're trying to induce the forementioned hesitation, you'll notice that the AFR becomes super lean for a fraction of a second. Transient throttle setting alone can't fix this in my experience. You have to give the high vacuum cells at <20% throttle at the problem rpm range some increase in the injector duty. Then more importantly, you need to play with "zero demand" fuel settings. I had mine turned off, and there was a world of difference when I turned it on. It's basically a fuel map when your MAP is lower than a set point. I set mine to -7psi. Tuning this is super easy. I just cruised around town and increased the numbers at problem rpm range until it got better. Again it isn't 100% but it's whole lot better than what it used to be. The transition is much smoother after I tuned the zero demand fuel map.
04-23-17, 09:42 PM
#2
Full Member
Thanks for sharing.
I have a similar problem, but seen more when blipping or revving from idle. I spent ages playing with the transient throttle settings and still had the same issue. No matter how rich I made it, it'd go super lean for half a second, as if it was lagging.
It's strange that we need to set up a zero demand fuel map. From my understanding, this table overrides everything, including decel cut. I've seen people say it's a legacy of older ECU software and not to bother turning it on. Did you find enabling it removed your decel cut?
Don't suppose you have a screenshot of your zero demand table you can share?
I have a similar problem, but seen more when blipping or revving from idle. I spent ages playing with the transient throttle settings and still had the same issue. No matter how rich I made it, it'd go super lean for half a second, as if it was lagging.
It's strange that we need to set up a zero demand fuel map. From my understanding, this table overrides everything, including decel cut. I've seen people say it's a legacy of older ECU software and not to bother turning it on. Did you find enabling it removed your decel cut?
Don't suppose you have a screenshot of your zero demand table you can share?
04-23-17, 10:17 PM
#3
I still have decel. Mine's attached. It's work in progress and I focused around 2-4k, so it doesn't really help anyone since every car would be different.
I think that lean spot has various fixes--combination of zero demand, transient, decel fuel enrichment, . I think the "jerk" after the lean spot is the fuel rushing into the combustion chamber. so it's delicate balance between not giving too much fuel but enough to minimize the "hesitation" and minimizing the "jerk" by not giving too much trying to overcompensate for the lean spot.
I think I am going to try zero demand based on MAP next time I take my car out.
I think that lean spot has various fixes--combination of zero demand, transient, decel fuel enrichment, . I think the "jerk" after the lean spot is the fuel rushing into the combustion chamber. so it's delicate balance between not giving too much fuel but enough to minimize the "hesitation" and minimizing the "jerk" by not giving too much trying to overcompensate for the lean spot.
I think I am going to try zero demand based on MAP next time I take my car out.