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Spring is here, and I've been using the cool weather to try to dial in my cold start (40-50F CLT) and I feel like I'm chasing my tail a bit (log after log after log..) One thing I am looking to understand is what the attached image indicates. I never have a problem getting the initial catch in 0.5-1.0 seconds, however sometimes (not all the time) it will catch, switch over to ASE/WUE and stumble at 5-600 rpm for a couple of seconds like the picture.Other times RPM will drop below my cranking RPM (400) and toggle between crank/start until it catches. And other times it will just catch pretty nicely (not often, though).
Too little fuel in the low RPM cells where it transitions out of crank? Too much fuel? Adjust ASE? Always hard to know if stumbling like this is too much fuel, or too little, and it's tough given one or two shots a day.
97 NA, 1.8L,FF640's, MS3 and DW200 fuel pump. Turbo manifold is in the mail...
2020-04-16_22.01.43_Startup_54 pictured below, notice period of stumbling around 5-600 rpm for 1-2 seconds.
Things I have tried:
Adjusting Cranking Pulse - I started very low, slowly increasing it. I have it to a point where it cranks and catches quite well, but the transition is the problem.
WUE - It's dialed in pretty nice, idles well once it gets started
ASE - Set it just high enough so that the car doesn't stall out once it catches. Perhaps it needs more? Worried about adding too much fuel, I had quite a bit previously and I think that was part of my problem.
Cranking Advance - currently at 14, was at 10 for the longest time, maybe helped catch a bit sooner
Cranking IAC duty - I've been slowly lowering DC, trying to keep the rpms low once it catches.
Most settings look pretty good. Even though I have heard you can flood with too much fuel, I have put tons in and not had that issue. Thus, I'm naturally inclined to think not enough fuel.
I would not have the VE table going so low at 500 RPM from 60 - 100 kPa. That is pulling fuel as you first start. I would suggest making the 500 RPM column closer to the 800 RPM column.
My ASE at 50 is about 80% adder, yours is 40%. Realize that this is one of the few places that MS ADDS, rather than MULTIPLY. Thus 180% / 140% is 29% more fuel, even though reading the numbers suggests that I am running twice as much.
I would not have the VE table going so low at 500 RPM from 60 - 100 kPa. That is pulling fuel as you first start. I would suggest making the 500 RPM column closer to the 800 RPM column.
I'll start there - I had been tweaking reducing 500 and 800 RPM cells in that region as I thought maybe I had too much fuel which was hurting the transition. I'll experiment increasing it a bit to be more in line with the 800 rpm column, and then maybe ASE after that. I've seen a lot of advice to start with less fuel than you think you need, maybe overdid it there.
For me Idle Cranking Duty Step is very helpful. Acts like you putting your foot on the throttle to get it started and going into its normal idle sequence. Higher is more air, like putting your foot on the throttle more and more. Don't go too high though as you will start to see the car rev hang once it catches.
04-17-2020, 04:44 PM
Looking for Cold Start Advice
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