Jorgeminator
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Golf MkIV 1.8T AUM
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« on: October 23, 2020, 03:20:16 PM »
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Background fact; I live in an area where we experience temperatures ranging from -35°C to 35°C (-31°F-95°F). Last winter, I tried experimenting with cold start enrichments for E85 but did not succeed. I ended up running pure gasoline for most of the time, still experiencing starting difficulties, usually having to crank twice. Turned out my 6 month old genuine Bosch fuel pump sh*t itself. Now I'm back in business. New pump, and the 1.8T is purring like a kitten.
My goal is tuning the engine for extreme cold starts on pure E85. With my current settings it starts perfectly (like on gasoline) down to 0°C (32°F) after cold soaking for 24h, weather hasn't gone below freezing so can't tune for lower yet. I've attached my current enrichment maps FKSTT (cranking) and FNSSM (post start). Notice they are NOT applicable below 0°C, that's "work in progress". More to come...
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« Last Edit: October 23, 2020, 03:40:11 PM by Jorgeminator »
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justinvw2646
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« Reply #1 on: October 24, 2020, 02:54:07 PM »
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Awesome that someone else is working on this. I did not know about FNSSM so in the attached image mine is unmodified. I have been using KFFWL in conjunction with FKSST. The coldest I have been able to test at was about 40F. The car was not happy with stock settings at that temperature, but now starts good. The only downside I have found thus far is on a cold start the engine revs to about 2,100 for an instant at the initial startup and then comes down to 1,500 for 30 seconds or so. I haven't yet taken the time to switch one of the maps back to see which one is causing the rpm flare.
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« Last Edit: October 24, 2020, 02:55:41 PM by justinvw2646 »
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BlackT
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« Reply #2 on: October 24, 2020, 11:59:30 PM »
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Start RPM see
KFNLLNST
KFNLLKHM
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woj
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« Reply #3 on: October 25, 2020, 02:19:45 AM »
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First, I'd like to thank you for this topic, I just found out that I totally missed FNSSM and generally the after start enrichments in my FlexFuel developments. Though I live in a climate that many perceive as cold (lower Scandinavia), the fact is that through one whole year of testing I managed to get below zero conditions a handful of times, and -10C only once. I ended up with an always first attempt start condition after a while (my FKSTT is not far from yours, but the ECU is different and I do not know your base FKSTT), but I did indeed have problems with maintaining the engine running after it caught on in some cases, which is clearly the after start thing rather than the start. What I found helping was increasing the after start torque demand, which (I believe) effectively opens the throttle more.
The fuel was actually E75, I never managed to find a gas station that would have anything above that, summer or not.
Besides the start, the real pain (and still not solved to a satisfactory degree) are transient enrichments, cranking and driving off right away at 10 degrees or lower was never smooth, the best solution so far is to let it idle for at least around 30 seconds, or more if colder.
Currently I suspended all experimentation due to several reasons, the outrageous price of E85 being one of them.
EDIT: Having said all this and noting my own experiments, I really do not see how you are going to make it work at very low temperatures without hardware mods, like warming up injectors, the inlet manifold, or something of this sort... Seems to me impossible just by map tuning.
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« Last Edit: October 25, 2020, 02:21:43 AM by woj »
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Jorgeminator
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Golf MkIV 1.8T AUM
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« Reply #4 on: October 25, 2020, 04:49:22 AM »
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I ended up with an always first attempt start condition after a while (my FKSTT is not far from yours, but the ECU is different and I do not know your base FKSTT), but I did indeed have problems with maintaining the engine running after it caught on in some cases, which is clearly the after start thing rather than the start.
That's exactly when FNSSM is active and why it's so important  At startup, after the engine reaches the speed set by NSTNM, e.g. 680 rpm at 0°C, the ECU jumps from cranking (FKSTT) to afterstart (FNSSM x KFWLL) tables. FNSSM is what keeps the engine alive those first few seconds while the cylinder walls and intake valves are still cold. It quickly tapers off at a rate set by FZANSSM(1-3) so that it becomes irrelevant after only 30 seconds or so. After that, most of the enrichment is determined by KFWLL. |
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« Last Edit: October 25, 2020, 04:56:18 AM by Jorgeminator »
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justinvw2646
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« Reply #5 on: October 25, 2020, 11:57:42 AM »
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Thank you Blackt I will have a look at those maps. Excellent last post Jeorgemin.....totally makes sense now. Looks like by the end of the month I am going to be getting some overnight lows in the 30s F so testing can continue on my end. As I am successful I will continue to post screen shots of settings.
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Jorgeminator
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Golf MkIV 1.8T AUM
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« Reply #6 on: January 05, 2021, 02:00:38 PM »
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Started without a hitch in -7°C after sitting for 5 days. Enrichments below.
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thedrill
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« Reply #7 on: January 05, 2021, 06:26:26 PM »
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Thank you Jorgeminator, I set up my E85 S4 with the FNSSM maps and it starts up a lot easier from cold.
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Jorgeminator
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Golf MkIV 1.8T AUM
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« Reply #8 on: January 15, 2021, 01:35:16 PM »
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New record. Started like a dream in -15°C, exactly like on gasoline. Same settings as last time. Unfortunately the oil cooler o-ring seems to be leaking  Heard they usually go in cold weather if never replaced. Gotta get that fixed before it starts spewing my oil everywhere. |
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