INSW20 Posted August 23, 2023 Report Share Posted August 23, 2023 I'm struggling to wrap my head around the best strategy for hot restart. IAT sensor is about 3" pre-throttle body in my charge piping. I had read previously that enabling IAT fuel trim and adding fuel in the 0% TPS "hot soaked" cells would help significantly with hot restart, but I'm still struggling. More recently, someone commented that charge temp approx is a much better method for fueling hot restarts. Any suggestions appreciated. It seems to me like it wants more fuel on hot restarts. 5sgte - 8.17.2023 rev1.pclr Quote Link to comment Share on other sites More sharing options...
Øyvind Ryeng Posted August 23, 2023 Report Share Posted August 23, 2023 'IAT Fuel Trim Table': I've got 'Engine Running Time' on one axis and 'IAT' on the other. When hot restarting, the 'Engine Running Time' parameter removes no fuel at 0 seconds, but my full -10% at +40C after 60 seconds has passed. With this approach, hot restarts work well without having to compensate by f. ex. turning up cranking- or post start fuel tables. INSW20 1 Quote Link to comment Share on other sites More sharing options...
INSW20 Posted September 13, 2023 Author Report Share Posted September 13, 2023 9.13.2023 - hot restart in garage.llg5sgte - 9.13.2023 - playing with hot restart.pclr9.13.2023 - hot restart in garage number 2.llg Added a couple heat-soaked logs and my latest tune file. It "seems" like it kind of wants more prime pulse and crank enrich, but I would appreciate any input you folks have. My cold starts are AWESOME. My hot restarts it kind of chugs to life, sometimes it will die and then start right up on the second cranking attempt. Quote Link to comment Share on other sites More sharing options...
INSW20 Posted September 14, 2023 Author Report Share Posted September 14, 2023 Does pre-crank prime only occur on the first crank after a key-on? So if I key-on a hot engine, then go to crank, it primes, then chugs to life, dies, and then I crank again, there is not a second pre-crank prime? Quote Link to comment Share on other sites More sharing options...
remski2 Posted September 14, 2023 Report Share Posted September 14, 2023 Heads up.. you can click on any variable and then press F1.. that will give you a description. I find Link's help file useful and well constructed. Ign Start Position - The injectors will be opened for the time specified in the Injector Prime Time table the first time the key is turned to the start position. This ensures that the prime fuel is not injected too early when the key is turned on, then turned to start some time later. This mode requires a Digital Input to be configured as Start Position and wired to the start terminal on the ignition switch. I'd bump pre-crank prime by 50% and see if it does anything.. If it does.. then lower it until you satisfied with the hot start. If that doesnt do much.. then go back to original value.. and bump your Crank enrich by 50%.. see how that plays out.. Try bumping First crank enrich too.. but just do one change at a time and see which one has the most effect. You could also change that to Key On and turn the key twice or more in order to gain idea if thats helping. Also.. I see the car started without much effort on the 2nd crank.. right after it didnt.. I've seen cars with fuel manifolds right on top of intake manifolds or in places where they touch hot parts.. this causes fuel to literally boil and may causes harder starts. Hope this helps. INSW20 1 Quote Link to comment Share on other sites More sharing options...
INSW20 Posted September 14, 2023 Author Report Share Posted September 14, 2023 Yep, that does help, I guess I was hoping for clarification where it says "the first time the key is turned to the start position." If I leave the key in the "run" position after it dies, does it prime again when I go to "start" or does it skip that since it's no longer the first time the key is turned to the start position on that key cycle. I ended up removing basically all of the pre-crank prime when hot and it seemed to like that a lot more. Thank you! Quote Link to comment Share on other sites More sharing options...
INSW20 Posted September 20, 2023 Author Report Share Posted September 20, 2023 Update: seems like injector timing was a big part of my issue. I have since updated to the following: Cold starts are still great, and hot restarts are very nearly as good; a HUGE improvement. I am now blending down and testing "warm" 130-140F restarts, but seems like it's moving in the right direction. Quote Link to comment Share on other sites More sharing options...
Adamw Posted September 21, 2023 Report Share Posted September 21, 2023 Looking at your map, your pre-crank prime is extraordinarily high for a hot start. As a test, can you try dropping the highlighted region down to about 10ms. See if that help or makes it worse. If it makes it worse then I would lean towards the issue being related to injector atomisation. INSW20 1 Quote Link to comment Share on other sites More sharing options...
INSW20 Posted September 21, 2023 Author Report Share Posted September 21, 2023 18 minutes ago, Adamw said: Looking at your map, your pre-crank prime is extraordinarily high for a hot start. As a test, can you try dropping the highlighted region down to about 10ms. See if that help or makes it worse. If it makes it worse then I would lean towards the issue being related to injector atomisation. Yes, I should have mentioned I also pulled out almost all hot pre-crank prime and reduced hot crank enrich. That also helped a lot. Thanks! Quote Link to comment Share on other sites More sharing options...
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