Scott, I can start a new thread if you'd like, but this all seems related...

Curly, can I adjust the AFR Temperature Adjustment Curve to target say 13.5 at 220 degrees and then run the Warmup Enrichment Wizard under Tune Analyze Live during a hot restart and have it compensate for the heat soak? I plan to try that out, but right now my car is in the garage on jack stands.

Thanks,

No, it's fine. More info the better.

Made some progress this morning. Let the car get up to 180F which is when WUE ends. Let it sit for about 20 minutes and the coolant was around 160F. Adjusted the ASE more aggressively over 120F and extended the ASE Taper time from 120F and up. My taper curve is more U shaped now. Car started much better. Maybe a second or two lean and then it dropped back into 13-14 AFR. Waited for the car to cool to about 140F. Started right up, no stumble and the AFR was immediately in the low 14s. Let the car get back up to temp, 180F, and then waited 10 minutes. Coolant was 165F. Started right up. Again it went lean for a second or two then then went to about 14 AFR. Looks like I need to maybe add a tiny bit more of fuel in the 160-170F range but as it is now it's way better than when I first posted about it. I'll have to clean up my ASE curve and then re-do the WUE but that's easy enough.

So, decent day. I went out and drove the car for an hour. I knew heat soak from driving for an hour would be a lot higher than just idling in the garage. When I got home I let the car sit outside and after 10-15 minutes when I tried to start it, it was stumbling again. Tweaked the ASE and ASE Taper some more and got it to a point where it is just stumbling for a few moments but then levels out and the AFR goes back into the 13-14s. If I just started driving the car right away it would really be a non-issue. Much more livable than it was but I'll probably try to keeping tweaking this some more. May just be heat soak from the fuel rail and IAT combined? The IAT will move into the intercooler outlet in front of the radiator so that should help reduce the IAT heat soak. Not much I can do about the fuel rail heat soaking though.

I believe (and my experimentation supports) that this is a result of the injectors (and to a lesser extent the rail) heating up. Touch an injector right after you have been running for a long time and everything is heat soaked ... not hot. Touch the IM, or any other piece of metal around there, hot. Let the car sit for 10 minutes (off) after the heat soak, touch the injector ... HOT. Fuel cools injectors, a lot. When the fuel isn't flowing, they get hot like everything else. MAT does not fix this, Curly is all over it with his suggestion.

You want worst case? Like you mentioned up there, run to heat soak, then turn the engine off for like 5-10 minutes.

For reference, those AFRs almost perfectly mimic the cold AFRs of the stock ECU (on my 99 at least, and cant say what the coolant temps are since I dont have a way to read that)


But yeah, stock ECU pretty much goes to 11/12ish as soon as the WB warms up, then tapers up to the normal ~14.7 over maybe 5mins of idling (obviously depending on the coolant/air temps at the start)

Yes, all this started to happen after the Flow Force injectors went into the car and from what I've read in the past the smaller size of those injectors are more susceptible to heat soak than the OE injectors. Wonder if heat sinks (like on a computer CPU) attached to the fuel rail would help dissipate the heat faster? Anyone try wrapping to injectors or would it not matter since it's heat soaking hot gas from the inside?

I believe the hot lean restart is a complex problem: IAT sensor + fuel temperature + injector heat soak(?).

1. We can almost eleminate the IAT sensor heat soak moving it to the front part of IC cold side.

2. MS has a built in fueling correction table based on a fuel temperature. But it requires a temp sensor in the fuel rail.
Below is a data from ID entered in that table.

3. I will measure an injector opening time related to a injector temperature on next weeked. I am running an injector service business and have a required equipment.
https://cimg9.ibsrv.net/gimg/www.mia...f13c3708e5.jpg

That would probably solve a lot of issues. May be worth installing a sensor in the rail just to get this feature to work... May have to look into it.

The continental flex fuel sensors output fuel temp as well - this is what I'm using. Goes over the same wire too, super useful.

I believe fuel temp correction is intended to compensate for the dependence of fuel density on temperature.

Beer and tuning don't necessarily go together...

I attempted what's in quotes above. I got her good and warm and let her sit for 10 minutes. I queued up the warmup enrichment autotune and started her up. CLT was 206 and MAT 139ish. It was below 80 ambient. The autotune thingy didn't do anything. I went into "Gauge and Settings Limits" and set "Allow WUE Below 100% (only for LPG)" to "Yes". I let the car sit for a while and tried it again. I had completely overlooked that as soon as the car started it would start to cool down. Time on the log was moving right and the curve had more enrichment (my initial guess) with hotter temps, but as it cooled down it wanted to move left along the curve. I believe I almost caused the MS to have an embolism. That said, warmup enrichment autotune DID activate. It attempted to richen up the heat soak, but also extrapolated the curve backwards so I had a million percent enrichment at 30 degrees. It also changed the rightmost box to 100%, even though I had 117% in there as a guess. I was going to change the curve to something like 30, 40, ..., 190, 210, 230, 231, 250 and set that last box at 100%, but the rain picked up and was blowing into the garage. I called it a day.

Is this worth pursuing?

No

Edit: use ASE

Tuning and beer...

Hey guys I would like to bump this thread, I’m running a BP05, Wallbro 255, 60psi return rail w recent addition of Flowforce 640’s. I run MSPNP, MX3 chassis but same issues.. The injector upgrade was part of a DIY package upgrade ending in the installation of the smaller machined pulley That will push my M 62 up to factory limits or about 1500 RPM at redline. Currently i push about seven psi and the stock injectors were fine but I have a feeling they’re going to max out by the time I get to 11 or 12. I actually experienced a mild version of the hot start issues with the stock injectors running lean to about 16 but rarely stalling. I moved my IAT to the intercooler. Tuning has gone surprisingly smoothly for me to this point but this hot start issue with these 640s is really starting to frustrate me. I have been all over several threads and I can make the issue better with aggressive ego control But the car may still stall. Anybody else had any breakthroughs with this issue? How did you solve it? I’ve been all over this for weeks now it’s driving me nuts LOL

Which version of the MSPNP?

Post 33 above. After you answer Sixshooter, I may be able to help.

MM 9495 ms2

Same TB/TPS/ IAC as 95 Miata.. Only major difference would be the cam dizzy vs wasted spark but I doubt that is relevant. She runs smooth under load, 640’s improved every condition but hot restart. After a few minutes coolant about 213, MAT 108, Not too far off of regular running range in Tennessee summer. MAT may hit 120, coolant steady around 200 usually. City driving tends to raise intake temps more than hard pulls, decent no name intercooler under moderate boost

I'm not familiar with what is possible with MS2. Please post a Tune and I can open it and see what MS3 things will port over.