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Cold starts are a breeze (relatively) and the car will always start up nice and smooth. Hotter starts are always met with crank, fire, hesitate around 600ish rpm, then rpms will go up to 1k or whatever the normal rpm range is. It's not smooth, but it fires up.
You can see here where it "fires" up, but only to about 600rpm, hesitates, then "fires" up again. It's very weird as it jumps to 600 very strongly but doesn't go any farther. Note this is on e85. Not sure how it is on 91, haven't run 91 in a while but I'd assume it's quite the same.
I fought that issue as well. Never got completely free of it. I'm not going to be much help. I've thrown a lot of stuff at it so I don't know what has helped, but I can also say that it is not fully cured.
When I first posted about it may years ago, the only advice I received was to go to a 36-2 crank wheel. I did, but that did not fix the problem.
I'm pretty sure it is fueling related, but not sure if rich or lean. Since you don't have much Priming pulse, I don't think it is too much fuel being pulled from the walls. I do also have a little of it on cold starts, but it is not as pronounced.
I also suspect EAE is part of the issue, but some of this effect seems there for me even when I turn the EAE off.
If I had one suggestion, it would be to raise your 190*F ASE to 23%.
TLDR: In to see if someone comes with a big revelation.
The cranking pulse is a function of req fuel and you are dropping to 72% at 190 degrees, but you folded the e85 stoich change into the VE table and have VEs of ~100% in the high load, low RPM cells. This results in a crazy whoopsie-doo in the PW when transitioning from crank to run. I suggest you set your cranking pulse at 190 to 100 and see what happens.
Raising ASE with increasing temperature after about 150 degrees or so is also tried and true as DNM recommended, and it looks like you are on a return style car (the alt is not controlled, so assuming NA) but have a priming pulse delay of 0. I suggest something around 1 second to allow for purging of the hot fuel (and any possible air) in the rail.
EAE doesn't appear to be the issue here, but EAE can be disabled during startup by placing 2 rpm points below your lowest expected idle. So say your idle is 800, you can have RPM coefficient points at 699 and 700. For added, you set the 699 point to 0, the 700 point to whatever it would be on the curve. For sucked you set the 699 point to 100 and the 700 point to whatever it would be on the curve.
The cranking pulse is a function of req fuel and you are dropping to 72% at 190 degrees, but you folded the e85 stoich change into the VE table and have VEs of ~100% in the high load, low RPM cells. This results in a crazy whoopsie-doo in the PW when transitioning from crank to run. I suggest you set your cranking pulse at 190 to 100 and see what happens.
Should I adjust the req fuel value then lower all the VE cells to correspond with the drop? Both logs posted and tune are set with cranking PW of 100. I don't notice much of a change in startup though.
Edit:now that I think about it, I would INCREASE my req fuel and lower my VE numbers correct?
Originally Posted by Ted75zcar
Raising ASE with increasing temperature after about 150 degrees or so is also tried and true as DNM recommended, and it looks like you are on a return style car (the alt is not controlled, so assuming NA) but have a priming pulse delay of 0. I suggest something around 1 second to allow for purging of the hot fuel (and any possible air) in the rail.
Yes it's a 1994 NA. Raised the delay pulse to 1 second. Seems to help get more consistent startups I think maybe its just a placebo not sure.
Originally Posted by Ted75zcar
EAE doesn't appear to be the issue here, but EAE can be disabled during startup by placing 2 rpm points below your lowest expected idle. So say your idle is 800, you can have RPM coefficient points at 699 and 700. For added, you set the 699 point to 0, the 700 point to whatever it would be on the curve. For sucked you set the 699 point to 100 and the 700 point to whatever it would be on the curve.
The two logs I posted are two 190ishF startups one with EAE using the settings you gave to disable during cranking and one without it entirely. The one with EAE is interesting as it kind of has a "double hesitation". The car shot up to 650rpm, went to go higher then triggered EAE, then hesitated, then it rose up like normal. Quite interesting. The tune I posted has the EAE settings you gave on it. Not sure if I input it correctly.
Ok I think EAE is at play here. I've also upped the ignition advance in the areas between the cranking and idle positions and I think that's helped a bit. I've also upped the cranking advance to 21 degrees but I'm not sure if that's doing anything or if it will cause issues or not. Still unsure what proper crank timing should be. For now I will turn off EAE and see if anything improves. I've attached the 3 logs and current tune. I'll be taking a look at the 106F start to see what makes it so good.
Heres 3 logs: Beautiful 106F Start with EAE 176F with EAE 178 without EAE
Use high speed logging (5msec SD)
Connect the car to another running car for multiple restarts, this eliminates voltage drop from being part of the equation
change 1 thing at a time, always review the data, back out changes that don't have any beneficial effects
Turn off EAE to begin with, get the appropriate fuel profile established with ASE, then add EAE back in and retune ASE
This looks to me like fueling, and I suspect you are too rich immediately after the crank-to-run transition. It looks like as soon as CL idle engages, the car gets itself into a good place. It is probably idle rpm timing correction that is adding tq and the motor speed increases, but the TS logs don't have good enough resolution to know for sure. This is why you log to SD.
Idle advance timing should decrease with load, not increase. This seems counterintuitive, but trust me. A curve that starts at 20 degrees, 25kpa curving down to 8 degrees at 40 kpa works well for me (lambda = 1). Basically, you will be running at a higher manifold pressure for low rpms than you will for high rpms. The piston speed is slower at low rpm, so you need less crank angle advance with a constant flame front speed. Science.
Use high speed logging (5msec SD)
Connect the car to another running car for multiple restarts, this eliminates voltage drop from being part of the equation
change 1 thing at a time, always review the data, back out changes that don't have any beneficial effects
Turn off EAE to begin with, get the appropriate fuel profile established with ASE, then add EAE back in and retune ASE
This looks to me like fueling, and I suspect you are too rich immediately after the crank-to-run transition. It looks like as soon as CL idle engages, the car gets itself into a good place. It is probably idle rpm timing correction that is adding tq and the motor speed increases, but the TS logs don't have good enough resolution to know for sure. This is why you log to SD.
Idle advance timing should decrease with load, not increase. This seems counterintuitive, but trust me. A curve that starts at 20 degrees, 25kpa curving down to 8 degrees at 40 kpa works well for me (lambda = 1). Basically, you will be running at a higher manifold pressure for low rpms than you will for high rpms. The piston speed is slower at low rpm, so you need less crank angle advance with a constant flame front speed. Science.
I will give the SD card logging a shot. I've never used it. Is it just like extra resolution? or does it give more info?
As for the procedure regarding tuning startups. Let's say my coolant intervals are 50F, 90F, 110F... etc. If I start at 50F and it starts fine, I just idle til 90F, stop the car, then start it up and see how it goes? Then obviously log to the SD each startup and what not. As for ASE, I would just check what the PW is after starting and see how that correlates with the RPM and go from there? By hook up to another car you mean as if I was jumping the miata right? Just wanna be sure...
Interesting about the advance. I've returned it back to the 10 degrees cranking and will return that crank-run zone back to the basemap. Thanks!
This hot-start issue is also being put on hold for a little, I think my CAS crapped out today
Ok, managed to get some hot starts logged on the SD card. Here they are. Tune is attached too, I pulled some VE out from the cranking-running zone which I think helped with some backfire happening as soon as the car started. From a quick glance, it looks like an excessive amount of PW may be the issue with the hesitation.
11-18-2020, 05:02 PM
Need some help dialing in hot starts
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