startup issue. log/settings included
 

put this off through the summer since it wasn't cold but time to give it another shot and get some help this time. I tried my best last winter to get my cold startup perfect but it just never happened.
usually cranks, catches, and dies right away the first time.. then fires right up on second crank. you'll see it in the log.
have tried more more/less crank pw (it may be on the high side right now, but less doesn't seem to help and I know more is too much)
have tried more/less cranking advance. it seems happiest at 10. any more and it kicks back
have tried more ase, doesn't seem to do a lot.
have added quite a bit of cranking pw from base tune.
my tune is good otherwise when running. it's an ms2 basic built by rev. all ive done otherwise is fix timing and autotune.

hoping someone more experienced might just be able to look at my log and tell me what's wrong.. willing to paypal enough for a six pack to anyone who can get it squared away. thanks

forgot to add ive got stock injectors ~250cc
car is a late '95
uhh theres probably more relevant info i should include. log was taken this morning at 54*F

been studying that log.. it shows cranking, then shows running for a second and ase turns on, but afr stays lean. it then goes back to thinking it's cranking.. although that may be because of lean afr.. but i can t imagine why my afr would stay lean when my cranking pw are so high.

it also doesn't make any sense to me that the second crank fires right up.

:eggplant:

megasquirt forumsays i need to up my cranking RPM to 500.. does that sound right to anyone on here?
(come on 200 views and no posts..)

I think mine is at 300

yeah mine was 350.. cant try 500 until tonight

so the tip I got from the MS forum was correct.. I bumped it up to 500 and it was definitely happier, but from the log seemed like it should be a little higher still. This morning I tried 650 at 46F and it fired up first crank with only a tiny sputter.. but by far the best startup ive had at this temp.

So the whole time I was thinking that the "cranking RPM" setting controlled the cranking RPM (F*&^ me, right?) but the MS has no control over cranking speed.. that setting just tells the MS when it's cranking.. and so when to deliver cranking PW.

so on startup, my car was stopping cranking PW at 350RPM even though my starter is cranking around 500-550 RPM.. so obviously, shitty startup at any cold temp. hopefully this helps somebody else out, since during my forum searches I never saw anyone talking about this and it seemed like quite a few people were having similar startup issues with the miata base tunes.. maybe the base tune cranking rpm for miatas should be higher??

your startup settings look unlike any ive seen. really really high prime and cranking pulses... youre probably flooding the motor right now.

i agree its super weird.. but it doesnt seem flooded from the log.. heres my log from this morning

you should actually tune your cranking pulse.

tomorrow morning, for that CLY temp, set it very low at 100%, increase until it starts. add a little bit for good measure. I bet you'll start better with a number SIGNIFICANTLY lower than what your tune is demanding.

well before messing with cranking rpm i tuned the hell out of it hah.. looking at my log my afr stays lean until it actually catches.. i will take your advice though.

i have screenshots of my original settings. i'll set it back down to that and try it. it was a linear line instead of a huge slope like my current crank pw

increasing the cranking rpm will help in general with consistency -- only leaving cranking when the motor is ACTUALLY running, not prematurely.

if the car catches, then dies, it's all in the after start tuning -- quite possibly really bad cells in your VE table, low-load ones you don't normally hit on a warmer day that are a touch too lean.


I cant look at the logs right now.

To verify Six and Brain's comments on Cranking amps. I spent lots of hours last year getting my starting solid over many temperatures and conditions (first start, after sitting 2 hours, etc.) Had it down pretty good.

Then about a week ago. All starts went to crap. Sometimes acting like too much Priming and Cranking fuel, sometimes like too little.

Turns out, my Cranking RPM had inadvertently been changed from 300 to 200 RPM. I set it back to 300, and all went back to good.

Note: My engine turns over at about 175 RPM, varying with temp.

300rpm is still low, imho. I prefer something in the 400-500rpm range.

on the setting itself it says "set a few hundred RPM above your highest cranking RPM" or something like that.. I think my starter gets up to almost 500 by itself..

I'm just wondering why my Miata barely starts at 350 and everyone else seems to do fine.. no matter what my crank pw are. I'm going to start it up this morning with much lower pw and ill post log

basically start with a very low PW, then increase until it starts. that's really the way to tune the cranking table and you can really only do it once a morning.

now that i think about it I probably need a higher cranking RPM because i'm one of the only dudes on here with stock injectors.. i went down to a much lower crank pw and set cranking RPM to 600 and it started like factory at 50F. Thanks for the help guys

set the cranking RPM too high and if there's ever an rpm dip for some reason below 600rpm, you could confuse the MS into thinking it needs to inject for cranking.

600rpm is usually were I would mechanically set my min idle speed on a normal day, so that shouldn't really be a problem, just probably higher than you need to set it all. all that value is telling the ms the point where youre trying to crank or run.