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-   -   cold start FTL (https://www.miataturbo.net/megasquirt-18/cold-start-ftl-13219/)

FoundSoul 10-17-2007 10:57 AM


Originally Posted by richyvrlimited (Post 163867)
that's the 1.8 browntops 1.6 bluetops are 205cc :)

That's what I had thought too originally, but I had based the 230cc off the FAQ... so I can do some digging, but which is it?

Here's the DIY Turbo FAQ entry on it:


The 1.6L (230cc) fuel injectors have enough room to run about 5-6psi. However at this level, the fuel pressure required to get enough fuel into the motor through the small injectors becomes so great, that the injectors can actually lock. If you are running more than 140-150rwhp, chances are the injectors are maxed out. A very common upgrade is to install the 1.8L injectors. These will should provide you enough room to run about 7-9psi of boost (170-180rwhp).

94-97 (tan) 265cc - #195500-2180
99-00 (red) 240cc (pass on these) -#195500-4430
01-05 (Lt. purple) 265cc -#195500-4060
Taken from https://www.miataturbo.net/diy-turbo-discussion-14/diy-faq-all-your-answers-one-big-post-4288/

Braineack 10-17-2007 11:01 AM

those numbers have been verified from a number of sources.

now if jerry can only solve my issue.

devin mac 10-17-2007 11:01 AM


Originally Posted by Braineack (Post 163889)
yeah, i dunno what the deal is now. even without heat soak it wont restart without tons of effort.

this morning i stopped by Rosenthal, intake temps of 50° coolant at 190°. stopped for about 3 minutes and came back out. Tried to crank it and no go, all temps about the same as when I left it. :(


have you noticed much of a difference with MAT only, CLT only, or averaged?

seems to me that if your intake temps are 50, and the coolant is 190, averaging them would put you in a spot where nobody's happy... i'm just supposing, though.

Braineack 10-17-2007 11:02 AM

no its clt only, i think i want to try averaging them.

devin mac 10-17-2007 11:04 AM

yeah, i was thinking about that the other day, when mentioned that i fired the car up with 43* CLT and 60* intake, but then later couldn't fire it with similar CLT and 40* intake.

richyvrlimited 10-17-2007 11:27 AM


Originally Posted by FoundSoul (Post 163931)
That's what I had thought too originally, but I had based the 230cc off the FAQ... so I can do some digging, but which is it?

Here's the DIY Turbo FAQ entry on it:



Taken from https://www.miataturbo.net/showthread.php?t=4288


i've read that FAQ a lot and never noticed it quoted different numbers than what I'm used to.... hrm

ah well always happy to be proved wrong :)

FoundSoul 10-17-2007 11:28 AM


Originally Posted by Braineack (Post 163932)
those numbers have been verified from a number of sources.

now if jerry can only solve my issue.

Don't know if I can magically solve anything-- but I'll surely try and help ;)

Firstly I don't know that i'd average IAT and CLT for this-- the engine temp is much more critical for this calculation. If you're averaging the two, and IAT is at 50 while CLT is at 190, you need a tiny little PW to start the car, but you're getting a much bigger one because the averaged in IAT reading in bringing the temp used to calculate cranking PW way down to a much lower temp, where a much higher PW is commanded, instantly soaking your plugs and flooding you out.

That would be my theory anyways...

FoundSoul 10-17-2007 11:33 AM


Originally Posted by richyvrlimited (Post 163939)
i've read that FAQ a lot and never noticed it quoted different numbers than what I'm used to.... hrm

ah well always happy to be proved wrong :)

Me too-- much better to be proved wrong, learn something from it and be better off the next time than hardheaded about it and dumb forever right? ;)

I had always used the 205cc value before on the 1.6 and 230cc on the 1.8, probably just forum misinformation which is all too common, and manufacturers really don't make this type of info the easiest to come by alot of the time. This is actually part (not all) of the reason why the AFR number used to set REQ_FUEL when scaling to different injector sizes on the MSPNP MM9093 and MM9495 isn't 14.7-- I had to account after the fact for the true injector sizes so it would scale properly for you guys. It won't change anything though as long as it's consistent.

Braineack 10-17-2007 11:47 AM

i guess ill try lowering the PWs a tad more and turning off the priming pulses.

Braineack 10-17-2007 06:33 PM

that seemed to have worked. i drove home and parked and waited untill 100* playing with my ait based corrections and PWs some more got it to start everytime from 80* to 108*

hopefully it will do the same tomorrow at 190* CLT and 50* intake.

Atlanta93LE 10-17-2007 06:40 PM

So...what 1.6L injector size did you use to rescale the diyautotune cold start pw values?

FoundSoul 10-17-2007 07:08 PM


Originally Posted by Atlanta93LE (Post 164095)
So...what 1.6L injector size did you use to rescale the diyautotune cold start pw values?

Actual injector sizes will apply for this as it was tuned with the actual factory injectors in the car, so 230cc for the 90-93, and 265cc for the 94-95.

FoundSoul 10-17-2007 07:09 PM

Glad to hear it looks like you've made some progress Scott--

Atlanta93LE 10-17-2007 07:39 PM


Originally Posted by FoundSoul (Post 164102)
Actual injector sizes will apply for this as it was tuned with the actual factory injectors in the car, so 230cc for the 90-93, and 265cc for the 94-95.

Thanks very much! Exactly the info I was looking for.

Braineack 10-17-2007 09:00 PM

they also use 13.7 as the afr multipler, however, iirc.

cjernigan 10-17-2007 09:09 PM

Anyone know why DIYs cranking/prime table counts down until it reaches 40F then it jumps up again and then continues counting down versus counting down the entire time?
This might just be an error of me not having MT setup to read their MSQ but I don't think that the values themselves would change because of that.

Jerry, what kind of AIT related air density have you used on turbo cars? Just curious if you have a table to share.

neogenesis2004 10-17-2007 09:39 PM

It never got below 40* in Atlanta, so they couldn't tune below that.

devin mac 10-17-2007 10:58 PM

i ended up cutting the DIY cranking values down, by multiplying them by 75%, and so far so good. only tested in 50* temps so far, though. tomorrow morning i should get a solid 40* startup try, so i'll see how it works tomorrow morning. optimistic, though.

cjernigan 10-17-2007 11:05 PM


Originally Posted by neogenesis2004 (Post 164140)
It never got below 40* in Atlanta, so they couldn't tune below that.

hahahhaha That's right, makes sense, i didn't think about that.

devin mac 10-17-2007 11:10 PM

heh, i had the same thought as you, cj. then the "oh yeah... atlanta... 40deg..." thought hit me, too.


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