Needed: base settings for NB idle using MS-I - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-28-2009, 02:50 PM   #1
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Default Needed: base settings for NB idle using MS-I

I decided to change from having the stock ECU control my car's idle to letting Megasquirt control it. This decision was made after discussions with Matt Cramer, Joe Perez, Paul, Abe, etc. .... I like to do my homework.

This is for an '04 MSM. I have MS-1 (not 2) with board 3.57. The good news: 3.57 already has the necessary parts for idle control, lucky me, no mod packs needed.

Matt explained to me - and Sam dummied down for me - that hardware-wise all I have to do is follow Pin 30 into my Boomslang, cut that wire, and connect it to ground on the IAC valve. Sounds easy enough.

Joe said he's got the base idle settings for an NA on MS-1 and an NB on MS-2, but not an NB on MS-1. Can someone please help me with that? LOL, my parents are happy to let me use their garage, but I don't like getting stuck there at the end of the day. :
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Old 08-28-2009, 03:41 PM   #2
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You're probably not going to get too much help, theres only a few select people thatare using MSI with an NB. I am also currently running MSI on my NB, but its wired parallel, like most other NB users. The stock ECU handles the idle.
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Old 08-28-2009, 03:56 PM   #3
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Originally Posted by Marc D View Post
I am also currently running MSI on my NB, but its wired parallel, like most other NB users. The stock ECU handles the idle.
That's how mine is now but the idle is a nightmare. It's decent when the car is cold but it's horrible when the car is warm. Always fluctuates wildly. It's all the symptoms of classic IAT heat soak, except Matt confirmed from my warm-start datalog that it's not heat soaking. I know the IAC valve itself is okay because if it were dead (or if the stock sensor were dead) then it wouldn't idle when cold either. Then I thought maybe it's the stock IAT sensor that's heat soaking (since as you mentioned the stock ECU controls idle) but there was no change in the problem after I covered the stock sensor with heat wrap material. Matt then pointed out that maybe the stock computer is just having a hard time because it can't control timing. Why idle works fine for other NBs, I have no clue. Bottom line, I'm sick of trying to figure out what the stock computer is doing, so I'm just going to let MS have a crack at it. It may not be as "good" at idle at the stock computer should be, but at least I'll have some control and insight. LOL, but with my luck MS will be fine at controlling idle and the stock ECU will give me a CEL.
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Old 08-28-2009, 11:03 PM   #4
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You might want to take a look into upgrading to MSII, its a better CPU all around
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Old 08-28-2009, 11:15 PM   #5
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I know. AbeFM tried hard to sell me on that. But right now I'm unemployed and can't spend money on this stuff.
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Old 08-28-2009, 11:31 PM   #6
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Well if it helps, try raising the idle. My car idles about 950 because of that fluctuating idle problem you're describing. I do experience the idle "searching" for its sweet spot, but it always misses when I first start the car from a cold or hot start. After driving for a good 2-3 minutes, the idle problem mysteriously fixes itself and settles at a somewhat steady idle at 900-1000. It still some what fluctuates, but its not noticeable from the outside. Only if you're staring at the tachometer will you see it ever-so-slightly trying to find the right idle spot.

This is of course, if you still want to try to stick with the stock ECU controlling the idle valve.

If not, there arent many options for MSI to control our idle valves, since our valve runs at a higher frequency than allowed by the stock MSI computer ( I think, MSII can only go to a max of 244Hz without duty cycle resolution loss). I don't know the maximum frequency setting MSI can output, but I would think it cant output anymore than an MSII chip can (or the software won't allow it). In other words, you may still have a really shitty idle after you switch. Might want to check with the guys at MSextra.com
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Old 08-28-2009, 11:37 PM   #7
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No, I'm talking about WILD fluctuation from 600 - 1600, very fast, over and over and over. Sometimes it stalls, other times I'll sit in traffic and it just keeps increasing little by little until it's at 1500, 1600, 1700, etc. .... that's downright scary. My gripe is not that idle isn't rock solid ..... it's that idle is virtually non-existent when the car gets warm. This is all despite having a new-ish IAC valve and despite wrapping the stock temp sensor in all kinds of heat shielding. Everyone I talked to (Matt C., Joe, etc.) basically concluded, "**** it, let MS have a try at your idle." If you have some fresh idea then I'm all ears, but turning the idle up a little isn't going to make any difference.
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Old 08-28-2009, 11:45 PM   #8
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well that sucks. I didn't think your idle was fluctuating THAT bad. Maybe you have some other problem somewhere else (i.e. vacuum leak)?
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Old 08-28-2009, 11:50 PM   #9
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The car runs great when I step on the gas. What kind of vacuum leak would only affect idle? (That's not sarcasm. I'd really like to know!)
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Old 08-29-2009, 04:05 AM   #10
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Have you set your MAT correction?
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Old 08-29-2009, 01:54 PM   #11
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Quote:
Originally Posted by Zaphod View Post
Have you set your MAT correction?
No. As I understand it, that's only needed to handle IAT heatsoak. My car doesn't have that problem.
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