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Old 01-13-2012, 01:38 AM   #1
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Default Stumble help please

Hey all you tuning gurus. I just changed to a smaller pulley on my Rotrex and have a major stumble around 6k. Would a lean spot feel like the car is tripping over its feet?
Stumble help please-jan2.png
I've run VE analyzer a couple of times, but it hasn't seemed to help.
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Old 01-13-2012, 01:49 AM   #2
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Post a screen shot of your fuel table please
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Old 01-13-2012, 01:50 AM   #3
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I'm pretty sure it's your fuel map...it probably has a nasty hole, and that's why you're unloading in 3rd.
But seriously, screen shot your fuel table.
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Old 01-13-2012, 02:03 AM   #4
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That photo says at 5855 RPM's your at 149 KPA and 13.459 AFR.
That means you're at about 7psi at almost 6,000 RPM's and you are wayyy too lean. You should be at around 12.0AFR, not 13.459. Richen it up some more. Is it detonating at that? Cause I'd think it should be.
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Old 01-13-2012, 02:09 AM   #5
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Here is the fuel map that is being used.
Stumble help please-megatune-screen.jpg
Just before the lean spot I'm at 11.8
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Old 01-13-2012, 02:16 AM   #6
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Last edited by Scooter25; 01-13-2012 at 03:11 AM.
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Old 01-13-2012, 02:27 AM   #7
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I'm going to bed, but I will say this. If you're on the throttle and you see leaner than 12.5 at 7psi or more, take your foot off the throttle immediately. Take a mental note of what rpms you were at when it was that lean, and how much boost you were running and add fuel in that cell, then taper the cells around it. You shouldn't have 1 cell read like 120, and the one right under it read like 89. Keep them close to keep the table smooth. Tomorrow morning I will post example fuel ve tables, and get back at ya about corrections. Expect to see me around 10 eastern standard time...(7am) California time.
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Old 01-13-2012, 03:08 AM   #8
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Here is a log with new fuel map... AFRs still go ape ---- and car stumbles.Stumble help please-megalogshot.jpg

jan122.xls

Last edited by Scooter25; 01-13-2012 at 05:02 AM.
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Old 01-13-2012, 06:00 AM   #9
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What version of firmware?
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Old 01-13-2012, 11:50 AM   #10
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MS1 029v
96-97 without MAF

Last edited by Scooter25; 01-13-2012 at 12:19 PM.
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Old 01-13-2012, 12:04 PM   #11
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Well, you did yourself some good there. Went from 13.5:1 to 13:1 in that area. Keep going. You're shooting for 12:1.

Hate to tell you, but the stumble you are feeling could very well be det.
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Old 01-13-2012, 12:04 PM   #12
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I still think it's too lean...I mean you're at 13.0 at that same RPM and MAP. Add more fuel in those cells and keep the surrounding cells within lets say 10 for now of the rest.
To add fuel to a bunch of cells at once, you can highlight a few cells at a time and click on the + symbol. Then you can type in the percentage to add and it'll take those selected cells up by that percentage.
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Old 01-13-2012, 12:05 PM   #13
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One more thing. What's your plug gap? Assume the ignition is stock (other than that it's being fired by the MSPNP)?
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Old 01-13-2012, 12:33 PM   #14
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I don't remember what plugs are gapped at other than within stock specs. I'll check when I get home tonight.
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Old 01-13-2012, 12:36 PM   #15
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That first fuel table looks awful. I don't know if VE rolls off in your car like it does in mine, but it should probably look more like these:

edit: This was a draft, its cleaner now.
older, before I fixed the intake valves:


It's generally a no-no if have anything but an increase in VE value from left to right, bottom to top, my car breaks this rule a little bit, but I call it "artistic license". With your revised fuel table, things are getting better and the duty-cycle line looks more reasonable, but you're still leaner than most of the NA cars I tune. Show us your AFR table, please.
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Old 01-13-2012, 12:37 PM   #16
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gapp them to 0.25-0.030"
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Old 01-14-2012, 12:47 AM   #17
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OK so I fattened it up a bunch more and did a short log on my way in to work. What the crap happened hereto cause the huge MAP spike?Stumble help please-jan13log-screen-shot.jpg

Also as soon as the car cools off I'm gonna pull the plugs to check the gap.
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Old 01-14-2012, 02:13 AM   #18
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Quote:
Originally Posted by hornetball View Post
One more thing. What's your plug gap? Assume the ignition is stock (other than that it's being fired by the MSPNP)?
Quote:
Originally Posted by Braineack View Post
gapp them to 0.25-0.030"
Ding ding ding, we have a winner. Pulled plugs and they were somewhere between .040-.045". Regapped them between .025-.030 and things are much better. In fact I need to go back and lean it out just a hair.
Stumble help please-screen-shot.jpg
You still need to fix that garbage fuel table.

Last edited by hustler; 01-18-2012 at 10:03 AM.
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Old 01-14-2012, 03:25 AM   #19
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It makes us here at MiataTurbo.net grow a semi rubbery one when we hear other members solve problems.
Glad to see your car is straightened out.
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