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Old 02-17-2008, 10:53 PM   #1
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Unhappy Megasquirt higher rpm fueling issues! help!

Hey guys.
I realize this may not be the best forum to post this question on, so please don't be angryyyy, but I've just started using megasquirt, and you're all much more skilled at tuning it than I!
I have a 1995 Mazda Miata that I've just installed individual throttle bodies on, and I'm using the Megasquirt PNP version for the 1994-1997 Miata with the most recent build and firmware.
I'm new to using megasquirt, but I can move my way around it pretty good.
I'm sure there's settings inside the ECU I don't know about that, which is why I'm in need of help.

The problem(s) I'm having are these:

1 : Because of the greater volume of air being consumed by the throttle bodies, any time i blip the accelerator, or floor it, the car bogs out, causing a lean condition as read on my wideband gauge, and sometimes stalls out. The response is very poor. The AFR gauge reads past the lean limit when this happens.

2 : Any rpm over 4500 at full throttle/load, the car leans out gradually, and goes past 19:1 AFR, and begins to bog. I've set the VE tables to almost their full values for all these rpm ranges, yet the results remain the same.


Under normal driving conditions, besides the initial acceleration bog, the car runs pretty well, accelerates well before the previously mentioned RPM range, and idles well when warm.

Things you should know/ things I've tried doing:

- I'm using Alpha_N mode for the fuel algorithm, instead of speed density.
- The TPS has been replaced with a Toyota unit, instead of a Mazda unit. The TPS has been calibrated, and works correctly from what I can see on the charts. (ADC: 50-205)
- I'm running a stock fuel pump and regulator. The regulator, with vacuum applied should allow fuel to go through the rail at 31-33 PSI. With vacuum unapplied, the regulator should allow fuel to run through the rail at 43-45 PSI.
-The injectors are larger than stock injectors. They are rated at 310 CC @ 46.5 PSI. I've entered the injector information in the ECU correctly.
- I've retarded spark back to factory settings in the spark tables.
- My AFR target tables have all been reset to 14.7 for all TPS/RPM ranges.

I'm under the impression the car needs an adjustable regulator, or a larger fuel pump,of which I've already ordered both.
However, I have a friend named Paul who's actually on these boards, and has a turbo miata, runs even larger injectors (550cc if I'm not mistaken) and puts down 271 whp. He says the stock fuel pump is more than enough for my application because he uses it in his own car, but the car still leans out way too much any rpm over 4500.


Can anyone throw some suggestions out there? Maybe some things I've overlooked in the MS setup?

It would be GREATLY appreciated.
Thank you!
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Old 02-17-2008, 11:03 PM   #2
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its a PNP for 94-95, not to 97
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Old 02-17-2008, 11:09 PM   #3
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Quote:
Originally Posted by yes this is jj View Post
- I've retarded spark back to factory settings in the spark tables.
- My AFR target tables have all been reset to 14.7 for all TPS/RPM ranges.

I'm under the impression the car needs an adjustable regulator, or a larger fuel pump,of which I've already ordered both.
However, I have a friend named Paul who's actually on these boards, and has a turbo miata, runs even larger injectors (550cc if I'm not mistaken) and puts down 271 whp. He says the stock fuel pump is more than enough for my application because he uses it in his own car, but the car still leans out way too much any rpm over 4500.


Can anyone throw some suggestions out there? Maybe some things I've overlooked in the MS setup?

It would be GREATLY appreciated.
Thank you!
- where the **** did you get the stock timing map values?

- 14.7 is a horrible AFR to shoot for across the whole table. you want to use 13 in the 101 row like I set you up with to begin with. see pic below

- i run 460's. been too busy to swap my 550's in
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Old 02-17-2008, 11:15 PM   #4
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Quote:
Originally Posted by yes this is jj View Post
1 : Because of the greater volume of air being consumed by the throttle bodies, any time i blip the accelerator, or floor it, the car bogs out, causing a lean condition as read on my wideband gauge, and sometimes stalls out. The response is very poor. The AFR gauge reads past the lean limit when this happens.

i bet they pull in like the same amount of air. haha.

anyway, there is a page for acceleration enrichments(acceleration wizard under Basic Settings). i have no idea what settings you need when you change to TPS based but that should be the key to your lean tip in issues.


try calling DIY Autotune or emailing them. Jerry or Matt should be able to help with settings for IRTB setup
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Old 02-17-2008, 11:17 PM   #5
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Dang it... I know I saw those maps somewhere, but I lost the link. They are out there... somewhere... I remember reading a thread about some guy reverse-engineering the timing maps from the stock ECU.
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Old 02-17-2008, 11:38 PM   #6
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Quote:
- 14.7 is a horrible AFR to shoot for across the whole table. you want to use 13 in the 101 row like I set you up with to begin with. see pic below
My mistake, I did set the values richer under high load and rpm, but for the whole bottom line I did in the 14's because the car was running so damn lean.

I tried messing with that acceleration enrichment ****, but it didn't get any better.
I will email them. thank youuuuuuu
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Old 02-18-2008, 12:40 PM   #7
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Could it be acceleration enrichment? Dirty fuel injectors?
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Old 02-18-2008, 01:00 PM   #8
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Disable acceleration enrichments. Set the threshold to 300 is using mapdot or 30 is using tpsdot. That will take AE out of the picture making tuning easier.
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Old 02-18-2008, 01:31 PM   #9
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I got the injectors cleaned by witchhunter performance recently. They all flowed around 305-309 cc out of 310. I'll try disabling the acceleration enrichments, though. : /
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Old 02-18-2008, 01:57 PM   #10
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A couple notes:

1. The part about turning off acceleration enrichment is because if your VE tables are too far off, acceleration enrichment won't cover for it.

2. The maximum value in the VE table is 255. If you're close to that, increase your Req_Fuel value.
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Old 02-19-2008, 08:56 PM   #11
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Alright, so I figured it all out!
I did what Matt Cramer said, and the reqd_fuel number was set to 18.
The car runs great, however, I noticed something else tonight.
Inside the basic settings>engine constants menu, there's a selection for fueling algorithms.
Speed density was checked, not Alpha_n.
The car died out from having too much fuel.
Thus the original problem is solved and Im building a new chart!
Thank youuuuuuuu!
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