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Old 04-23-2011, 03:53 PM   #1
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Default Recommendations and IAC question

I decided to start a new thread because my old thread was titled with "timing", I no longer have any timing questions as that was answered fully.

I have a 91 stock miata. DIYmspnp. Originally it would run extremely lean, so I richened it up by increasing req_fuel from 11.2 to 16. I can get it to idle at 11.2 by richening the VE table. So, my question is, should I continue to mess with the VE table? Or, just use req_fuel? I don't know how many cells I'd have to richen, but, for example, in order to idle with an AFR around 14, I had to change from the approximately 33 to 40-45 range. Has anyone else experienced this with the stock engine? I'm wondering if my injectors are just crap.

Additionally, I have an IAC question. When I start up, after the engine is warm, my IAC is at step 77 or so, rev the engine a few times, and it drops to 15 steps. Is that normal? It also jumps back to 77 after I Burn to ECU after making changes to the VE table. Not sure if this is normal or not.

My idle with the valve at 77 is 800-900, at 15 it's 1500. So I'm assuming I need to adjust my idle screw, then fix what ever is making it idle low at 77. Is this correct.

I think I'm only going to work on this a bit more before returning to the stock ECU so it can be a daily driver. There's always next weekend though! In the mean time, I think I'm going to read as much of the msextra tuning manual as possible.
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Old 04-23-2011, 04:08 PM   #2
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You should set your Req_Fuel by your car and then leave it alone. The rest of your VE tuning should be done entirely within the VE tables. What are your VE values in the idle area?
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Old 04-23-2011, 04:11 PM   #3
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In order for the car to not attempt to run at 19 AFR, I had to richen the VE idle area to 40-45 range
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Old 04-23-2011, 04:13 PM   #4
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Ok, and when you drop your RF again you'll have to raise those values even more. Mine are set around 55-60
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Old 04-23-2011, 04:15 PM   #5
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At idle? When I set my required fuel to the correct value, that's when my idle VE numbers are around 40-50. Your values being so high makes me think I'm actually on the right path. I wonder why the start up basemap had them so lean?
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Old 04-23-2011, 04:19 PM   #6
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Yep, that's at idle. No idea why it's so much higher than the base map. I remember when I set the correct Req_Fuel on the basemap in mine it went very lean as well. Just bump up the VE until you're at your target AFR.

Last edited by D.dutton9512; 04-23-2011 at 04:31 PM.
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Old 04-23-2011, 04:27 PM   #7
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91. Someone swapped the engine in it though, luckily it's got the long nose crank in it.

If you put your key in "run", can you hear your IAC?

Thanks for the advice btw, I'm going to richen up the idle area and see how she does. I'm still concerned that there is something wrong with my IAC though.
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Old 04-23-2011, 04:31 PM   #8
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EDIT: Nevermind, I had the wrong number for the 1.6 injectors, some sites say 212cc and some say 230cc
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Old 04-23-2011, 04:34 PM   #9
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11.2 is what the calculator gave me when I entered 1600 cc for the displacement, 240cc/min injectors. It comes out to 11.7 if I use 230 cc. The basemap I downloaded said the injectors were 240, but I think the stockers are 230. So I should at least change the required fuel to 11.7. Stock injectors.
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Old 04-23-2011, 04:50 PM   #10
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Looks like blue tops are anywhere between 205 and 230 so anything between 11.2 and 13.1 will be about right. Don't stress about it too much, just go with what the calculator is giving you and start working on your VE table.

Also, for the IAC, post your MSQ.
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Old 04-23-2011, 05:11 PM   #11
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Attached is my MSQ file. It's actually labeled wrong, I used 12.7, not 11.7, for my required fuel, using 212 cc/min for injector flow.

I also attached a data log from my idle, you can see the rpms and the IAC steps change as I rev it a few times.

So far your help is greatly appreciated. Any more help with what I think is an IAC problem would be amazing.
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