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Microtech why does AFRs go lean when i drop IATs

Old 11-01-09, 05:55 PM
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why does AFRs go lean when i drop IATs

i got a water to air IC system, small rad.,, circulation pump,, and resevoir tank.
when im just cruisin around ,NO boost , my AFRs ,map and drivability are great , no probs. so i do not turn on pump, MPG are better with pump OFF !!, , IATs average around 110-120*F.

now when its time for boost,I switch on pump,takes about a minute to drop air temps to below ambient, 80-90*F, but my AFRs go way up,like 16-18, LEAN at cruise.

what im askin is, can i run two maps, one for cruisin and good mpg, and someway to switch to a power map, for hi boost ,and keep afr in safe range.?

I have not tried a boost run when afr reads 16-18 lean,, in stge on afr is 10.5-10.8 when pump is off , boost maybe 12-14. but i think there is somethin left if i went to 18-20 boost

rx72c any ideas ?? or anyone.
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Old 11-01-09, 07:52 PM
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cooler air has more density = more oxygen = needs more fuel to burn it up

the fact that when your air temps drop ,, AFR climbs
this indicates you have nil or the wrong correction values in the air temp look up tables
( or the air temp probe is faulty/ missing )

take note of what air temps are when the IC is being effective,,, find the corresponding screen 25 bins,, add some fuel to them,, simple


alternately,, you can use the aux in ( enabled when water recirc pump functions )
and setup enrichment and also timing adjust in the screen 29 aux enrichment screens
( using inpEnrich and inpTiming functions )
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Old 11-02-09, 06:55 AM
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That above is correct.

But really if your ECU had the air temp correction map configured correctly it would compensate accordingly.
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Old 11-02-09, 06:12 PM
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I got a small problem tho!! LTX-8

my Microtech came out of PR, and no air temp map(guy said did not need it) ,it was ordered for race only.
i have tried the stock FD sensor on it and it reads 99,wont change at all when i try programing.
sendin back to OZ is much prob.

this sounds a little intimidating, but let me think about it.

you guys run thru this stuff like its nothin, but im on my 3rd engine, in three yrs!!
so im a little gun shy !!
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Old 11-02-09, 06:18 PM
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this may help! DUH
im usin an aftermarket IAT gage, standalone.

so wont match up to MT
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Old 11-02-09, 10:07 PM
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Well the reason your ecu is not compensating for air temps is cause you dont have it connected. You already figured that out.
So you can send ecu back for reconfig, you can pm me if you want more info on that, i can do it.

But really your engines are not surviving because you either have a bad tune or bad engines.


tunes should be done so they are safe regardless of most variables. At least for a road car anyway.
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Old 11-23-09, 07:27 AM
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hey ronbros...
you may have another problem every FD-owner has.
Not only wrong IAT-correction parameters will lead to lean AFRs (as bumpstart said).
A big problem is our bad IAT-sensor which is really really slow reacting.
So your IAT drop but the ECU doesent even get the information to correct it because of the slow responding sensor.

there is a fast reacting Sensor available.
Search for it or PM me...
only with fast reacting IAT-sensor AND the correct values in your ecu your problem will be solved!

kind regards
Marc
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