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Old 03-13-2006, 02:03 PM   #1
quickscooby
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Default Effects of maxed stock MAF

When the stock MAF is maxed out how does it affect the tuning? Will the ecu pull timing, add fuel, taper boost, etc? Just wondering if the ecu is smart enough to pull out timing when it sees too much airflow on the maf to help protect the engine.
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Old 03-13-2006, 03:39 PM   #2
Freon
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I don't believe thre is anything in the ECU logic to do so.

But once you max your sensor you have no idea how much air is really going into the engine. All you know is it is "a lot", or more. You pretty much lose control of AFR, and can only use one timing value per RPM site.

This is something that shouldn't happen until your car is tuned and modified quite a bit, so you should see it coming ahead of time and prepare accordingly.
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Old 03-14-2006, 12:45 AM   #3
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I think in general, when you max out your MAF, you also max out what your ECU is going to inject for fuel. I.e. when your MAF hits 5.0, or whaterver you ECU reads for MAX reading, its stopps adding fuel and keeps it at whatever you ECU would normally add for the max reading, no matter what the amount of air you are actually adding.

I know this from personaly experience on a dyno. You could see that at 6000 rpm I would suddenly go dangerously lean at the moment I "maxed" out my MAF.

What I did was swap a differnt MAF in that is able to read a slightly higher amount of air before maxing out. Havent had a chance to dyno tune it since then though.
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Old 03-14-2006, 08:21 AM   #4
quickscooby
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Hmmm interesting. I thought it would go super rich because the ECU would try to protect the motor.
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Old 03-14-2006, 10:01 AM   #5
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Old 03-14-2006, 10:02 AM   #6
Freon
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Well with the ability to tune your flash, when you max your MAF, you only get one load column to guess how much fuel to use. Generally without tuning you'd go lean the farther past your MAF you pushed. But you could add fuel to your top load column and compensate, but you still have lost any sort of control on AFR.

Ex. if your MAF maxes out at 4.9v, and that indicates, say, 8g/s/cyl, and your last load column on your fuel map is 7.5g/s/cyl. If you put "11" into the target AFR fuel map, you will get 11 AFR until your MAF maxes out. Keep pushing it, and you actually pushing 9g/s/cyl but your MAF maxes out at 8g/s/cyl, so you go lean even though the fuelmap says 11:1 AFR. The ECU doesn't even know it is "screwing up". You can compensate by looking at a wideband. You put 10:1 into your fuel map, then you get 10:1 at 8g/s/cyl, and 11:1 at 9g/s/cyl. But you'll still lean out if you push more than 9g/s/cyl. So you can compensate more if you think you'll hit 10g/s/cyl. So you put 9:1 in your map. You get 9:1 at 8g/s/cyl, 10:1 at 9g/s/cyl, and 11:1 at 10g/s/cyl. You can see how this becomes a problem eventually... As you fly through load columns, you're running 11:1 (what you want), then you get to your final load column, your car dumps fuel for a moment, then starts to lean back out as you push farther past your MAF limit. But there is no way to not have that jarring fuel dump because you have no precision. And you're still screwed with weather changes.

If you are just peaking out your MAF you can compensate somewhat, but I'd still consider it dangerous unless you've got a full time co-driver staring at your EGT and AFR gauges to make sure you don't pop your engine.
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