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Old 12-20-2011, 01:53 PM   #1
Elliotgofast
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2005 MAF Flow limit

I'm working on a 2005 Focus that has a prototype supercharger system. I'm using an SCT pro racer package. The engineering customer wanted a less restrictive MAF system to reduce the pressure drop in front of the supercharger. The new MAF housing is 3in. Obviously this completely changed the MAF curve and basically moved the entire curve up. At 3000rpm and higher and above about 3volts on the MAF, it forces it into open loop and pegs the wide band meter full rich till it misfires rich. This is at highway cruising speed. This equates to about 30-35 lb/min of flow. Is there a MAF limit on this ECU software package? Similar to 2003/2004 Cobra that is limited to about 64 lb/min and hard coded in the software..

Do I have to rescale the entire ECU for more range? It is quite a head scratcher because if I'm in boost, I go open loop and my fueling is ok. If I'm below 55mph, everything is fine and my adaptives are in good shape. Anybody else's experiences with this would be appreciated and if there are any other work arounds besides rescaling the ECU.


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Old 12-20-2011, 02:53 PM   #2
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The MTF itself is off. So you'll have to turn adaptive off and go back through it and rescale it.

There isn't a limit on flow per se, but when you rescale the MTF you will decrease the accuracy as the upper limit of flow increases. You can not go over 5volts (4.9x actually).
So work from your upper limit and go down from there.

Also be sure you upped the flow limit of the MAF in PRP, MAF --> Scalar --> MAF Maximum AD Counts, stock is 980 and you want to change this to 1023 (which is 5 volts).

My current MFT vs stock:




You can see that in stock form the resolution is greater around the 400 count area, which corresponds to highway speeds and light acceleration. Ford wanted a lot of accuracy in that area because that's where 75% of your time is spent.
The problem as I see it is, the ECU doesn't go point by point when looking for the MTF, it goes by an algorithm. If the scaling in not uniform or the ranges go up and down, the algorithm becomes more complex and this take more CPU power to compute. This is why I rescaled mine so the ranges are all uniform. Though I can not prove this plays any part in speed or accuracy. I can however prove that the space between the points, the fueling is predictably accurate, which to me means the algorithm is very close to perfect.


But, go back through your MTF and re-do it. Don't worry about any limitation on part throttle tuning, as in don't limit yourself to 400 counts and all after is for WOT tuning. That kind of mindset only works if you haven't doubled or tripled the max flow of the engine.
I do part throttle scaling up to 600 counts and I have no issues with rich conditions or the ECU thinking I'm asking for a different throttle mode than I really am. 500 counts and under 70% throttle I want to be near Stoich and that is what the ECU shoots for.
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Old 12-20-2011, 06:07 PM   #3
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The MAF has little to do with the ECU going into open loop its more a TPS count that sets the switch to OL

You first need to get the injector size set right this also will throw off the MTF and if your running say 42lb Inj you cant always use the value file for 42lb Inj

There is a lot of things that have to be right not only the MTF

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Old 12-20-2011, 08:32 PM   #4
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The injectors were scaled using the high and low slopes, and breakpoint for the base application that the injectors came from. This vehicle has been running with these injectors on the stock MAF with boost for almost 2 years now doing testing with this company. The only thing that changed just now is the MAF tube was increased to 3in to remove the pressure drop in front of the supercharger. All other calibration values not related to the MAF are the same values the car has been running on for the last couple of years.

The open loop TPS table is set to 500 counts. When I get to the condition described, I'm running 320-350 counts of throttle.
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Old 12-20-2011, 10:41 PM   #5
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I will be glad to help , I gave you my contact info

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Old 12-21-2011, 12:14 PM   #6
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Occasionally the car is throwing a P0102 code for MAF circuit low. This is probably because of the larger MAF housing causing a lower voltage output. It's easy enough to turn that code off but hints that there diagnostic or fault issues going on.
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Old 01-02-2012, 08:09 AM   #7
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We were able to find the issue. When the customer plugged in the MAF, they accidentally missed a pin and forced a pin to bend and touch another pin. This basically made the MAF inoperative. We had checked the connector, fuses, and wiring but of course looking in the end of the MAF sensor was the last thing checked. Thank you to everyone that responded and supplied ideas to look at. The car is back up and running and the customer is continuing their testing.
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