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Discussion Starter #1
Last year, I pulled out the inside tubes between air filter and the MAF to see if that made any improvement in the performance. I did see an increase in boost by about 2 psi.

However, when I logged the Long Term Fuel Trims (LTFT% error), I saw they were way out of whack because the now bigger volume area before the MAF reduced air velocity, so the ECU LTFT % error was over 9% at WOT high RPM. The driveability was worse and power delivery at light throttle was not smooth. The incoming air obviously was more turbulent as it passed the MAF sensor causing a widely variable LTFT % error at low throttle opening. Also, I saw 4° of knock retard at WOT over 5000 rpm.

I bought a pair of air straighteners (see below) for $20/ea and inserted them in the air filter housings just before the MAF sensor. I used HP Tuner scanner again and the LTFT % error was very steady and consistent. After a few copy/paste from the HP Tuner's scanner to the HP Tuner's Editor, reflash, and the LTFT % now is under 2% at low throttle and near zero before WOT. Driveability much improved.

You will have to trim the inside of the filter housing with a Dremel to get it to fit the 3" OD airflow straightener, but that's no big deal. Airflow straighteners like this are not new. They have been used by many OEM manufacturers to get consistent MAF readings.

573840

Purchased from: Performance MRP. Size: 3.0 OD x .5 Airflow Straightener Screen .187 honeycomb cell.
 

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Still Stock 2017 ATS-V 6MT CWT Sedan, Tuned 2016 Explorer TT
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545 Posts
What is the purpose of this exercise? To trick the ECU into running the wrong AFR?
 

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2015 ATS 2.0T (gone), 2016 ATS-V, 1968 Corvair, 1974 Corvette, 2003 HD Road King
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Only change is to the MAF table due to the removal of the tubes in the air filter housing I outlined above.
Now that you have already tuned it, why not put the hardware back to stock and contact someone like Scott at Tapout and do it right?
 

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2016 ATS-V Coupe (Catti-V)
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So the MAF sensors are very sensitive to any changes to airflow or velocity. Thats been known for quite some time now. You seem to have done your homework though and didn't just change something and then ask everyone whats wrong, that is very refreshing. I do wonder what the objective was. If you have to add something to make the airflow the same as it was before what was the point? This car doesn't suffer from lack of airflow, so unless you go with one of the tested intakes that do not disturb the flow over the MAFS, it really makes no sense to mess with it. Even the tested intakes make minimal gains, even with a tune, so again...is it really worth it?
 

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Discussion Starter #7
Since I removed the tubes and used my Dremel to removed the lip which opened up the air filter box somewhat. I had to do something to fix the MAF. The LTFT% were 10%+ before, so I installed the air straightener and changed the MAF tune by about 10%. At low throttle openings, power delivery was lumpy.

To go back to stock, I'd have to buy a new air filter box or glue the tubes back into place. The air straightener has totally eliminated the driveability problem at low throttle openings. I've monitored the LTFT% with HP Tuners and its well within a few % and many times less than 1% at cruise.

As with any mod, the benefits are many times questionable. I would agree the air filter box mod has little gains.
 

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Discussion Starter #8
What is the purpose of this exercise? To trick the ECU into running the wrong AFR?
No, the opposite. To get the MAF sensor to read the correct amount of incoming air so the A/F ratio (LTFT%) was as close to zero as possible. Do you understand how the MAF works?
 
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