t8 MAF scaling results..

Intake MAF scaling results from August -08..
Ok so as most of you know the biggest problem with aftermarket intakes (k&n, simota etc) is the MAF scaling issues related to airmass cuts or limp home..   BSR solves this by using a factory piece leading to certain success.  Others try with not so great results.  The test car is 9-3 Aero 2.oT 6 speed. Hardware is Catback, BSR stg1, Large Intercooler and 91 octane gas.

The stock MAF is 2.75″ but internally has a D shape so the full area is not present. Most aftermarket use a 2.75″ OD tube of round cross section and .065 wall. This gives slightly more area. (Will calculate it sometime.)  I built one like this just to see a few years ago for the -03 linear.  Worked ok until it got hot out and then had issues.  Same for the -04 aero on stock software. On tuned software it gives undesired results.   While I had my Aero on the dyno testing the new intercooler we swapped to the special intake.

Run 3 is stock airbox 4 and 5 with it after playing for a bit to adapt it. Here you can see the MAF worked well above 3k but under it hurt power.  You can feel this on the road. Peak HP went from ~215 to 228 and tq from ~260 to ~271 with nice gains across the range. This is from lying to the ECU about load.  Remember T8 goes for target airmass to make the desired torque. Your basic garbage in garbage out.

This becomes more apparent when you see the boost and A/f   With the big IC inlet temp is nearly a constant.  Bost is a little lazy and all over the place.  Airfuel is leaner due to the lower load signal sent to the ECU.  This is why the boost is higher, the ECU is trying for more airmass not knowing it is actually making it.  :)
I have some aluminum flanges we cncd for 3″ pipe and plan to try one of those later. Will probably have to add some fuel pressure to sort it out.

1 Comment  »

  1. AdrianW says:

    I hope you don’t mind, but I remembered a couple things I’d researched some time ago which may be helpful here.

    1- The turn in the piping between the air filter and MAF will cause some vorticity in the pipe. The stock D-shaped pipe would have helped dissipate such vorticity, and that was probably part of its design intent.

    2- There is a transition from laminar to turbulent flow over the sensing and heating elements in a MAF. When I was mathematically modeling the correlation between airflow and signal value in the T7 MAF, I noticed that the correlation changed from quadratic to cubic at a certain gas speed. Since that value is constant regardless of practical pipe size, it can cause problems with the linear scaling of MAF output, as it will get erroneously scaled along with all the other values. Also, the linear scaling of two non-linear variables will cause some problems in the ECU.

    Anyway, it might turn out to be something else, but I thought those would be worth mentioning. Again, apologies if I’ve overstepped any bounds.

    Cheers,
    -Adrian

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