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Discussion Starter #1
I have been power limited by my MAF output voltage for a few weeks. Basically I'm hitting 5 volts at about 10 PSI of boost. My new 4" silicone couplers finally came in. So, this afternoon I installed my 4" O.D. Mass Air Flow sensor housing. Images below.

Thoughts: going from my eBay 2.875" bore to this cleaner 3.75" bore was not as simple as scaling the linear slope of the sensor output. For the most part the Denso sensor was linear after swapping pipes. My area scaling factor worked amazingly well (-0.5 AFR average) In all but one area. Warm idle flows read about 40% lower than expected compared to cruse. I suspect this is due to the fact that the sensor is nowhere near the center of the flow pipe. Even with 3/4" thick honeycomb straightener the reading is off from center line flow. Unfortunately I do not have quick access to a flow bench to come up with a new calibration curve. So, for the idle area of my maps I will be retuning a bit. I also dont have room to run a stock MAF in series in the engine bay. Sorry if you're looking to upgrade easily.

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I can run MAP with the MS3. In fact I ran the IAT to the engine. Technically its supposed to be IN the intake manifold. I just haven't gotten around to pulling the manifold to weld on a bung. Plus, this is an interesting experiment since I haven't done such a large MAF on a tiny 1.8L before.

Update: The flow meter voltage log from this afternoon shows a minimum of 0.85 volts. That is well above any SNR level that would be concerning. I was able to tune the idle to stabilize within 0.05 AFR with the O2 closed loop turned off. So, it LOOKS like the verdict is that you can use the Denso sensor in a 3.75" ID pipe. So for those of you looking to boost the 1-2ZZ with a blow through MAF you should be ok up to several hundred horsepower over stock.
 
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