I was troubleshooting a friend's car, that was hard to start. Also lacked power going up steep hills. Checked the usual stuff: ignition, fuel filter, air filter, exhaust sensors blah blah. The only defect I found was the honeycomb laminar flow straightener was missing from the MAF sensor. I obtained a replacement (cheap Chinesium copycat) and behold, it now starts fine. So does the missing honeycomb cause the airflow to be under-estimated?
My guess is .. yes
I suspect that the "straightener" might increase the air velocity as it goes past the sensor - a bit like wot a venturi does in a carburettor ?
The sensor probably cannot measure volume, so has to work it out from velocity and throttle angle.
Also, most petrol engines are designed to operate with an air filter in place - and as soon as its removed the fuel/air mixture will be compromised.
I found more to confirm this on website of V8 performance accessories. They said lack of honeycomb may cause "too lean" ECU error codes. Some revheads remove it, believing it restricts airflow, but end up with less petrol from the injectors. Without the straightener, flow becomes turbulent. So the air going past the hot wires must be less than the average air flow.
To confuse matters yet more, I suspect that there might be another sensor on the other side of the throttle plate to measure the manifold depression.
And the moral of this story is ... removing random bits from motor vehicles will reduce weight but may not improve performance.
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