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  • mass air flow sensor query (flow straightener)?

    From Johnny Jick@rightwing@oldfarts.co.uk to uk.rec.cars.maintenance on Fri Sep 16 15:31:04 2022
    From Newsgroup: uk.rec.cars.maintenance

    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?
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  • From Abandoned_Trolley@fred@fred-smith.co.uk to uk.rec.cars.maintenance on Fri Sep 16 09:51:31 2022
    From Newsgroup: uk.rec.cars.maintenance

    On 16/09/2022 08:31, Johnny Jick wrote:
    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.
    --
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  • From Johnny JIck@jj@gurlsquad.org to uk.rec.cars.maintenance on Sat Sep 17 10:42:26 2022
    From Newsgroup: uk.rec.cars.maintenance

    Abandoned_Trolley wrote:
    On 16/09/2022 08:31, Johnny Jick wrote:
    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-a .. yes

    I suspect that the "straightener" might increase the air velocity as it
    goes past the sensor-a - a bit like wot a venturi does in a carburettor ?



    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.
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  • From Abandoned_Trolley@fred@fred-smith.co.uk to uk.rec.cars.maintenance on Sat Sep 17 09:26:54 2022
    From Newsgroup: uk.rec.cars.maintenance


    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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