afm help

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afm help

Postby hijakd » Wed Dec 27, 2017 10:06 am

hey guys iv tested a fair few analogue airflow meters,recently i did a honda accord with a k24a engine and i found on a snap throttle it would hit the factory cut out at low rpm so i cannot get an accurate wave form of the afm pls enlighten me on how you guys do it
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Re: afm help

Postby Steve Smith » Tue Jan 02, 2018 12:29 pm

Hello and thank you for the post

Can I confirm by the factory cut out you refer to RPM limitation due to PCM control?

To clarify, this is a PCM feature to prevent max RPM at zero road speeds.

If so (and if the PCM will allow) there may be an over-ride feature where RPM limitation can be disabled with a Scan Tool

If not (and I have never seen such a feature) a road test has to be remaining option which will incorporate load.

Here then a WOT road test monitoring the analogue AFM output (for max output and rise time) with PicoScope in conjunction with the Scan Tool for the measured Air Flow Quantity (e.g gm/sec) will provide the necessary information you require to confirm the integrity of the AFM

Be aware of existing faults that could influence peak airflow (restricted intake/exhaust)

I hope this helps, take care......Steve
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Re: afm help

Postby Autonerdz » Tue Jan 02, 2018 6:19 pm

If the vehicle had a manual throttle, the MAF will peak on the intake fill on initial full throttle plate opening. No need to hold it and raise the RPM to cut out.

If the vehicle had electronic throttle control, then you cannot peak the MAF in this manner because you cannot snap the plate open. These require a dyno or road test to achieve max air flow.
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