[Diy_efi] VAF MAF

[Brian Dessent]

Alexei Pavlov wrote:

> There is no 'accelerator pump' effects with the Bosch MAF (VAF).
> The flap follows the flow rate, that's all. If you see spikes
> on the MAF output, that means your intake manifold needs more air.
> 
> If you replace a flap MAF with a hot-wire/film MAF you need
> introducing a temperature/ambient pressure compensations.

I have a vane-style airflow meter, and I've driven around with a scope
attached to its output.  It indeed does have some overshoot, especially
on transitions such as rapidly opening the throttle from closed at
higher RPMs.  It's an underdamped system with fair amount of overshoot. 
I don't know how exactly the ECU uses this fact, but it's there and I've
seen it mentioned in documentation about this particular engine
management system.

Brian

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