MAFs

[Axel Rietschin]

From: "Chris Conlon" <synchris at speakeasy.org>

> >You mean you can get a faster response from the MAF (less lag) when it's
> >located closer to the engine because the plumbing volume introduces an
> >additional delay? I didn't think if it at first but I see no problem with
> >that.
>
> Hmmm I have not thought about it in terms of faster/slower. When the
> MAF is pre-compressor it actually reads higher, sooner than it would
> post-compressor, for a brief time when boost is rising. It's measuring
> the air that's actually going into the engine plus the amount of air
> needed to pump up the post-compressor plumbing to X psi of boost. The
> situation is opposite as boost falls, some of engine's needs are fed
> from stored boost post-compressor and the MAF does not see that air.
> (It saw it earlier during boost ramp up.)

Got it. However, post compressor is likely so see a lot of reverse flow at
times which could be accounted as forward flow by the MAF. Maybe the right
amount of filtering could get rid of the 'irregularities'.

> >Definitely. For info, I use a custom-made air temp sensor (using a
> >Thermometrics FP07 NTC sensing element) for my own engine. This baby has
a
> >time constant of 100ms in still air (7ms in water), just to say I'm
_very_
> >concerned with sensor response :)
>
> I'm with you all the way. Currently I'm using some lightweight NTC
> thermistors, suspended in the middle of the airflow. (Higher flow rate
> past the sensor helps a lot.) I'm still not happy with the setup though.
> I'm using glass thermistors because I originally spec'ed a very high
> max temp rating. At this point I'd rather have a faster responding
> sensor though.

Check out www.thermometrics.com Look into Products -> Automotive and search
the page for FP07. You'll find a PDF with the specs. I was able to purchase
a couple of samples from one of their distributors and I put it in a
recycled regular Weber-Marelli sensor housing which fits into my inlet
manifold.

--Axel



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