Re: LS1 Air Mass Meters

["Bruce Plecan" <nacelp@bright.net>]

Then it sounds like the problem is in the calibration, not the measuring.
Like the guys that work on the flow benches that swear x% increase in flow.
How many engines do you know of that the intact stream is at a steady rate
of flow?.
Grumpy


> We've been beating on this old horse over on the LT1_Edit mailing list
> as well (and also on the 4th Gen F-body list)... If you consider your
> "standard" late model LT1/LS1 OEM MAF sensor as having the honeycomb air
> straightening screen, as well as the large airfoil in the middle, and
> the "aftermarket" units removing this screen and airfoil, there's a
> pretty considerable amount of surface area that's opened up.
>
> In the LT1 PCM (and this will be similar for the LS1), the calibration
> curve table values are entered in Frequency, and they correspond to a
> grams per second value. If you remove the above items from the MAF
> sensor, you have thrown off its calibration, as its frequency will no
> longer correspond to the "correct" g/s value. This has the effect of
> making the car run leaner, and since the LT1 platform runs rich in the
> first place, it shows a slight increase in horsepower... Think about it,
> the MAF doesn't sense the whole amount of air going through it, so it
> measures the air as less than it actually is, so the PCM calls for less
> fuel than it really would have used before...
>
> A couple of LT1_Edit users have redone their MAF calibration curves by
> changing the value by about 5%-7% and are able to obtain proper (128)
> integrator numbers. However, a number of people complain that with home
> ported MAFs that they experience rough idling and intermittent other
> strange behaviour.
>
> Now, are these companies compensating for this with a "calibration"?
> Making the frequency line up with the appropriate grams per second
> values in the PCM table? That I do not know. There is a company selling
> them here in the US as well - as a "calibrated" unit. Honestly, I have
> my doubts. But who knows, maybe they do diddle with the electronics a
> little bit. I've never even seen one of these aftermarket units in
> person, though, I just know about the LT1/LS1 OEM units...
>
> -Andrew
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