Aftermarket Injection, Why no MAF? Options

[McMark]

I was just thinking about how all the aftermarket injection systems all use vacuum signal which can cause problems with wild cams. How come nobody is using a Mass Air Flow sensor? It can't be that complicated. Famous last words.

[gaz914]

QUOTE (ClayPerrine @ Dec 20 2004, 12:34 PM)

You can use a Hot Wire MAF. It doesn't get screwed up by the reversion pulses (no moving parts). Hot wire MAF can be retrofitted to a Motronic system.

I don't agree.

If a cam is "wild" enough to generate recursion pulses of enough significance to affect "flap type" metering, then the hot wire will also be affected.

Granted the "problem" is different but there must be an effect.

If you can imagine a "block" of air being sucked past the MAF, stopping and then pushed back out again (reversion) - what does the MAF "see".

What it "sees" is 1 block of air moving past, then another block of air moving past - it cannot dscriminate which direction the air is travelling.

The effect? The air is metered TWICE, so at low speed (where the reversion occurs) the mixture will be very rich.

I think that most "serious" engines use TPS mapped (alpha-n) fuel injection for this reason.