[Diy_efi] Speed-density vs. MAF/MAP...

[Grant Beaty]

> If you have a MAP sensor that reads > 1BAR absolute, then
> you could do SD above 100% VE.  Also, at > 100% VE, where
> is your high pressure point?  I'd presume that the
> intake tract prior to the Cylinder is your high pressure
> point and thus that's where you'd need to put the MAP
> sensor pickup.
>
> --Perry

Hmm? Why not just put the sensor in the plenum? As you said before, take a
sample at the same crankshaft position each time, and calculate VE from the
MAP and RPM tables. I've certainly seen many (all?) speed density setups
that don't take readings at the intake valve and work just fine.

What exactly is the difference between measuring TP and MAP? If TP is low
enough to cause any power drain on the engine, wouldn't the MAP be lowered?
Of course I assume we are talking about a 2 bar MAP sensor (if its an NA
application, maybe 3 or 4 bar if FI).

Kinda unrelated, but if you had a MAP sensor on the intake and exhaust
manifolds, you wouldn't even need a barometric sensor would you? And you
might even be able to leave the map unchanged with different turbo setups...
(Of course its a silly idea in terms of reliablilty and accuracy - the
exhaust gauge would bounce around way more than the intake gauge, and
missfires would screw with it too).

Confused, as usual,
Grant Beaty


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