pgmfi.org

I have a question.
I know of a bunch of people using VAFC's and SAFC's along with 450cc injectors in their turbocharged cars. The idea is to lower the MAP voltage so as to keep it at vacuum levels while on boost. That way you avoid CEL's and control the larger injectors. This is done by leaning the mixture by upwards of -40%. Now, what would happen if I were to take a potentiometer and lower the MAP voltage by 40% accross the board before it enters the ECU, then tune it as you would a NA?
What's wrong with this idea?

http://pgmfi.crx-forum.org/phorum/read. ... =292&t=292

jason davis and george are working on it.

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Potentiometer != work correctly.

The MAP acts as a variable resistance, as it changes you vary the voltage drop across the potentiometer. In other words, as you drive the cut does not stay stable at -40%. It varies hugely.

Hunt up a voltage regulator with the part number "7803." Power, ground, and 3 volt output - it doesn't get any simpler.

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you mean using 4k/6k resistors as a voltage diviser on MAP's output isn't linear?

I tought as long as the AD converter isn't drawing any current the drop should be linear

Ah, sorry, I had you confused with someone trying to use a regular potentiometer in line, not as a voltage divider.

FYI, a voltage divider isn't linear, either. The MAP sensor acts as a variable load as pressure changes, which alters how much voltage is dropped across the MAP and how much is dropped across the voltage divider. There is a reason filetofit/Chris used an opamp to adjust a seperate voltage divider for idle characteristics with his method.

http://www.digikey.com grab a 7803 and call it a day. My $0.02. Or, hell, that Ghetto-whatsis program is supposed to have boost support soon.

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