j9fd3s

so ive been driving around with a voltmeter on the afm all week on my gsl-se and heres what i've found. the gsl-se uses a flapper door afm, like the s4 fc. the gsl-se is a 12v system, and the voltage goes up as the door opens. idle voltage is about 5.06v and wot voltage is about 8.80v. i notice that you can get full voltage at about 4000-4500rpms.



while i was in there i plugged in an fc afm, and it wont work for 2 reasons.

the first is that the voltage goes down as the door opens. the other thing is that the fc is a 0-5v sensor so the voltages are off.



thru some experimantation, i was able to raise the wot voltage from 8.66 to 8.88, and its fixed my high rpm fuel starvation problem, the afm spring is adjustable for tension



mike

DJ Rotor

Cool. I'd think, then, that you could make a circuit fairly easily that would be able to adapt the FC unit. Would have to invert and proportionally reduce the voltage. Would it be worth doing? I mean I know the FB AFM is horrid but how much better is the FC unit?



J

j9fd3s

well i was actually thinking about a map sensor and a safc, and just didtch the afm altogether



mike

DJ Rotor

That would be the best way to go, no doubt



J

Smog Fighter

My preference (through 15 years of tuning various fuel systems) is a

hot-wire type air flow meter. (90-up 300ZX and 89-93 5.0 Mustang come

to mind)

MAP (Manifold Absolute Pressure) sensors are a Vacuum/pressure type

sensor. they sense absolute pressure changes and the computer

interprets these changes as load variances. Not real good for

lumpy/lots-of-overlap cams.

I would think this type of system would not be too reliable in a BP,

and definately wouldn't work with a PP motor.

MAF (Mass Air Flow) sensors measure the total amount of air going into the motor. The computer then calculates the proper amount of fuel based on the incoming air.

Granted, the AFC style (spring loaded door & variable resistor) adds

a restriction in the air inlet and therefore limits the total amount of

air and fuel allowed into the motor.



Oops, long winded

Raul

j9fd3s

yeah you're bascially right, if i had a bp or something a maf would make life easy



mike

j9fd3s

so to add to that the gsl-se has a sping loaded stopper, presumeably to keep the door from slamming open, that the fc does not. its adjustable on the gsl-se, so you can bascially dial in the wot fuel, independent of the flapper spring.

i have found the sping to affect mostly the low and midrange, the stopper does wot, or woafm (4500+rpms at wot), so you can basically have everything



mike

Smog Fighter

There's nothing like NOT needing a computer to adjust the fuel rates on an

analog system.



Do you have a WOT switch like the 280ZX? also what pressure are you running

at wot? you might get a little more out of her if you get an adjustable regulator.