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| | |-+ Speed density processor in a mass air car
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Author Topic: Speed density processor in a mass air car  (Read 6623 times)
David Claflin
Big Block
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Posts: 7827

Location: Redneck Riviera (Ft Walton Beach Florida)

« Reply #15 on: March 17, 2017, 07:12:05 pm »

Just to throw some follow up on this, after a loooong time. Ive been fiddling with this off and on, mostly off trying to get it to run better using the speed density processor I have. It's a DB1, that "looks" good on the circuit boards, but theres obviously no way to test it.
I tried running a mass air BAP sensor and while it would run, it idled high, and had other issues. I swapped in a MAP sensor from a speed density car, and that let it idle at normal RPM, but still was not quite right.
I noticed that at idle, cruise and WOT the trace on the volumetric efficiency table stayed right at 100%, which means it thought it was at WOT all the time, so no matter what I did with the rest of the table it always stayed maxed out. Mind you this is on a mild 306, that idles at 15-16" of vacuum.  I don't know yet, if there's something I did wrong, or need to change in the tune, or if there's something up with the processor.
I bought a 4 hole throttle body and modified a vic jr to run edelbrock fuel rails, so may mess with it more if I stumble across a known good DA1 or DB1 processor. I've got a JV1 processor that is from a 1986 AOD car, but I don't want to take a chance burning anything up on it. I've also got a complete car and EFI harness from a 1986GT, and a buddy has a stripped 1985 coupe, so they might all get thrown together on it to run a complete factory speed density EFI system and a 4 hole throttle body sometime in the future. If all else fails the Mega-Squirt systems seem to be pretty decent, may try one of those.

1990 Red LX, 306, 75MM, ported gt40's, Holley SMII, accufab longtubes, 3" exhaust, 4.10's, 318RWHP/316RWTQ
1985 LTD LX 302, ported TW's, XE-264 cam, ported Holley SMII, 75MM-R TB, MAC 1 3/4" longtubes, 4R70W, mach 1 brakes
1988 GT long term project
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