[Diy_efi] New project

[Dennis Noordsij]

An update for those interested in maybe installing EFI (on a boat) also,

Have the TBI unit in front of me, GM TBI, 2 injectors with the "orange/blac=
k"=20
designation, which is listed on the diy-efi/gmemc page, and flows 55 lbs/hr=
 @=20
13 psi each.  They are about 1.2 ohms impedance, which I guess means I need=
=20
to find a suitable peak and hold driver circuit.=20

Have a GM MAP sensor, +5 and GND in, variable voltage out, need to calibrat=
e=20
it or maybe find a reference on the net.

TBI unit has a TPS sensor, same deal.

TBI has an idle bypass valve which is controlled by a stepper, but PIC has=
=20
hardware PWM built-in so should be OK once I figure out the pinout :)

Will use speed-density, and perhaps switch to Alpha-N at higher RPM's IF/wh=
en=20
the MAP signal becomes less usefull.

Because of having only gear, the MAP vs RPM relationship is constant (withi=
n=20
+- 300 RPM depending on boat load), so instead of a 2 dimensional VE table=
=20
(similar to used by megasquirt) with MAP and RPM on the axes I might go for=
 a=20
set of trimmers to adjust the VE along one dimension, so you don't need a=20
laptop to tune it but just a small screwdriver :-)

Many posts I've seen in the archives, as well as the fact many cars don't u=
se=20
it, seem to indicate problems with sticking an air temperature sensor in or=
=20
near the intake manifold, giving dodgy readings influenced by air flow=20
characteristics. So air intake temp should be approximated based on engine=
=20
coolant temperature and other factor(s)?

I wonder how many times posts like this have been made over the years :-))

Cheers,
Dennis


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