Custom electronic fuel injection and ignition

[dlbass93]

Since my truck has a waterproof distributor that works fine but is hard to find parts for, and I like to make things more challenging than they should be, I've been working up a plan to first convert my Patrol to EFI and then to electronic ignition. I figured I would share my work here so you can either tell me how to make it better, or maybe to talk me into keeping it stock. It is mostly a learning exercise...

The plan currently makes use of the following parts to get EFI going:
Microsquirt ECU (documentation).
Two 42 lb/hr compact fuel injectors for a GM 8.1L
GM throttle position sensor
GM manifold air pressure sensor
GM intake air temperature sensor
GM coolant temperature sensor

So far I've modelled a prototype throttle body to replace the Rochester IV carburetor. More work is needed to fit the sensors, but most of it is there.

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Once all this is done and working, the distributor can be replaced with a custom camshaft position sensor bracket and it will probably need a crankshaft position sensor on the front pulley to get timing signals to the Microsquirt to set up electronic ignition as well. I'm thinking the total cost of all this would be comparable to one of the off-the-shelf EFI kits that doesn't do anything to upgrade the ignition. So that probably means it will wind up costing three times what an off-the-shelf would be

[RiverPatrol]

Definitely interested in watching the progress on this.

[Esteban]

Congratulations!

A must follow thread!

[dlbass93]

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Made some progress on the idle control circuit, and intake air temperature bung (not pictured). This dream is getting closer to being something that might actually work.

And then someone is complaining to the county about my "junk" cars in my yard. I guess time planned for projects on my "junk" Patrol will have to wait until I build a very tall fence.

[dlbass93]

Many things got in the way of finishing the EFI project, but that provided time to have some more ideas about it. Car show season is here, so I set an unrealistic deadline to have this wrapped up by OCT 16.

This week, an all-new design was Crayola'd together, and since the first prototype did not fit, and the second prototype (was supposed to be the first functional part) did not fit, more changes will be made (or maybe a third all-new design) and printed tonight.

I decided to dump the Idle Air Control circuit. There are too many unknowns in there that I just don't want to fool with. Plus, I slapped a spare carburetor on the truck and it starts up fine without the choke plate on a carburetor, so maybe it's possible to get it to start without a computer-controlled air-leak. If not, it was a fun exercise anyway.

Since machining a fuel rail with injector bungs set opposite each other with two strange angles is just not probable with my tools and knowledge, and I can't weld aluminum, there is now an individual 'hat' for each injector that will accept a rubber hose for now.

Intake air temperature is read above the throttle plate, throttle position is tracked directly from the throttle shaft, manifold pressure (vacuum) is read from the throttle body to avoid modifications to the truck itself, and two 42lb/hr injectors will share the responsibility of delivering fuel. Hopefully this is all enough information for the ECU to get a baseline to work from. Future improvements may include sensors for airflow, coolant temperature, and exhaust lambda.

The AMP EFI Microsquirt ECU is currently being assembled in Gainesville, Georgia, and will hopefully arrive early next week.

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[faux40]

This is the EXACT project I've been wanting to do for years! I actually have the microsquirt kit sitting in my office! I like your solution for injectors. I was thinking of finding an old TBI system to hack up.

John

[Johnny Roadkill]

Can't wait to see how this pans out - an injected P motor is something I've wanted to do for a while now !

From a lot of reading and helping a mate get his Chrysler slant 6 injected with a Megasquirt system I'd suggest the coolant temp sensor will help a lot when the motor is below operating temp and the lambda sensor is a great tuning tool, but the airflow sensor may be less beneficial. For a slow-revving high-inertia motor like the P the MAP sensor should work well.

Keep us posted please...

Cheers,
D

[dlbass93]

faux40, We talked about doing something with an old GM TBI system. I liked the idea of going with something that is known to work well, and there's even a guy who modifies old slide-type carburetors for Triumph engines to use the GM injector inside each carb body. It's very slick. I decided, for no reason other than gut feeling, to go with extremely common aftermarket parts. Just in case this actually works as well as I hope, other people who want to do something similar on their trucks can use my R&D to get their own thing going without special tools. I guess we'll see

Johnny Roadkill, thanks for the notes. I'm going to go ahead and begin the search for an appropriate coolant temp sensor now, and throw the MAF idea out since that one was a whole new headache I didn't want to deal with anyway.

I took the prototype by my friend's engine machine shop for show and tell this morning, and they really liked it; so that's reassuring. We were going to make the injector "hats" from aluminum on his HAAS VF-4, but after studying the plastic ones, I think I'll first try a little finishing work inside the bores and see what happens. The parts and 3D printed in PETG plastic, which should be up to the task of not deforming in the heat and should be fuel safe. It's the same base plastic as drink bottles and fluid containers and that sort.

Thanks for the encouraging comments! Hopefully I'll be back with good news soon. The printer is whirring away on two new injector hats now, and then it will be about an overnight job for it to make the new (hopefully final) throttle body.

[dlbass93]

Progress is slow, but here are some pictures. We're gearing up to mill the throttle body and injector hats from aluminum, but I'm trying to prove the design works before wasting all that metal. You might notice some super-glued brass fittings where I broke the fragile plastic.

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The ECU finally arrived, and it is so much smaller than I was expecting. It looks like it will fit nicely inside the glove box, but behind the center panel so you won't even know it is there. That just means I have to poke yet another hole in the firewall to make the wiring look factory-ish, and I do hate poking holes in an otherwise perfect sheet of steel...

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After overthinking a dozen different setups for where to fit the new regulator, pump, and filter; I finally decided to weld some captive nut tabs on the outside of the tank carrier to attach a mounting plate. It ain't pretty, but if I wind up liking it, might get one laser cut so it won't look so redneck. This is probably not the best place, but I really didn't want to add any more stuff under the hood.

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[dlbass93]

After a little scope-creep, and some well-intentioned plans that turned out to be nightmares, the wiring is complete and validated. The combination fuse box and relay panel seemed like a grand idea, but wound up being a lot of extra work that I might should have done differently to look more in-line with the OE electrics. It's done now, though, and once the wires are tucked away and covered in loom, it should look fine. So much soldering, and then redoing it because I forgot to slide the heatshrink on first, and then redoing it because I left too much wire, and then needing to redo it again because there's still too much wire. It is that it is, at least for now.

Now I have to figure out how to direct pressurized fuel into those two injector hats. Then comes making real parts from aluminum once we know this design works.

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