Electronic Control of Mechanical Fuel Injection

Why?

What do you expect to gain?

Something unique. To boldly go... a hybrid of old and new. And eliminate all those expensive injectors and wiring.

And what wires cost more than the fuel lines and what mechanical injectors cost less than electronic ones exactly?

Not buying it I say. A proper functioning EFI control over a MFI system is going to have just as many wires, if not more, plus a lot more dedicated plumbing as well.

Not sure you are familiar with MFI and EFI. They both have fuel lines. And there are no mechanical injectors; fuel is delivered thru jets similar to carb jets. And I 'm not trying to save money, but do something that hasn't been done before.

Sounds like an overly complicated version of a homemade electronic carburetor or throttle body injection system but with more parts and less reliability.

There's probably a reason you never heard of an electronically controlled mechanical fuel injection system. No one could make one work reliably enough to ever make it to pubic knowledge.

It's been done before. There's a TBI upgrade kit for Small Block Chevy engines. A lot of the racers like it, because it's a lot more reliable than the old Quadrajet carbs. Also, the Holley 650's didn't work great in the Small Blocks - I actually liked the driveability and gas mileage of the Quadrajet over the Holley, however the Holley did make the motor sound good. I've heard that people successfully used the old Carter AFB in a Chevy Small Block. I thought the AFB was the best 4 bbl carb - I had one on my 1964 Chrysler with a 413 Wedge.

I posted the link in my other comment. Let me know if this is what you were thinking of.

I guess I'm not getting what exactly you are changing, but it does seem to be an issue of precise control and a fiddly can of worms....

http://www.roadandtrack.com/car-culture/a26665/mechanical-fuel-injection/

https://www.alkydigger.net/hilbornbarrelvalve.php

http://www.automotivetroubleshootingsecrets.com/P0232_OBD2_fault_codes_8.html

Here's a solution you may be looking for. When I was in college, the GM TBI was a desirable upgrade from the old Rochester Quadrajet carbs. I think Chevy was able to get their IROC Z's up to 245 HP back then ( the number sticks in my head). Here is a link on how to modify an old Chevy Small block to accept a GM TBI system. Note that there are a lot of sensors and wires. http://www.gearhead-efi.com/gm-ecm-pcm-conversion/tbi-efi-conversion.html

To clarify, I want to have an MFI like this:

...but with the barrel valve controlled by an EFI ECU. One thing I haven't quite figured out is how to get a MAP signal for the ECU. And what would be the best interface between the barrel valve and ECU? The guts from an electronic throttle body might do it; it's just a simple motor driven PWM by the ECU. And PWM is what an EFI ECU uses to control the injectors.

You could get a MAP reading by drilling and tapping small holes beneath the butterflies and installing fittings which are connected to a "manifold" with the sensor at the ninth port of the manifold. All of this would be done with small (-2) tubing.

I have seen electronically-controlled Hilborn systems, but they went the route of simply installing solenoid injectors beneath the butterflies.

Yes, I've thought of that, Ed. I'd like to hide anything I have to add. Maybe I could tap into the ports beneath the MFI and make such a vacuum manifold.

I've seen the EFI conversions of MFI and they are pretty messy. Kinda defeats the look.

And what I really want to try is constant-flow vs pulsed-flow. I can't think of why it wouldn't work just as well. Constant-flow is very similar to batch-fire EFI; the mixture just waits for the intake valve to open and suck it in.

And with the individual runners in the typical MFI you avoid the potential for mixture stealing. I had that problem with cylinders 5 and 7 on a SBC with an open plenum manifold and batch-fire; see pic. 5 would suck some of 7's mix. Had to fab dividers and weld them into the manifold.

"The manifold absolute pressure sensor (MAP) responds to changes in manifold pressure (vacuum). The ECM receives this information as a signal voltage that will vary from about 1-1.5 volts at idle to 4-4.5 volts at wide open throttle.

A scantool displays manifold pressure in volts. Low pressure (high vacuum) reads a low voltage while a high pressure (low vacuum) reads a high voltage.

If the MAP sensor fails the ECM will substitute a fixed MAP value and use the throttle position sensor (TPS) to control fuel delivery."

http://www.fieros.de/en/v6help/code34.html

SSC a few years back there was a guy in Cali-outwest some where that Car Craft or Hot Rod did an article on doing this type of conversion for street drivability. One of the thing that I remembered was there was a forward tank with a float that supplied fuel to the pump on the front of the motor, with an electric pump in the tank keeping the front tank full on demand as the float requested fuel. If my memory doesn't fail me he had a multi pill/jet block set with different orafice sizes. The were set for different throttle positions as to which jet was used with a return jet to rear tank so as not to over fuel. For the life of me I just can't remember how far back that was. (AND WHAT HAPPENED TO SPELL CHECK)agh!

LD, that sounds like a real kludge! Load (MAP) FI is superior to throttle position FI. But I always like to see experimentation. I think Edison said "success is 1% inspiration and 99% perspiration."

The article said it made a very drivable unit and did not require a computer to make it run. It just worked.

Your mission, should you choose to accept it, is to find that article and send it to me. Good luck, LD.

This message will self-destruct in, oh, 1 billion years.

I finally found it. It was an article from Marlin Davis in October of 2010 in Hot Rod.