More generic EFI talk

The MH44 EFI runs real good, needs some cold weather tuning.

I would not leave the O2 sensor on once tuning was done, pops the cost up about $400.

I would like to make something that bolts on where the Zenith was, tired of all the harnesses and mounting, it is just to much work to mount all that. I really liked the picture that was posted of the integral unit.

I would make the throttle bore bigger, and make a reducer that slides in to size it according to the engine, no sense having huge throttle plate on small engine. An original throttle plate would then be used so it matches the reducer bore.

I do think it is better to mount the fuel injector upwards in the manifold, this reduces the problem with cold manifolds and icing.

I would almost be tempted to mount the fuel pump in the tank.

I used the Microsquirt ECM, but I think I can do the required functionality with an Arduino, at 1/10 the cost. The tuner studio program I use has a build for the Arduino, so user interface would be the same.

My goal would be cut the cost from $1200 to $500 and include spark control.

I am in will buy the first unit..Just let me know where to send the funds..

Boy, I could sure use a 5 axis mill for this.

You are the man on this project. Good work. Ron MN

Would it be possible to use an OE carb, but remove the venturi, bore up through the bottom of the bowl, point the injector up at the bottom of the throttle plate?

I think the injector needs to be outside the throttle plate, at least that's the way the old throttle body systems were, I assume for atomization and distribution.

I would think the stock carb would have a large enough bore for a small, governed engine, especially with the venturi removed. Keeping the original carb would also keep the governor original, the air filter original, some original look.

Just thinking out loud here, you've already been there...

Boy, I could sure use a 5 axis mill for this.

Click to expand...

Maybe not. I'm going to start cutting this on my 3 axis CNC tomorrow. Two CNC ops and one manual mill op.



You can cut some pretty complex parts with just 3 axis.

..... Keeping the original carb would also keep the governor original, the air filter original, some original look.

Click to expand...

If I was thinking about a project like this, I'd incorporate the governor in the ECM. Stepper motor driven throttle plate is just an expansion on how idle speed is controlled on EFI automobiles.

Why is the O2 sensor so expensive? Seems to me that there are plenty of them in the $50 to $75 range available. Or is it the wiring and programming that pushes up the price tag? While an oxygen sensor would be a helpful thing to have for diagnostic purposes, it would hardly be necessary for the engine to run.

What you propose should be possible and cheap if mass marketed. I recall Hot Rod or Car Craft testing a bolt on kit for a Camaro that replaced the carb. Probably late 70's or early 80's. Like the later GM TBI systems it was probably more of an electronic carburator than a port injection system but it was a bolt in replacement for the stock rochester carb and produced power and fuel economy improvements.

The low cost O2 sensors are "narrow band" type. Great for the ECM to tweak the fuel trims while driving,but tough to use for working out the fuel maps while setting up a system.

To set up a system, you need a "wide band" sensor. The one I have for my toy car was about $450.

Since tractors are usually used in one small geographic area, it's relatively easy to get a base map that will work well without an O2 sensor. This would be considered an "open loop" control.

For cars and trucks, it helps a lot to have the O2 sensor data feeding the ECM to help with fueling need changes. Imagine driving from a low elevation to a mountain pass. Input from the O2 sensor in conjunction with a barometric pressure sensor lets the ECM stay closer to an ideal fuel/air ratio. The O2 sensor makes the control system a "closed loop" system.

Interesting project. What do you think the potential market demand could be? EFI retrofit kits for older cars and pickups never really took off in any volume. Even at a low price of $500 I can't imagine very many pre-1960 tractors being converted to EFI, and US gasoline farm tractors died out by the early 1970's.

I think you are on the right track looking at 1960's gas tractor engines that are still in regular use today and were sold in higher volumes: Deere 20 series Dubuque engine tractors, IH 74 series utility tractors, IH 460 to 756 six cylinder gas tractors, Deere 4020 gas, Oliver Waukesha gas tractors 1600- 1855 maybe 77 - 880 too, Case big 400 to 830 four cylinder gas tractors, maybe Ford utility tractors and Massey-Ferguson utility tractors. The largest "gas hogs" would benefit the most. Were gas tractors popular in any foreign markets, or were they all mostly diesel long before the USA?

Swapping in a complete throttle body injection body for the carburetors could minimize modifications to the intake manifold and keep total costs down. Common diameters of existing bolt on exhaust extensions could be inexpensive mounts for O2 sensors (temporary or permanent), eliminating the need to drill and tap corroded and fragile exhaust manifolds to add a sensor. I'm not sure I would rely on many 50 year old tractor distributors to still be within factory specifications. Would you rebuild them, replace them or switch to coil bank computer controlled ignition? Could popular (inexpensive) GM HEI and Chrysler electronic ignition distributors be re-curved and used on tractors to keep costs down.

Follow up to the post above about complex parts on the 3 axis CNC.



This is a grab handle that bolts to the top of the vee-drive in a fast (120+mph) boat.