Re: MH44 EFI

Posted by David G on September 20, 2015 at 07:43:13 from (71.217.208.243):

In Reply to: Re: MH44 EFI posted by Bill in IL on September 20, 2015 at 06:54:06:

I am using a Microsquirt controller.

I research and calculate initial settings, then adjust for best operations. I am on my third upsize of fuel injectors, trying to meet the maximum fuel demand, but still get a good idle. There are basically two ways to do fuel injection, he first is throttle body, the second is port injection. Throttle body is by far the easiest, as it is really just a more precise carburetor. You still have all the intake runner warming and fuel dropout issues that a carburetor has. The second method is port injection, where the fuel is injected as close as possible to each intake valve. This method removes all the limitations of an intake manifold, so it does allow more precise injection.

I started with throttle body, it really works very well, but I am taking the challenge of moving to port injection, really just for the challenge.

Now for some talk on port injection. The best operation has all the fuel delivered at the intake valve right before it starts to open, so it can warm. You will notice that all newer inline engines have the intake manifold on one side and the exhaust on the other side. This is easy to fuel inject, because the manifold has a dedicated port for each cylinder. The older inline engines combined the exhaust and intake manifolds into one to help warm the intake passages and prevent fuel dropout. This is a PIA for injection because two cylinders share an intake runner (Siamese), and there is usually an overlap between them on the intake valve openings. My engine operates at a maximum of 1500 RPM, so that equates to 40 milliseconds (ms) per revolution, or 10ms per cylinder, even though two cylinders are not firing during that cycle. I need large enough injectors to get the fuel in, shut it off, get ready and inject the adjacent cylinder.

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