"Black Sheep" 81 GS550L EFI conversion

[Rickta]

That looks neat Grant, it all fitted together really well.

It should turn out nicely.

Cheers,
Rick

[GrantMonast]

i re-installed the stator cover with a new coat of paint, new sockethead bolts, and a shiny new stator coil inside.

Untitled by Grant Monast, on Flickr


i also made a custom bracket to mount the fuel pump in between the frame rails just above the valve cover. it tucks up nicely and is almost invisible with the tank in place. i still need to take it back apart and paint it black.

Untitled by Grant Monast, on Flickr

[salty_monk]

How are you going to pressurise and run a return back to tank? The units I've seen in the past need some sort of small accumulator tank gravity fed from the stock and then a return line back to the main tank.

Not sure how visible it is on this KLR running an EX650 Fuel injected twin engine but it's the aluminium tank above the right footpeg.

If I remember VW's have a small accumulator built into the filter unit & I've heard of guys using one of those on car builds in the past...

KLR with EX650 engine.jpg

[GrantMonast]

I wasn’t planning on using an accumulator or “surge tank” but I will add one if it becomes necessary.

EDITED: I admit I haven’t done that much research into the fuel system until just now. After reading up I can see I’m going to need a second outlet on my fuel rail. I was going to put the regulator in the wrong place in line.
It should go

Tank——>pump——>fuel rail—->pressure regulator—->tank return

i am making a custom Petcock with a return port. Probably a brass tube inside pointing away from the intake so I don’t pickup heated fuel

How are you going to pressurise and run a return back to tank? The units I've seen in the past need some sort of small accumulator tank gravity fed from the stock and then a return line back to the main tank.

Not sure how visible it is on this KLR running an EX650 Fuel injected twin engine but it's the aluminium tank above the right footpeg.

If I remember VW's have a small accumulator built into the filter unit & I've heard of guys using one of those on car builds in the past...

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[GrantMonast]

I believe I have come up with a simple solution without modifying my fuel rail. It is not ideal setup but I think it will work fine. It is somewhat based off a returnless EFI system common on earlier cars. Except technically I will have a return.

If I install the regulator with a “tee” fitting between the pump and injector rail I can effectively regulate pressure across all 4 injectors and return the excess back to the tank. Although the fuel will have to take a less efficient path.

[Grimly]

Do you mean, take the excess fuel spill from the regulator and T that into the main fuel feed from the tank?
That would work.

[salty_monk]

I think you’ll need an accumulator unless you never run your tank less than half full... maybe even then.

[metalfab]

Fuel timing isn't as critical as ignition, like you said. What you explained is similar to what has been used in the automotive world for years; batch-fire. I know it's used in V engines for sure, and I assume it was/could have been used in inline engine applications as well. Basically in a V type engine, the pulse all injectors in the the bank at a time, alternating banks. Injector pulse duty cycles determine fuel mix ratio, not the interval between firings, if that makes sense. Batch fire isn't used in DI but it is used in "normal" port EFI.

The old Bosch mechanical CIS injection sprayed continuously. Mercedes, Audi, BMW, VW and others used it. Spraying continuously when there is air flow, and when there is no airflow equals out. Factors like heat, air movement, and the fact that the fuel is atomized as it is sprayed is what makes it work. You have heard of sequential injection, those are the electronic injection systems that are timed in pulses. Most of the non sequential electronic systems just continuously sprayed.

I would love to get an old mechanical Bosch CIS fuel injection system and install it on a GS1100E. It is totally mechanical with a fuel distributor and mechanical air flow meter determining the amount of fuel to inject. There is a control pressure regulator that varies fuel mixture with temperature, it even richens for startup like a choke. One odd quirk is if the pressure drops, the system goes rich, and if the pressure goes high it leans out. The fuel pressure acts like a spring in the air flow meter to produce this odd lean/rich conundrum. VW Rabbits used this system a lot. They are not too common nowadays, but they would a a cheap donor.