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"Black Sheep" 81 GS550L EFI conversion

  • Thread starter Thread starter GrantMonast
  • Start date Start date
75232AB7-2E87-4B6D-AD5D-A935BE292D1E.jpg
Old carbs compared to the new throttle bodies.
Carb outlets are 32mm and the new TBs are 38 mm
 
Cool project! Megasquirt is used a lot on VW bug projects, most often in tandem with a turbo. Without turbo, it's more of a "because you can" project. Why not go all the way and fit a turbo too. It's a safer route to extra horsepower with a turbo since the extra hp comes from torque instead of extra rpms.
 
efi.jpg

If you've used Megasquirt before then you should be OK, I found the split throttle bodies easier to space than the ones that you have which separate into two banks of two.
 
Steve said:
Sure, carbs can be cleaned, fixed, etc., but EFI sounds more interesting. I think more people would find it to be more practical on a larger bike, but once you blaze the trail, it might not take as much experimentation to find a larger system that will work.

As Nessism said, several have tried, but we haven't heard of any that actually succeeded, so please let us know. Also, don't be afraid to post some of the stuff that you have tried and found it doesn't work. Someone might be following along and would be happy to avoid that mistake.

I have heard that in 'normal' engines (not Ferrari, Lotus, etc.), fuel timing is not all that critical. There is so little time in between intake strokes, you could almost spray constantly. At 4000 RPM, there are 2000 intake events per cylinder per minute. that is 33 per second, or 30 milliseconds apart. I don't know how long the injectors actually squirt for each event, but it probably won't make much difference where they fire in the crank rotation. You could probably fire them all at the same time and get away with it.

.
Click to expand...

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.
 
salty_monk said:
That in a Lotus 7 replica? I used to have a couple of those over in England...
Click to expand...

I would love a Lotus 7, the old girl probably performs a little bit like a Lotus 7,It's an old Mk3 Austin Healey Sprite made a little more honest with a 5 speed, a stage 2 rebuild on the Kent 1600 crossflow prior to fitting EFI, the modern online world is a bit of a trap,
you pull your old Sports car engine out for a leaking rear main seal causing the clutch to slip, then you realise that it should have a Stage 2 rebuild, then you realise that the 45mm weber won't suffice and you need twin 45's,
then you google some more because you don't have enough vacuum to run the dizzy with the lack of vacuum then you end up with fuel injection, I never would have contemplated such a project 20 years ago but the online
world helps a fair bit, Sorry for HiJacking your thread Grant. Cheers Rick
 
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i have the throttle bodies mounted to the engine. i ditched the old rubber boots long ago, they were dried an cracked. i had these aluminum flanges custom machined by my dad who is a machinist and joined the throttle bodies with a short length of rubber hose

Untitled by Grant Monast, on Flickr

As some of you have mentioned batch fire fuel will hopefully be adequate for the application as the megasquirt ECU only has 2 banks of injector drivers when i have 4 injectors. they will be set up similar to the ignition coils, i believe they operate in a wasted spark timing. so i may have 2 injector pulses per combustion cycle. not 100% sure until i get more of the wiring and setup done and do some testing
 
That looks neat Grant, it all fitted together really well.

It should turn out nicely.

Cheers,
Rick
 
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
 
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
 
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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

salty_monk said:
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...

View attachment 58566
Click to expand...
 
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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. :confused:
 
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.
 
I think you’ll need an accumulator unless you never run your tank less than half full... maybe even then.
 
93Bandit said:
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.
Click to expand...

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.
 
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