"Black Sheep" 81 GS550L EFI conversion

[Rickta]

I have recently put fuel injection on a 1970's naturally aspirated Kent 1600 engine using Yamaha R6 throttle bodies, the Speeduino module that you show is used to filter/smooth out the trigger circuit, trigger circuits are used on engines to know where the engine is, you usually use a trigger wheel with either a VR sensor or Hall effect sensor to pick up the missing tooth and know where the engine is, Speeduino helps filter out a bit of the noise that can be generated in home installations. Whether you decide to trigger fuel or ignition or both you will need an ECU to control all of these functions, I used Megasquirt for my car, it is very programmable and people run them on bikes. I would say if you enjoy a project then go for it, I did it for performance with a stage 2 build on my engine with your 550 it is not going to deliver magic performance, it will give more reliable running less susceptible to degrading performance but it will cost you more than getting those carburetors serviced, if you are doing fueling then you might as well do ignition as well because you have invested in an ECU that should do both, . Google "Megasquirt" "HomeBrew" to do some more research.

[GrantMonast]

I absolutely am going to replace these tires, I checked the DOT numbers on the sidewall. The front tire was manufactured in 1980 so that’s original. The rear tire has a date code of 1994 probably replaced with factory matching Dunlop

i have the Megasquirt v2.2. It was one of theirs first iterations I’ve had it for over 5 years. It is designed to be used for fuel only installs which is all I want. I plan to use the stock VR trigger for rpm input.

Im not trying to make a performance increase just reliability in all temps. This no way practical but I have been wanting to complete this project as a test of my engineering skills. That’s what I went to school for after all.

[GrantMonast]

Here is the wiring diagram provided by diyautotune.

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[GrantMonast]

You do have coolant, and it's easily tapped into - I'm assuming the GS550 lump is the same as its larger brethern and there's an oil passage at the rear of the block, where lurks a blanking plug. I'm using that on mine for an oil temp gauge sensor.

I will have to check for that. I can either use the cylinder head temp or oil temp. That is up to me to decide which will be more appropriate.
The temp sensor is mainly used for fuel enrichment on a cold engine and leans out when it hits a predetermined temperature.

The fins on the head may heat up faster than the oil. Both will work just have to experiment and test different cutoff temps

[Grimly]

I will have to check for that. I can either use the cylinder head temp or oil temp. That is up to me to decide which will be more appropriate.
The temp sensor is mainly used for fuel enrichment on a cold engine and leans out when it hits a predetermined temperature.

The fins on the head may heat up faster than the oil. Both will work just have to experiment and test different cutoff temps

Yes, that would be the problem. I find the oil gauge moves within a couple of minutes of startup, but it takes at least ten minutes of riding before it's anywhere near the normal range of hot enough to be useful for this. Probably not what you need. Cyl head temps obviously much more immediate, but the sensors might be more vulnerable and shonky. A decent industrial or aerospace temp probe designed to last is what's needed. I've seen various ones designed to go under spark plugs or cyl head bolts and I've not been impressed, to be honest. They look shonky and I don't think they last very well.

[salty_monk]

Used these guys for megasquirt stuff in the past... It's open source but you can buy it from them ready built https://www.diyautotune.com/

[GrantMonast]

Used these guys for megasquirt stuff in the past... It's open source but you can buy it from them ready built https://www.diyautotune.com/

That’s where I got mine. I assembled it myself from a kit.
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[GrantMonast]

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

[LarsKroghStea]

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.

[Rickta]

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.

[93Bandit]

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.

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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]

[ATTACH=CONFIG]58423[/ATTACH]

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.

That in a Lotus 7 replica? I used to have a couple of those over in England...

[Rickta]

That in a Lotus 7 replica? I used to have a couple of those over in England...

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

[GrantMonast]

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

[GrantMonast]

click the picture to watch a short video showing how the TB's are mounted and twisting the throttle

Untitled by Grant Monast, on Flickr