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Jun 13, 2020 20:30:29 GMT
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there is a spi inlet for a mini that is 1 big injector, it sprays onto a heated plate, and it makes a mist of fuel/air, its like an electric carb.
There is a kit you can buy for a mini to turn your carb motor into injection with a special throttle housing, it has 2 injectors, i think they both fire at the same time, that i think is 2 small are cheaper than 1 little one maybe.
So if the two injectors pulse, how does that over come the charge robbing of the simease port problem?
I'm thinking of making an inlet out of a Su, so it looks more factory.
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Jun 13, 2020 21:59:47 GMT
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Unless the injectors are timed to fire into the inlet stroke for a specific cylinder I don't think it will stop it any more than twin carbs would.
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Jun 13, 2020 22:09:46 GMT
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with the twin carbs all the air going in is mixed with fuel, but with the injectors its pulses. So i don't get how the twin injector set up dosnt make one cylinder really weak or one really rich.
the spi i get fires its load onto the heater plate , that then atomises and gets sucked in.
thats the bit i cant work out
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beejay
Part of things
Posts: 207
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Jun 13, 2020 22:56:10 GMT
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The MPI minis had an injector on each inlet port, I converted my old mini using an MPi manifold and a megasquirt to drive it all. Its a few years since I had the car so can't remember all the details. This site is one I remember that explains the issue and is how I set the injection timing up originally. I later added a cam sensor which I think meant I could time the injector to fire once through the the intake events of both cylinders on each siamese port, so you don't have fuel sat on the back of a closed valve. Adjusting the injection timing balanced the mixture between the inside and outside cylinders. I had a lambda sensor in the central exhaust port and one for the two outer cylinders to check the mixture on the inner and outer cylinders separately. On my car each injector was controlled and timed individually, I guess that would be the same of the kit you mentions (was it Specialist Components who did it? Been a while since I've looked into the Mini scene!) The turbo minis forum is a good source of info on injecting Minis
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Jun 13, 2020 23:02:00 GMT
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it was specialist components stuff, i could not remember the name of it.
You must have used the ms2 with simease code? I'm looking at using speeduino seafox , that wont do that code.
So if i am to go injection, i need the spi inlet then?
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beejay
Part of things
Posts: 207
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Jun 14, 2020 21:54:27 GMT
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I used a MS3. I thought it had the Siamese code but at the time (this is about 3 years ago) it hadn't been written into the MS3 code. I didn't need the siamese code to get it working. I can't remember what the siamese code adds, but assume it would have been easier to set things up using it.
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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simease ports and injectionslater
@slater
Club Retro Rides Member 78
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Jun 15, 2020 20:23:48 GMT
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The short answer is it doesnt. Like you say it's basically an electic carb. It is basically the same concept as spi. It only uses two injectors as you cant get enough fuel out of one. Each injector sees all of the cylinders so it doesnt matter when you fire them in relation to the cam.
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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simease ports and injectionPhil H
@philhoward
Club Retro Rides Member 133
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Jun 15, 2020 21:17:04 GMT
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I thought the A series MPi system was a bit “funky” - Rover managed to patent it anyway.
It does have “two shoots” per port, then switches over to the other port so you’re firing basically into the opening valve.
It needs some seriously timely control over the injectors as they need to be severely oversized (compared to normal port injection); this makes sense when you see the timing diagram. Each injector can’t ever have more than 50% duty but has twice the fuel to flow so you end up with 2 400cc/min injectors or something of that ilk?
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Last Edit: Jun 15, 2020 21:18:46 GMT by Phil H
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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simease ports and injectionslater
@slater
Club Retro Rides Member 78
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Jun 16, 2020 13:17:56 GMT
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Yeh pretty much. The injectors need to deliver the fuel while the valve is open so you need big injectors but not so big you cant control the fuel precisely at idle.
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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simease ports and injectionPhil H
@philhoward
Club Retro Rides Member 133
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Jun 16, 2020 13:55:11 GMT
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It's not the open time that's the issue - it's the fuel that passes during the opening and closing phases you have fun with as it's a fixed amount even if it's only "fully" open for 1 microsecond - or worse case doesn't actually get fully open before you need to close it again...
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Jun 16, 2020 19:29:48 GMT
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right thanks for the information, ive just bought a spi inlet, and will be buying arduino seafox very shortly too!
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