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Old 01-31-2012, 11:09 PM   #1 (permalink)
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2 stroke low pressure fuel injected engines

Since I have several old cars, I have been reviewing some of the diy ECU options and there are a few.

One of my cars is a little 2 cycle, I have noticed that many newer boat motors advertise that they have converted their existing platforms to low pressure direct injection.

This reduces emissions and improves fuel economy by injecting gas just after the valves close, in this way no fuel exits out the exhaust pipe during the intake stroke.

I am curious if anyone has encounted a list of motors that use this technology, I know of foreign mopeds and domestic boats but that is about it.

My hope is to find an existing EFI 2 cycle motor of similar characteristics AKA 2 cylinder 360ccish that is on the used market or damaged to steal the system from.

What I have read so far is that they have converted existing platforms by simply adding the injector and the O2 sensor and support circuitry.

I would think a small tapped hole with its location carefully chosen would work for the injector without increasing the likelyhood of failure.

What makes this unique to the typical gasoline injector is that it is tuned to inject only at a specific time in the cylinders stroke while the pressure is still low.

If it would be possible to tune the injector to only fire at certain times like the spark only fires at certain times I could possibly use a standard injector from a small engine. (1L 4 banger or so I would guess)

Anyone know of anyone else who has already attempted this paticular conversion?

It interests me more than the normal EFI conversion on a 2 cycle because it removes the biggest fuel and pollution waste.

Thanx
Ryan

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Old 01-31-2012, 11:27 PM   #2 (permalink)
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snowmobiles.

there are PLENTY of 440's out there with fuel injection - Artic cat uses Suzuki technology. Skidoo uses bombardier which is also good.

A few comments. You MUST inject the oil into the crankcase to lubricate the crank and rods.

You want to inject the gas into the transfer ports, and you want to inject starting at BDC, then delay from there.
For WOT, they often run a second injector into the crankcase just to get enough fuel at WOT.

Also, the 440's I am talking about run 8500 to 9000 rpm, and make easily over 100 horsepower. for your order car, you can probably use the low RPM circuit only.
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Old 02-01-2012, 02:16 PM   #3 (permalink)
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Quote:
Originally Posted by drmiller100 View Post
snowmobiles.

there are PLENTY of 440's out there with fuel injection - Artic cat uses Suzuki technology. Skidoo uses bombardier which is also good.

A few comments. You MUST inject the oil into the crankcase to lubricate the crank and rods. .
My car injects oil already. Now are they throttle body or direct low pressure?

Ah, neither and the system might work on my 2 cylinder car.

Quote:
Originally Posted by drmiller100 View Post
You want to inject the gas into the transfer ports, and you want to inject starting at BDC, then delay from there.
For WOT, they often run a second injector into the crankcase just to get enough fuel at WOT.

Also, the 440's I am talking about run 8500 to 9000 rpm, and make easily over 100 horsepower. for your order car, you can probably use the low RPM circuit only.
My car is on the order of 35hp max and runs up to about 6500rpms, I have never gotten a true redline but would estimate bad things start happening above 8k.

So if the 440's should work fine and solve fuel delivery issues, but I would still have the issue of fuel going out the exhaust.

Now I wonder how you would tune a system like that?

Thanx
Ryan

Last edited by rmay635703; 02-01-2012 at 02:22 PM..
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Old 02-01-2012, 04:54 PM   #4 (permalink)
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Quote:
Originally Posted by drmiller100 View Post
You want to inject the gas into the transfer ports, and you want to inject starting at BDC, then delay from there.
For WOT, they often run a second injector into the crankcase just to get enough fuel at WOT.
That does not do the same thing as direct injection. You need the piston past the exhaust port before you start injection.
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Old 02-01-2012, 06:37 PM   #5 (permalink)
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Quote:
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That does not do the same thing as direct injection. You need the piston past the exhaust port before you start injection.
From what I remember the marine variations used the same block with a modification for a low pressure injector to inject directly just after the valves close, not sure if that can be replicated in a shop with a system in hand from another motor. I assume a small port drilled in from the side or even top would work.

Also of the DI 2 cycles I have not yet found one in anywhere near the size # of cylinders or horsepower rating as my motor which is an issue. 3 does not work with 2 cylinders.

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