EFI and Two-Strokes

[sdelanty at sonoma.net]

Cool stuff about turboing 2-strokes deleted..

> The problem is that the exhaust port opens (is uncovered) before 
>the transfer ports open, and then closes after the transfer ports 
>close. So, any boost pressure above the naturally occurring crankcase 
>compression will only serve to shoot air-fuel straight out the exhaust 
>port, wasting fuel and losing boost pressure.
>The key to avoiding this (and this is where my memory gets hazy) is 
>to modify the porting so that the exhaust opens after the transfer.
>There had to be something else involved - otherwise you'd have a 
>cylinder full of burning gas exhausting down the transfer ports into 
>a crankcase full of air-fuel mixture - ouch.
>Maybe it was direct injection.. 

Even with direct injection You still would have exhaust gas polluting Your
fresh air charge and trying to blow Your crankshaft seals out.
Having the transfer port open before the exhaust port sounds like a bad
thing to me. Also, isn't the exhaust gas backpressure caused by the impeller
usually higher than the amount of intake boost pressure created? I don't
think a port type 2-stroke would take well to that...
 I don't think it would be possible to effectively turbo a standard port
type 2-stroke setup. GM figured it out with their 2-stroke diesels, but
that's a horse of a different color.

how do two-stroke turbo diesels work? 

This one I know some.
The only 2-stroke diesels I've seen are Detroit/GM/Grey Marine diesels, and
they are an odd item...
 The crankcase is not part of the induction system. It is a closed, oil
filled case like any normal 4-stroke.
 The intake ports are on the side of the cylinder like a normal 2-stroke.
 The exhaust uses 2 cam operated poppet valves in the head like a 4-stroke,
but both are exhaust valves, and the cam operates at *crankshaft speed*!

 The key to getting any air charge into the cylinder is that nice fat GM
blower that You will *always* find on Detroit diesels. The blower keeps that
intake port pressurized so the cylinder gets filled. These engines will not
run at all without the blower. The exhaust valve/cam keeps all the goods
from just being blown out the exhaust port like a normal 2-stroke would. The
pistons have extra rings down low on the skirt, always below the intake port
so that air doesn't pressurize the crankcase.
Fuel is injected into the head in relatively normal diesel style.

On turbocharged versions, the turbo pressurizes the inlet of the blower. (-:

I've worked on V12 detroits that have *two* 671 blowers with *two* turbos,
one feeding each blower. Awesome torque at 1800 rpm...
 Cool concept too; dual turbo, dual blower, 852CID V12 2-stroke!
I've also seen one that scattered a turbo, turbo bits went through one
blower, and parts of turbo and destroyed blower wasted a whole bank of 6
cylinders...
-VERY- expensive.  )-:

>	Good luck with it. If you can solve these problems and double a 
>two-stroke's power, you could just about go into orbit.

I always wanted to nitrous my 2-stroke Kawasaki triple...

Happy motoring,

 Steve Delanty (sdelanty at sonoma.net)

  1971 F100, FE390, T-18 4-speed shortbox.(fender mounted spare)