Four Stroke Fuel Injection

[fairdeal]

Boscoe's post about 2-stroke waste spark didn't hold much interest for me;

I've never believed a 2-stroke engine can actually work - the very idea is implausible.


But it reminded me of another mystery,

and that is the injection timing of Yamaha 4-strokes


As described in the F150 SM:





So: fuel is injected on the compression stroke. Quite right.

but WTF?

Half of the fuel is injected on the exhaust stroke ?

Hello? "allows a simpler fuel injection control system"

No doubt it does.

But how in the world can it not - at best - literally "waste" 1/2 the fuel

and even detract from the energy produced on the power stroke
by making "more work" for the piston on the exhaust stroke?

[pstephens46]

Interesting. So I wonder where in that exhaust stroke the injector fires. Top?

[boscoe99]

It is injecting fuel into the intake manifold while the piston is on the exhaust stroke yes. But the intake valve is closed. The fuel sits around being mixed with air in the intake manifold. Then when the intake valve opens that fuel and air gets drawn into the combustion chamber. No fuel gets wasted. It is all burned.

[pstephens46]

Not a direct injection.

[fairdeal]

It is injecting fuel into the intake manifold while the piston is on the exhaust stroke yes. But the intake valve is closed. The fuel sits around being mixed with air in the intake manifold. Then when the intake valve opens that fuel and air gets drawn into the combustion chamber.

ah!
or rather - "D'oh!"
anyway, I can rest easy now....

[TownsendsFJR1300]

But how do you explain the waste spark on a diesel engine?

Or better yet, a Wankle engine? Is the CI, x's 3 for 3 chambers or just one?

[99yam40]

But how do you explain the waste spark on a diesel engine?

Or better yet, a Wankle engine? Is the CI, x's 3 for 3 chambers or just one?

OK, I have had a few already.
what is a CI

[TownsendsFJR1300]

OK, I have had a few already.
what is a CI

CI cubic inch / displacement

IE, 350 Chebby, 350 Cubic Inch displacment engine

[99yam40]

OK , CDI might have got me there but I kind of doubt it.
as we were shooting at spark I think

[TownsendsFJR1300]

A Wankle engine, (if they ever got the bugs worked out), would be a great OB engine.

Just a rotating mass, no pistons, no connecting rods, One combustion chamber(probably depending on the configuration), compact...

And for Boscoe, NO waste spark!

[pstephens46]

2 stroke or 4 stroke diesel

[99yam40]

A Wankle engine, (if they ever got the bugs worked out), would be a great OB engine.

Just a rotating mass, no pistons, no connecting rods, One combustion chamber(probably depending on the configuration), compact...

And for Boscoe, NO waste spark!

remember the AMC Pacer?
it was designed to a rotory.
they ended up with a I6.
not enough room under the hood.
back 2 cylinders were under the windshield.l
pain in the A$$ to even change valve cover gaskets

if they could have got the seals to hold up over time they would have changed things( wankel)

[pstephens46]

American Motors was a unionized POS company and their cars demonstrated it. I remember seeing cigar ashes dug out of new car paint jobs...They didn't care. Good example of why companies like Yamaha accelerated so far past them.

[TownsendsFJR1300]

I don't remember the Wankle in anything but the Mazda.

American Motors (as I re-call) seemed to be a basket full of other manufactures parts.

Never really cared for their designs...

[99yam40]

think I saw a motor cycle and Vet with Wankels in magazines(maybe prototypes)