CV Carbs

[dcb]

Originally Posted by Coyote X

CVK40

how a cv carb works They are a pain to get performance out of but they are pretty good at mileage.

After thinking about it I think if there was a way to measure slider position that would relate really well to fuel flow for everything except wide open/idle. And for that A good guess would probably be close enough.

I don't know if it would be easier to figure out how to measure the slide position and guess, OR retrofit fuel injection

But for fun, lets consider some strategies for measuring the slide position:

1. a "fish finder" type circuit (needs single digit microsecond accuracy at these distances) above the diaphragm to measure its position.

2. a cds/light source sandwiching a window with a tapered shaded area that moves up and down with the slide.

3. a variable inductor in the diaphragm (liking this one best so far)


Any others? I suppose one could test the fuel flow rate at different slide positions on the bench and build a map from there.

[dann_04]

I think most people get a larger jet and exhaust when concerned about performance on cv carbs, don't they? I beleive most scooters use cv and they have a ton of aftermarket jetting kits and exhausts to get more air and fuel through to increase performance(but not economy of course). What kind of vehicle are we talking about here?

[dcb]

So I received a map sensor from Coyotes old metro. And was thinking about tapping into the top of the CV carb (above the slide diaphragm, assume I wont interfere with the slide movement) and am having a little bit of trouble theorizing what it will detect if anything.

I want to think that it will be proportional to the needle position, assuming a strong enough signal, because it "looks" like it should work that way. The vacuum compresses the spring. The more the vacuum the higher the needle.

I don't know if it will have enough pressure for good resolution though because it doesn't take much force to compress a cv spring and that diaphragm is pretty large.

Any predictions?

134

[RiderofBikes]

I too have CV carbs, My gas tank uses a vacuum release petcock to activate flow to carbs... There must be a vacumm outlet on at least one of your carbs in the set? Do you think it would be possible to figure out an estimated rate/flow of gas via vacuum gauge?

[JasonG]

Just a side note, CVs are from the devil.
Darn diaphrams are a pain.
Be careful not to damage one or cause an air leak with the pressure tap.
If one goes out the slide drops immediately leaning out that cly and burning a hole in the piston.

Not fun going down I95

If you can, change to the round or flat slides. (CV?)
You also can add a position indicator to them.
As they are mechanical, any slide pot would work.

Just my $0.02

/rant