Carburetor 4-Way Crossover Equalization

[chameleon]

found this in my travels, an interesting mod some dudes have come up

Anyone done this mod??

The Carburetor 4-Way Crossover Equalization Manifold is a simple assembly of hoses, T-connectors, and hose clamps which is placed over the existing vacuum spigots between the carburetors and engine. These spigots are normally capped with rubber covers which are removed only when performing a carburetor synchronization.

Credit for introducing this idea goes to the creative Mr. Bill Jinks of the Owners Association.

Theory:

The idea is to connect the carburetor outputs/engine intakes for the purpose of:

Balancing out the vacuum impulse demands between the carburetors.
Equalizing the vacuum variances of each individual cylinder's intake strokes.
Normalizing any air flow variances between the carburetors.
Slightly increasing the amount of fuel/air charge available by providing each cylinder access to all four carburetors thereby increasing the effective size of each carb.
Another theory, from MikeGTX: As each pair of pistons (1&4 and 2&3) rise and fall together, one is on the induction stroke and the other on the firing stroke. So, one set of inlet valves only is open at a time. The mod connects two inlet stubs together, so as the induction stroke of one cylinder takes place, it is able to draw through the link pipe as well as it's own carb. My theory is that the additional flow through the vacuum stub creates a bit of swirl in the inlet air flow itself. This could help to hold larger fuel droplets in the charge, rather than them falling out onto the inlet tract throat. Tuners sometimes modify the heads to induce this kind of swirl a bit further downstream as a means of helping to fill the combustion chamber more efficiently.

I am admittedly not a carburetion theory expert so I can't attest to the validity of these ideas. Preliminary testing with clear crossover tubing did reveal the presence of raw fuel droplets forming in the hoses indicating true crossover functionality....
http://www.cartestsoftware.com/fz1/carb ... ifold.html


Update:

Bill Jinks now recommends an simpler manifold as an alternative. Use two lengths of hose to connect cylinders 1 to 4 and 2 to 3 separately. The benefits from this setup may be nearly equal to the more complex four-way manifold. It also has the benefit of eliminating all the connections made necessary by the 'T' connectors and the additional potential of air leaks.

[Felix]

I tend to think that if it was so easy and would provide some kind of benefit, then they would do it at the factory to start with...

Don't know that it can hurt, but I don't think I'd be in a rush to do it. I mean, you could always go as far as making a manifold up and sticking a single large carb on the front...that'd be good for bottom end grunt, smoothness and mileage, but I think there is probably a reason we don't do that to bikes...

[bonester]

1 and 4 are connected from the factory on a ZZR1100- the vacuum line is tee pieced to the vacuum switch on top of the valve cover. Guess you are half way there anyway. I reckon mine runs better with all four capped separately.

[chameleon]

Yes, just so! I have read from a few in the know that this idea is next to useless and I'd delete the whole thread if I had my way

[billwest]

Tried it with both the ZRX and ZZR 1200s.

ZRX - runs a little cheaper. My feeling was that one cylinder "robs" the other of vacuum, thereby inducing (sucking) less fuel into the cylinder.

ZZR - didn't like to be upset by this mod. Idle wasn't as good, acceleration seemed down. No savings.

Both have reverted to capped spiggots, except one ZRX vacuum line to the fuel tap.

Bill.