The International CBX Owners Association

I'm in conversations with fabricators about developing a 1>6 intake manifold for single carb operation. I will update as necessary if it progresses past the feasibilty stage.

Interesting idea, Bill. But why, if I may ask? Why not then taking it all the way and sticking a single cylinder motor - or a V-Twin, if a single would be too radical - into that CBX frame

I don't know, the Mt. Everest effect, I suppose. That and no more carb synching. lol

bdento59 wrote:That and no more carb synching. lol

That's for sure - Unless you find some way to make all 6 runners equal, the last time all 6 will have been in synch will be the day you took off the individual carbs.

Doubt there would be enough interest in such a thing to make the project economically feasable

Don

Now 6 Amal GP's with 3 matchbox floats sounds like a plan...

would those work on the 3/4 cyl's okay?

Actually......John Janosik has an early model with 3 Amal GPs. Yuppp...I saw it run at very high speed on a long straight on Rt150 at one of the Marlinton Nationals. There is a video of this somewhere, someplace.

It ran great, never missed a beat and sounded super

In most respects this was the most amazing thing I ever saw and thought to be impossible until then since the BSA Goldstar RR I owned years before that only had one cylinder and the one Amal GP never worked right the tens of thousands of miles I rode it nor could anyone figure out what to do to fix or tune it...........so three Amal GPs on a CBX working perfect....did not then...not still does not makes sense to me....but it happened.

[/quote] Unless you find some way to make all 6 runners equal, the last time all 6 will have been in synch will be the day you took off the individual carbs. Doubt there would be enough interest in such a thing to make the project economically feasable
Don[/quote]

Yes, I'll work on that, although there are about 30 million Chevy, Ford and Dodge V8's in the world that have been running just fine with unequal runners and insufficient plenum volume, so hopefully I can work something out. Maybe not, though, we'll see. And I'll only be needing one for myself, so economically feasible is off the table...

It will be a real challenge, Bill. As soon as you try to feed all cylinders air/fuel mix through one large chamber, the outside cylinders will have trouble breathing. Even in a supercharged motor, the single plenum is a problem. Personally, I would put up with the work on six little carbs rather than solving this issue. But if you feel you want to give it a shot, go for it!

EMS wrote:It will be a real challenge, Bill. As soon as you try to feed all cylinders air/fuel mix through one large chamber, the outside cylinders will have trouble breathing.

Yea, I here that. I'm wondering if a manifold like the attached photo might work...

http://www.supramania.com/forums/showthread.php?t=6519

bdento59 wrote:
Yea, I here that. I'm wondering if a manifold like the attached photo might work...

http://www.supramania.com/forums/showthread.php?t=6519

Hi Bill

The issue with this approach in my view is there is no room on the left of this manifold for whatever carb you are going to mount....most likely it will foul/hit/hurt the riders left knee and/or stick out too far, look odd and be vunerable in any tip over -or- all of these.

I am thinking... what you want to do is very possible, but the carb/whatever should be mounted in the middle of the manifold facing the stock air cleaner area. There is plenty of room there .....even a new air cleaner setup has a place to go.

Given this is my first and hopefully last tech advice on anything for the last 3 years.....for good reason since I am not that good at it..........you have to take this into consideration...........please

You going to the Winter Rally in Columbus........if so we could ride out together....whatever.......think on it.

Mike

bdento59, Just a tip, think round....Air travelling in square ducts remains static in the corners. This will cause "fuel puddling". Always go with round or at a pinch, oval ductwork. Air doesn't like to change direction ( it has mass,) if the setup looks smooth, it is. Good luck, don't be put off by early failures.....

Thoughts from a non-engineer:

A single carb might work fine at high flow/high rpm. But at low flow, fuel puddling will occur Especially at the extremes of the manifod. Larry said air has mass, but fuel has even more mass. The fuel will not be totally vaporized, so it will be even less likely to make it around the corners than the air. In fact, this might lead to a lean condition in the cylinders closest to the carb.

A single carb positioned far back from the motor with 6 long intake runners might get around this problem?

Perhaps a simpler solution would be 3 carbs. In fact, using 3 stock carbs for each pair of cylinders might work better than the stock set-up since the air basicly has to stop and start every other revolution. Firing order would need to be considered......

Excellent advice Rick, I tend to over simplify things....

bdento59 wrote:Yes, I'll work on that, although there are about 30 million Chevy, Ford and Dodge V8's in the world that have been running just fine with unequal runners and insufficient plenum volume, so hopefully I can work something out. Maybe not, though, we'll see. And I'll only be needing one for myself, so economically feasible is off the table...

Depends on your definition of 'running just fine' - Yes, they run fairly well and they don't burn valves . . . . guess to some that's 'just fine'

I seem to recall that the engines from the '60's which which ran best had a pair of dual throat Webbers on 4 cylinders or 4 dual throat carbs on 8. Getting a 'new' engine to run well at both low, middle and high RPN's from a single carb will be quite a challenge . . . . there isn't much you can 'tune'

With a single carb V-8, we have no idea how much power each cylinder makes, how rich or lean each cylinder is but the 'experts' over many years have massaged everything possible (except for making all the runners equal) to make it run as well as it can, given the limitations. You'll need to do the same thing - Optomize all the variables you can to make for the best running engine you can . . . . hopefully without destroying your CBX engine in the process. I really doubt it's going to turn out to be as simple as a single carb on one end of a large tube feeding all six of your cylinders though - Even an old V-8 has closer to equal length runners than that

Good luck and please post whatever you learn in the process as that will surely help the next guy who tries something similar

Don