C.V. carbs, can they be converted for boost?

As the title suggests, any ideas? has it been done?

Thanks in advance.

 

Yes, but they must be sealed properly to keep the boost inside. You will also need a fuel pump and pressure regulator to keep fuel going to the carbs when on boost.

 

Thanks for the reply. When you say 'sealed" would you elaborate, i have a fair idea, but would like to check.

Also how does the c.v. section of the carb work? wouldn't the boost push the slide closed?

Im guessing you may have the 650 turbo? how are the carbs on that set up?

Sorry for all the questions, but thanks for any help.

 

When you add boost, you're putting multiple atmospheres of pressure into the carbs. They're not designed for that, and seals blow, causing boost leak, and poor performance.

You need gaskets that are designed to seal and stay sealed under the pressure losing gaskets and hunting down boost leaks with a bottle of soapy water is miserable, so do it right before strapping the snail on.

With regards to the actual construction of the carbs, I can't be of any help.

 

The bowl vents and slider vents are all internal, and the added boost is presented to all vents and passages, so the slider still works on an internal pressure difference- - not referenced to the outside air.

It would only take a half pound of boost to shut off a gravity fed fuel supply. Just like a gas tank that doesn't vent will shut you down.

The center 2 carbs are jetted richer, so anyone wanting to use "regular" carbs should look into that.

 

Thats the answer i was looking for thanks wizard.
So basically a low pressure electric fuel pump, and routing the carb over flow pipes so they can flow back into the tank and a rejet, and sorting out any possible seal problems... and i should be good

Now to figure out how to fit the water cooling to the turbo lol.

 

The carb overflow will need to either be blocked off, or flow into the pressurized plenum just before the carbs.

You might want to PM Chacal about getting the 650 Turbo carb shaft seals put in your 900 carb, see if they fit, if they are different or needed, discuss possible jetting, always good to chat with Chacal.

 

But if the over flow was blocked wouldn't that cause an over fueling issue and leave no where for excess fuel to go?

And if they where fed into the plenum wouldn't any extra fuel just flow into the plenum and cause mixture issues?

I just figured they would need to be setup like a car carbie and flow back to the tank above the fuel level in the tank.

Just throwing out ideas.

 

There's a Turbo bike forum that would have better answers, but at 15 pounds of boost, the float bowls are pressurized, and the 4 overflow vents would be sending all that pressure and vapours to the tank.
That's a ton per square foot.

That'll ruin your paintjob :lol:

 

Ever see a GT35 with no wastegate or BOV overboost a honda engine?

Good times.

 

You cant just swap out throttle shaft seals, install a fuel pump, plumb the overflow back to the tank, and expect the setup to work. The fuel system on the 650 turbo bikes is actually pretty complex when you get down to it. The carbs are completely different and none of the special parts will swap with any other model carb. The fuel pump puts out around 60 psi which is regulated depending on boost levels. The float valve setup is different to allow for pressurized fueling. The fuel is returned to the tank from the pressure regulator not the carb vents.

There is a reason why the seca turbo was the only bike to use carbs with a turbo setup. It is much easier to have a fuel injection setup and much more reliable also. Yamaha took the cheap way out but went to great lengths modifying the carbs to allow for boost. They own the rights to the design so no aftermarket parts are available for the turbo model carbs. Yamaha quit producing replacement parts for them so you have to rely on NOS kits and such.

If you are turbocharging your bike you have three options ; fuel injection, single carb set up for pull-through, or adapt a set of 650 turbo carbs to your bike. It will be a waste of time trying to rig your carbs up for blow through. My vote is for efi, using common automotive parts and a megasquirt computer.

 

Thanks TIMEtoRIDE, i was only looking to run around 6psi, i have a very small turbo with smal A/R's so it should come on very early and not boost a great deal. but yeah i know running boost is a rather large snow ball that can grow very quickly. I turbo'd a car that was never intended to be turbo, it took two years to build

Thanks organizedinsanity, I remember reading a thread on here of a guy who fuel injected his XJ, seemed to be a pretty large head ache.
Any sugestions on a single suck through carb that would work on a bike, and could handle 900cc?
Maybe a Daihatsu charade 900cc 3cly turbo carb? I know the primaries are small though, so would not allow much flow.

 

How much HP does a Daihatsu turbo make? Right CC, but wrong HP.
A 900 makes 97 HP. With a Turbo, it's up to 140 when it's all sorted out.
You should try to find a carb from something common and reliable that makes 130 - 150 HP. You will need to jet and tune, of course.

You may want to look into a Weber that the VW guys run, as they are a racing carb, new, with ample tuning parts and jets.

You guys have dune buggies- - right ??