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Who can rebuild carbie for blow through turbo?

Discussion in 'Modifications and Projects' started by hyper24, Feb 21, 2007.

  1. Does anyone know of a place in Melbourne that can rebuild bike carbies to take a blow through turbo.
    Im talking about sealing it all up so we dont get air/fuel coming out of places its not suppose to.

  2. I'm not even sure it can be done.

    CV carbs rely on the pressure in the carby being less then atmospheric. If you presurise the carbies, then they just wouldn't work.

    I'm not sure how it would effect the float and choke circuits either.

    I'd look at adapting a FI system first or a such though system
  3. Yeah i know, but thats apart of the modding the carbie.
    Because a suck through system is easier to setup in theory, but then you would have to find a way to mount the turbo between the carbie and the intake which in a car would be easy but on a bike much harder.
    Thats why were going to go with the blow through system.

    What people do is they put the carbie in a box and pressurize the whole box, this way when the turbo starts to boost the pressure in the carbie starts to rise but the pressure in the box also rises (has a pressure regulator) so the pressure inside the carbie will still be lower then "its" atmosphere in the box.

    But ontop of that the carbie still needs to be modified (well old ones do) so fuel doesnt come out of places its not suppose to because you are forcing air into it.

    It might be better if I could talk to some guys at a workshop who have done this kind of stuff before, anyone know of anyone?
  4. OK, that make more sense.

    So unless the is a higher differential between the outside of the carby and the inside, then I can't imagine how you would need additional sealing. So you might be right just putting them in a box.

    Which has it's merits over sucking air/fuel through an intercooler.

    What's it on?
  5. Try Gas research, i think there in Melb.
    Red Cliff dyno (Qld thoigh) do after market blow through carbs i think, may be have a chat to them.
    F.I.S.T. Performance & Audio (also Qld) have done a blow through set up.
    CAPA performance in SA
    Or you could just have a go at it yourself i guess
  6. I Had a blow-through Turbo Mini ....

    I used a HIF-6 SU from an MG Metro Turbo - (1300cc)
    My enigne was 1000cc, and the carb was excellent !

    maybe use one of thee with a rising rate fuel pressure regulator ?

    What sort of bike ?
    What size engine ?

    drop me an email, maybe able to chat through some issues :)


    james "at" portaloz "dot" tv
  7. Its a gsxr 750 97 model. Bone stock at the moment.
    Me and a mate are going to use it as our little turbo project.

    We want to go blow through as this way we can still add in a front mount cooler and blow off valve for bigger wank factor.

    Plus it would be way to hard to add the turbo between the carbie and engine for a suck through.

    I just though if the carbie was sealed well enough, it wouldnt need to be boxed, just the fuel line would have to be above the boost pressure, so when the boost comes through the fuel still gets drawn in.

    So im back to square one, rebuilding the carbie to take boost and put in a rising rate fuel pressure regulator to keep the fuel line above boost pressure, or box the whole carbie.
    Probably easier for the earlier.
  8. A few things need mods for a blow thru carb to work. Plastic floats. Brass ones simply crush.
    A rising rate fuel pressure regulator -referenced to the boost pressure before the carby.
    To seal the throttle or butterfly shafts I have modded a Holley 600 with mechanical secondarys in the following way. Space might be a limiting factor on bike carbs though. Remove the throttle shafts. Drill & tap small holes from the external side of the carb into the throttle shaft bores. Plumb these holes back to a reference point between the carb & turbo. This simply equalises the pressure between the inside & outside of the carb. Sure a tiny bit of air will leak out but no air/fuel mixture.
    Seal up any sort of power valve or vacuum enriching device that may be in the fuel circuit. And the emulsion tubes will most probably need to have the air bleed holes enlarged. Turbo motors on carbs tend to richen up as the boost climbs (and the jetting is right at lower boost levels)
    Yamaha used this setup in their XJ650 turbo & it was way more succesful than the fuel injection that Honda tried with the CX500 at the time. (Don't know about sealing the throttle shafts) See if you can find an old microfiche or google up some info on the disinformation superhighway. It can & has been done :)
    I believe blow thru is a far better way to go than trying to keep the carbon face from seals drawing oil through your turbo. And any EFI turbo can be used.
  9. I believe you may be able to get FI from a latter model onto that bike.

    I still recon the CV carbies won't work unless you box them.

    As to the turbo fitting, either way you are going to have to make an inlet manifold. So you could junk two carbies and run suck through.
  10. As I said, Yamaha did it with 4 30mm Mikuni CV carbies at up to 14lbs boost. No box around them. Google is your friend
  11. As a Turbo yamaha owner i can vouch for there existance, and they work even when turbo is removed, ran mine for years de-turbo'd.
    This is handy if your turbo blows and you are a looonnnng way from home

    trust me

    roadside removal and crimping of oil feeds 2 hours later I was on my way
  12. Must have plumbed boost pressure to the diaphragms to do it.
  13. Yeah, ive been doing my research, and im pretty sure i know whats going on and what needs to be done.
    But it would still be great if i could talk to a workshop who has done this kind of stuff before. Gas research in melbourne dont do stuff with turbos, well thats what their website said.

    We could put the FI from a later bike, but that is just an extra cost (big one) that we can do without. It would be nice if it was injected, but then just the conversion cost and then the custom comp would put the prices through the roof. No point doing that when the carbie will be good enough.

    Ive emailed F.I.S.T, capa and redcliff dyno so we'll see what they can help with, but will be hard cuz their in all interstate.

    If anyone knows of a place in melbourne that would be great!.
  14. The best place to see is s and r pro mate. The reside in Sydney unfortunately for us poor victorians. (penrith i think)
    All ya need is a rising rate reg , a set of boost referenced carbs, Who is makin ya manifolds and piping ? I would probably consider moving to fuel injection of ya really wanna play the game. Lotsa old FI bikes out there. Think gpz 1100 had a fi model somewhere wayyy back. (mid80s) ?. I have been thru the heartache of turboin bikes. Be prepared mate. It aint all beer n giggles. Havin said that, think a joint in the states makes a full kit ?
  15. I done a blow through setup on an old toyota 18RG years ago and i put the carbs in an alloy box..it bolted together around the carbs and worked perfectly
  16. Im studying mechanical engineering at uni (automotive minor)
    So i live for this stuff, i would never buy a kit because I see the fun it making it up myself, I know it will be a headache and a million problems on the way, but thats what projects are for.

    A FI setup will be the next one, but me and my friend want to do this setup just for the sake of it. Like i said, the fun is in the work of making it, not the final product (well to us anwyays)

    We have access to a mig setup, gas and all. And a few mates who weld for a living, so were going to give it a shot ourself.

    After talking to CAPA, we are going to go with boxing the carbie and pressuring the box, this way the carbie doesnt need any special treatment like sealing shafts. Just need to design a box for the carbie to sit in.

    Not sure if the carbies are going to have to be pulled off the bike, or we can build a box around it, which would probably be the easiest.
    Then plum the box to the turbo so as the turbo starts to boost the pressure around the box will rise, so the overall pressure difference from the outside and inside of the carbie will always be zero.
    Then with a rising rate fuel reg it will keep fuel flowing aswell.

    What i am thinking of doing is, making a box that is in two pieces, left and right (yellow bit in pic) with a rubber seal all around the ends that will touch the carbie (blue bits)
    Then there will be a clamp that will pull the two sides of the box together tightly and the rubber seals will stop and pressure from escaping keeping it sealed.
    Hows that sound?

    Also since the net pressure difference will be the same (0psi) does this mean that the jets dont need to be changed?
  17. heres what you should do..... get an alloy plate of about 4mm thick and thats as high and as wide as you want the box....them trace out the manifold pattern in the centre,drill the holes and mount the plate to the head and cut out the ports (a wood router with a tracing bit works well for this....but use plenty of crc and hold it really tight!)Then simply bolt the manifold rubbers up with the plate sandwiched between them and the head ....then just but 4 side plates up and drill and tap them to tak 3mm fine screws....seal the cable up by using a teflon bush...its easy....your dodnt need capa ....ive done it and it works
  18. actually.....you wont be able to use a CV type carb eitheir.....i think the boost will blow the diaphram/slide assy shut.....
  19. OK I'll try to describe this. Instead of the box above, why not have the box finish on the outlet side of the carbies and completely contain the carbies at the front.

    That way you are pressurising the entire carby, without the need for the extra plumbing.

    You could pull the carbies off(easy job) and do the whole lot on the bench.

    What you would then have is a box with a spigot on the inlet side to plumb to and 4 spigots on the the back which slip straight on to your original boots
  20. I have been doing a bit more research and it is definitely possible to setup a CV carbie for blow through forced induction.
    I have found a few good examples on the net, and found an awesome site with loads of information about how to do this work to a CV carb.
    have a look at that site, 4th post down by gsxr1100turbo, he seems to be the pro on that site for turbo carbie advice.
    Also this forum is pretty good too lots of info aswell http://www.rrzone.com/forums//showthread.php?t=1583&page=1

    Just the float bowls need to be moddified (pressurized) so they can operate properly, remember a carb doesnt car ehow much pressure is on either side, its all about the pressure difference.
    I know its easier said then done, but its been done before and it is possible, so it will just be a matter of time and some more research before i start to get into the nitty gritty of modding my carb.