Turbo bike Carbs

[24kilo]

How's it going, I'm new to this forum but have been doing some research on setting up a turbo on bike carbs. I've worked on bike about all my adult life but have never turbo'ed one. So this is what's going on, I have a 2.2 Dodge omni that Hopped up some (15 sec 1/4 with the 2.78 gears and an auto trans) and I'm putting bike carbs on it (Cheaper that Dual webbers)CVK36's .All the mods that need to be done to make it N/A are done...But I got to Thinking It would be cool to do a blow through on it. I can get the turbo stuff easy, But don't know how to Convert the carbs over to Turbo. Is there a step by step I can get, Pics would be awsome. Any machining won't be a problem as I'm a machinist be trade. TIA

24kilo

[MagicRat]

Are you going to have 4 carbs, with each one feeding its own intake port?

Your carbs are of the constant velocity type, with vacuum diaphrams, so its probably best to use a 'blow through' set up where all the carbs are enclosed in a sealed, turbo-pressurized box. You could probably fabricate one out of sheet aluminum pretty easily.
The key here is the intake charge and the air around the carb must both be pressurized in order for the carb to function properly.

If you can, jet the carb richer than stock. It may lean out lots when boosted. Turn the wastegate down and keep the pressure low while listening for detonation. Use an octane booster with the highest pump gas you can find. Use a cold air intake and try to insulate the carb box from engine heat.
Finally, what kind of compression are you running? Are you using a 2.2 engine that originally had a turbo? I believe they were internally stronger and had a lower compression ratio than an N/A unit, so boosted cylinder pressures would be less likely to detonate.

[UncleBob]

here's a website I threw together to answer some of the basic questions about this.....it is generic, if you have any questions about it after reading it, let me know

http://www.unclebobsturbos.com/newbie.html

I would be a bit worried that 36mm CV's might be a little small for your engine, but it really depends on how the engine is set up. I'm sure it will work fine, I'm just worried the carbs will limit maximum output.

You might consider going a step over that, get some 40mm CV carbs off a ZX11. They are semi-downdraft, but that shouldn't be hard to incorp into your design, I would assume. You CAN run them side-draft though, if necessary

I got your PM btw, and I'm glad you decided to post it here....I too easily miss the PM's because I don't check this forum very often

[UncleBob]

Originally Posted by MagicRat

The key here is the intake charge and the air around the carb must both be pressurized in order for the carb to function properly.

whether it is car carbs or bike carbs, the only thing that matters if the bowl vent. Nothing else on the carb(s) externally needs to be pressurized. You will have a small leak from the throttle shafts (NA or turbo'd) but it is negligable and not worth worrying over

depending on the design, some accelerator pumps can leak under boost, but that is usually easily fixed.....but those are specific to very few carb setups, so I won't go into details about that (CVK's dont' have accelerator pumps anyway)

it used to be believed that building a box to cover the carb assemblies was the only method to make everythign work. But smart cookies have worked out the details long since. Its a waste of energy to go that route IMO

[24kilo]

Magicrat
They're one per port, I already have the the mains out to185, Slides drilled clips dropped all the way and have blended all the sharp edges new springs on the slides and floats setup.

Unclebob,
Thanks, I'll go through your website. Looks like it'll answer most of my questions if I do the turbo later. The reason I went to the 36mm (that was before the turbo idea)is the ports on the 2.2 Suck,I've ported the head but Lost some low end. From what I can get off the net is they flow 175-200cfm per, That's what I need for a little lower end. This motor is only going to spin to 6K, Again Thanks for the post

24kilo

[UncleBob]

I wouldn't worry about the peak RPM, was more worried about the CFM flow of the port vs the carb

I put a set of these same carbs on a modified 22R....it has yet to run, but will soon. But the port enterence is actually bigger than the carb ID. I think it'll work OK, but it definitely will be at least a little limited by it

[24kilo]

From the math I need a 58-60CFM per Hole.I'm running a Weber 32-36 on a modded single plane right now No low end TQ but I'm running 2.78 finals also Thos will be changed to 3.02 soon. The ports on this thing are small like 1x1.4"gives me a area of 1.4 the 36mm's are 1.766sq" If I'm correct that should flow all I need, Is this correct?

[UncleBob]

Originally Posted by 24kilo

From the math I need a 58-60CFM per Hole.I'm running a Weber 32-36 on a modded single plane right now No low end TQ but I'm running 2.78 finals also Thos will be changed to 3.02 soon. The ports on this thing are small like 1x1.4"gives me a area of 1.4 the 36mm's are 1.766sq" If I'm correct that should flow all I need, Is this correct?

that sounds very good. Definitely smaller than the 22R

[MagicRat]

Originally Posted by UncleBob

whether it is car carbs or bike carbs, the only thing that matters if the bowl vent. Nothing else on the carb(s) externally needs to be pressurized. You will have a small leak from the throttle shafts (NA or turbo'd) but it is negligable and not worth worrying over

depending on the design, some accelerator pumps can leak under boost, but that is usually easily fixed.....but those are specific to very few carb setups, so I won't go into details about that (CVK's dont' have accelerator pumps anyway)

it used to be believed that building a box to cover the carb assemblies was the only method to make everythign work. But smart cookies have worked out the details long since. Its a waste of energy to go that route IMO

IMO a box is easy to do and guarantees consistent mixture especially if the diaphram housings have a less then perfect seal.

Otherwise, you make some excellent points. I was also wondering about the 36mm carb bore being too small, but the last time I looked at 2.2 engine ports they seemed no larger than that, as far as I can remember.

[UncleBob]

Originally Posted by MagicRat

IMO a box is easy to do and guarantees consistent mixture especially if the diaphram housings have a less then perfect seal.

I've ran CVK's over 30+psi of boost. I've never had a problem (without a box over them)

But either way, a box will work, but it is far from easy with ITB's, nor is it necessary

[MagicRat]

Originally Posted by UncleBob

I've ran CVK's over 30+psi of boost.

Wow, that should move like this!

[24kilo]

Originally Posted by UncleBob

that sounds very good. Definitely smaller than the 22R

Was reading some back posts and you were looking for jetting and such for your 22R, If you got it fine if not your welcome.

Mains out to 185 or #49 drill, pilot ADJ should be 2.5-3 turns, Cut one coil off slide springs, drop the clip to the bottom, Drill the slide bleed hole on the slide to .125". That should get you in the Ball park.

Here's a link for you. They do MK's but it crosses over to the CVK's. Also look up Bogg Brothers, They do alot of the bike carbs on cars in the UK.

http://www.totalvauxhall.co.uk/resou....tech60697.pdf

[UncleBob]

Originally Posted by 24kilo

Was reading some back posts and you were looking for jetting and such for your 22R, If you got it fine if not your welcome.

Mains out to 185 or #49 drill, pilot ADJ should be 2.5-3 turns, Cut one coil off slide springs, drop the clip to the bottom, Drill the slide bleed hole on the slide to .125". That should get you in the Ball park.

Here's a link for you. They do MK's but it crosses over to the CVK's. Also look up Bogg Brothers, They do alot of the bike carbs on cars in the UK.

http://www.totalvauxhall.co.uk/resou....tech60697.pdf

wow, thats some pretty radical changes to the jetting!

I'm stubborn, I'll start off with roughly stock jetting and see where it leads me. I figured it would take some notable adjustments, but those recommendations are quite a ways out there

I got a WBO2 so I'll know pretty quickly how far I need to go. I'll post the results

BTW, assuming those numbers are what you are using for N/A engine, the only thing you will likely need to change (as I mention in the article) is the main jet, and that only depends on the pitot tube, when you go turbo. Leave everything else alone until you get it running. You might need to lean out the idle and needle a tiny bit

[24kilo]

That's fine, I just thought I'd throw it out there. I did Hours and hours of research before I went there, Locost UK forum is great, Also go to You tube and search "Bike carbs", Lots of guys on there, They'll help if you ask.


Some more links

http://www.locostbuilders.co.uk/

http://www.boggbros.co.uk/fabrication.html

http://www.youtube.com/results?searc...rch_type=&aq=f