Dual Singles

[tat2edangel]

hey can anybody tell me a little about this dual single set up.

Pro's, Con's, what type of carbs.

I can build manifolds from carbon fiber.

[earthquake]

Those are 1 barrel Weber 34mm ICT's, a very common carb used on Volkswagen's. you can pick them up pretty cheap but they almost always need to have the throttle shafts re bushed. I have a set that I just had re bushed that are going on my 74 VW, I thought about making a set of manifolds for a Wing but it never went more then that. They also made a version that have a choke on them, they are 34mm ICH's but they are hard to find in the USA. Parts are easy to get for them from "Pierce manifolds" in Kalifornia and other places

Casey

[earthquake]

Here a picture of a Weber ICT, Its a little dirty and has a air cleaner adapter/velocity stack I made for it

Casey

[sunnbobb]

Good info!

[tat2edangel]

I was on Holly's Web site and found a calculator for measuring peak CFM. This Calculator says that 62 ci and a max rpm of 8500. Ideal street flow is 125cfm for street and 155cfm for racing. Not real sure how I measure that on these small carbs, and is that per cylinder?

I have several feet of carbon fiber/Kevlar weave and tons of epoxy and hardener so i think I'll make a manifold and a little front fender.

[gregforesi]

62cu-in in a 4 stroke burns 31 cu-in/rev.
31 cu-in/rev = .018 cu-ft/rev
.018 cu-ft/rev*8500 rev/min = 153 cu-ft/minute
That is for the whole engine. Divide that by the number of throats to get the flow/throat. The dual single-throat setup being considered needs to flow about 75 cfm per throat.
Flow at idle (1000 rpm) is about 9cfm through each throat. Getting the venturi to provide fuel into the air stream within the throat at those low flow volumes is the key to having a setup that will idle nice and provide good power at redline.
Going with a slightly smaller flow (125 in your Holley example) means a smaller throat diameter and that means better low-end torque. The trade-off is that there is some restriction at redline and that will effect horsepower up there.

That is one of the things that Honda did (cam profiles were the other) to change the power band when they decided to start to move the GoldWing from a pavement wrinkler to a touring platform (78-79 carbs have smaller throats than 75-77 carbs).

[earthquake]

Dual 1 barrels on a VW usually run a cross over tube to help balance out the intake pluses so they will idle better, they also have a tendency to only idle on 1 cylinder a side but catch up quickly when revved. In the video of that bike it seems to idle pretty good so maybe this is only on VW's, There several dual 1 barrels that are run on VW's that should work on GW's
Dellorto FRD 34mm, Kadron 40mm [same as Solex 40mm], EMPI EPC 34mm [which is a copy of the Weber ICT but the quality is not to good] one nice thing about Kadrons is they have a replaceable venturi so you can adjust them for smaller motors, you might have to have them made for for a Wing though because they were made for motors in the 1600-1900cc range but they dont cost much.

Casey

[gregforesi]

Looking at the photo:
It appears that besides coming up to a single plenum at the carb, the manifold kicks out away from the bike a bit. If you go straight up from the intake ports it's hard to get a filter on the top. That is one of the issues with Randakk's manifolds (you have to modify either the shelter covers or the aircleaner housings).
The plug wires are changed to straight ones because there is no longer sufficient clearance to pass between the intake runners. With the dual 40IDF's there is barely enough room.

BTW mine idles fine and runs excellent.