I have some spares I can sell you. I'll send pics.
Mikunis are mounted on X-flow
- Thread starter MustangSix
- Start date
i have a question about the pic that panic posted. if you used this setup with carbs would you be able to use a blow (push) through turbo setup on it or would there be an unsafe level of "boost" to use or would it be better to use a pull-through. it seems like a push through on multi carbs with the intake box would be much easier to us.
thanks
dan
thanks
dan
A
Anonymous
Guest
Hi, Podboy;
The only 'fly in the ointment' with blowthrough on these CV type carbs is the loss of the venturi vacuum that lifts the piston. The pistons will always stay down when blown thru.
The only 'fly in the ointment' with blowthrough on these CV type carbs is the loss of the venturi vacuum that lifts the piston. The pistons will always stay down when blown thru.
A
Anonymous
Guest
If Jack's car had of existed around the time he was born, it would have WON the Indy 500!
They weren't slow back then either!
John
They weren't slow back then either!
John
A
Anonymous
Guest
podboy;
Yes, but bike carbs with butterflies are usually vacuum piston type.
What you'd want would be classified "slide type" carbs. These have either a flat slide or round cylinder that is pulled open by either a cable or a crank that's mounted to the side of the carb. They're far more widely available than the piston type, less fussy about dirt and intake runner lengths, and are easier to tune.
I've had some experience doing blow-thru with these: mostly what happens is the venturi becomes less efficient (like most blow-thru situations), so the jetting has to be set far richer than you might expect to get the 14.7:1 ratio into the cylinders. These types pull the fuel up thru an 'emulsifier tube' after it gets metered by the main jet, then the correct amount of mixture slips thru the opening between the top of this 'emulsifier tube' and the tapered needle that is mounted in the slide. As the slide gets pulled up further, the thinner portion of the needle engages the tube, so more fuel can flow IF the venturi action has enough vacuum to pull the fuel up. The boost pressure must never exceed the vacuum capability or the fuel will not flow.
When you blow thru these carbs, add fuel pump pressure to them. Normal gravity feed for these is about 1.5 PSI, but at 6PSI turbo boost, you need (6PSI+1.5PSI)=7.5PSI to keep the bowls full of fuel. It can be tricky, because the fuel pressure has to 'follow' the boost pressure - you end up with some tricky adjustment gadgets by the time it all works.
I think pull-thru would be easier: the blowered SuperHawk 305cc used a Harley Linkert carb (44mm dia.) with drilled-out jets (.110" hole!) and a pull-thru Rootes charger from a 1300cc Volkswagon. That was a fun bike!
Yes, but bike carbs with butterflies are usually vacuum piston type.
What you'd want would be classified "slide type" carbs. These have either a flat slide or round cylinder that is pulled open by either a cable or a crank that's mounted to the side of the carb. They're far more widely available than the piston type, less fussy about dirt and intake runner lengths, and are easier to tune.
I've had some experience doing blow-thru with these: mostly what happens is the venturi becomes less efficient (like most blow-thru situations), so the jetting has to be set far richer than you might expect to get the 14.7:1 ratio into the cylinders. These types pull the fuel up thru an 'emulsifier tube' after it gets metered by the main jet, then the correct amount of mixture slips thru the opening between the top of this 'emulsifier tube' and the tapered needle that is mounted in the slide. As the slide gets pulled up further, the thinner portion of the needle engages the tube, so more fuel can flow IF the venturi action has enough vacuum to pull the fuel up. The boost pressure must never exceed the vacuum capability or the fuel will not flow.
When you blow thru these carbs, add fuel pump pressure to them. Normal gravity feed for these is about 1.5 PSI, but at 6PSI turbo boost, you need (6PSI+1.5PSI)=7.5PSI to keep the bowls full of fuel. It can be tricky, because the fuel pressure has to 'follow' the boost pressure - you end up with some tricky adjustment gadgets by the time it all works.
I think pull-thru would be easier: the blowered SuperHawk 305cc used a Harley Linkert carb (44mm dia.) with drilled-out jets (.110" hole!) and a pull-thru Rootes charger from a 1300cc Volkswagon. That was a fun bike!
Mark,
thanks for the info, i guess this will give me some things to think about until i get my head here. the idea of a pull through is new to me since i have never messed around with em much, but i think i mentioned before that the carb and turbo set ups are new to me as well. good thing i am getting my everyday driver back so i can really mess around and try this stuff out.
also how would you set up a multi carb intake with a pull thru charger, seems like a pain in the ass.
dan
thanks for the info, i guess this will give me some things to think about until i get my head here. the idea of a pull through is new to me since i have never messed around with em much, but i think i mentioned before that the carb and turbo set ups are new to me as well. good thing i am getting my everyday driver back so i can really mess around and try this stuff out.
also how would you set up a multi carb intake with a pull thru charger, seems like a pain in the ass.
dan
A
Anonymous
Guest
"the venturi becomes less efficient (like most blow-thru situations), so the jetting has to be set far richer than you might expect"
True, the venturi can only respond to changes in velocity, not density. It can't count the molecules coming past and add more fuel, so you have to compensate manually. I'm not really happy with the fuel curve produced by referencing fuel pressure to boost pressure. You still need it to keep the fuel supply positive (i.e., at least the same number above atmo as the boost), but as a metering device it doesn't "track" what the motor actually needs very well.
Vizard has a nice explanation in the Mini book on how B-L did this on the Metro with a simple ring added to the air horn.
True, the venturi can only respond to changes in velocity, not density. It can't count the molecules coming past and add more fuel, so you have to compensate manually. I'm not really happy with the fuel curve produced by referencing fuel pressure to boost pressure. You still need it to keep the fuel supply positive (i.e., at least the same number above atmo as the boost), but as a metering device it doesn't "track" what the motor actually needs very well.
Vizard has a nice explanation in the Mini book on how B-L did this on the Metro with a simple ring added to the air horn.
A
Anonymous
Guest
sure does look great jack, im wondering if you could use like a 3 2barrel air cleaner setup i wish i could get that on my american 250 sure looks greatSimilar threads
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