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I would expect twice more fuel and air. Why is that bad?
But... it is Not twice as much air... even with completely Independent runners [which is what I had]
Remember each cylinder draws what it requires independently, thru a Common Manifold... ie, as an example, if yer running an ""E", each head/jug, sees an "E"..
stands to reason that two "E"'s will be required if you adopt independent runners and true dual Carbs...
Originally Posted by 0maha
Over carbing a motor makes it sluggish. The motor can only flow so much air. As long as you've got enough carb to supply each (approx) 13 units of air with a unit of fuel, you've got enough carb.
Two carbs on a Common plenum/manifold, yes... or simply too large for a good "signal" ...also a yes... as we saw zero gain with a Bored "D" from a bored "G"..
yet the few Manners required of a Dragbike disappeared.. making it a High RPM Only, proposition...and since that engine only required the air provided by the "G", it did Not go Faster... simply lost the ability to recover from any little Riding error [and I was certainly able to produce Errors]
Screams 90s excess bling and 'all about the looks' to me. As if gas isn't expensive enough. They were around $900 new.
The two carbs feed the plenum, a box, and then the cylinders suck it in from there. Strikes me under power it'd be sucking unevenly from the closer, straighter path carb and not so much from the longer, having to take a turn back on itself, second carb. How would you jet and adjust for that? How would the collision of gases affect the flow?
If it's look, they'd have been better to make one like an old fashioned Shovelled cooling scoop.
Did anyone ever make a two carb conversion for big twins using XR style head set up? Two front heads? Again, I read of guys doing such conversions to Sportsters but coming back saying performance wasn't worth the work.
I suppose these days, with short track fuel injection and CNC heads, you could make a far more compact conversion with much straighter tracks.
Someone else did the same with two, dual 45mm Webers for a cool $3,000 plus.
^^ Gasoline Powered carbureted, Drag Bikes have long attempted to Utilize a Plenum... mostly in order to Store a Charge, and improve flow to whatever cylinder is after it... requires a much larger Plenum than normally thought...and works best with very large displacement Engines...in summary... On the Average street bike, under 120 inches...we stick to "Convention"...Ignore that man behind the Curtain!!!!!!
In Fact... lots of Injected Bigger engines are getting on just fine with a single ThrottleBody...
Did anyone ever make a two carb conversion for big twins using XR style head set up? Two front heads? Again, I read of guys doing such conversions to Sportsters but coming back saying performance wasn't worth the work.
I suppose these days, with short track fuel injection and CNC heads, you could make a far more compact conversion with much straighter tracks.
Someone else did the same with two, dual 45mm Webers for a cool $3,000 plus.
The Trock X-head was in fact two Rear Heads.. easily done on a Sporty certainly..
But, the Intake is a Nightmare [needs to be longer than you might at first imagine]...and since we had to Hand build every damn piece... it took alot of time..
Ron [Sr.] wanted to try 2 Bored CV's... we just never got around to it...and now, of course...it is too Late..
My Biggest Bitch...again, was the hand strength required to twist two conventional Carbs WFO in 1/4 of a Turn.. I was never Limber enough to get along with 1/2 Turn!!!!! Much better 1/8 turn for my lazy ***!!!!!
To answer your Question... Not at the Race track... and not that actually Worked...nor certainly worth the $$$$
And... it was Not for lack of trying.. But, I would Not tackle a big twin... mostly because of the cost of One-off Cam... that is at risk of Damage Every Pass!!!
The Sportster X-Head cams remained the Very Same!!!!! Ron was pretty Swift like that!!!!!
Last edited by Racepres; Oct 26, 2019 at 02:05 PM.
I understand that part of the idea of a scoop, and a plenum, was to build pressure so when the engine opened its throat, it had a whole lot more rammed down it than it could have drawn in itself.
But the Kuryakan's are fake scoops too. They are open at the back so any extra air coming in blow right out. Presumably they did that to get around the jetting problems of having a whole lot more pressure at 90mph WOT than 20mph WOT. So would this design build pressure? I doubt it. I would say it's just mixing chamber with gases going everywhere due to its square shape; and what happens at the crossroads where the two tracks meet?
I'm not up on injection units. Has anyone played around with direct injection systems?
I understand that part of the idea of a scoop, and a plenum, was to build pressure so when the engine opened its throat, it had a whole lot more rammed down it than it could have drawn in itself.
But the Kuryakan's are fake scoops too. They are open at the back so any extra air coming in blow right out. Presumably they did that to get around the jetting problems of having a whole lot more pressure at 90mph WOT than 20mph WOT. So would this design build pressure? I doubt it. I would say it's just mixing chamber with gases going everywhere due to its square shape; and what happens at the crossroads where the two tracks meet?
Ram air sort of works.. if not such a big scoop that it upsets the Bike ...ie Umbrella hanging off the side.. trust me you don't want a very big Funnel...BTDT
I can tell you...you feel it over 100, and can't get to 125, 130, before it really has a Detrimental effect....No Fun
Best one could do would be a Still air Box... problem is...again to be effective...it needs to be much to big to be Practical...Nope... best we ever found was the correct length intake tract, with a very well rounded [formed] bell on the Velocity stack..
Interesting side note... either our front cylinder was more efficient than the rear... or the "draft" was more beneficial than ram air...as the rear facing Carb. in the X configuration.. could handle richer jetting...ie getting more air...than the front facing [rear cylinder] Carb.
Just an Observation...
Originally Posted by Warren Peas
I'm not up on injection units. Has anyone played around with direct injection systems?
I'm seeing it at the track... Certainly Nitro Bikes... Gas is coming that direction.. more control and accuracy... sadly, Electronics as sophisticated as fuel injection is out of my realm of ability...
Last edited by Racepres; Oct 26, 2019 at 06:10 PM.
