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This is the background...
Rivera DUAL runner with dual 42mm Mik's
or anyone having luck with the older siamesed style manifold (2 into 1)
Anyone run these? What size engine and what did you think of them? Help or hurt drivability, response, hp/torque? Did you have trouble setting it up/ idling?
I am going to possibly try the dual 42mm on the new Rivera dual runner manifold. Price? OUCH. Anyone know of any good deals out there?
One other guy, a dealer, in the area said he was told to run dual 45mm's on his 113" set-up. He was told he needs these on a 113". I think this is going to kill his throttle response, signal to the carbs at idle due to drop in port velocity, and pool the fuel in the manifold...I don't even think top end hp will be higher for 45mm over 42mm because 42 should flow more than enough all the way past 6500 rpm. I am NOT revving mine past that... any insight here?
I have a 113" I just put a new cam, port/polished heads, cleaned-up. I think 42's would more than support this based on there published airflow numbers...opinions?
Thanks
Zack
HammerDown:
I use the real deal...Dellorto DHLA 40 Work great for me.
Puzzled uses twin Mikuni's with a plenum manifold...he seems to like them.
But I would think twin 45's are a bit much for almost any V-Twin.
I thought the same, talked yesterday with the guy taht designed the mikuni carb and the whole dual set-up.
He said the 42's run super rich. Reason why, the port velocity is incredibly high, therefore it's really hard to get them leaned out enough = engine always runs rich. The 45's a a better csrb overall and they slow down the velocity somewhat. This makes adjustment / fine tuning/ signal to meter fuel A LOT better. He said they have proved it on several bikes and the single cylinder engine they used to develop the system. He said and I questioned this, on same engine on dyno same day just a swap of dual 42's to 45's made 25 more hp. That seems ASTRONOMICAL. Would like to see a dyno print out and some air flow numbers....
Oh, by the way, he also told me they quit making the 42mm Mik. I understand for duals, but what about the guyd runnin' singles. He said the characteristics of the 45 are just that much better
Also called Rivera tech desk, don't even bother. Response I got was 45 is a better carb. I said how? Reply, it's a better carb. But WHY? Because it's better...
Geesh
Zack
HammerDown
"velocity is incredibly high, therefore it's really hard to get them leaned out enough "
Hmmm so the larger 45's slow down the port velocity, OK but that intake track really builds torque/power like a tunnel ran on a V8...slow down the intake speed> would that then make the fuel want to drop,puddle or not have enough vacume signal to properly atomize the fuel at lower RPM???
This is why I kinda like the Dellorto DHLA...you can tune that carb to work great on a toaster...almost a infinite amount of tuning capabilities.
I agree about Rivera...their CS isn't what it was 10 years ago.
Bottom line...the Mikuni/Edelbrock Twins are popular...they came about because everyone at one time wanted the Dellorto/Weber look hanging off their Engine...but were hard to find. This is also why "ForceWinder" came about. I'm sure they work or Mikuini wouldn't develope it...or would they do it to cash in on the original (dellorto/webber) side draft demand?
Sometimes it's all about the look...and the Manufactures and Marketing know it.
I also asked about puddling in the manifold/ falling out of atomization. He said NO WAY - very definitive. I also asked about carb signal, low RPM throttle response being sluggish and he replied it will be A LOT better everywhere...
I do like the duals, gotta say they look great, but I'm not one to spend a ton on looks without gettin' some performance. I have been told some guys have bought a "cheap" dual set-up only to put a block-off plate behind one carb. Dual look with out any hassle or change in performance. 1. I don't have that money and am an engineer so it needs to be used 2. If it's not too harsh to say, I'm not that vain...
I'm still trying to figure out the velocity thing... The engine will only pull as much air as it can physically pump. The high velocity part I believe because it's acting like a tunnel ram. But does the carb flow more fuel at a higher velocity even though the mass of the air passing through the carb is the same. ie, if it were a larger carb, the velocity would drop, but would the fuel? If the carb is large enough that it is not a restriction, then the engine would still pull the same air mass on every rotation just at a lower velocity. So does velocity help meter the fuel or does it act like a SUPER strong carb signal and cause a rich condition?
Zack
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I'ed shit can that crap and put a Hilborn injector on it myself. :)
What's the point of this post anyway? I don't get it to tell the truth.
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Just putting up the background info first so when everyone asks, what about this/that, it's already there... the last paragraph is why I posted... velocity meters the fuel more tahn mass air flow?
Zack
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ah, ok
So that was like the superbowl's pre game show.
Not quite like Janet's boob but I get the idea.
I will put some pop corn on and sit back and watch then.
Carry on :cool:
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and I thought boaters were the normal, laid-back, easy going people...:)
Guess your not supposed to have more than one passion...lol
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Originally posted by razor1115
and I thought boaters were the normal, laid-back, easy going people...:)
Guess your not supposed to have more than one passion...lol
Ya might want to ask over at the virtual biker site.:cool:
