Lotus Elan

Mikuni carburettors

PostPost by: Jens » Thu Feb 22, 2007 10:36 am

Just out of curiosity I am wondering if anyone here has put a bridge og Mikunis on his/her Twink. Am thinking of trying it when mine is running as it should, but am eager to know if has been tried.
I know some of the guys driving rallye O**ls are running them with lots of pleasuer. Also had the opportunity to see a test with a Pinto engine using first Webers and then Mikunis - the power output was much higer with the Mikunis because of the airflow being less disturbed than when using Webers.

I know they are made for Japanese Bikes, but hey - if it works and is easily made undone (slight purist...) - then it might be fun on track days, not to mention at the red lights.

//J - longing for his baby
"Make the suspension adjustable and they will adjust it wrong - look at what they can do to a Weber carburetor in just a few moments of stupidity with a screwdriver..." (CABC)

My one problem is that distance keeps me from my Elan. (36/5395)
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PostPost by: rgh0 » Thu Feb 22, 2007 10:53 am

Jens

The operating basis and internals are not radically different for dual side craft Mikunis, Webers or Dellortos. Any differences observed are more likely related to how well set up the carbs are for the particular engine they were mounted on rather ultimate superiority of any of the carb type.

I am sure that if Mikunis are truely superior for twinks then a lot of hard core racers over the last 40 years would have discovered that and change over.

Just reread you note and realise you may be talking about single throat slide throttle bike carb mikunis. They have the potential to be superior with similar throat sizes at wide open throttle as no internals apart from the needle however a suitable larger sidedraft carb throat can flow the same air. The challenge of this type of carb is that it hard to get good fuel / air ratios at high and low air flows ( engine load and speed) at the same throttle opening. Ok in a race engine or light bike where you have a narrow operating range but a real problem in a heavier car where rely on a broad torque band. CD style carbs ( SU or stromberg) were developed to overcome this problem with moving needle carbs in cars.

Ther is a guy in the US on the Yahoo Europa site who runs a Renault engined S1 Europa with slide throttle Mikunis in SCCA slalom racing with good results. Thats the only Lotus I know running them.

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PostPost by: Jens » Thu Feb 22, 2007 11:22 am

Thanks Rohan,

The idea was brought to me a few years ago when I wrote an article about a guy in Seden who installs the Mikunis on cars. As I recall there was also a Ch*vr*l*t C*rv*tt* with the Mikuni set up that ran in the Swedish historic racing series.
As the engine it was tested on was a Pinto - wich I assume in a way is fairly equal to the twink in terms of construction, albeit it hasn't got the dohc - I thought int might be a nice thing to try.
I guess an Elan should be suitable if it is best for a light car or a motorbike. What would be the obvios disadvantages?

//J
"Make the suspension adjustable and they will adjust it wrong - look at what they can do to a Weber carburetor in just a few moments of stupidity with a screwdriver..." (CABC)

My one problem is that distance keeps me from my Elan. (36/5395)
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PostPost by: Petter Hval » Thu Feb 22, 2007 11:46 pm

Hi Jens.
I.m about to build a new tall block T/C conversion and have
decided to go for the bike carbs. You can contact me in
Swedish on
[email protected]
Regards
Petter
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PostPost by: lotuselan2 » Fri Feb 23, 2007 12:59 am

I like the idea of Mikuni flat slides as a replacement for two Strombergs, not for Webers or Delorttos. My son raced 2-stroke GP bikes and the flat slides are the bong! Good for a road in a car? I'm not sure but worth a try. Plan on LOWER mileage.
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PostPost by: jayrz » Fri Feb 23, 2007 6:38 pm

This has been done very succesfully in the past on other cars, I think the twink is just so uncommon that it hasn't been tried.

www.PRIRACE.com make triumph stuff and their Keihin Flatslide conversion supposedly does wonderous things for a built spitfire engine. I see no reason Keihin CRs wouldn't work well on a well built twink.

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PostPost by: mac5777 » Fri Feb 23, 2007 10:11 pm

Performance Research Industries PRIRACE does and has been installing Keihin carbs in spitfires in different stages of performance with great results. I had a 1970 spitfire that I restored and was talking to him about rebuilding the engine. But found my lotus and sold the spitfire.
He lives in my old neighbor hood in Oregon. He did not think he would have any problems with a lotus twin cam, but wanted to see my engine first.
It has been a couple of years now and I have not been able to visit him yet. He says the carbs have a very fast response and once they are set, they stay tuned. He may have had a chance to install one but I don't know. I always thought about the Keihin but know of nobody that has done it. And if it was such a good system for the lotus, why hasn't anyone used it and reported the results?

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