Lotus Elan

Xeber concern

PostPost by: seniorchristo » Sun Jun 17, 2018 5:54 pm

Esprit2
I thought the main circuit started taking affect as low as 1500 RPM's. This would be at odds with your quotes below. I guess I have to read through my Weber books again. :)

"50F8 is the combined Idle Jet (50), and the Idle Air Corrector (F8). The Idle Circuit feeds the engine up to 4000 rpm, then hands off to the Main Circuit. When you get the engine running, do the following tests to evaluate the Idle jets:

Take the car for a drive on a road that has little traffic, and make a full throttle acceleration run in an intermediate gear... 2nd or 3rd (you'll rip through 1st too quickly to be helpful, and 4th will just get you a speeding ticket). If the engine stumbles approaching 4000 rpm, then the Idle Jet is too lean. Go richer until the stumble 'just' disappears, no further. If the engine doesn't stumble on the first run, then you can't be certain if the Idle Jet is correct, or too rich. So go leaner until a stumble just becomes apparent, then go back a step richer until the stumble just disappears.

The Idle Jet and Idle Air Corrector affect one another. So if you do end up having to make a change to the Idle Jet, then go back and re-check the Idle Air Corrector once again. Adjust the Idle Air Corrector for off-idle hesitation, and the Idle Jet for a full throttle stumble at around 4000 rpm."
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PostPost by: nmauduit » Mon Jun 18, 2018 8:33 am

Many aspects of Weber tuning and illustrations from the litterature can be found on the net, e.g.

http://240260280.com/Tech/Carbs/Weber/D ... uning.html

in particular the overlap of the different circuits

circuit-overlap.gif and
weber circuit overlap


as they say, actual transition zone may vary (for variation of including, but not limited to, choke size, progression holes number size and location, jets size etc)...
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PostPost by: diablo » Wed Aug 01, 2018 7:21 am

Hi you all
My car is very very difficult to start . From my previous post , I suspect the carburation ; then I remember having read that very often the carburetion trouble are ignition trouble . I went back to the ignition ; I had fitted a pertronix with a Lucas racing coil . The pertronix needs a 3 ohms coil for 4 cylinder engine ; the Lucas is 1,5 Ohm . Hourrah ! That's the problem , I ordered a pertronix 3 ohms coil and ......no improvement . The engine started OK only after I put some drops of fuel in the carbs , this made me think a fuel level problem . I had checked this many times ; 8mm float height was OK . I decided to check the level in the carb with a vernier depth gauge . Result : 35 mm ! it should be 25 .
I have change the float height to 6 mm ; fuel height in the carb is now :25/26 mm . Why ??? I read a member of the forum had the same problem . Now , the car starts first kick ; but i have still to finalyse the tuning of the Weber .
Thanks for your informations
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PostPost by: seniorchristo » Wed Aug 08, 2018 2:26 am

Dablo
I believe the 25mm is measured from top of the lower carb body where the cover attaches. Is this where you got 35mm?

Question about Weber 151's with plastic floats:
What is the measurement when checking float to cover distance? I read somewhere it should be 12mm. Is this for all Elan applications?
Thanks
Chris :)
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PostPost by: diablo » Thu Aug 09, 2018 7:44 am

Chris
Yes , I took the 25 mm height from top of the body , concerning the plastic float ( round one ) , I had put them on my original carb , from the 143 carb I bought ; set them at 8 mm and had a bad result ; that is why I put back the original brass one on the carb , with 8 mm setting and bad results again before I went to the 6 mm setting . Perhaps with a 6 mm setting , the plastic float should be OK .
I have no experience of the 151 carbs .
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PostPost by: prezoom » Thu Aug 09, 2018 6:43 pm

I have 152G's on my Zetec Plus2. Plastic floats and set at the recommended 25mm per Keith. The difference between them and the standard 40mm Webers on my Elan S2 is amazing. No hesitation/flat spots from Idle up. While originally told that the five progression holes were no good, on at least the Zetec, they are perfect.
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