Lotus Elan

erratic slow running

PostPost by: ericbushby » Tue Nov 01, 2011 10:03 pm

Well here goes. You may not like this.
My Elan runs rough when cold, but improves a lot once warmed up. If I bring it out of the garage it will stall before I have shut the door. If I increase the slow running speed, then when warm it will tick over at 1800 RPM. As yet even with experienced help I cannot improve this.
It runs and drives well once up to normal temperature.
So- I have fitted a servo motor to adjust the slow running speed!

It consists of a chinese geared motor from ebay operating on the unused slow running hole on the other carburettor and a double pole change over switch on the steering column fixing screw.
lotus elan mod 003.jpg and

The motor shaft has been extended with an M5 thread to suit the Type 151 Weber carburettor.
The motor stands on this thread and is flexibly fixed to the carb cover screw allowing it to rise and fall and not rotate
Nothing on the car has been altered and the system can be removed in 5 minutes.
lotus elan mod 005.jpg and

It works like a dream and I can now adjust the tick over from the drivers seat.

The motor is 7 RPM and in case you are worrying, due to the spring return centre off position on
the switch there is no 12volt supply to the motor except for the few seconds it is running
I,m now going to hide behind the settee and see if the computer sets on fire
Eric in Burnley
S3 SE Type 45
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PostPost by: gjz30075 » Tue Nov 01, 2011 11:33 pm

Hmmm, don't know what to say here :? other than, have you tried adjusting the air 'correction' screws that are under the white caps? I found my 151s were far from 'bolt on and run' condition.

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PostPost by: types26/36 » Wed Nov 02, 2011 6:28 am

I'm also not sure of the point of the post....are you advocating people should consider using this mod rather than looking for the root cause of the problem or are you asking for advice on how to cure what appears to be a carb fault?
I tend to agree with Greg that a starting point would be to adjust the idle air bi-pass screws but at the moment you are just adding equipment that should not be necessary in order to mask a fault.....not a great idea IMHO.
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PostPost by: robertverhey » Wed Nov 02, 2011 7:00 am

Aaaah the naysayers! Nice easy mod, does the job, good on you. I'd have probably gone for an idle " step up" solenoid connected via a thermoswitch, 'cause I like things that adjust themselves automatically.

Personally I've always found webers more than willing from cold, but it's warmer here in oz. But maybe you could have got the choke to do it's stuff better?

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PostPost by: types26/36 » Wed Nov 02, 2011 7:14 am

robertverhey wrote: I like things that adjust themselves automatically.
Robert


Have you considered fitting an automatic gearbox to your Elan....sounds like it would be perfect for you :roll:
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PostPost by: ericbushby » Wed Nov 02, 2011 8:40 am

Thankyou for the comments.
Greg and Brian,
I know it is not right, but the point is I have so far failed to cure the problem. Two sessions on different rolling roads have improved things a little and a friend who used to tune webers in the 60`s has helped. I have spent many hours stripping and cleaning the carbs having never worked on one of these before. I did have a TR2 in the 50`s with twin SU`s but it was new.
This mod can be temporary and has made the car usable until I cure it.
Air correction jets are next then. Any tips would be welcome.
The engine seems to be running on three cylinders when started cold.
All ignition components have been replaced.
This car has not been on the road for over 20 years but is now running.
This mod cost £12 and works.
Here is a photo of the car to try to get my stripe back:-
lotus elan mod 004.jpg and


Eric in Burnley
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PostPost by: types26/36 » Wed Nov 02, 2011 9:13 am

Eric,
My comments were not meant as a criticism and it is your car to do with as you please, its just that the old saying "two wrongs don't make a right" comes to mind.
The 151 carbs are not original to your car and although they are regarded as excellent carbs I just wonder why they have been changed.
With the normal 40dcoe's there is no adjustment between the butterfly's in the same carb, the 151's do have a by-pass bleed to equalize the air flow, as Greg points out they are under the plastic cover, not everyone knows about this adjustment and are "theoretically set in production"
Although you have had it looked at by a professional the problem may not even be related to the carbs but I think a complete check of all the systems is needed by someone who is familiar with Twin Cams.
PS. your car looks very nice :D
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PostPost by: elansprint71 » Wed Nov 02, 2011 2:42 pm

Eric, out of interest has your car been on the rolling road at Minisport? We've has the Mini over to them a couple of times and the improvement has been staggering (currently 73 bhp from a 998 Minisport engine with single 1.5 SU). I was wondering what they could do with an Elan.
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PostPost by: ericbushby » Wed Nov 02, 2011 5:52 pm

Hello Pete,
Yes, Minisport at Padiham spent quite a long time on it, mainly checking and confirming basic things such as valve timing, ignition advance and compression. They seem to have a good set up there and because they were not satisfied with the results charged me considerably less than they could have done.
They suggested a second opinion on another roller so I took it to R E P at Bury and achieved further improvements. I seem to be slowly getting there and the car is now drivable but there is still something else wrong.
Thankyou for your suggestions
Eric in Burnley
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