Lotus Elan

Soft soot in combustion chambers

PostPost by: JonB » Wed Oct 30, 2019 9:47 pm

Eh up

At last I?ve started my engine seal refresh. Head is off and I?ve found soot in the combustion chambers. It?s quite soft and comes off fairly easily so I am not concerned by it. Except, it seems to indicate the car?s been running very rich.

Which is odd, because it looks OK with the Colourtune.

So what might the problem be? Worn or incorrect jets? Acceleration pumps (I have Dellortos) incorrectly set up? Some other thing? I set the static timing at 12 degrees BTDC and the advance looks good.

Any advice while the carbs are off? They work perfectly at the moment..
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PostPost by: rgh0 » Thu Oct 31, 2019 8:46 am

Standard tuned Webers or Delortos run rich in order to get the engine response needed with what is a large carb set up for a small road engine. You can tune them to run leaner but you will then start to struggle with performance in other areas. Keiths work on new design emulsion tubes and jets improves the situation enabling a leaner tune without performance loss,

I would not worry to much about carbon in the combustion chambers

cheers
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PostPost by: JonB » Thu Oct 31, 2019 12:22 pm

Hi Rohan

Who's Keith?

Anyway, the stuff comes off pretty easily:

img_6195.jpg and
Sparkle sparkle




If the Dellortos can be tuned to run a bit leaner then I suppose that would improve fuel consumption. A worthy objective given how much the stuff costs in the UK. Is there any written guide to making these mods anywhere?

Cheers
JonB
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PostPost by: TeeJay » Thu Oct 31, 2019 4:27 pm

Its a guy called Keith Franck.

I looked into his improvements for my Weber's.

Here is a link which hopefully you can go forward for your Dellortos.

Link;- viewtopic.php?f=40&t=40588&start=
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PostPost by: Grizzly » Thu Oct 31, 2019 9:05 pm

Colour tune will only tell you your idle mixture roughly, it has a use for balancing the mixture on idle before you tweak it to the correct afr but thats about it...... If you want to get into changing the actual set up of the carb you need a wideband Lambda set up.

I'm not sure how much of Keiths Weber tuning info is transferable but his 'white paper' is a must read for anyone trying to set up their carbs.
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