Fuel consumption, CO

(Paul Wigton) #41

Just about a sure sign the carbs are running too rich.

(Frank Andersen) #42

Champion is my favourite, Nick…:slight_smile:

But you will not notice much change in fuel consumption if the carbs are the culprits…

xj6 85 Sov Europe (UK/NZ)

(nickhill) #43

Hello everyone,

Back from the garage following ignition timing and carb overhaul.

Immediate result is no more smelly exhaust and fuel consumption now about 20mpg at 50-70 mph. Which feels more like what it should be.

Thanks for your help.

Nick Hill

XJC 4.2 (1975) Canadian spec

(Frank Andersen) #44

That’s about as good as it gets, Nick - unless you are a fanatic…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

(nickhill) #45

Forgot to mention the entertaining CO stats:

Legal limit in France: 4.5%
Before carb overhaul: 8.86% (!!)
After carb overhaul: 1.36%

(Jochen Glöckner) #46


1.36 % CO seems a bit too lean for my taste - I’d rather aim for 3 % and you even stand a chance that your mileage increases further because the richer tuning gives more low-down torque and reduces revs.

I envy you for the loss of the smelly exhaust!

Best wishes


75 XJ6L 4.2 auto (UK spec)

(Frank Andersen) #47

I agree with Jochen, Nick - carbs are set fat to ensure consistent performance through load and rev range.

Principally; lean running requires more pedal for the same output - not necessarily good for mileage. But if your engine behaves, no harm done…

xj6 85 Sov Europe (UK/NZ)