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Question on fuel consumption of my BN6

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BN6_2197

BN6_2197

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Hi gents,


depending on driving style and weight of the co-pilot my BN6 uses 18-20 liter fuel per 100 km. In my perception that is pretty much. I refurbished the carbs last year without any noticable improvement. Also checked the emission, but nothing remarkable on that.

Is that much consmption expcted? If not, does anyone have an idea how to proceed to improve the situation?

Volker
 
Hey Volker,
Gonna have to convert that over to gallons for us Yanks ! I had a 58 BN6 that did average around 25 miles per gallon when driving around a constant 55-60 mph. Would think usual would be in low 20's. One thing you might check is if you are running too rich which would impact the mpg. On the other hand though, if it's running good, don't touch it as I like to practice the "if it a'int broke, don't fix it" philosophy !!!
Regards
Mike
 
Hi Volker
Sounds about right given the differences between the Liter and The Imperial gallons
Odometer accuracies, tire sizes and driving styles.
 
Last edited:
Mike,

I checked if I am running too rich by measuring the emission of the car. According to my garage I am running more less than too rich. I share your opinon that you should not touch a running system. My car is indeed running fine.

Did I understand it right, that in your opinion 18-20 liters per 100 km (for a German guy) is not neccessarily unusual? When driving on a high way constantly about 60/65 mph at 3000 rpm the car consumes a little bit less (15-18 per 100 km).

Regards,

Volker
 
Assuming 4 liters per gallon and .6 miles per kilometer, 20 liters/100 km comes out to be 5 gals per 60 miles, which is about 12 miles/gal. Most healeys get around 20 mpg I think. I'd say you're either running really rich or leaking gas.
 
Keith,


I checked if I am running too rich by measuring the "CO-Value" by putting a sensor into my exhaust pipe. It seems to be good according to my garage. What is a "good" CO-value from your point of view? By the way: In my understanding the "CO-value" is the portion of the carbon monoxide in my exhaust.


What do you mean by "leaking gas"?


Volker
 
Volker,
I have no idea what a good value for CO is, but maybe someone else on the forum will know and chime in. I tune my carbs using the "lift the piston a fraction and listen to the rpms" method. And by "leaking gas" I mean quite literally gas dripping from somewhere in the system; float bowl overflowing, gas leaking from the bottom of the jets, loose gas line connections, etc.

Hope this helps. I do think that 12 mpg is low for highway driving. It might get that low for very spirited around town driving.
 
I'm running a Denis Welch DW8 cam, two HD8 SU's, California oxygenated fuel, headers and a lead foot in my 3-liter BN4. Last I measured, I was getting 17 mpg (14 liters/100 km).

By "leaking gas", I think he means liquid fuel is leaking on the ground and not being used by the engine.
 
Your fuel consumption equates to about 15 miles per imperial gallon (real gallons). That is high consumption for a BN6 which should be getting about 20mpg at least.
 
My BN6 runs about 11-14 liters/100 km. depending on the driving style. Check if the correct carb needles are fitted.
 
I also had bad mileage. Highway MPG was where it should be. Around town/highway combination was terrible. Seem it was the distributor. Had it rebuilt and mileage increased to what others were getting.
 
I get 23-25 mpg in my 100 Lemans with the larger SU's and a DW "Fast Rallye" cam.

As I recall my ex-wife's stock 3000 gave about 21-23. I sure miss that car.
 
"AUSMHLY", can you explain me the dependecy between the distributor and fuel consumption, please. I cannot imagine any :-(
 
.. unwanted resistance and bad voltage ...
 
"BigGreen", can unwanted electric resistance and bad voltage really influence fuel consumption? Indeed that could be a good starting point for further analysis. I would really appreciate if you could detail on this. Volker
 
Incomplete combustion or incorrect timing can have an effect on fuel mileage. If the distributor is not advancing properly that can effect it.
 
The standard needles for a stock BN6 are CV. (Those identification marks are on the upper portion of the needle). Rich needles are marked RD and lean needles SQ.
 
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