Hi all
Got back from the Le Mans Classic on Monday, and after an 872 mile round trip at last I've got some empirical fuel consumption results.
When I drove my new car home from the dealers last September it was about 170 miles of mostly 60-80mph (indicated, officer....) on dual carriageway plus some stop-start crawling and took almost a full tank of E5, working out to 13.6mpg. At the current UK E5 average price of £1.59/L (RAC) that's 53p per mile.
The car just didn't have the performance one would expect, it smelled of fuel and it was a very reluctant starter, hot or cold.
The car now has Pertronix electronic ignition and, of course, a Holley Sniper with an ethanol-proof fuel system. As I've said in recent posts it now runs very well, starts quickly hot or cold, has a rock steady idle and rpm's cleanly with no hesitation or fluffing aparrent. The plugs are the right tan colour instead of being caked in soot.
After fitting but before the Le Mans trip it did 14mpg on E10, which at the current UK average of £1.45/L (RAC) that's 47p per mile = 6p per mile reduction.
On the Le Mans trip the car started full, used 3.5 tanks and so had half a tank left when I got home. Filling it up to get back to where I started brought the total fuel used to 250.5L/55.2 gallons. Thus the overall fuel consumption for the 872 mile trip was 15.8mpg, on E10 = 42p per mile at current UK average.
The detail by tankful is:
1st tank 14.2mpg (lots of crawling on UK M11, M25 & Eurotunnel plus 70-80mph on autoroute Calais-Abbeville)
2nd tank 15.8mpg (almost entirely 70-80 mph/3-3500rpm on autoroute to Le Mans with slow stop/go drive through Rouen)
3rd tank 16.7mpg (as above)
4th tank 17 mpg (50 miles of 70-80mph on autoroute, queues at Calais Eurotunnel, 100 miles of 60-70mph in UK plus 5 miles of crawling at Dartford crossing).
So in round figures I've spent c.£2000 to save roughly 10p per mile, which is a 20k mile payback or roughly 7 years. However, and it's a big however, the improvements in overall driveabilty are such that even if there was no improvement whatsoever in 'economy' (if that's the right word....) other than the move from E5 to E10, I'd do it all again. I accept that a more refined aftermarket system - Edelbrock's Pro-Flow, for example - would probably yield more efficiency, but the entry cost is higher. And a new carb would be cheaper, better than the old carb but not as good as a throttle-body efi like the Sniper. EFI = rifle, carb = shotgun. So ya pays ya money and takes ya choice.
And I haven't even thought about refining the target fuel/air ratios in the Sniper's ECU map yet........
Thanks for your interest in my little adventure.
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