09-10-2022, 01:58 PM
I've been driving Austin Sevens for 45 years now and can share the following on fuel consumption:
1) The fuel consumption is wildly affected by the temperature of the engine. On a long run, 40mpg+ may be possible but on short runs, this figure drops to the low twenties or worse. By a long run, I mean over 40 miles or more in one, continuous go.
2) My Chummy, with lightly tuned engine and SU carburettor can achieve 50+ mpg on a long run. The Top Hat, with a standard engine and 24T2 updraught struggles to get to 40mpg.
3) Later cars are much worse, my Ruby with standard hi-comp, 3 bearing engine could achieve 35mpg at best (i.e., on a long run, engine hot). A later, 1934 Box Saloon was a little better but not much. A 1931 SWB Box I once owned achieved nearly 50mpg, but this was on a non-stop, Norwich to Wiltshire run with a strong NE wind blowing!
4) All my tests were carried out in the same way, fill tank, drive, refill tank to same point and note quantity, divide into mileage recorded. Yes, I had checked the odometer was reading correctly and yes, I was refilling to the same point!
A lot of people will want to shoot me down, but these are cold facts delivered in a long A7 career.
1) The fuel consumption is wildly affected by the temperature of the engine. On a long run, 40mpg+ may be possible but on short runs, this figure drops to the low twenties or worse. By a long run, I mean over 40 miles or more in one, continuous go.
2) My Chummy, with lightly tuned engine and SU carburettor can achieve 50+ mpg on a long run. The Top Hat, with a standard engine and 24T2 updraught struggles to get to 40mpg.
3) Later cars are much worse, my Ruby with standard hi-comp, 3 bearing engine could achieve 35mpg at best (i.e., on a long run, engine hot). A later, 1934 Box Saloon was a little better but not much. A 1931 SWB Box I once owned achieved nearly 50mpg, but this was on a non-stop, Norwich to Wiltshire run with a strong NE wind blowing!
4) All my tests were carried out in the same way, fill tank, drive, refill tank to same point and note quantity, divide into mileage recorded. Yes, I had checked the odometer was reading correctly and yes, I was refilling to the same point!
A lot of people will want to shoot me down, but these are cold facts delivered in a long A7 career.