MPG

Squarehead · Post by **Squarehead** » 20th May 2007 - 7:46pm

..anyone point me at some sort of average MPG for my 412?- seems to be guzzling gas, but plugs look fine!
- tank is 10 gal, yeah?
- are fuel gauges normally accurate? ( unlike splits!)
cheers

Post by **Editor** » 20th May 2007 - 10:39pm

If Type 3 or 4 fuel injection is giving bad mpg, it's probably either

1) the voltage output from the voltage regulator (should be about 14V at mid-rpm) or

2) an air leak in the hose from the manifold pressure sensor to the intake air distributor. It's a vacuum pipe and if there's an air leak, the brain thinks you have the throttle full open so injects more fuel.

I would expect something around 28mpg (UK gallons) average with maybe 30+ on a journey.

You can never really trust the gauges - the resistance wire gets higher resistance as it ages, and the gauge gets pessimistic - ie more fuel left than it suggests.

Best way to work out consumption is fill full, note mileage or set trip to 0, run low then refill and note gallons put in (well, litres!), divide miles by litres and then x by 4.54 to get mpg.

Squarehead · Post by **Squarehead** » 21st May 2007 - 6:13am

...many thanks. Have been doing the latter, & hope its the gauge!- the plugs look fine, so doubt its rich.Will fill up & run dry to test.
Cheers

Squarehead · Post by **Squarehead** » 8th June 2007 - 10:49am

...ran the tank dry ( 10 gal) averaged 27 ( with a lot of town work) & is running a little rich...

Post by **Editor** » 11th June 2007 - 1:36am

It might do a bit better than that, though town running isn't its most economical mode.