this should speed things up (using small calibrated fuel canister for testing mods)
 

ok well im sick of filling up and then trying to get perfect result for one test through that whole week so ive got an idea

im going to buy a 1L fuel can and mount it in the engine bay and connect it to the fuel pump with a switch that will let me go between fuel tank and fuel can.

this way i can quickly evaluate fuel economy decreases/increases. that i will be doing soon.

now i just need to find a good straight road and i think i have the one.
i believe this is good for simple "bolt on items" as then i can really see the difference between timing changes, hotter thermostats etc..

anyone care to share thoughts

- I take it your car is carbureted, not fuel injected (MPGuino not an option?)

- Another option which I've seen used: calibrate your fuel gauge with a digital multimeter connected to the sending unit.

- I also assume your car doesn't have the pressurized "return" fuel line, and in-tank fuel pump?

- I've seen a few "Mythbusters" episodes where they use a small removable fuel tank which they weigh between tests to compare consumption.

- And I know of a guy (the guy who built this streamlined Model T Ford in the 1930's) who put a small graduated fuel container in his car to do the same thing.

yep good old trusty carby
and nope standard mechanical pump with no return line

hmmm my fuel gauge needs calibration anyway... its a bit saggy (full tank looks like 3/4 tank on my gauge)

would you care to teach me or divert me to a link on how to do this calibration you speak of

"digital fuel gauge" DIY
 

There's a post on GasSavers that member krousdb wrote (he's a member here too, inactive now). I'll see if I can find it.

In a nutshell though: he connected his multimeter to the fuel gauge sending unit on his car and measured its resistance, if I recall.

Effectively: he made a digital fuel gauge with vastly better resolution & accuracy than the analog OEM gauge.

He started from an empty tank, then recorded the readings as he progressivlely added a small measured amount of fuel (quarter gallon at a time?) until the tank was full.

He made a plot of multimeter reading vs. fuel volume from empty to full.

Since he always parked in exactly the same place each night (tank in the same attitude as when he calibrated it), he could then fairly accurately measure daily fuel consumption from his commute by comparing the multimeter reading to the plot he made from the calbration exercise.

The main thing that comes to mind that would mess it up (slightly) would be thermal effects on fuel volume.

Found it:

(from Feb 2006. Funny what sticks in your memory...)

Vacuum Guage and Digital Fuel Gauge - GasSavers.org - Helping You Save at the Pump Hypermiling and Fuel Efficiency Forum