View Single Post
Old 09-25-2014, 10:41 PM   #210 (permalink)
Changfa diesel + Suzuki
changzuki's Avatar
Join Date: Jul 2012
Location: Northern, NY
Posts: 527

Centurion - '74 FIAT X1/9 Centurion Full Race DNA
Last 3: 143.5 mpg (US)
Thanks: 160
Thanked 463 Times in 235 Posts
Originally Posted by sendler View Post
Everyone here would agree that the best way to tell what economy a vehicle gets is by logging several back to back tanks. Your tank is small so the thermal expansion errors will be less but they can be substantial in competition for something like an Insight with a 11 gallon tank and such a small amount needed to top off. It works like this. You show up to the competition which starts early in the morning, empty or with a cold, overnight tank. Fill the tank to the brim with fuel out of the ground which is at 10*C. Go to the track and drive your 130 miles. All the while the fuel is flowing to the hot engine area and back to the tank through the return line. You go back to the station to fill up again except you have used 1 gallon out of the tank and now it is at 30*C. That 10 gallons that should be left now measures 10.2 due to the thermal expansion of gas at 1% per 10*C. So the consumption is measured at .8 gallon instead of 1.0. The 130 mpg just became 162.5
Sorry Sendler - you're posting above is incorrect in regards to Centurion. If you took the time to actually look at my postings you'd see the "details"... In the pic below, the supposed heated return line to the tank you speak of does not exist - so therefore the tank of fuel is not heated.. I guess I just got lucky on that detail... Right???

Last edited by changzuki; 08-03-2018 at 11:08 PM..
  Reply With Quote