M.P.G. fluctuation...

[playswithfire]

Hey all,

 

I'm a chronic and incurable observer of my car's fuel economy, mainly because it's a great way to watch for changes in my car's health. My carbed (stock hitachi 2bbl) '86 4X GL wagon was getting a consistent 24mpg on my commute and daily driving. I dropped in an Accel super coil and the mpg bumped up to 27.

 

Now here's my question... I recently started getting 30 mpg without changing any driving patterns or buying higher octane fuel. I was happy and just thought my car was spontaneously healing itself. Then during a routine underhood inspection I noticed that the pre-heater hose that runs from the exhaust to the air cleaner had come disconnected. I put it back on and guess what: I'm now back to 27 mpg.

 

Is the cold air intake making that dramatic a difference in performance?

 

Ideas anyone?

 

Aiden

Canby, OR

[c150L]

I would think that colder air may have some effect like that. The volume of air passing throught the carb may be about the same, but the air itself would probably be carrying more oxygen due to the molecules being closer together. In a sesne, the engine is probably be running a bit leaner. I had 2 EA82 wagons, both 4x4, one carbed one SPFI, both averaged 27.5mpg. Last one started dropping to about 22, but still run the same. Found the fuel pump was rusting through and pumping the extra fuel onto the pavement.