Every engine manufacturers setup is different....but I have info from someone who claims to have found that the cam timing on a Toy 1.5L engine was 11* retarded and he was reporting some pretty high mileage:
"Its too soon to tell, and I've been doing too much highway mileage to say normal economy, but my last 3 tanks were- 41, 46, 29. More highway on the first 2 obviously. Highest I've ever seen was 49mpg, pure highway. And no, it wasn't a quirk fill-up, because it happened twice in the same day on the same trip. How you like them apples?
Oh, and btw, the last 3 trips, when on the highway, have been with 3 other "adults" (17-21) and my 1-year-old niece in the car."
Since he got the t-belt setup right...he now claims more power at lower rpms.
Before...he tended to rev it a lot....and with this car his highways revs were probably above 3K...maybe 3.5K.
I normally see around 32-34 mpg mixed with some mods with essentially the same car...though I did hit 47 mpg one day with a good tailwind.
The new EPA avgs for the car are...23 / 29
I tried advancing the cam timing by one tooth or 9* and the car lost power by 59%...as tested in 5th gear. I might have messed this "test" up by not pulling the dist and trying to reset it...though I thought I still had quite a bit of adjustment.
This engine...a 3AC ('83 to '88 Toyota)...has a 9 to 1 compression ratio and ignit timing is 5* BTDC standard.
With cam timing at OEM spec...the power can be upped with this engine by at least 20% though....by advancing the ignit.
Has anyone tried this on a stock engine and seen better mpg?
Obviously... the ignition timing would need to be set on the road to get it to run right.