Metro XFI Cam Advance Experiment

Well, I just finished with a fairly long experiment. I have been moving the cam timing around on my car to see what effect it has on mileage. Keep in mind that I have shaved the head .040″ so the car cannot tolerate as much advance as when it was stock. I have tried from -2 to +11, and for each of them I ran the maximum ignition timing that I could run without knock. I gave up trying to do 2 tanks each due to the weather, and my having to drive less to work means that it takes me 2-3 weeks to run a tank of gas out now so it would be almost a year to do this test the long way. I did short tanks of at least 100 miles and filled the tank to the top with the car sitting at an angle to keep the air bubbles out.

The numbers are probably not 100% perfect, but they are pretty close and fit a curve reasonably well, so they still give useful information.

Cam Position VS MPG

The curve is not perfect; I am pretty sure the 5 degree advance number is a bit lower than what it should have been. I would say advancing a stock XFI engine 5 degrees is ideal, and advancing one with the head shaved 3-4 degrees is probably ideal. I will redo this experiment later on going in one degree increments from 2-5 degrees advanced to see if I can fine tune my timing.

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8 Responses to “Metro XFI Cam Advance Experiment”

  1. What are the differences between a base Metro and a Metro XFi?

  2. you got it my friend.the difference is only the ingection.both they have the same engine G10 -993cc,55 hp.i took off the ingection system from geo metro xfi and i put it after that on my geo metro regular and now i have 55 mpg .i am very happy to have the most fuel efiicient car in USA except Honda Insight but it is about 20.000 $ and it is only two seat has only 2 seats. you can have the same MPG if your Geo is 3 cilinder and manual transmission. thank you YAVOR

  3. The XFI model has different ignition than standart model?

  4. You can counteract the surging by holding the throttle at 2000-3000 rpm and adjusting your TPS. I got the best throttle response and driveabilty by tuning my TPS to match what mods I’ve done. It will surge at the stock setting, and just turn it back and forth until it smooths out and revs quick. Lock it down when you get a sweet spot.

    I love these cars. I used to hate them, until I bought one.

    Keep up the good work.

  5. No, like Rick said, the cam, the computer, and the gear ratio are all different. The XFI has the smallest cam and the tallest gear. The computer is programmed to work with these differences. Even an XFI cam and computer will help mileage.

    I got tired of the three, and installed a Suzuki Swift GTi twincam four cylinder engine in mine. While losing mileage, it gained tons o fun, and still get as good of mileage as a Saturn.

  6. Did milling the head .040 get you any more mpg? Jeff

  7. I have a 91 geo LSI convertable, /gets about 31mpg. Will having cam ground to XFI specs and that alone help the mileage?

  8. Hi, I have purchased a 1992 LSI Yellow Convertable. I get between 39 and 44. I am wanting better MPG. I purchased a reground cam and a set of pistons. I do not know anything about working on motors so I am going to have to find a mechanic to install these. I really want your opnion on if I will see a difference in MPG. I bought the car for $1900.00.


    Deas M. Richardson Jr.