The #1 question I get is why I don't build XFI models
The answer is because no one likes to drive them, going from 57hp to 47hp hp in a Car that is already under powered is awful.
I took this from wiki link
Metros came in three trim levels: XFi, Base or LSi. The XFi's engine has less horsepower than the base and LSi and achieved a startling gas mileage of 53 MPG (city) 58 MPG (highway).
First off I am going to simply point out some pro's and cons on the XFI vehicle. My opinions are based on factual driving and dynometer testing of the engine. Just to compare a base model or LSI (they are virtually all the same) EPA numbers are 41 MPG city and 46 MPG highway.
So this is one of the first things you see when you Google up Geo gas mileage and link in to XFI. I usually start with reminding every one if they remember a few years back when you could not trust the mpg sticker in a new car window. The fact a few years back Congress changed the LAWS rules and the MPG dropped dramatically for every cars sticker. Mostly because car manufactures manipulated the tests to the point where CONGRESS HAD TO GO BABY SIT THEM FOR LYING TO THERE CUSTOMERS.
So lets remember the numbers were all fudged a bit for what ever reasons.
Now I know there is enough controversy out there over the XFI MPG numbers. People are asking why they cant get those EPA numbers. So since every one in the world wants a Geo XFI and I could build them out of base models or LSI models into a xfi with some parts swapping, well why don't I do it?
The answer is simple I have never stopped trying and I have never seen this extra 20 percent increase they are suppose to offer. I have 3 to 4 test metros running with mostly custom parts I have built. One is a perfect bone stock XFI. one is a perfect base model 4.1 final drive which is the most common Geo out here. I would be happy to arrange a test drive so you can fill the tank personally and drive it for 60 miles and refill the tank. I have log books on every car and the XFI. It currently has 5005 miles from a brand new engine two months ago and averages a perfect 48 mpg every tank. When ever I add or try a custom part to the engine that I might sell to all of you. Not only does it get tested on a base model a lsi model and third (late) generation model it is done to a xfi.
The only people that seem to get the good gas mileage out of the XFI are the same people that can get it out of the base models as well. For example most 1995 and later 3 cylinder 5 speed cars get about 39 to 40 mpg driven normally. Base models Metros and XFI's always get 53 or better and on long trips. Tank to tank driving is what we call this. Non stop cruising.
What bothers me is that even the XFI does not get measurable mileage above a stock base model Metro. So why drive it? Its 8 hp short it has such sluggish pick up in traffic it feels broken and its all most impossible to drive through the mountains with passengers or camping gear of any sort.
Over the years I think I could say I have redone more XFI's than any on else. The issue is not one single time have I ever gotten one that was anything but a shadow better than a base model. I know the shadow of better mpg is from its from the higher ratio transmission. On that same not if you take a base model or even a LSI model and simply install a set of taller 13" tires you get about the same ratio or close enough that the mileage comes right around to about match.
There are other tricks on the xfi. They take the passenger mirror off to make it more aerodynamic. C'mon really no mirror more MPG. Test this yourself take your mirror off and check the mileage.!? Take both off?! I have never seen it work yet, tried it more times than I can count. Plus I hate not having a mirror on the car while driving.
The piston is missing the second compression ring and no longer has the chrome hardened ring. This is the only Geo or Suzuki piston done like this. It is a practice used in racing but not on engines that will be used for long distances. I have never known a engine builder or manufacture to remove the compression ring and hope for longevity. They say this lessons the friction on the cylinder allowing the engine to be more efficient. On the dynometer I have never seen a difference. I did read that it is most effective above 8500 rpm. Even if this did add say even a tenth of a mpg it still would not off set the early ring failure they have compared to a standard 3 ring piston.
There is a different ecm part number, Its to help control nitrous oxides for California cars because of the cam shaft change they have made in this car. I have swapped this ecm in and out of restored cars so many times looking for a MPG boost with this ecm. I can report in that I cant tell a difference. I cant see it on the emissions test either so I have no idea what the factory was really up to. I actually think they lied to keep the car out there longer on the emissions issue it had with this new ecm number.
Lets talk camshafts and cam gears that is what every one thinks makes the xfi metro a miracle Geo. So the cam for the XFI is the same profile as a standard Geo but with two modifications. The first is they take and grind the camshaft exactly 1mm shorter. Then they advanced the cam grind on the shaft by 6 degrees. The rotating the shaft before building the cam is the reason another cam gear is required to correct the timing marks enough to allow the distributor timing to be set correctly in the housing. Many of you have bought 5 and 10 degree advanced cam gear from after aftermarket sources or built your own. I have never seen an advanced cam gear give better MPG though they do make a nicer power pick me up.
The shorter cam shaft grind stops the volume of air by about 20% which in turn kills about 20% of the rated HP. Now this one thing can help with mileage. You can do the same thing by installing a spacer under neath the TBI that has 20% smaller diameter hole. Basically it stops 20% of the fuel all the time no matter where your at in the throttle.
So your thinking that's it I just need the cam. Its what every one thinks. But when you drive the XFI with a voltmeter hooked to it and you see your about 20% more in the throttle to make up for the lack of power from the lack of engine HP from that funky cut XFI cam shaft.
Now if your keeping track I have always come up with the same mpg in virtually all the pre 95 models.
Now I will tell you why I think the xfi gets good numbers posted at least on line or by its owners. First: Most XFI owners are Geo enthusiast and there trying to get good mileage. Second off if you put a scan gauge in a stock base Geo metro which when the car is restored and like new it will tell you at 30 mph in 5th gear they get over 70 mpg.
This is either the XFI a base model and or a LSI. Also it wont matter what transmission gears or final drive ratio. I will tell you that if they did get better mileage I would build one every time we spend a lot of time tweaking Metros up to get plus 60mpg driven by normal folks.
So if your looking for a Geo metro in my opinion there is very NO reason to use any XFI parts to build a great gas mileage vehicle and in the end with XFI's being so over rated and inflated on cost it simple doesn't make enough sense to me to spend the extra money on one. Put the extra money in the gas tank.