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Discussion Starter · #1 ·
The SDI's get 20 mpg (for the sake of easy calculations). Carbed get 10 (for the sake of easy calculations). One quart of oil to a tank of gas gives you about a 40/1 ratio. On that tank of gas the SDI goes 200 miles and the carbed goes 100 miles. All things being fairly equal the SDI engine has turned twice the rpm's that the carbed one has on the same amount of oil. I don't think this is a good thing. My dealer set the oil pump to a quart of oil to a tank of gas which is still lean if you look at it this way but the plugs are looking black not tan so I'm going to go with this for a while. No fouled plugs yet but only 500 miles on it. I hope this doesn't open a can of worms but just curious about your thoughts.
 

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You need to fill your gas and oil tanks to a set mark. Then after riding most of the tank of gas refill both both. Be sure to use a measuring bottle for the oil so you know exactly how many ounces used. For the gas multiply the gallons used by 128 ounces. Divide your ounces of gas by your ounces of oil. That is your gas to oil ratio. I believe it should be 50:1. At 50:1 ration you should only use a guart of oil to about 200 miles on your SDI. Your plugs should be a nice tan color. If yours is like mine from stock you can open the pump up all the way and still have way too much oil consumption. I had to bend the bracket that the cable goes through to get to my current ratio. But be very careful so as to not bend too far. I was at 170:1 for 77 miles until I checked it. Now I'm down to 66:1 and turned it down some more. Stock I could not get it better than 24:1 and that was after a new pump was installed under warranty and I opened it up as far as it would go which was like 21 mm. Actually ran great for those 77 mles but I'm sure wouldn't last long that way. Running great now but will feel better once I get it to 50:1 ratio. By the way I run Blue Marble oil.
 

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Discussion Starter · #3 ·
The question is should the oil ratio be based on gallons of gas burned (which varies with mileage) or on engine rpm's per mile (which are fairly constant). I know how it is calculated now.
 

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The SDI burns less of both fuel and oil because it basically runs on the edge of meltdown all the time rather than the carbed which for the most part run pretty rich.

Your fuel/oil ratio should still be the same but your air/fuel ratio is going to be a bit leaner on the SDI.

So if that made any sence at all... Theirs nothing wrong here...
 

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Discussion Starter · #5 ·
By using the same oil to gas ratio as lower mileage sleds (half the mileage) your oil amount entering the engine is half what the lower mileage sled is for the same amount of engine rpm's. Just wondering if this could be causing the blowups and bearing problems.
 

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When you push an SDI. lots of full throttle. mileage goes down considerably but still all thing being equal probably 4-5 mpg gal better than a carb 600, however it's a lot better in normal driving conditions.

We just came off a fast trip, 500kms, I used 76 liters (17 mpg imp) of fuel and 2.6 liters of oil (almost 30:1), lots of 7/8 - full throttle lake riding and 4-8 cm of new snow. The best distance I got was 600 km, the last 100 kms the oil light was on, I checked frequently and babied it that last 100kms, still had 2 cm of oil in the bottom of the tank when I got home.

I've seen 21-24 mpg (imp) hardly used any oil, haven't duplicated that again however, I guess I'm just driving faster, just for your info and a surprise to me, the oil light came on when I got home (500kms) soon as I put the sled on the jack stand and wouldn't go off untill I filled the oil tank.

This SDI is always at least 30% better on fuel than any other sled that rides in our group (non SDI).
 
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