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Old 05-13-2011, 01:08 PM   #96 (permalink)
Rusty Marina
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Originally Posted by cleanspeed1 View Post
The old IDI 6.9/7.3 in that chassis will do in the 14-16 mpg range all natural, will do better if turbocharged with either the factory ( nee ATS ) or a Hypermax system. The biggest problem with these engines is simply gearing.
From the factory, these engines are geared too low, and if the gearing were changed to lower the speed to 1600-1800 in top gear at cruise, the mileage goes up substantially.

I used to frequent an IDI site, and one of the founders took a stock 6.9 IDI and a 5 speed OD transmission and put it in a F150 pickup with 3.08 gears in the back. Got 30 mpg out of it.

If there was a gearset in the 2.73 to 3.08 range for the 3/4 to 1 ton rear axle that was readily available, buying an IDI truck would be an mpg dream

Thanks; yea Im told some topped out at 75 because of the gearing. The GM trucks had their 6.2 as an option in the 1/2 tons, so Im wondering if one of those would be easier on the budget, despite the fact I know the 6.9 was a much better engine

Originally Posted by Arragonis View Post
The original Mini competed against the Porsche 911 in rallies in its later days - thats 1293cc (rally engine) vs something >2 litres...
If the 1293 you speak of was a bored out 1275 cc "A" series engine those are neat little engines (I have a couple old Morris Minors outback)
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