Quote:
Originally Posted by 98frontier
Hello, this is my first post as I just registered today, I was curious to know what kind of mileage increase I could expect if I were to install a 3.54 rear axle in my 1998 Nissan frontier in place of the 4.33 axle I have now, my engine is a stock 2.4 Dohc with a four speed auto, my truck is 2wd and I am running 235 75r15 tires in place of the factory 215 65r15.
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*You need to know where you are,with respect to road load horsepower and the engines Brake Specific Fuel Consumption (BSFC)profile.
*For every engine rpm and combined aero,plus rolling resistance load,you'd see a particular rate of pounds of fuel per brake horsepower hour,after factoring in the driveline efficiency.
*This is best done on a chassis dynomometer,where all the loads can be simulated.
*With all the data,you'd construct an engine 'map' which showed a number of islands of constant BSFC,with one in particular yielding the best mpg.
*This would be the best your engine can do.
*And it may be that Nissan has already optimized the gearing for your automatic 4-spd,and changing the ratio arbitrarily might actually lower your performance.
*Until you figure out a way to get a map,you're shooting in the dark.