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Originally Posted by pdxmotorhead  The M44 and M42 don't like low rev lugging. Wrong tool for the job...
Dave |
+1, Lowering the RPM's doesn't necessarily improve fuel economy. While it may help you in 5th gear at highway speeds, you have to consider city driving and stop and go. If you're struggling to take off and get up to speed, you're wasting more fuel than you'd be saving on the highway. Couple things you can do to conserve fuel, replace your o2 sensor(s), replace your air filter, check/replace you spark plugs regularly, correct tire size & pressure, and most importantly have a light foot.
I've heard so many people ask why their gas mileage sucks, only to see them driving their car like it's a rally car. Take it easy. I mean it's cool to stretch your engine out once a week, I do it, but hey if you're always in a rush to get somewhere, perhaps you can just plan your day out a little better. You'll notice the rewards at the pump if you'd simply slow down.
And finally, maybe not a practical option, but it's been tested and proven that some forced induction applications have actually shown improvements in fuel economy. Now this doesn't mean if you supercharge your car you're gonna get great gas mileage. Most people install superchargers and what's the first thing they do? They go out and try to race everything on the road. Well there went fuel economy right out the window about seven blocks back there.
But yes, if you have a supercharged or turbo'd engine WITH PROPER TUNING, you will notice a significant increase in fuel economy provided you don't drive like a maniac. The reason being, your engine will burn fuel more efficiently as it takes less energy for the engine to get your car up to speed and maintain it. However, I should remind you about not being practical. Considering that a supercharger costs $3800, how many miles would you have to drive before you save that much in fuel costs? Probably a couple hundred thousand
Then you have the reliability issue. Most forced induction applications need special maintenance such as turbos/blowers being rebuilt/replaced. They usually result in abnormal or excessive wear on other components that are forced to work a little harder.
I just realized this is a diff thread, so I'll try to get it back on topic. E28 3.25 open or LSD, E30 rear cover, E30 output flanges, E30 halfshafts, shimmed ABS sensors, new diff cover seal, fresh gear oil = lower RPM's @ highway speeds and reasonable acceleration around town
