Why Carb and non OD a Gen 3?

DionR said
Really good point. Comes down to what people want out of their rig.

I live 30 minutes from the "big town" of Spokane, Washington so almost any use of my car involves at least 30 minutes at 60+ mph. That's certainly within the two hour drive window, but it's enough for me to say I want OD. Even if I lived in a bigger town and ever got on the freeway, or maybe even a main road that had a speed limit of 50+ mph, I would probably want OD. But that's me, I just don't like the motor spinning at 3K rpm. Thankfully I am not everybody, that would be boring.

I might add that another "for me" reason is mileage. The better the fuel economy an OD gives means that I can enjoy the car more and drive it further. Not everyone has that limitation, and it is somewhat self imposed, but it is still a limitation for me. For some, economy is pointless because 10 mpg isn't much better than the 8 mpg the car gets without OD, making OD kind of pointless. And some rides are rough enough that driving it more than 30 minutes at a time is unpleasant, so why would they want to drive it more anyway. And for some the point isn't to drive it, it's to go fast or look good, all valid. But my goal is to make my Duster something I can enjoy as much as I can which means driving it all that I can.

To each their own.

You know, one joke I've always had with my car since the day I bought it was that no matter what I do, it gets 20 mpg, period. I had a 318 with a 4 speed and low 3.something gears (I think, don't recall what was actually in the rear end when I bought it) and it got 20 mpg on the highway. Swapped to a 5.7 Hemi with a carb and kept the 4 speed originally and it got 20 mpg on the highway. Converted to fuel injection and a T56 and low and behold, 20 mpg on the highway, lol. Granted I'm probably getting twice the horsepower of the 318 now and I have half the cruising rpm I used to, but I think aerodynamics are the ultimate limit of what the car is going to do consistently. It's a brick, there's no getting around that. With better tuning I have finally managed to make that number budge a bit and have seen 25 on the highway on my instantaneous gauge readout, but it's basically low 20s.

It all kind of makes sense when you think about it though. A car needs X amount of horsepower to travel at 70 mph. Doesn't matter how you make it, that's just what it takes to overcome drag, friction, etc. You can spin an engine at 4000 rpm with almost no throttle input and make the 60 hp or whatever it takes to push you along or you can spin it at 1500 rpm with your foot halfway to the floor. Both make the same horsepower in the long run. Yeah, you might lose some extra horsepower to rotating friction and stuff at higher engine rpm, but it's likely fairly minimal. The main difference comes down to the volumetric efficiency of the engine at those different operating points. You can kind of parallel that with the torque curve of an engine, though the effects of less than WOT make dyno charts somewhat less useful for that. Generally speaking though if you have a nice flat torque curve then the engine is probably pretty efficient at any operating rpm and your actual cruising rpm may not really make a huge difference on fuel economy.