Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post

pete c · 04-17-2016, 09:54 AM

Recently, I rented one of those Fiat SUV things. Looks like a Fiat 500 that got overinflated. It was a nice little rig and it has a 9 speed tranny.

I don't have any problems with that and it sure as hell beats an old 3 speed, but at what point does gear count become driven by marketing rather than engineers?

I think 9 is about a gear or two into that territory. I am currently renting a Kia Soul with a 6 speed and I think that is about right. 6th gear at 75 mph cruising speed is around 2700 rpm. And it is in 6th by 45 mph, assuming a light throttle. The Fiat, I noticed didn't get to 9th until somewhere around 70 and even looking at the throttle caused a downshift.

More gears means more weight and more complexity. Also, a tranny that is in the middle of a shift is less efficient than one in gear, so I think that it might actually mean a miniscule drop in efficiency. I would think that an 8 speed with the same final ratio would be just as efficient with an immeasurable loss in performance.

Another example of this is the new Vette with the 7 speed stick. That motor pulls like a freight train over almost all of its range. I have read reviews of it and they say that it doesn't shift as well as the 6 speed, which makes sense, because now you have 4 rows of gears rather than 3. One of the reviewers said it needed a 7 speed like it needed square wheels.

04-17-2016, 09:54 AM	#1 (permalink)
pete c Master EcoModder Join Date: Oct 2011 Location: ellington, ct Posts: 829 Thanks: 44 Thanked 104 Times in 80 Posts	Bazillion speed auto trannies. Recently, I rented one of those Fiat SUV things. Looks like a Fiat 500 that got overinflated. It was a nice little rig and it has a 9 speed tranny. I don't have any problems with that and it sure as hell beats an old 3 speed, but at what point does gear count become driven by marketing rather than engineers? I think 9 is about a gear or two into that territory. I am currently renting a Kia Soul with a 6 speed and I think that is about right. 6th gear at 75 mph cruising speed is around 2700 rpm. And it is in 6th by 45 mph, assuming a light throttle. The Fiat, I noticed didn't get to 9th until somewhere around 70 and even looking at the throttle caused a downshift. More gears means more weight and more complexity. Also, a tranny that is in the middle of a shift is less efficient than one in gear, so I think that it might actually mean a miniscule drop in efficiency. I would think that an 8 speed with the same final ratio would be just as efficient with an immeasurable loss in performance. Another example of this is the new Vette with the 7 speed stick. That motor pulls like a freight train over almost all of its range. I have read reviews of it and they say that it doesn't shift as well as the 6 speed, which makes sense, because now you have 4 rows of gears rather than 3. One of the reviewers said it needed a 7 speed like it needed square wheels.