After 2 years with my Yaris I have one complaint

[Idahotom]

Higher and higher gearing can be overdone. Just try driving the 5 speed in top gear at 35 mph and see how good of mileage you get. While the rpm's may be construed as "high" (relative to what....) the engine is not working hard/manifold pressure is low. Granted it is a balancing act, and in theory I'd like a 10 speed to play around with, but I don't sweat not having a higher gear in my Yaris as much as I do not being able to open my rear windows!

I've seen different airplane drivers fooling around with ground adjustable pitch props, going coarser and coarser (like higher and higher gearing) hoping and getting lower revs at a certain cruise speed, but you reach a point where the economy doesn't improve past a certain point. Let's face it the Yaris is a inexpensive car, so the engineers' split the difference, a 5 speed instead of a 6 is one of those compromises. If you are obsessed with lower revs at a certain speed, it would be more practical to get larger tires and wheels. Keep in mind they'd weigh more and raise the vehicle thus more drag, probably canceling out any gains in MPG.

[DMZ]

Originally Posted by Idahotom

Higher and higher gearing can be overdone. Just try driving the 5 speed in top gear at 35 mph and see how good of mileage you get. While the rpm's may be construed as "high" (relative to what....) the engine is not working hard/manifold pressure is low. Granted it is a balancing act, and in theory I'd like a 10 speed to play around with, but I don't sweat not having a higher gear in my Yaris as much as I do not being able to open my rear windows!

I've seen different airplane drivers fooling around with ground adjustable pitch props, going coarser and coarser (like higher and higher gearing) hoping and getting lower revs at a certain cruise speed, but you reach a point where the economy doesn't improve past a certain point. Let's face it the Yaris is a inexpensive car, so the engineers' split the difference, a 5 speed instead of a 6 is one of those compromises. If you are obsessed with lower revs at a certain speed, it would be more practical to get larger tires and wheels. Keep in mind they'd weigh more and raise the vehicle thus more drag, probably canceling out any gains in MPG.

Well stated. I know from operating both 2 and 4 stroke motorcycles most of my life that there are "sweet spots" in the power curve, where the engine is operating efficiently and with little effort, (it is usually on the front side of the torque and HP curves). This is where you want to be to maximize your mpg, but also to extend the life of the engine. For a Yaris 1.5L, that seems to be between 2,250 and 2,650 RPMs. That is where my engine is most .

[Flipper_1938]

Originally Posted by Idahotom

Higher and higher gearing can be overdone. Just try driving the 5 speed in top gear at 35 mph and see how good of mileage you get. While the rpm's may be construed as "high" (relative to what....) the engine is not working hard/manifold pressure is low. Granted it is a balancing act, and in theory I'd like a 10 speed to play around with, but I don't sweat not having a higher gear in my Yaris as much as I do not being able to open my rear windows!

I've seen different airplane drivers fooling around with ground adjustable pitch props, going coarser and coarser (like higher and higher gearing) hoping and getting lower revs at a certain cruise speed, but you reach a point where the economy doesn't improve past a certain point. Let's face it the Yaris is a inexpensive car, so the engineers' split the difference, a 5 speed instead of a 6 is one of those compromises. If you are obsessed with lower revs at a certain speed, it would be more practical to get larger tires and wheels. Keep in mind they'd weigh more and raise the vehicle thus more drag, probably canceling out any gains in MPG.

Echo was 3.54 final ratio. Yaris appears to be 3.72

That is only 5% different...sure seems more.

The diesel in Eruope has a six speed with 3.55 final ratio and more overdrive on the higher gears. It would be nice to get ahold of one of those it it would bolt to a gas engine.

[Betrivent]

Originally Posted by Flipper_1938

Echo was 3.54 final ratio. Yaris appears to be 3.72

That is only 5% different...sure seems more.

The diesel in Eruope has a six speed with 3.55 final ratio and more overdrive on the higher gears. It would be nice to get ahold of one of those it it would bolt to a gas engine.

It wouldn't bolt on.. the D4D engine is far different in shape than the 1Nz.