it's all about gears!

[serialk11r]

Originally Posted by Old Mechanic

More gears allows you to have an engine that was designed to take best advantage of more gear choices. Low RPM high torque without top end performance. Eliminate the maximum power output and make the reciprocating masses lighter. More diesel like power band.

regards
Mech

Or, you could have a race-car like power band from an Atkinson cycle engine (at high rpm the late valve closure aids volumetric efficiency), which gives you "extra gears" in the sense that at lower rpms you have not much power but good efficiency, and at high rpm you have more power. More gears lets you take advantage of that by giving you the option of staying in the powerband or staying in the "efficiency band".

The only thing stopping performance engines (with single cam profile) from good efficiency is really the overlap and somewhat the exhaust cam being too big. Bigger intake cam means more top end, less bottom end, more efficiency at low speed

@Frank Lee 7 is useful if your engine produces a lot of power and the car goes fast, otherwise 6 is okay.

[Frank Lee]

The Coupe has a 5-speed m/t and most of the time I skip one or two gears. With a six or seven speed I would skip three or four gears plus be powering all those extra gear meshes 100% of the time. :/

First gen Tempos had a 4-speed "fuel economy" transmission option.

[serialk11r]

Originally Posted by Frank Lee

The Coupe has a 5-speed m/t and most of the time I skip one or two gears. With a six or seven speed I would skip three or four gears plus be powering all those extra gear meshes 100% of the time. :/

I skip gears on my 5-MT too but I loaf around in 3rd and 4th when I can't get past 20mph. On the highway I can't use 2nd to accelerate, so it's 3rd or 4th if I need some extra power, but 4th is kind of useless on the highway and 3rd doesn't have much grunt.

Admittedly though, the spacing in this gearbox could be better. If 3 were closer to 2 it'd be a lot more useful, and if 5 were significantly taller than 4 that would be a lot better too. But add an extra gear like in the C60, with slightly taller final drive, you now get a shorter 1st (good for the clutch), a much shorter 2nd (good for low speed acceleration, don't need to use 1 to do as much acceleration), a versatile 3rd, 4/5 for more power on the highway and rolling around at low speed, and 6 for cruising, at the cost of 10 pounds of weight and one more gear mesh. I think that's worth it.

7 is sort of hard to justify even with a 8500rpm 2ZZ or a K24/2AR-FE now that I think about it. However if you look at Porsche's 3.4L 6MT for example, the gearing is fairly standard for a 6MT in terms of spacing of gear ratios but they use a tall final drive. Those cars turn 3000rpm at 75mph, which sucks, and everyone complains about the final drive being too tall since gears 1 and 2 are so tall. Here 7 speed makes a lot of sense, 7th would be a highway only gear, and 1-6 would be your acceleration gears which is necessary on a car that can do 180mph.

[gone-ot]

...or, they (auto manufacturers) could simply go BACK to putting OVERDRIVE units behind their normal gearbox transmissions...as was SO popular in the 1950's. Simply a "bolt-on" option!

[Joggernot]

Originally Posted by Old Tele man

...or, they (auto manufacturers) could simply go BACK to putting OVERDRIVE units behind their normal gearbox transmissions...as was SO popular in the 1950's. Simply a "bolt-on" option!

Wouldn't that be nice?

[serialk11r]

Originally Posted by Old Tele man

...or, they (auto manufacturers) could simply go BACK to putting OVERDRIVE units behind their normal gearbox transmissions...as was SO popular in the 1950's. Simply a "bolt-on" option!

But then for the people complaining about the power that idle gear meshes consume especially, the constant mechanical efficiency loss of a overdrive unit would be unacceptable.

Apart from the primary reduction gear that exists on some gearboxes, what other gears are not strictly necessary? Can the differential incorporate a gearbox? Hmmmm....Food for thought. It would certainly solve the issue with >6 speed manual transmissions having a strange shift gate for gear 7.

[Thenorm]

Originally Posted by serialk11r

Apart from the primary reduction gear that exists on some gearboxes, what other gears are not strictly necessary? Can the differential incorporate a gearbox? Hmmmm....Food for thought. It would certainly solve the issue with >6 speed manual transmissions having a strange shift gate for gear 7.

almost, the modern front wheel drive already has a transaxle. the differential is incorporated into the transmission housing, already saving weight and space.

I'm also reminded of the Acura SH-AWD which has planetary gear sets on each axle in their Rear diff. so they can overspin the outside wheel which pulls the car around turns.

[cRiPpLe_rOoStEr]

Originally Posted by Thenorm

almost, the modern front wheel drive already has a transaxle. the differential is incorporated into the transmission housing, already saving weight and space.

And their assembly is usually already too space-constrained to find a gap for the overdrive

[P-hack]

as well as every transaxle I've ever seen already has overdrive int the upper gear(s). Just looking at civics all but 1 are in overdrive by 4th gear (ratio < 1).
Honda Tranny Gear Ratios

[cRiPpLe_rOoStEr]

Originally Posted by P-hack

as well as every transaxle I've ever seen already has overdrive int the upper gear(s).

Sure. Way more practical than trying to fit something like a GV auxiliary overdrive unit or any other kind of gear-splitter...