The Mazda6 Needs 8 Gears

midnightdriv1

I disagree with Mazda's assertion that their 6-speed transmission has enough gears. This is 2019 and the competition is way ahead in this regard. The lack of ratio spread in the Mazda6 auto-transmission has two big disadvantages:

First, the Mazda6 engine revs at 2700 RPM at 80 MPH in top gear. In contrast the Toyota Camry which has an 8-speed only revs at 2000 RPM at 80 MPH in its top gear. This is a major factor in the Camry getting 3-4 MPG better than the Mazda6 on the highway.

Secondly, 1st gear in a 6-speed will be taller than 1st gear in a transmission with more gears and thus slower accelerating off the line. The Honda Accord 2.0T for example which has 10 gears will get from 0-60 MPH over a full second faster than the Mazda6 2.5T even though the Mazda's engine is bigger and has substantially more torque. I realize there are other factors at work with regards to acceleration like turbo boost, etc, but a transmission upgrade would certainly help close this gap.

A car like the Mazda6 with great style and superior driving dynamics deserves a better slushbox.

kyfdx

The number of gears doesn't decide the final drive ratio, and the resulting RPM at 80 mph. That is just a choice by the engineer who designed the transmission. An 8-speed and a 6-speed can have the same top gear.

And, by the same logic, they can make first gear whatever ratio they desire, as well. They can just spread out the four gears in-between.

Doesn't mean the transmission is a good match for that engine, but more gears doesn't necessarily = better transmission.

PF_Flyer

It is interesting what choices are made about gear ratios sometime. In my 6-speed manual transmission vehicle, I've always felt that 1st gear was geared WAY to low and I'd trade it out for something above the current 6th. You barely move before you need to shift, and as long as I'm not on an uphill grade, I can easily start out in 2nd.

I'm certain the engineers had their reasons

midnightdriv1

Agreed. Of course the number of overall gears in a transmission doesn't dictate the ratio of the lowest and/or highest gear, however more gears provide the engineers more options. Since Mazda's credo is performance they likely wouldn't want much spacing in-between ratios, so in that regard you would have shorter gears and higher RPMs. Its all about compromises, my point is that increasing the number of gears would help mitigate those compromises.

All that being said you obviously run into diminishing returns once you hit a certain number of gears. 8 speeds IMO is plenty. I think anything above that is overkill and the benefits can be outweighed by too many shift points and added mechanical complexity, etc.