FR-S Gear Ratio Comparison

[wparsons]

Originally Posted by serialk11r

It's a consistent 0.713 ratio between gears on the AT I believe, so your rpms will be 0.713*7450 (is that right lol)=5311.

The ratio between each gear isn't constant, so the RPM after each shift (at redline) will be different depending on the gear you're starting in.

[AlexTheGreek]

I think it comes down to meeting targets set by the market

MT: 0-60mph faster than a GTI
AT: 34mpg highway

In this way they can appeal to people that are looking for good fuel economy and people looking for good acceleration.

I think it's really smart.

[3MI Racing]

Originally Posted by wparsons

How did you calculate the RPM drop with the other final drive? Gear spacing shouldn't change with a shorter or taller final drive, just the speed you're going for any given RPM would change.

I made a quick spreadsheet which matches yours with the stock FD, but if I change the FD it doesn't change the RPM drop to the next gear, just the output RPM at the wheel (I didn't calculate speed, just wheel RPM).

You're right and I didn't even notice that when I quickly tossed it together. With that being said, I just looked into it and in my haste accidentally carried the 3.727 ratio into my 4.1 FD section for both the 'Start RPM' and 'RPM drop' columns.

With that being said:

[p1l0t]

Originally Posted by SpeedR

FR-S Gear Ratio Comparison
____AT ___MT __# differenc _% difference
1 _3.626 __3.538 __0.088 ____2%
2 _2.188 __2.06 ___0.128 ____6%
3 _1.541 __1.404 __0.137 ____10%
4 _1.213 __1 ______0.213 ____21%
5 _1 ______0.713 __0.287 ____40%
6 _0.767 __0.582 __0.185 ____32%
R _3.437 __3.168 __0.269 ____8%

Did they make the AT ratios higher so it would not be significantly faster than the MT cars?

Yeah auto and manual are swapped and I believe the final drive ratio is 4.1 in the MT unless it's different for the BRZ?

____MT ___AT __# differenc _% difference
1 _3.626 __3.538 __0.088 ____2%
2 _2.188 __2.06 ___0.128 ____6%
3 _1.541 __1.404 __0.137 ____10%
4 _1.213 __1 ______0.213 ____21%
5 _1 ______0.713 __0.287 ____40%
6 _0.767 __0.582 __0.185 ____32%
R _3.437 __3.168 __0.269 ____8%
F __4.100__4.100?__0.00_____0%


http://www.cusco.co.jp/en/pdf/86%20BRZ%20Gears_A4.pdf

http://www.cars101.com/subaru/brz/brz2016.html

[Icecreamtruk]

Holy thread necro! Yes he had the MT and Auto swapped, it was mentioned a few posts down after. The final drive is 4.1 for both auto and manual, but the ratio he was giving for R was for reverse not the final I believe.

[p1l0t]

Originally Posted by Icecreamtruk

Holy thread necro! Yes he had the MT and Auto swapped, it was mentioned a few posts down after. The final drive is 4.1 for both auto and manual, but the ratio he was giving for R was for reverse not the final I believe.

Yeah sorry I'm digging up stuff while I wait for mine to get built. (Factory order) These are like stop light gears, well with an overdrive which isn't a terrible thing. Minus the OD I think these ratios are taller than the 04 JDM STi driveline I swapped into my 03 WRX.

Sent from my SM-G920P using Tapatalk

[Icecreamtruk]

They are very tall indeed, but most of them are really close (except 1-2 and 2-3, damn those are apart). 6th gear is very tall on its own and a big drop from 5th, so long that the car cant pull it (maxing top speed aerodynamically rather than gear limited). A final drive swap makes it much better, at least for NA applications. For example, the car can completely pull all the way redline on 6th gear with a 4.88 or bigger FD, while tops out almost at redline with a 4.44 FD (will of course depend on elevation changes and wind direction and velocity).

[KoolBRZ]

How about the difference in how it actually feels to drive each, MT and AT? The MT puts a lot more attention on the drivers skill level. Clutching, rev matching, and the rpms at shift are very important factors in the MT experience. While in the AT, suspension, tune, and how much throttle is applied contribute far more to the AT experience. The rpms at shift, when using the AT manual mode, is even more critical than in the MT, since the AT engine has less mechanical advantage than the MT in every gear, less power in other words. The gear spread is wider, and it is harder to shift and keep it above the torque dip in the AT than it is in the MT. The AT really needs two power peaks, one for cruising at low rpms, and one for accelerating at high rpms. I highly recommend a UEL header for AT's to give them two power peaks for the best DD configuration. The tune of the engine is even more critical in the AT than the MT, since the AT has so much less mechanical advantage than the MT, so the AT drivers experience more of how well they're engine is running. I drive an AT, tune it myself, and I can tell the difference between clear sky's and cloudy weather just by how the engine handles running slightly richer or leaner. I've even played with different tunes for different weather, but thought that was a bit much. There has to be a really big difference in a tune for an MT driver to tell any difference with they're "Butt Dyno", but, an AT owner can feel the slightest difference in how they're engine is running, since they feel so much more of the engine running through the taller gears. With an AT, the drivers feels good about a manual shift when the engine pulls without bogging down after the shift. With an MT, the driver feels bad about a shift when it bogs down, because that means they just shifted from 2nd to 5th, instead of from 2nd to 3rd, because shifting without bogging down is just a normal shift with an MT.

[Icecreamtruk]

@KoolBRZ sumarized really well. Btw, I have a MT with EL headers, full exhaust and tuned. I can HEAR the difference when there's different weather (specially going from not only from wet/dry but hot/cold), but as you say, I cannot feel the difference on the butt dyno. I think I have been lucky enough to drive manual most of my life (since I was 16 in fact) and usually cars with worse trannies so I have luckily never miss shifted, on upshifts nor downshifts (i sux at rev matching tho, thats a story for another day).