Official BRZ MPG Numbers. Big Gear Ratio Differences?

[serialk11r]

10 years? :O whaaaaa
So what does it mean if an automatic car is in highest gear, and your foot is on the pedal such that pushing it any further will cause the car to downshift, yet the car doesn't have enough power to maintain speed with your foot in that position... I have serious doubts that the engine doesn't actually have enough power available in 5th gear. I'm guessing it's probably a compromise they strike since you want the transmission to downshift when you really do need the power, yet they're not going to try to max out (or nearly max out) engine torque in each gear before it shifts as that would be too late.

[arghx7]

^ It's all based on the mapping inside the control modules and whatever the engineers decided to do for a given application. There's always a balancing act of fuel economy requirements, emissions requirements, driveability requirements, and component protection. Sitting there in top gear with the throttle open could result in high exhaust temperatures, which degrades components or requires enrichment to keep the cat from heating up. Enrichment will hurt fuel economy and emissions.

If you run a big business and buy a gazillion fleet vehicles (vans or maybe pickup trucks) you could be looking for a vehicle calibrated to be sluggish and less likely to downshift. Sluggish might mean 1 extra mpg multiplied by a gazillion miles driven, meaning a lot of money saved. A regular consumer might want something more responsive.

[aLiskov]

@arghx7 Thanks for the schematics. Really helpful and interesting. I read all of the responses and I agree with @Jordo!, it really comes down to test driving the car and getting a feel of what better suits your personal needs. I'm gonna test drive the manual and hope that I end up liking it more than the auto, because I always wanted a light RWD manual car. As far as the mpg goes, I agree that manual can be just as economical and sporty at the same time.

[arghx7]

^ It's entirely possible that the automatic just happens to work really well with the way the EPA calculates the fuel mileage. Real world fuel economy may very well be closer between the two transmissions.

[cossey]

the two big differences between manuals and autos on the EPA test are:

Manuals have prescribed shift points (ie you shift to a certain gear at a certain speed) which don't really take into account gear ratios so short gear cars end up running at higher revs and are less efficient. Autos can use their own shift strategy

the gear ratios are much long on the auto (for the auto 4th is a straight through where as it is in 5th for the manual) this allows the higher speed portions of the test to still be run at low revs. This also means that the manual will be faster on a track as it can keep at peak revs for power better.

as mentioned above auto boxes have much lower losses than before so now the extra inefficiency in terms of drive train losses is less than the fuel savings from running the engine at a better BSFC point.

This is also the main reason why in Europe manual gearboxes are being dropped on a lot of sports models because of the fuel consumption legislation (BMW M5, Audi RS4, Ferrari, soon to be Porsche 911 etc)

[dhpinoy]

I thought manual/stick gets more mpg than automatic? How come Auto has more? I might be wrong but I thought thats how it worked.

[Lonewolf]

No gearing info yet?

[7thgear]

Originally Posted by dhpinoy

I thought manual/stick gets more mpg than automatic? How come Auto has more? I might be wrong but I thought thats how it worked.

for fucks sake, did you not bother to read the technical discussion posts right above you?

[Lonewolf]

...

[Lonewolf]

...

[serialk11r]

Originally Posted by Lonewolf

No gearing info yet?

...plenty of gearing info since months ago.

[Khyron686]

Just throwing this out there, that even if the manual was 10mpg worse and 30hp down on power, I'd still have the manual on a car like this.

[Lonewolf]

Originally Posted by serialk11r

...plenty of gearing info since months ago.

Thanks for the help. What about the info that matters? Rear axle ratio for the auto/manual?

[serialk11r]

Manual transmission has same ratios as the S15 Sylvia (6th gear is 0.767), auto has same ratios as IS250 or something (evenly spaced, starts at ~3.6-7 or something, 6th gear is 0.582, 4th is 1.000), both are 4.100 final drive in the US. Markets with the stripper model have a 3.727 open diff option. The 6th gear in the manual transmission revs 30% higher than the 6th gear in the auto, which a lot of people are kinda upset about.

It's been posted at least 20 times already...it came out with the BRZ specs/options brochure in December/January ish. You seem like you usually post good stuff, I was hoping you'd find it in a search.