Swapping Trans in the Motor-Rolla

[jeff88]

I've pretty much abandoned the idea of a full tranny swap. What I'm considering is swapping just the first two gears for shorter ones. I want to get into the third and fourth gear ASAP and (correct me if I'm wrong), shorter first and second gear will get me up to speed faster, making the ECU switch gears sooner. Am I wrong in that thinking? If so, than this whole idea is definitely nailed inside a coffin.

As an aside, just for the first and second gears, what puts more torque to the wheels, shorter or taller gears?

[some_other_dave]

Shorter gears always put more torque to the wheels.

I don't think you want shorter gears for the first couple of positions. They will tend to run the engine at higher RPMs, which is exactly what you don't want for fuel economy.

If you want them for faster acceleration, that's a different story--but that's not efficient.

-soD

[jeff88]

Maybe I will put this project behind me then. I am indeed trying to get some better acceleration. I want to get into 4th gear as quickly as possible. (Faster to tallest gear, faster to highest MPG cruising.) I wonder how I can do that without reducing my FE?...

[Occasionally6]

Originally Posted by jeff88

O6- I still cannot find a full bsfc map for the 1zz. It's certainly holding me back, so I can't fully understand my car. Any ideas on where I can find it or at least start my search, other than Google?

Find what you can for engines with a similar spec. to yours. They are all pretty similar. For qualitative purposes that will help. Lines of constant power can be calculated if you have BMEP or torque and rpm.

Availability aside, you can swap TCs?

Within the same trans. and engine family, likely. Any ECU or TCU might object if there are fault code parameters for difference between engine and trans. rpm though.

Originally Posted by jeff88

I've pretty much abandoned the idea of a full tranny swap. What I'm considering is swapping just the first two gears for shorter ones. I want to get into the third and fourth gear ASAP and (correct me if I'm wrong), shorter first and second gear will get me up to speed faster, making the ECU switch gears sooner. Am I wrong in that thinking? If so, than this whole idea is definitely nailed inside a coffin.

Swapping some (lower) ratios in a planetary gear set is not possible without also affecting the taller ones.

Is it an issue though? Are you using WOT (getting into closed loop enrichment) to accelerate at your desired rate now? To put it another way, are you accelerating slower than you would like to, while accelerating with the engine near it's peak efficiency load and speed? If not, shorter ratios won't help.