6speed mpg

[anti-hu]

i know there's 1 maybe 2 ephatchers who did a 6speed swap (racerdre and i dont remember who else) well anywho. I was wondering what your mpg is now that you have a 6speed. how many miles to the tank you get?

[TrippZ]

s800racer did it too

[DavidT]

Probably pretty close to the same because their 6th gear is the same ratio as our 5th gear, only the final drive is different so they're revving alittle lower in 6th than we are in 5th. Here are the ratio charts from Honda:

Si:
1st 3.062
2nd 1.769
3rd 1.212
4th 0.921
5th 0.738
Reverse 3.583
Final Drive 4.764

RSX-S:
1st 3.267
2nd 2.130
3rd 1.517
4th 1.147
5th 0.921
6th 0.738
Reverse 3.583
Final 4.389


So lemme do that math. If both the RSX-S and the Si used 24-inch total diameter tires traveling @ 70 MPH, that means the Si will be do'n about 3448.65 RPMs in 5th gear and the RSX-S will be revving about 3177.19 RPMs in 6th gear. All because of the .38 difference in the final drive. So in average they will probably get 1 or 2 MPG more in a long steady drive, in normal driving situations (especially city) there won't be a difference at all.

[jandetuning]

I haven't had a long trip that I can compare against the 5 speed, but I have lost around 2-3 mpg in the city due to more spirited driving.

[anti-hu]

i do not know very much about transmissions but if you could answer these questions i would appreciate it :)

is it possible to just switch out the final drives for better mpg on highway?

does switching the final drive do anything to the other gears?

have not purchased a vehicle yet, joined ep hatch to do some research on the si.

trying to decide right now between the si and the ex accord sedan. im sure my decision will come down to the cars insurance rates.

[Surprise]

Is it worth the possibility of voiding your transmission warranty for a few extra MPG. Even if you did see an increase of mileage with the new transmission you wouldn't see a net gain of cash for atleast 30,000 miles. You should have bought the Civic HX or Hybrid if you wanted good fuel economy.

But yes as far as I know you can change the final drive ratio, it would have the same effect as putting tires with a larger diameter on your car resulting in slower acceleration but better highway fuel economy.

[DavidT]

Originally posted by anti-hu

is it possible to just switch out the final drives for better mpg on highway?

does switching the final drive do anything to the other gears?

Yes it is possible to switch out the final drives. EGk20hatch has a RSX-S 6spd with a TSX final drive (Basically the same as our final drive). That means he has even shorter gearing across all six gears. If you switch the Type S final drive into our EP's you'd have longer gearing (Meaning you'd be able to go to a higher speed in each gear) but you'd loose acceleration. There are always trade offs.

[BarracksSi]

So, a Type-S motor/tranny with a TSX final drive will give the fastest acceleration with US-stocked parts?

FIWIW, the Motor Trend comparison test back in 2002 between the Si, Focus SVT, Sentra SE-R, and Golf 1.8T actually had the Si second fastest to 50 MPH by a couple hundredths to the Golf. That darned 2-3 shift at about 56 MPH wrecks the common 0-60 time that everyone pays attention to.

Still, if I went through with it, I wouldn't be happy unless I went with the JDM ITR motor.