Wanted to gather some collective wisdom on this

Comparing the specs of the 09+ Fit gearing (to the CR-Z):

1st: 3.308 (3.143)
2nd: 1.870 (1.870)
3rd: 1.303 (1.303)
4th: 0.949 (1.054)
5th: 0.727 (0.854)
6th: N/A. (0.689)
Reverse: 3.308 (3.307)
Final Drive: 4.62 (4.11)

Tires: 185/55/16 (205/45/17 )

Plugging this into a gear calculator yields the following:

Stock for stock, this graph illustrates better 1st-3rd acceleration with the Fit gearing (CRZ is in red).



Here, I equalized redline and compared both with 09 Fit sport wheels to level the playing field. I also swapped 4th gear from the CRZ to the Fit (CRZ is still in red). This might be a good idea for those who complain of sluggish freeway on-ramp acceleration or those who want a little more "oomph" when passing on the highway:




Here you can see the dramatic effect of lowering wheel diameter...this graph should be compared to the first graph. In this case I'm using my wheel setup - 195/50/15. This is like swapping in a higher FD (CRZ is still in red).




And here I've maintained the same smaller wheels, but now using the same redline. I also swapped 4th and 6th over from the CRZ. This would retain the sporty "city car" with excellent highway economy and improved 4th gear passing (CRZ is still in red).


My limited understanding is that shorter gear = faster acceleration, taller gear = better fuel economy, higher FD = faster acceleration. Thoughts? Criticisms? Anybody consider a gear swap? This might push Fit Hwy MPG consistently over 40.

On the otherhand...the taller gearing with the CRZ final drive would be good for those GD members who are boosted.

 

Awesome info! Thanks for posting

However, i find it ironic that such an educated post has a thread title using the word "tranny" in regards to what should be properly called a "transmission" or "gearbox". Sorry, i just hate it when people call it a "tranny"... It's like calling a differential a "diffy"

 

There's alot of info above...I guess to summarize, a good gear swap would be taking 4th (for performance) from the CRZ as well as swapping 6th in place of the Fit's 5th (for economy). 1st-3rd in the Fit is better for acceleration...

 

if only it were that easy lol

 

I thought taller was for economy and shorter was for acceleration... hence the difference in the AT vs MT Fits.

 

For somebody looking to install a LSD, this might be a perfect time to swap gears.

 

Fixed. Sorry, I meant higher numerically. Indeed...taller, as graphically depicted above, is for economy.

 

Okay, I guess it all comes down to terminology.

And right now, my head is about to explode from trying to sort it out.

I need to do some surfing about this later (not on my iPod).

 

Fixed that for you..... This is just another attempt to wring a little more out of this great little car


Regarding your previous comment, I was wrong....thanks for correcting.

 

First...nice graphs!

Taking the 4th gear from the RS here or CR-Z (same thing) would result in dropping out of VTEC on the upshift from 4th to 5th, not good if out on an actual circuit since your 4th would be limited to just 103mph compared to currently 114, guess all depends though on circuit layout and if even exceeding that speed anywhere. Though it would result in 4th being in VTEC upon shiting into at a redline of 7000(limiter) on the upshift as compared to being 200rpms short of VTEC with normal gearing, but falling out in 5th would hurt overall.

For me, I'm more intereted in keeping my 2-5 and swapping to the CR-Z 1st, it will increase speed in 1st by about 5km/h and bring 2nd 400 rpms closer to VTEC (4200 vs the 3800 now). Our 1st here is a 3.461 compared to your 3.308 and the CR-Z' even tighter 3.142. J's sells the 4.62 final from the Fit there to replace the 4.29, but really it is only good on very tight circuits and the top speed in each gear drops. 1st would go to 31mph from 34, 2nd 58 from 62, 3rd 83 from 90, 4th 103 from 111 and 5th 127 from 137 (theoretical top speed, drag and power is not going to allow the Fit to reach that speed really and the USDM top theoretical is 149). On top of that, the RS would drop a few more rpms on each upshift, 4th and 5th would still fall into VTEC, but 2nd and 3rd are slightly less and 1st drops a little over a 100rpms.

I think the best gearing in reality is the CR-Z 1st, RS 2-5 and the CR-Z (possible new RS) 6th tied in with the RS final of 4.29. I really believe this is why Honda went to the 6MT in the RS, our 5th at highway speeds (much lower, top legal is 100km/h) puts the revs at 3150rpms (not really high at all) but with the 6th gear it would drop 600rpms at 100km/h, very good for FE and for stateside with just say 75mph highway speed it would be at 3100 versus around 3500 now, again good drop for some FE gain.

 

Excellent points...this is exactly the type of discussion I was hoping to stimulate. The website I'm using (Fatboy Raceworks Graphical Transmission Gear Ratio Calculator) doesn't display RPMs...but this would be extremely helpful as we want to maintain vtec after 1st gear.

In this graph, I compare two Fits...both with smaller 195/50/15 tires...except the red plot utilizes 1st and 6th from the CRZ. This will drop you into 2nd at slightly higher RPMs but the consequence will be having to spend more time in 1st gear waiting for the revs. If your Fit has been modded with intake/exhaust and subsequently lost some low end torque...this might not be the best idea since the taller gear (lower numerically) would climb through the revs more slowly.



Here is the same gear swap except with stock 185/55/16 tires. Again, the red plot utilizes 1st and 6th from the CRZ. Notice the speed difference coming out of 1st.

 

I have a question... is this all assuming that the Fit's engine will have enough torque to push the rpms up as fast as it's own gearbox or the CR-Z's "dual" engine (gas + ima).

I remember seeing other members mention that whenever someone else mentions doing a trans swap.

 

look at custom gear'd d and b series hondas. they dont just put a tall 5th gear in there.

 

Goobers the Fit will have enough low end to work with the gearing. Just look at the difference already between the North American model and the one available here in Japan. We here have a much tighter 4 and 5 for a more sports oriented feel, but the North American model makes up for that somewhat by having the 4.62 final drive versus our 4.29.

Really what this comes down to is what Honda releases with the new RS and possibly Sport model in the US with the 6MT. If it is using the exact ratios of the CR-Z, by exact I mean the final drive of 4.111 we'll know for sure. I'm almost certain it will retain 1-6 ratios of the CR-Z, since 2-5 are already the same between the current RS and CR-Z. Honestly though as I stated, I belive the best gearing for the Fit in a mekatuned(NA) configuration is the CR-Z gearing 1-6 and the current RS 4.29 final.

And one way to get through the revs quicker...a lighter flywheel and clutch combo.

 

So this never really made sense to me. I could see how a lighter flywheel/clutch would allow you to rev the engine faster at idle and during gear changes. But, I don't see how this would allow the engine to increase RPMs while engaged...b/c this requires the car to move forward (b/c speed and RPMs are related).

Does this simply allow the engine to rev faster...but the actual speed of the vehicle is less than with the stock clutch at identical RPMs