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Old 06-30-2013, 02:23 PM   #3 (permalink)
Cyborg ECU
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Join Date: Mar 2011
Location: Coastal Southern California
Posts: 6,297

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
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Originally Posted by WD40 View Post
Thanks for the info California98Civic.
So now I need to look for a 88-91 CRX HF D15B6 5 speed transmission ...
I read that the 88 has different spline, so it would need a matching clutch.
Other years match the VX clutch.
The difference in gearing would make 5th gear at 1700 RPM doing close to 56 vs the current 1900 RPM at close to 56.
That should pay for itself pretty fast as I currently get approx. 80-95 MPG at 56.
I see a few on CL in the USA, but none in Canada yet, but I will be searching.
If that chance does not emerge because of costs related to getting both the trans in good condition and a clutch you could also look into whether the 4th gen HF final drive can swap into the fifth gen VX tranny. Now that I know the VSS gears in the 4th and fifth gen spin the same, I would bet the speedo gears are the same too, as they are for fifth and sixth gen Civics. Since the Cali HF trannys had the same final drive as the VX, I wonder if the 2.95 final drive from the VX would swap. That would give you nearly all of the RPM change you describe. It would be a bigger job maybe, but could be interesting too.
See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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