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Old 05-06-2020, 11:04 PM   #2 (permalink)
Cyborg ECU
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Join Date: Mar 2011
Location: Coastal Southern California
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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 EcoCivic View Post
Hello everyone, I am wondering what y'all think of replacing my 2005 Civic's 4 speed auto with a CVT from a Civic Ferio, EU3, or HX. I am wondering what effect this swap would have on MPG and acceleration compared to the 4 speed auto.

I already looked to see what I would need to change to swap to a CVT and I found that the swap would actually be pretty simple. The sub frame, axles, and mounts are the same, so the CVT would bolt right in just like the auto did. Sweet! The only things I would need to change would be the ECU and wiring harness and maybe the shifter and shifter cable, so nothing too bad or expensive. Much simpler and cheaper than converting to a manual transmission since I wouldn't have to install a clutch pedal and lines, or replace my sub frame, axles, and front motor mount like I would need to if I converted to a manual transmission.

The main concern I have is I have heard that CVTs are generally pretty delicate as is and my engine is significantly more powerful than stock. The most powerful car this transmission came in is the Civic Ferio with the D17A engine (what I have) making 128 HP, and I have done some mods to mine to get it above 150 HP and I don't know that the CVT can handle that much power, it might slip the belt or something?

So my questions are:
1. Could this CVT reliably handle 20-30 HP more than stock?
2. How much could I expect my gas mileage to improve?
3. How would acceleration times compare to the stock 4 speed auto or a 5 speed manual? The CVT can hold the engine at its power peak for the best acceleration, but the manual trans is lighter and more efficient. I don't think this CVT is particularly efficient.

Thanks in advance, I am looking forward to hearing your opinions on this.
I would caution against swapping in an HX CVT, as they had a terrible rep for failure. Perhaps the initial install would be simpler than installing a manual, but the second and third CVT installs would be a pain. Don't do it. You could easily increase the size of your wheels and tires some to get a gearing advantage over stock. Not a great one but something. What are the ratios on a 2005 Civic auto trans?
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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The Following 3 Users Say Thank You to California98Civic For This Useful Post:
Ecky (05-07-2020), EcoCivic (05-06-2020), Fat Charlie (05-07-2020)