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Old 05-06-2020, 10:49 PM   #1 (permalink)
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CVT swap? (Into 2005 Civic, replacing 4-spd auto)

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.


Last edited by MetroMPG; 06-11-2020 at 10:12 AM.. Reason: (added info to title)
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Old 05-06-2020, 11:04 PM   #2 (permalink)
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Quote:
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?
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Old 05-06-2020, 11:14 PM   #3 (permalink)
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Here they are... So what you gain from a CVT is obvious, but how you drive will affect your returns. The CVT does not look a lot taller than the AT or the MT at freeway speeds.

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Old 05-06-2020, 11:24 PM   #4 (permalink)
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Quote:
Originally Posted by California98Civic View Post
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?
Thank you for the information, I don't want an unreliable piece of crap. I wonder how many of those failures were caused by lack of mainline or abuse though. I'm not interested in taller wheels and tires as that would negatively affect acceleration and I have nice light alloy wheels that I really like the look of.

My transmission is from a Honda Stream (a small station wagon) so it's geared shorter than the stock one for more torque since its from a much heavier vehicle. Despite the shorter gearing, I didn't seem to lose much MPG and acceleration has improved quite a bit. Here are the gear ratios of my transmission compared to the stock one
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Old 05-06-2020, 11:36 PM   #5 (permalink)
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Quote:
Originally Posted by California98Civic View Post
Here they are... So what you gain from a CVT is obvious, but how you drive will affect your returns. The CVT does not look a lot taller than the AT or the MT at freeway speeds.

Thanks. The gearing is taller than my 4th gear (0.71 with a 4:36 final drive).

The main benefits of a CVT would be:
1. Potentially better acceleration since it can hold the engine at peak power
2. More efficient acceleration since the RPM can be kept lower and it has no torque converter to slip
3. Lower cruising RPM. I would drop my RPM at 60 from around 2600 to 2200 if I get an HX, EU3, or Ferio CVT, which could possibly result in improved highway fuel efficiency but I'm not sure about that.

The HX CVT has a final drive of 5.81 with a gear range of 2.47 to 0.45. Same as the GX CVT but with a lower final drive.
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Old 05-06-2020, 11:42 PM   #6 (permalink)
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Ok. I see. Wanna try something radical? There have been efforts to swap MTs across the seventh gen and sixth gen Civics. It seems like they can bolt up, which also means a 5th Gen CX/VX transmission possibly bolts to the seventh gen Civic. There would be more fabrication, including a work around the imobilizer, but the 5mt CX/VX trnamission has a 3.25 FD and a 0.710 5th gear. Tall!
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Old 05-06-2020, 11:57 PM   #7 (permalink)
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I wouldn't do a transmission swap unless it was to a manual.
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Old 05-06-2020, 11:59 PM   #8 (permalink)
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Quote:
Originally Posted by California98Civic View Post
Ok. I see. Wanna try something radical? There have been efforts to swap MTs across the seventh gen and sixth gen Civics. It seems like they can bolt up, which also means a 5th Gen CX/VX transmission possibly bolts to the seventh gen Civic. There would be more fabrication, including a work around the imobilizer, but the 5mt CX/VX trnamission has a 3.25 FD and a 0.710 5th gear. Tall!
I'm not interested in a ridiculously tall geared transmission either as that would negatively affect acceleration. I know that any D series transmission will fit any D series engine, so bolting it to the engine shouldn't be a problem. The mounts and the axles may be different though, not sure.

I don't have to worry about the immobilizer because my JDM ECU doesn't have one. Besides, just changing the transmission isn't going to affect the immobilizer.
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Old 05-06-2020, 11:59 PM   #9 (permalink)
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I wouldn't do a transmission swap unless it was to a manual.
Yeah I think a manual would be the most reliable
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Old 05-07-2020, 12:16 AM   #10 (permalink)
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Quote:
Originally Posted by EcoCivic View Post
I'm not interested in a ridiculously tall geared transmission either as that would negatively affect acceleration. I know that any D series transmission will fit any D series engine, so bolting it to the engine shouldn't be a problem. The mounts and the axles may be different though, not sure.

I don't have to worry about the immobilizer because my JDM ECU doesn't have one. Besides, just changing the transmission isn't going to affect the immobilizer.
Huh, I thunk you are right. I thought I had read over on d-series.org about a guy swapping a D17 trans onto a D16 block and working around the immobiliser but now I can't find that problem cited. A 1996-00 HX would be next tallest with the 3.722 FD. Then maybe the DX/LX with like a 4.011 FD or something.

Definitiely, by rep, manual is more durable than the CVT. But maybe you'll not abuse it and maybe with maintenance it ain't so bad.

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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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