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.

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?

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.

https://ecomodder.com/forum/attachme...1&d=1588821208

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

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.

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 wouldn't do a transmission swap unless it was to a manual.

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.

Yeah I think a manual would be the most reliable

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.

Just because they're new doesn't mean they are better.
CVT does no favors for the consumer.

Maybe the CVT transmissions are just more delicate and don't tolerate abuse like ignoring the fluid for 200K miles or changing directions while moving. I don't know how reliable the CVT would be when driven and maintained correctly, but my opinion is that a lot of decent products get a bad reputation simply because they are owned by an idiot who abuses it or has unreasonable expectations and I wouldn't be surprised if that is the case with these CVTs as well. People complain about Honda autos all the time, but I got 243K miles out of mine before it failed, likely because it has been maintained correctly since it was new and has never been abused. Getting nearly 1/4 million miles out of a transmission isn't too bad IMO.

Yeah. That's wise skepticism.

CVTs are still often pointed out to be more suitable to lower torque outputs. But anyway, they are substantially different from a traditional geared automatic. It's a matter of understanding its operating principles. I'd be more concerned about the integration between the ECU and the electronic controllers of the CVT itself.

Thank you. I'm not worried about the ECU's integration, my plan is to get a CVT ECU and harness and everything will plug right in.

Why so? Curious.

I'm curious about this as well. Presuming a CVT is reliable, and I see no reason why it couldn't be, I see it as a good option for someone who wants the fastest and most fuel efficient automatic transmission possible. I'm one of the people who doesn't hate the feel of a CVT, likely because I understand the undeniable benefits that they provide.

I can't speak for the HX CVT. I can speak for the Insight CVT, however.

-Generally speaking, an Insight CVT will get 55-60mpg where a manual would be getting 80+. Part of this is due to the manual having a higher top ratio.
-The CVT Insights purportedly have better acceleration down low, where the manual doesn't have many ratios to choose from. They're favored for autocross.
-The CVT is considerably heavier than the manual - something like 65lbs vs 180lbs
-The CVTs have a reputation for early failure. The manuals can last 500k+ miles, whereas it isn't unheard of to see Insight CVT failures before 150k even with 30k fluid changes, and a 250k mile CVT is a rare beast indeed. And, it isn't just one point of failure either.

This CVT is a contemporary to the HX's, being produced from 2000-2006. I would not buy a CVT Insight, if that helps.

That is good to know, thank you for the information! One reason I wanted to go with a CVT is that I can floor it at pretty much any speed and get maximum power. Unlike a manual, it holds the RPMs right at the power peak at full throttle, has a wide range of ratios, and still allows me to cruise down the highway at a low RPM.

With the EX 5 speed (the one I would probably go with) I would be at about 3200 RPM going 70, but I could drop that to around 3000 if I change the 5th gear to the DX/LX gears. With a CVT I could cruise at 2500 RPM going 70 and still have maximum power available at almost any speed.

It's a shame there were no 6 speed D series gearboxes.

My first reaction is to wince, because CVT. It's a great idea but mechanically, nothing beats an actual box of gears. It's the old rule that In theory, there's no difference between theory and practice. In practice, there is.

Taller gearing only matters in lowest gear and highest gear. It's great in fifth, and in first... at least with an MT you're already in first, while the guy next to you is hoping his TCM helps him out a bit. In between low and high, it's your responsibility to juggle power output and gearing. If you want to simply floor it and have the power, buy an electric. It's the right tool for that job.

Until I get a Tesla, I'm in a manual. The limitations of gas engines and my requirement for responsiveness dictate it. If I need to downshift before stomping, so be it- I'll still get the results I want faster and better than an AT or CVT. When I finally get an electric, I can finally give up babysitting the powertrain.

I agree that gears are better and I prefer the feel of a solid connection over a CVT or auto with an unlocked torque converter, but I don't hate the feel of a CVT and I can live with the less direct feel if it provides a tangible improvement in performance and efficiency, but a CVT is heavier and isn't nearly as mechanically efficient as a manual so in practice a manual may be the fastest and most efficient.

As for the gearing, unfortunately things aren't that simple. Transmissions that are geared taller often have wider spaced gears, so the engine will be at a lower RPM after a shift and therefore acceleration will suffer. For example, let's say I am racing someone from a stop. With an EX transmission, I could reach 36 MPH in first gear and be at 4120 RPM after I shift to second. With the taller geared HX transmission I could reach 37 MPH in first, almost the same. However, when I shift to second, I would be down to 3451 RPM. That's going to hurt acceleration.

Another scenario- Let's say I am getting onto the highway at 40 MPH. That's too fast for first gear on either transmission, so the lowest gear I could choose would be second. With the EX transmission I would be at 4578 RPM, pretty decent. However, with the HX transmission, I would only be at 3731 RPM. The difference in power between 4600 RPM and 3700 RPM is dramatic with my engine.

With a CVT I could floor it going 40 and almost instantly be at 6K plus RPM, which is a dramatic difference compared to the 4600 I could be at with a manual and also drop my cruising RPM significantly. Best of both worlds! In theory anyways. In reality the manual transmission is going to be the clear winner if the CVT takes a crap and leaves me on the side of the road. Also, considering the superior efficiency and lower weight of a manual transmission, the difference in real world performance and efficiency differences between the manual and the CVT may not be as much as I think.

It takes a while to understand a CVT won't operate in the same way a traditional automatic does.

I'm not sure what exactly you mean by that? I have driven cars with CVTs before and I don't mind it the feel, it is more different than bad in my opinion. I have never owned a car with a CVT though so I may not be understanding what you are saying. Also, all 2 of the CVT cars I have driven have had a torque converter instead of a start clutch, so maybe that's a different feeling.

It might be due to our different perspectives, notice we're from different countries and only in recent years the automatics became more widespread here in Brazil. Some people who have previously driven cars with other types of automatic transmission might not expect the feeling of a CVT once they drive one for the first time. Getting used to the lack of engine-braking while driving downhill is also more critical for someone who also used to drive manuals more often than automatics.

Oh okay that makes sense. Honda's CVTs have 3 different modes: D, S, and L. Mode D basically chooses the highest gear possible for the best efficiency. Mode S is sort of a sport mode and keeps the RPMs a bit higher than mode D for better response and more engine braking. It also makes the trans more eager to downshift when hitting the gas for a more sporty feel.

Mode L is the mode I am confused about though. I know that L stands for Low, but it is unclear to me whether mode L will simply lock the transmission in the lowest "gear" possible and not allow it to upshift or whether it just sets a higher target RPM than D or S. In other words, what happens if you put it in Mode L and floor it from a stop? Will it just max out and bounce off the rev limiter or will the trans continue to upshift as the car accelerates? If anyone has an answer to what exactly Mode L does please let me know, I would really like to know and no one seems to have an answer. Thanks

the civic GX is a CNG engine

Are the 0-60 or 1/4 mile times better with a CVT Civic over the equivalent manual Civic? I don't feel like looking it up myself. But from what I remember, both the MPG and acceleration of the CVT version fell somewhere between the auto and manual versions.

https://www.zeroto60times.com/vehicl...-60-mph-times/

^ According to this, the Civic Hybrid is faster to 60 with its tall manual transmission than with the CVT - 11.1 vs 12.6 seconds. I don't see any other obvious comparisons, but that manual transmission is the tallest available in that generation.

I can't find the 0-60 time for the Civic HX CVT, but I found this video of someone doing 0-100 KPH in a Civic Ferio with the same engine I have (the EX VTEC engine) and a CVT and I timed the 0-60 MPH at around 8.8 seconds, faster than the short geared EX 5 speed. No idea what the weather conditions were like or anything, but it's the best I could do. https://www.youtube.com/watch?v=Cqr-FxrjRn8

With the tall geared 5 speed I found that the HX does 0-60 in 10.2 seconds with a quarter mile time of 17.7 seconds. The shorter geared LX 5 speed (with 1 less HP) does 0-60 in 9.3 seconds with a quarter mile time of 17.2 seconds. The short geared EX 5 speed with 11 more HP than the LX and 10 more than the HX does 0-60 in 9 seconds with a quarter mile of 16.5 seconds.

Unfortunately the LX, HX, and EX all have different engines, but the gearing seems to be a significant factor since even the LX with 1 less HP than the HX still did 0-60 0.9 seconds faster with a 0.5 second faster quarter mile. I wish I could find a comparison

EDIT: I found that the 0-60 time for a Civic Ferio 1.7 5 speed is 9 seconds with a quarter mile time of 16.8 seconds, the auto version does 0-60 in 10.6 seconds (slow!) with a quarter mile time of 17.6 seconds, and the CVT version does 0-60 in 9.4 seconds with a quarter mile time of 17.1 seconds. All these cars have the same 1.7 VTEC engine. Here's where I found the specs: https://www.automobile-catalog.com/m...edan/2004.html

It took that car until almost 100kph to reach 6000RPM India lowest gear. Meaning if you punch it at 40mph (~65-70kph) it wont jump to 6K. Having driven all three mentioned types of transmission, I definitely prefer manual. Want response? Downshift. The manual can be geared to take advantage of whatever traits you want

As an added bonus, the manual doesn't shift based on load, it shifts when you tell it to. So it's already in the right gear when you do stomp on it.

Right! No waiting for the PCM to say, “alright throttle is down, we want second gear” and the trans to go “what, are you sure?”

I think the computer's programming is poor since the transmission is mechanically capable of redlining the engine at any speed of 36 MPH or more since its lowest ratio is 2.49 with a final drive of 5.81. I don't know why its programmed to start upshifting before the engine reaches its power peak with the throttle wide open, seems stupid to me. I wonder what it would do if put in L while driving at speed? Or floored from a stop in L?

That is true, some autos have a very noticeable lag when flooring it. Compared to most of the automatic cars I have driven mine actually downshifts pretty quick when mashing it. I wonder how much time it takes the CVT to downshift

And that's after the PCM and its friends finally agreed that third was worth a try. :D

It might depend on terrain conditions and driver's behavior, just like any other automatic transmission with fuzzy-logic electronic controls.


It might be just like downshifting in a manual or in an automatic with sequential mode. Depending on the difference between the low ratio and the regular, you might experience the engine increasing the RPM in order to keep the speed, or it may slow down with a less noticeable impact on RPM.


Then it might be more likely to retain lower ratios for longer, and become more rev-happy.

Surely the shifting logic would depend on terrain conditions and driver behavior. However, with the throttle wide open, maximum acceleration is clearly desired above all else, therefore the ECU should adjust gearing to hold the engine's RPM at the power peak, 6300 RPM in the case of the vehicle in the video I posted. This means not upshifting until 6300 RPM or close to it is reached regardless of the mode the transmission is in.

I can't imagine that the engineers who designed these transmissions didn't know that, I think they designed it this way so it feels more like a traditional auto instead of just holding one specific RPM. Sort of like the stupid "simulated shifting" they do with CVTs these days where they shift it in steps, which defeats the entire purpose of having a CVT to begin with.

I asked the guy who made that video what happens if he floors it from a stop in L but he said he never tried it and he sold the car since making the video so he can't retest it.

I'm not so familiar with the CVT behavior in a Honda, but anyway, now with all that emissions and fuel-efficiency concerns this may be the reason for the cars with a CVT being tuned the way they are. Even in a certification test won't reflect real-world usage, there is no way to overcome it without the risk for the automaker to be under a scrutiny similar to what nearly led Volkswagen to bankruptcy due to the Dieselgate.

You are probably right. I wonder if certification tests include any full throttle operation? I wouldn't think they would since no one floors it because they want good mileage, but we're talking about the government here so we can't expect their "logic" to make any sense.