This article will be technically geared towards the CRX and other Civic models from 1988-2000. However, the general implications of these changes are applicable to almost any make and model of car or truck. I will detail my own changes as well as cite a few cases of fellow members from my primary forum: ecomodder.com as well as give resources that will allow you to make your own decision on the matter. While I will be primarily discussing the transmission that will give you the best mileage, there are many forms your gearing can take to meet all of your goals.

First things first, what I did with my CRX. I began with an automatic and could barely squeeze 40 MPG out of it. Needless to say I was very frustrated with its performance. Not only did I hate the gas mileage, I hated the way it drove. So, I embarked on the mission to begin my auto to manual swap. That’s a whole other ordeal, which I will discuss in a dedicated article, but suffice it to say that when I weighed my options I chose the most fuel efficient transmission I could. I wanted the most bang for my buck, and I got it; I picked the transmission up for free from a www.honda-tech.com member. In the end I’ve averaged ~51 MPG over my last two tanks with the stick shift, and I’ve loved every minute of it.

On the technical side of things there are 5 basics transmissions found in 88-91 Honda Civics: the auto, the DX/LX, the Si, the HF, and the STD.

• The automatic is just that, automatic. It gets terrible mileage and doesn’t have much potential. If this is what you have a swap is highly suggested for greater gas mileage. Even with the most fuel economy-minded transmission the car will seem to have more power. If you can’t drive stick, learn; Hondas are very easy cars for new stick drivers.
• The DX/LX manual transmission is basically the middle of the road; it is basically the same as the Si transmission with a lower final drive ratio.

The Si transmission has the shortest gearing of an US civic transmission from this era. As far as fuel economy is concerned this transmission should be avoided, it will give you ~3,000 RPM at 65 MPH.

• I have the HF transmission in my car. It was built for fuel economy and it certainly delivers. The gearing is longer than any other car you’re ever likely to drive and delivers a healthy 1700 RPM at 55 MPH on the highway. Without this transmission I doubt I could so easily hit 50 MPG.
• The STD was the super economy Civic, and as such received a 4 speed manual transmission. This thing is just a step above an automatic and should be eliminated at all costs!

To compare on the technical side of things, here are the gear ratios from the four most used options you will have:

For those of us with newer Civics refer to the following tables (gears from these two tables are mixable but not final drives or complete transmissions):

For those of us with even newer Civics use this table:

With these go to this gear ratio calculator and take a look at cruising RPM and shift points that various transmissions will afford you.

There’s not much more I can do to arm you with information, so at this point I will give you some statistics from my own swap and some other information I’ve dug up over the ages. Here is what my gearing looks like across the board (you can see how high it is, my transmission top speed is something like 220 MPH): Now, you must be thinking that with such a transmission acceleration would be brutal, but this is not the case either! My shift points are as follows:

• 1 –> 2; 1500 RPM, 8 MPH
• 2 –> 3; 1500 RPM, 20 MPH
• 3 –> 4; 1250 RPM, 25 MPH
• 4 –> 5; 1250 RPM, 30 MPH

That leaves me in 5th gear accelerating from 30 MPH. Sure it’s slow, but the fuel economy is amazing, so I don’t mind. My lifetime automatic mileage was 35.8 MPG, and so far I have managed 51.2 MPG with the 5 speed CRX HF transmission; quite the difference, if I don’t say so myself (40%, beat that, acetone)! You can check out my online gaslog here at www.ecomodder.com.

Another forum member, named Darin (MetroMPG) swapped to a transmission with longer gearing and saw what he approximates as a 5-6% gain. This may not seem like much, but when you’re pumping out 75 MPG tanks and 117 MPG segments, it’s nothing to scoff at. You can check out his findings and process in his swap thread here.

I also helped another member upgrade from his 4 speed STD transmission to a 5 speed CRX HF transmission. Not only was the swap a lot of fun, but look at his gaslog. His driving isn’t exactly consistent and he doesn’t drive for great mileage, but the improvement is there. He’s gone from 38.8 MPG before the swap to 43.9 MPG after, an improvement of 13.2%. You can also see a correlation between engine off coasting and gas mileage, but that’s something for another article.

There will be more success stories to come! If you have any questions about parts, prices, or procedure feel free to email me and I’ll give you all the advice you need.

PS: If you’re wondering how to determine which transmission is which for EF Civics/CRXs, check out this picture:

Trackback URI | Comments RSS