Choosing a Fuel Economy Transmission
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: www.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:
|
|
Civic STD |
CRX HF |
Civic/CRX
DX/LX |
Civic/CRX
Si |
|
Clutch Type |
Cable
|
Cable |
Cable |
Cable |
|
Trans. Code |
L3 |
L3 |
L3 |
L3 |
|
First |
3.250 |
3.250 |
3.250 |
3.250 |
|
Second |
1.650 |
1.650 |
1.894 |
1.894 |
|
Third |
1.033 |
1.033 |
1.259 |
1.259 |
|
Fourth |
0.823 |
0.823 |
0.937 |
0.937 |
|
Fifth |
- |
.694 |
0.771 |
0.771 |
|
Reverse |
3.153 |
3.153 |
3.153 |
3.153 |
|
Final Drive |
3.888 |
2.95/3.25
(CA) |
3.888 |
4.250 |
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):
|
92-95 Civic DX/LX/S |
92-95 Civic EX/Si |
92-95 Civic CX/VX |
96-00 Civic LX/DX |
96-00 Civic CX/HX |
96-00 Civic EX |
Clutch Type |
Hydraulic |
Hydraulic |
Hydraulic |
Hydraulic |
Hydraulic |
Hydraulic |
Trans. Code |
S20 |
S20 |
S20 |
|
|
|
First |
3.250 |
3.250 |
3.250 |
3.250 |
3.250 |
3.250 |
Second |
1.761 |
1.900 |
1.761 |
1.782 |
1.782 |
1.909 |
Third |
1.172 |
1.250 |
1.066 |
1.172 |
1.172 |
1.250 |
Fourth |
0.909 |
0.909 |
0.853 |
0.909 |
0.909 |
0.909 |
Fifth |
0.702 |
0.702/0.750 (HB) |
0.702 |
0.702 |
0.702 |
.702 |
Reverse |
3.153 |
3.153 |
3.153 |
3.153 |
3.153 |
3.153 |
Final Drive |
4.058 |
4.250 |
3.250 |
3.722 |
3.722 |
4.250/4.058 (HB) |
For those of us with
even newer Civics use this table:
|
01-05 Civic DX/LX |
01-05 Civic HX |
01-05 Civic EX |
Clutch Type |
Hydraulic |
Hydraulic |
Hydraulic |
Trans. Code |
|
|
|
First |
3.462 |
3.461 |
3.143 |
Second |
1.870 |
1.750 |
1.870 |
Third |
1.241 |
1.166 |
1.241 |
Fourth |
0.970 |
0.857 |
0.970 |
Fifth |
0.711 |
0.710 |
0.757 |
Reverse |
3.231 |
3.230 |
3.231 |
Final Drive |
4.111 |
3.842 |
4.412 |
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:
Contact me with questions or comments!
- Ben aka SVOboy
Visit Ecomodder.com to discuss!
