1997 Civic CX to HX engine/VX trans swap! 63 MPG @ 62 MPH

[turbovr41991]

I still think 60 mpg at highway speeds is do-able. My morning commute had traffic on the highway, so my speeds and lean burn were limited. I did have a 10 mile stretch where I was able to run lean burn in 4th gear going 55-60 mph at 2200-2300 rpm and averaged 60-63 mpg!

I should be taking a long trip up north tomorrrow and putting over 400 miles on the car in a day, so that should be a good indication of fuel economy.

[seeodywhy]

I didn't read all the posts, sorry. How are you monitoring lean burn? I've done the same swap and am curious.

[seeodywhy]

I stayed with an hx tranny because of the rpm's at which lean burn is active. I would be going way to fast with a vx tranny because lean burn doesn't activate till around 2300 rpm. Plus I live in the city.

[turbovr41991]

Originally Posted by seeodywhy

I didn't read all the posts, sorry. How are you monitoring lean burn? I've done the same swap and am curious.

No problem. I will probably try to consolidate the first post after my trip today to have the bulk of the info in the first thread to make it easier on people.

For monitoring I run a ScanGauge 2 and an MPGuino

The ScanGuage 2 is manily used for holding lean burn entry conditions, detection to know when I enter lean burn, and key perameters to continue being in lean burn. I have a X guage programed to show when the car is in lean burn and when it is not. When it reads 0, and I am not in DFCO, it is in lean burn mode.
I also display LOD (engine load), TPS (throttle position sensor), and RPM. These 3 of the peramiters help me achieve the ideal conditions to enter and maintain lean burn. For entry it takes me LOD less than 70, TPS below 20, and RPMs 2300 to 2599. To maintain lean burn I need LOD to be less than 90, TPS below 30, and RPMs higher than 2000. (sometimes higher RPM is needed to stay in lean burn if my speed is lower or LOD is high.)

The MPGuino I use to monitor instant and trip/tank mpg. It uses injector and speed feeds to properly calculate mpg, even lean burn. So more or less, the MPGuino is a great tool to monitor the MPG effects of lean burn.

Originally Posted by seeodywhy

I stayed with an hx tranny because of the rpm's at which lean burn is active. I would be going way to fast with a vx tranny because lean burn doesn't activate till around 2300 rpm. Plus I live in the city.

I don't think i would find myself using lean burn at lower speeds even with the HX trans. There is too much benifit for pulse and glide and DFCO at slow speeds. But you might be right about the lower shift point. With the VX I honestly dont find myself going over 2k RPMs ever unless I am on the highway and entering lean burn.

[seeodywhy]

I had a voltmeter setup to monitor LAF voltage to see when I am in lean burn. I have an mpguino that I got back in 2009 and never installed. There was a how to on gassavers.org. I think that maybe I can If I knew which ecu wires corresponded with the LAF wires from that how to. I spent two years looking at LAF voltage and that is the best indicator of how one should be driving.

[turbovr41991]

A MPGuino will also let you know when you are lean burning. It is not as simple as a setting reading 0, or a lean burn light (some people have designed this). But if you are familiar with your normal MPG, you should be able to quickly notice the instant MPG jump between normal and lean burn.

The MPGuino is really easy to install. I have an aftermarket stereo in the car, so I just grabbed the power and ground there. The other two wires I got from under the hood.


1) constant power (yellow wire on the aftermarket stereo)
2) ground (Black wire on the aftermarket stereo)
3) Injector was from the tan wire on injector #1. I was told any of the non yellow wires would work though.
4) Speed (VSS) was the blue and white wire going to the speed sensor in the transmission. This is located under the intake piping that runs between the air filter and the throttle body.

[seeodywhy]

I'm a little fuzzy on the programming.

[turbovr41991]

Originally Posted by seeodywhy

I'm a little fuzzy on the programming.

It is just two numbers and really easy to do. They have a spreadsheet with the input numbers listed by car type. Pretty simple.

Then you might need to calibrate of fine tune it. Make sure your miles match a GPS and then check your fuel usage when filling up!

[turbovr41991]

Tried to sumarize things a bit in the first post and added preliminary results!

[seeodywhy]

I completed the power window swap in mine. What you need depends on the year of the HX