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

[turbovr41991]

Originally Posted by 02ws6

The hatch has a hx/vx swap now? Hows the trans?

The car had a VX trans before I did this swap. The only thing new is the HX engine/ECU. I bought the car with a bad trans and instantly put in the highly geared VX J5F trans. But it is nice, crusing highway speeds 1700 to 2000 rpm

The other VX trans was not installed yet. :/ I was planning on putting it in the HX first, but after having coolant leaking from the water pump in the CX, I just decided to pull both engines and just swap it out.

[turbovr41991]

***Update***
The donor car is just about back together and 100 miles have been put on the CX with the HX engine. Low end power and torque are MUCH better than the CX engine. I am able to accelerate at a lower RPM and use higher gears relative to the speeds than before.
I am still calibrating the ScanGaugeii . I am about 150 miles into the tank. I find myself doing more tests with lean burn than I am EOC /DFCO so fuel efficiency will suffer a bit. After programming a X-Gauge feature on the ScanGaugeii to display when I am in lean burn, I found I was not going into lean burn easily. On a 35 mile stretch I will only enter lean burn 1 or two times for a short period of time. When put in under the ideal conditions (warm temp, on highway, and 15% TPS) to engage lean burn the check engine light has occasionally come on with the code P1164 (front O2 sensor.) I suspect this is the main reason it is struggling to get into lean burn. So I ordered an OEM sensor (This is one expensive O2!) and will see if this solves the issue.

Also, if anyone is planning to do this swap, it was 100% plug and play. Get an HX dropout, 5 wire (fed spec) manual trans harness and a Manual trans ECU.

Only a few slight differences:
1) Throttle cable is completely different. You could make the CX/DX/LX work , but I would recomend getting the stock cable as well as the mounting braket that bolts to the strut tower.
2) Fuel line return. Probably not large enough of a difference to NEED swapping, but they are slighly different in lenth. Also swap the bracket that holds it to the intake manifold. (Depending on your needs, Power steering also shares the same braket and can be separated by drilling out a spot weld on the bracket.)
3) Brake booster hose. Is formed completely different. Will need a new one.

[96vtec]

Nice work! Nice to know that you didn't run into too many issues.

The HX does have very little torque and I found it struggling going up a hill on the freeway on my way to San Francisco from Los Angeles. I often needed to drop it to 4th gear but believe the oxygen sensor was near ready to get replaced. You might wanna make sure you clean out the vacuum lines as well.

Definitely staying tuned for the mpg results once it's fine tuned!

[turbovr41991]

More pictures. Not much driving this weekend though so still waiting for numbers. :/

Engine

Altered fuel rail bracket to exclude the Power steering part.

Note - NO POWER STEERING!

Whole car

[96vtec]

Great to see my previous idea come to life! How does the car feel without power steering? Is it about the same with the CX engine?

[California98Civic]

Very nice.

[Jakins]

Nice dude?so really the only way to use the lean burn is to watch it with a scan gauge? Is there any way you see if it is working without one? I normally cruise at a lot less than 15% throttle. Are you supposed to give it more?

Also one really important thing to do if you havnt already is take your fuel rail off and get to the egr and egr passage ways and unclog those holes. I literally felt like a 10 ft/lb torque gain.

[turbovr41991]

Originally Posted by 96vtec

Great to see my previous idea come to life! How does the car feel without power steering? Is it about the same with the CX engine?

Its feels like it has more power and torque. Much easier to accelerate at lower RPMs in higher gears. It also is able to maintain lean burn going up hills better.

Originally Posted by California98Civic

Very nice.

Thanks!

Originally Posted by Jakins

Nice dude, so really the only way to use the lean burn is to watch it with a scan gauge? Is there any way you see if it is working without one? I normally cruise at a lot less than 15% throttle. Are you supposed to give it more?

Most people can tell they go into lean burn when the car hesitates a little and becomes a sluggish on acceleration. After knowing what it feels like I can tell when it is going to do it and when it kicks out of lean burn mode, but I like having a concrete method to let me know. Others have used gauges or LED circuits to show when their VX, HX, or insight, is in lean burn mode. I might go down the path of having a green LED iluminate when in lean burn mode, but that is low on my list right now. As for the mechanics of lean burn, I can't find the link to it, but there are some really good write ups on how it works. from what I read, 15% should be fine though.

Originally Posted by Jakins

Also one really important thing to do if you havnt already is take your fuel rail off and get to the egr and egr passage ways and unclog those holes. I literally felt like a 10 ft/lb torque gain.

Yep. I tacked that before the swap. Man it was clogged up. My ECU stopped tripping the CEL and it instantly idled better. Did not drive it much before this, so I don't have much to compare, but it feels great now.
http://ecomodder.com/forum/showthrea...-hx-22824.html

[brucepick]

I checked speed vs rpm's in my HX this morning. Before using Marvel Mystery Oil in my fuel, it needed approx 2500 rpm or better to get lean burn. Nowadays I can run lean well below 2000. So try for LB above 2500 to test.

Today I noted:
ScanGauge "LOD" below 60 to go into LB.
Once in LB, LOD over 90-91 will put it out of LB.

Up till today I was using the TPS for same purpose,limits were 19 max to get LB and over 32 would end it. But the TPS limits actually vary with your rpm's, I think LOD numbers are a more consistent guide.

[Jakins]

Is LOD scan gauge talk for something?

And is there any write ups on what to wire an led or gauge up to see when you are in lean burn?

I really hate to thread jack, I'm sorry haha. I'm just a really curious person. The car looks great with the HX wheels by the way. I'm surprised you opted to keep the a/c