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

[turbovr41991]

Success! Updated first post with improved results. My first full tank over 60 mpg. Majority of the trip was staight highway maintaining 60+ mpg getting an average of 63 mpg in lean burn and 5th gear at 2050 rpm.

[Jakins]

So what's the secret?

[turbovr41991]

Originally Posted by Jakins

So what's the secret?

I installed my front bumper skirt and lawn edging again which helped reduced the high speed drag. But I think it is more that I am just learning how to deal with a picky the car. 5-10 minutes into a drive when the engine just hits full temp the car will try to go into lean burn at low RPMs. Once in and I maintain LOD (engine load) under 90, TPS (throttle position sensor) under 30 and RPMs over 1900 (I try my best to keep over 2k just to be safe though.) Once Ido this and get into lean burn, I can maintain in lean burn at low RPMs for 200+ miles. In my normal commute, it would kick out due to traffic. It is very rare for me to have an open stretch of road to maintain 60 mph for a long period of time. Also, knowing that if i kick out, it owuld not aloow me to reenter at low RPM, I was sure to anticipate hills and get up to 2200 or 2300 rpms before large hills.

There is still a problem limiting it from re-entering once the engine is warm, but this at least shows what it is capable of on a long trip if I can hold and maintain lean burn.

[Jakins]

So didn't the guy fool his map sensor to make the car think it was under a certain lod?

[turbovr41991]

Originally Posted by Jakins

So didn't the guy fool his map sensor to make the car think it was under a certain lod?

I remember reading someone was sending a false speed signal to the ECU to allow a VX to go into lean burn at lower speeds and idle, but I don't recall the LOD thread. Got a link?

Personally I would rather lower my LOD and resistance the old fashion way of areomodding the car and reducing rotating mass, but still nice to read what others are doing.

I think my next test will be looking for engine temps at the entry of low RPM lean burn vs. the when the car only allows 2400 lean burn. Perhaps it is as simple as the thermostat letting it run too warm? Not likely but worth testing.

[California98Civic]

Originally Posted by turbovr41991

Success! Updated first post with improved results. My first full tank over 60 mpg. Majority of the trip was staight highway maintaining 60+ mpg getting an average of 63 mpg in lean burn and 5th gear at 2050 rpm.

That is completely awesome.

[MetroMPG]

Nice work on this project. Congrats on the good results!

I added it to the front page. Do you happen to have a better current photo of the car than this one?

[turbovr41991]

Originally Posted by MetroMPG

Nice work on this project. Congrats on the good results!

I added it to the front page. Do you happen to have a better current photo of the car?

Thanks! I will check on my home PC to see if I have any better pictures of the car.

I just started pulling off the rear struts in preperation for new lowering springs, struts, and a few other alignment related changes. So worst case scenerio, I will take some fresh pcitures after it is lowered.

[MetroMPG]

Okey doke. No rush.

[brucepick]

Nice work!

As for temperature and lean burn, I haven't seen any issues getting or keeping Lean burn up to about 202-204 deg F. Very little experience hotter than that due to tstat was 172 deg until yesterday.

Now running a 180 deg tstat and engine temp is mostly around 190-195. Pretty sure my car needs its grill block to achieve that in winter. When driving without it a couple winters ago, it would only get up to about 175.