Dreaming...lean burn manual taller transmission Civic sedan...or get an Insight
 

During the final days of driving Silver Aero I got into the 50s mpg with hypermiling. Automatic, no lean burn.

What if I were to sell my car, buy a manual 7th gen sedan, and have an HX engine & tranny swapped in?

My car with all the maintenance done to it could probably sell for close to $4000. There's a rusty HX with good engine and manual tranny for $600. Found a clean '03 manual civic sedan with bad engine for $900 obo. That would leave me close to $2500 to pay for the swap and any additional changeover & maintenance, plus whatever from if I could sell or scrap extra parts.

Would all the lean burn and necessary fixings swap over into a manual 7th gen sedan body? Or would it be better to just put $$ into the HX only? I prefer the 7th gen sedan over 6th gen coupe but whatever works. The HX has 317k miles

Not something I could do anytime soon; it wouldn't be until next year May at the earliest, but would something like this work? With manual, lean burn, and kill switch I'm sure 80+ mpg is possible with maximum hypermiling, and 60 mpg with regular driving.

Didn’t they make a 7th gen HX?

They did, but coupe only.

All the coupes in the area are rusty, and insurance is less for a sedan.

I've also read that HX motors are troublesome to maintain and lean burn is picky to engage; what if I were to get a CRX HF manual trans with the 2.95 final drive and swap it into a manual 7th gen sedan? Would it fit? And do taller transmissions hurt city FE? If so, would RE92 insight tires help?

EDIT: Looks like the CRX HF transmission is cable instead of hydraulic; what about a CX or VX transmission? Would it fit in a 7th gen civic body? Found some manual 7th gen civic sedans with bad trannys for $850-$1000. Or some shells (need both engine & tranny) for $250-$300.

What would be the best engine + transmission option that works for fuel economy in both city & highway driving that fits in a 7th gen sedan body style? Or 6th gen (possible consideration)?

From what I understand, the 7th gen Civic still uses a D series engine, so a CX/VX trans should bolt up to the engine, I’d build a high compression D16 and the tallest transmission I could run behind it... I’d go for lean burn but you may decide to skip on the more expensive O2 sensors

I'm stuck here on two options. Both are priced based on stuff I found tonight, but similar options are found everyday:

- 2000 Civic sedan Manual shell $300
- HX engine $400
- CX/VX transmission $300
- ECU tune $500
- RE92 165/65R14 tires $377
- Tire balance $80

Total: $1957
Labor: $2500
Cost: $4457
Sale: $4000
Final standing: -$457

Or

- 2001 Civic sedan manual bad trans - $900
- CX/VX trans $300
- Tire rebalance $80

Total: $1280
Labor: $1500
Total $2780
Final standing: +$1220

Obviously the first option is more fuel efficient due to having lean burn, but is significantly more expensive. Per ecomodder research a CX/VX transmission makes it difficult to engage lean burn at lower speeds, which is why I'd downsize the tires. That or tune the ECU for better lean burn + possibly bypass o2 sensor & cat.

Other option would leave me over a thousand in pocket, same car but manual for better efficiency plus kill switch capability, and taller transmission, which if I'm getting 60 city 56 highway hypermiling the crap out of my auto, should get me to 70+ city and mid 60s highway.

What do y'all think? Advice? Due date to have this all figured out by is May lol.

Edit: or what about a Honda civic hybrid and then bypass the battery when it does? Does it still have lean burn without the battery? If so does that make it comparable to an HD in terms of fuel economy? If so that would be much cheaper.

Why not seek out a VX hatch? It’s way older than your Gen7 but it’s proven to work

EDIT: there’s a HCH1 in the for sale section right now for $500... why not look for one of those?

These fantasy swaps are a fun game. The swap you are thinking of is interesting. But it might be more hassle and cost than you might really want. I like the HCH1 option. A 2003-2005 Civic Hybrid manual. If you sunk a fraction of the money you might spend on the seventh gen HX/LX conversion, you could have a fully refurbished traction battery and gearing taller than any HX had (6th or 7th gen). It is a sedan too.

Also... be careful about older engine into newer body swaps. Some states won't let them onto the roads (Cali, for one example) because of smog regs.

Not obdii compliant! Insurance as a 2 door hatch would be as bad as a coupe. There was a a halfway decent one locally but...

Batteries. That's why. And bypassing the battery throws a CEL which doesn't let lean burn engage, defeating the whole point of getting one.

Sigh. I was stagnant at mid 60s mpg for my last several weeks and I want to keep climbing!

Problem is that every so often it's another $2K to replace the battery, and bypassing it prevents lean burn so mpg won't be any better than my current setup.

What about buying a 7th gen sedan manual for about a thousand and having a cx tranny & kill switch installed?

The HX engine of both generations has maintenance issues or just one generation?

I do not understand the popularity of coupes. Cheaper? Sure. They look better? People have strange opinions regarding appearances. Even when I rarely have passengers, I have always preferred being able to access the back seats via doors.

How long would the cheaper insurance take to pay for the complicated swap?

The only HXes that I have seen lately are a 2002 with 156,000 miles, but only 46,000 on the engine for $3,000, and a 1997 corpse in Tucson for $800.

I personally wonder about--hear me out--a 6th generation HX engine swapped into--hold on--a 6th generation Civic HX.