Lean and Mean - 1998 Honda Civic HX Project Log

[cbaber]

Despite a 40 degree drop in average temperature since August, I still manage some good trips. I finished the 50 mile commute just under that number, I had to sit in some traffic near the end!

[cbaber]

Hey guys, it's been awhile since I have been on EM. I haven't even kept up with my fuel log for a few months. I took a little break from ecomodding and just drove 70 mph and didn't worry about MPG. It was a combination of the cold weather defeating my summer highs, and gas prices going down under $3.

Anyway, I have started to come back to it. Here is whats going on:

CX/VX Transmission Swap
Complete! There was a day last month where it was over 50 degrees so I decided to swap out the transmission for my CX unit. It took longer than planned, and I ended up working into the next day where it was about 20 degrees! But I finished the job, and boy am I excited.

Not only is my annoying input shaft bearing noise gone in this new transmission, I have even lower RPM's on the highway thanks to the longer gears in the CX/VX transmission compared to the HX. I now cruise at 2000 RPM at 60 mph. Thats roughly 250 RPM lower than with the HX. It may not sound like much, but it helps. And the other gears feel longer too. I believe it helps my acceleration MPG.

Do I have improvement numbers? No. I haven't even been logging fuel consumption, and its really cold so I cannot compare it to anything. If I crush 50 MPG this summer, I think I can put a check mark in the success column.

Lean Burn Update
If you haven't followed along until now, here is the short story about my lean burn. Basically I haven't been able to go into lean burn since I replaced my engine a couple years ago. Around that same time my original O2 sensor when to crap, so I replaced it with a cheap one. I thought the new cheap O2 sensor was the problem, but it wasn't.

After some research I decided that my aftermarket exhaust manifold setup was causing the problem. My setup moved the primary O2 sensor from its original location right by the engine head, to way down below the car where the downpipe meets the CAT. I ordered a manifold that has the O2 next to the head, and BOOM I have lean burn functioning again. Look up at post 41 above to see a picture of the new manifold so you can see what I mean.

So I haven't had a full tank of lean burn yet, so I cannot report any improvements. Plus, it is cold and I have nothing to compare my numbers to. I will need to wait until summer to see if I smash my previous MPG record tanks.

Alternator Delete
I've cancelled this project for now. It's just not worth the extra effort and expense to make the switch over to deep cycle and to charge the battery every night. If I were going for max MPG without concern for price then this would be a good idea. But for me it's just too much work and money to justify even a 2-3 MPG improvement. Plus, I want my trunk space back!

[California98Civic]

Nice work with the swap. A day and a half is quick, by my standard. Did you replace the clutch plate? I chose not to, since I never yet have had problems. I was at about 205 thousand miles then, and I'm hoping to get 300,000 from this clutch. And yup, my CX trans turns about 2050 rpms at 60mph and that's about a 400 rpm improvement. All the gears are taller, as you're guessing, but I actually think it is not so good for mpg in stop-n-go situations, though great at cruising speeds in 4th and 5th at low load and low rpm.

[cbaber]

Originally Posted by California98Civic

Nice work with the swap. A day and a half is quick, by my standard. Did you replace the clutch plate? I chose not to, since I never yet have had problems. I was at about 205 thousand miles then, and I'm hoping to get 300,000 from this clutch. And yup, my CX trans turns about 2050 rpms at 60mph and that's about a 400 rpm improvement. All the gears are taller, as you're guessing, but I actually think it is not so good for mpg in stop-n-go situations, though great at cruising speeds in 4th and 5th at low load and low rpm.

I replaced the clutch and pressure plate when I replaced my engine, about 60,000 miles ago. They should last as long as you don't abuse them, and with my driving (mostly highway) I didn't feel the need to replace either. It's a good practice since you have it apart, but I am cheap!

I did replace the flywheel, which was badly needed. The car has 230,000 miles and it was probably the original flywheel. The car would lug violently sometimes when taking off. It was annoying in stop and go. The new flywheel made it much smoother, and I didn't opt for the factory VX lightweight unit due to cost.

The ScanGauge isn't accurate due to my lean burn working again, but it's showing 48 MPG on this tank so far. On the previous fills the SG indicated I used more fuel than reality, so I am going to guess this first tank with VX+lean burn will be very good. When you take into account the temperatures around here have been below 35 everyday, that is incredible.

[California98Civic]

Originally Posted by cbaber

The ScanGauge isn't accurate due to my lean burn working again, but it's showing 48 MPG on this tank so far. On the previous fills the SG indicated I used more fuel than reality, so I am going to guess this first tank with VX+lean burn will be very good. When you take into account the temperatures around here have been below 35 everyday, that is incredible.

Yeah, that sounds like success. Cruising at 60 or 65 mph, down around 2000-2200 rpms, with lean burn, you have the car dialed-in very nicely now.

[1slw4dr]

What is your current tire size setup you're using? I recently purchased a HX in hopes of making my commute less hard on the wallet. I want to at least run a 15x7 but not sure what tire size to go with. I'm stuck with 185/60 or 205/50 I'm very particular on the handling of my vehicles but still trying to get this car to give me 40-45 MPG and you sir are my current motivation lol

[jedi_sol]

Originally Posted by 1slw4dr

What is your current tire size setup you're using? I recently purchased a HX in hopes of making my commute less hard on the wallet. I want to at least run a 15x7 but not sure what tire size to go with. I'm stuck with 185/60 or 205/50 I'm very particular on the handling of my vehicles but still trying to get this car to give me 40-45 MPG and you sir are my current motivation lol

I used 205/50 on my del sol and was still able to achieve 43-45 mpg. Skinnier tires will give you less rolling resistance for better mpg.

[cbaber]

Originally Posted by 1slw4dr

What is your current tire size setup you're using? I recently purchased a HX in hopes of making my commute less hard on the wallet. I want to at least run a 15x7 but not sure what tire size to go with. I'm stuck with 185/60 or 205/50 I'm very particular on the handling of my vehicles but still trying to get this car to give me 40-45 MPG and you sir are my current motivation lol

Stock tire size is 185/65-14. I have aftermarket 15 inch wheels with 185/75/-15 tires. That extra diameter lowers my RPM's a bit. I would honestly stick with the stock HX wheels or a similar width wheel. The HX's are lighter than most aftermarket wheels, and they allow you to run a skinny tire which helps fuel economy. If you are set on wider wheels for handling, I have run 205/50 on previous cars with good results. Also 195/55. I usually just pick the one with the best prices.

[1slw4dr]

Alright I'll keep that in mind. Thanks!

[cbaber]

It's been a couple months since the last update, I thought I would share some thoughts and plans for the upcoming "eco-modder season". I'm jealous of you guys that only hit 40 or 50 over the winter. This winter has been brutal in Missouri. Within a 7 day span a few weeks ago the temperature went from -1 to 70 degrees. Heck, just yesterday I drove to work and it was 80 degrees. When I got off 8 hours later it was 30 degrees and snowing! As the temps start to go up so will my MPG. My fill yesterday was 45 MPG. I am confident once the average temp. starts to feel like summer I can hit 50 MPG.

Goals:
1. Hit 50 MPG consistently
2. Complete some aero mods (grille block, front belly pan, etc.)
3. Perform some maintenance tasks I have been putting off

The Plan:
Hitting 50 MPG shouldn't be too difficult. Last summer I was hitting 46-48 consistently for a stretch, and I even made it above 50 MPG on one tank but I consider that a fluke. I have added a couple significant mods since last summer, including removing the power steering and swapping in a VX transmission. I've also managed to fix my lean burn problem. Combined these additions should significantly increase my MPG over last year.

As far as aero mods and the maintenance, I want to create an upper grille block, and a partial block for the lower grille. I really need to replace my rear wheel bearings, one side is making a really annoying sound at highway speeds. There are also some little things on the car here and there that I want to repair/replace. The headliner needs replaced, the drivers side door seal is cracked/torn (from having to break into the car 3 times with a coat hanger), and the passenger side door needs a power lock motor and a power window motor. The biggest thing besides the wheel bearing that bugs me is my drivers side fender which is dented. Ideally I would find a used one that is the same color, but that has proved difficult. I might just have to buy one and get it painted.

It should be an interesting summer. Gas prices are on the rise, but so is my fuel economy. I'll try my best to keep this thread updated with all the latest stuff!