Lean and Mean - 1998 Honda Civic HX Project Log

[cbaber]

Still working out the details on the transmission. I'm hoping to pick it up Sunday for $50. In this case, the guy swapped his engine/transmission in favor of a higher performance setup, and the stock stuff is considered junk. One mans junk is another mans treasure!

On another weird note, it seems I am having some issues with the EGR system. Ever since I replaced my engine (Feb 2012) I have been getting EGR CEL's. I tried cleaning the passages but only recently did I realize I wasn't cleaning out the ports that connect to the individual intake manifold runners. They were completely clogged, and this was the reason I was getting the CEL. I ordered a new EGR gasket and installed it about the same time I completed the remote battery installation.

So for the last couple days I have had the EGR electrical connector hooked back up (I disconnected it since Feb 2012 so my car wouldn't try to go into lean burn). No more EGR code and it seems the EGR is working again. Still no lean burn (I thought it might fix the issue, but it seems I need a new O2 sensor) but it seems with the EGR functioning I get way worse MPG.

On the first trip to work with the EGR connected I got 42 mpg, scangauge indicated. My normal is 45. It was about 80 degrees with A/C. On the return trip only 41.5 mpg, no A/C. Yesterday on the way to work I tried really hard and got 43.3 mpg, no A/C. Fed up with my poor results, I disconnected the EGR connector for the drive home. 47.3 mpg scangauge indicated without EGR. What the heck?

I plan on running a full tank with EGR connected to verify the mpg numbers on the scangauge. Maybe since the engine is using the exhaust gases again, the scangauge is indicating low? Not only did I notice less mpg, I noticed I had to drive at higher loads than with the EGR disconnected. All I can think is that maybe the extra fuel being cycled back into combustion is causing the scangauge to read incorrectly. I will find out in another week or so after another tank.

[cbaber]

Best tank ever! 46.86 MPG! I am still following my 60 mph speed limit on the highway. I am getting better at selecting loads to climb hills so that I use less fuel. I never allow my speed to fall below 55 mph though.

[cbaber]

Picked up a CX/VX transmission this morning for $50! Needs to be cleaned. I'm going to purchase a new flywheel and install it within the next couple weeks.

[California98Civic]

Experiment with a lighter flywheel? What do you think? I have seen guys on here saying in helps a lot in the lower gears and that the VX had a lighter flywheel. Maybe you saw those comments too?

[cbaber]

Originally Posted by California98Civic

Experiment with a lighter flywheel? What do you think? I have seen guys on here saying in helps a lot in the lower gears and that the VX had a lighter flywheel. Maybe you saw those comments too?

I've thought about it. The racing guys do it to their motors, and a lot of the modifications for racing are about efficiency which also translates into better mpg sometimes. But in this case I don't believe a lighter flywheel will help. From the research I have done here on ecomodder, many seem to believe a lighter flywheel actually hurts because the motor cannot store as much energy. In daily driving duties that stored energy in the flywheel helps when taking off and shifting. The energy the flywheel uses is not parasitic like an alternator or power steering pump. With that in mind I can't see how a lighter rotating mass will improve fuel economy.

The racing guys lighten the flywheel so the motor will rev easier. On the downside for us, lighter means less energy stored. So you would need to apply higher load and RPM for takeoffs, and your RPM's would drop quicker while shifting. The only advantage I can think of would be for EOC. The motor would die much quicker since their is less "momentum" in the engine.

I think the reason the VX came from Honda with a lighter flywheel was because the motor had less power and torque than the standard Civic motors. Obviously a heavy V8 flywheel on a 4 cylinder would feel sluggish. Maybe with the VX's reduced power Honda figured it needed to lighten the flywheel to keep up the throttle response.

[02ws6]

The cx and vx have the lighter flywheels of the d-series engines from what Ive read. The vx being around a half a pound lighter of the two.

There are a number of aftermarket companies that make even lighter flywheels for this car.

No matter what you go with, atleast get the old one you have machined to ensure its durability.

[California98Civic]

Originally Posted by cbaber

The only advantage I can think of would be for EOC. The motor would die much quicker since their is less "momentum" in the engine.

Not only that, but when you are rebuilding parts of the car with the EOC in mind you know that you'll be cutting the engine anyway. That stored energy routinely gets "wasted" because we know the energy stored in the car as a whole is better maximized with the engine off. So flywheel weight matters less for us than it seems it would (for a "normal" driver). But then there is also how lots of us get to speed: I do P&G techniques most of the time--nearly all of the time on some routes. That means I'm at 75-80% load and acclerating virtually the whole time I am burning gasoline. I'm often accelerating from stop or low speed, in low gears that spin a lot per mile. Under conditions like that, a lighter flywheel makes sense, right? And at cruise, out on the freeway, I would think a lighter flywheel is less rotating mass for the engine to keep spinning. Seems like a win all around if you do P&G and EOC a lot.

I wish I could go back and do the swap, but someday by 207,000 mile clutch must wear out and then I'll be going back in, maybe with a lighter flywheel ready to go.

james

[cbaber]

I think you are correct for P&G driving. This article explains it better than I could:

Flywheel lightening & performance gains from lighter flywheels

I'll probably look into getting a stock VX flywheel or whatever I can find cheapest. I don't see any harm in trying a VX flywheel. I doubt I'll go any lighter due to the cost of aftermarket, and I haven't seen any results indicating I could benefit with my driving style (steady speed highway).

[California98Civic]

Originally Posted by cbaber

I think you are correct for P&G driving. This article explains it better than I could:

Flywheel lightening & performance gains from lighter flywheels

I'll probably look into getting a stock VX flywheel or whatever I can find cheapest. I don't see any harm in trying a VX flywheel. I doubt I'll go any lighter due to the cost of aftermarket, and I haven't seen any results indicating I could benefit with my driving style (steady speed highway).

Do we know what the weight of a flywheel on these cars is, exactly? I have heard that my DX probably has a 20 lb flywheel, but I don't know. How heavy is the VX or HX flywheel? Exedy lists flywheels for the sixth gen Si that run as light as 9.5 lbs and claims each pound is like take 50 lbs off the car (I don't believe it).

[02ws6]

Id bet that 50lb rule pertains to racing.

And from what Ive read, the vx flywheel is 15lbs 9oz.