New problem, so I started a new thread.

I just got a new clutch, lightweight flywheel, ss clutch line, and ESMM inserts installed on my 2005 ep3. (I made a thread about that too, asking about labor prices.) The shop I used did great work for really cheap.

Anyways, I got everything installed 2.5 weeks ago, and my gas mileage has been horrible since. Before I had the work done, I averaged 305-315 miles per tank (mix of highway and city). Even on the low end, I was getting 24-25 mpg, usually about 27-28 (~12 gal. / 305 miles = 25.4 mpg)

I just filled up my tank on Friday: 225 miles driven since the last fill up, and I put ~12 gal. in the car, for a grand total of ~19 mpg. My driving style has not changed, I keep the tire pressure at 35psi, and oil/transmission fluid change ~1000 miles ago.

The only difference between my fuel economy a month ago to now is the new clutch, flywheel, ss clutch line and ESMM inserts. Would these mods lower my mpg?

I know they removed the sub-frame to install the clutch/flywheel, so could it be the alignment?

V6 mileage would be ok, so long as I got V6 power too, but with a k20a3 we know that's not the case.

As always, any help is appreciated.

 

No check engine codes?...

 

Disclaimer: I have no hard and fast experience with the OP's situation; just speculating here...

Given that all 4-Cylinder and 4-Stroke engines are "torque reversal" engines, and given that it is the rotational mass (aka. angular kinetic energy) stored in the flywheel is responsible for driving the engine during the (roughly) 40° period between when the current combustion stroke cylinder stops providing power to the crank and when the next combustion stroke cylinder starts providing power to the crank; theoretically (to my mind at least), if the flywheel is too light then the engine will slow down too much between power strokes (especially at lower engine speeds) and effectively mess up the timing of the peak pressure point of the combustion stroke (which is typically between 14° and 20° ATDC depending upon engine). If the peak pressure point comes too early (which I'm guessing is what is happening here) or too late, fuel economy will suffer.

Hmmm, reading what I just wrote, I'm thinking I might need to don my NOMEX suit and duck for cover.

 

Paul, yes the CEL is on, but it's for the cat that I haven't replaced yet. When I replace the b-pipe, I'm gonna put a Magnaflow cat on there as well.

Shipo, the flywheel I had installed is 11lbs vs. ~14lbs stock. So yes, it is lighter, but would a 3lb reduction warrant a 5-6 mpg loss in economy?

 

As I wrote before, I was merely speculating as to the cause. That said, the actual weight of the flywheel isn't really as relevant as where (as in how far from the axis point) the weight is distributed in the flywheel. If the new flywheel has virtually all of its weight located out at the outer edge (kinda like a bicycle wheel or a kid's gyroscope), then the new 11 pound flywheel could actually store the same amount (or more) of angular kinetic energy as the OEM 14 pound unit.

Of course, given that we're talking about a flywheel containing a friction surface (which requires a pretty substantial amount of thermal mass/weight) for a clutch disk we know by definition that a significant portion of the mass isn't located at the outer perimeter. So, if the two flywheels have similar mass from the center out through the outer edge of the friction surface, and if the OEM flywheel has say three extra pounds located at the outer edge of the disk compared to the aftermarket unit you bought, then there will be a HUGE difference in the amount of energy stored at any given RPM.

Long story short, light weight flywheels are great for engines which spend their time on a track and are operated consistently in the upper RPM ranges; for a daily driver they're pretty worthless, IMHO.

Another thing to consider; Honda engineers are pretty darned smart, and they didn't just pull the weight (and more importantly the weight distribution) out of a hat, they did the calculus and determined what would be the optimal configuration (which by definition is always a compromise) for a car which will see both stop and go driving as well as high RPM operations.

Once again, the above is merely some (slightly) educated speculation; I've not done the math to actually prove what I've written.

 

If that were true about Honda engineers, then why did they give the ITR a light weight flywheel? It's fine for daily driven applications.

Yeah, it's pretty obvious you're talking out of your ***.

 

Not all "lightweigh flywheels" are created equal; the weight and the distribution of said weight is key; don't be foolish enough to compare a BrandX "lightweight flywheel" and one from Honda designed by them for one of their cars.

 

Theoretical physics aside, let's get back to the point. Why would I lose approx. 25% in mpg by installing an 11lb flywheel, stage 1.5 clutch, ss lines and ESMM inserts?

Would an alignment help? I can't think of any reason why these mods have lowered my fuel economy by so much.

 

Short answer; no.

 

Ok so if the alignment out of the equation, what's next? What else could have affected my fuel economy so suddenly?

 

Are you expecting a different answer this time?

 

i have an 03 ep3 (NO MODs) all stock. Ive done the oil changes normally,tranny fluid has been changed (honda MTF),Spark plug changed(NGK iridium),Alignment was done last saturday AND my gas milage is HORRIBLE. I had a half tank,drove my car roughly 60 miles and my car is on EMPTY. I drive like a normal human NO Speeding. My car has about 90k and i use Chevron 91. WHAT U THINKS THE PROBLEM?

 

Hard to tell, any engine codes?

Regarding the Chevron 91; unless I miss my guess, you're using fuel with too high of an AKI rating; doesn't your Owner's Manual recommend 87 AKI fuel? If so, that could be a reason your fuel economy is lower than it should be.

 

Can anyone else aside from Shipo offer some insight?

 

fuel tank and owners manual says use premium fuel only. No CEL,i also did valve adjustment not long ago. Im the Original Owner so i know all maintains has been done.

 

Sorry, I missed my guess regarding the fuel quality (missed the RSX/EP3 reference in the forum name). Question, does 91 AKI fuel qualify as Premium fuel in your part of the country? I ask because here in New England, 91 AKI fuel isn't available; we get 87, 89, and 93. Is 91 considered Premium?

 

yes 91 is the best fuel u can buy in California beside 100 octane...

 

Good to know, thanks.

 

I don't know much about aligning a new clutch, but would a slightly misaligned clutch cause a mpg drop? Then again, if it is misaligned, you'd notice more issues, probably slipping & clutch odor right?

Assuming none of the recently installed parts could cause a 5-10mpg drop, I'd concentrate on the regular tune-up items: plugs/ignition/fuel delivery, valve job, etc.

Although it seems like the CEL & no cat existed prior to the parts install & MPG drop, getting rid of the emissions engine code would be first on my list.

 

Paul, that's a good place to start.

Thanks for providing the only worthwhile advice on the thread.

 

No prob.

Another guess: I've read our in-tank fuel pumps just have a metal mesh/screen around them to filter, as opposed to an in-line fuel filter; so chances are the pump wouldn't be clogged... but would a failing or worn pump cause a drop in mpg?

 

This will sound crazy, but it's free and can't hurt you, so give it a try: Reset the ECU and then perform an idle relearn.

1) Disconnect both battery cables.
2) Connect a jumper wire (if you have one with alligator clips, this will be easy) from the positive cable to the negative one. Make sure neither cable is touching the battery!
3) Leave it there for 10 minutes.
3.5) Reconnect the battery cables to their respective terminals.
4) Start the vehicle. Let it idle, do not touch the gas. Wait for the cooling fan to cycle on and off, twice.
5) Switch off the engine, then immediately restart it.

I'm going on the assumption that if, as another poster said, the lighter flywheel could have that sort of effect on the cylinders firing, then doing this could possibly correct that. Or, it could be that the shop that did the work disconnected the negative terminal before starting the clutch replacement; it's rare, but some technicians will actually follow every step outlined in a repair procedure, and disconnecting the ground is often step 1.

Outside of that, I can't imagine how a clutch/flywheel replacement could have any effect on your fuel economy, which is determined by the ECU and its supporting cast of sensors, the failure of any of which would result in DTC and warning light.

 

Never experienced this on my ep3 but I know my friends ep3 is going through the same problem

 

Is this your first tank? Maybe it's normal since at the installation it's possible there is some grease/oil on the flywheel and on the clutch surface and therefore the energy transfer to the transmission is not efficient. But after awhile everything should become normal, the same as new break installed it won't stop the car well until awhile it become normal.

Anyway, I really doubt it's due to grease/oil (wish it's be the case then problem will be auto-resolved in a few hundred miles later). What I'm afraid is that the new flywheel as you mentioned is light than the original. Hmmm your engine must put more force (which result in more gas) to compensate your light poor flywheel that try harder to turn the transmission whereas before it didn't have to try hard since it was heavier and stronger.

 

What if there is friction that was't there before. Let's say the gearbox wasn't alligned
right after the clutch/flywheel work. Or a bearing that is turing tight?
Can this happen? Or is the gearbox / engine pairing foolproof.

Wild guesses, I'm trying to help.