Just how much lighter is that aluminum flywheel? If you remove enough weight, or change the mass center enough the engine will not rotate smoothly and thus the sensor has erratic readings. Which of course means the computer rushes to do erratic firing pulses.

 

mahout>hmmm...not too sure what the exact weight was, but I'm pretty sure it was 40% lighter than stock. But recently changed back to stock and check engine lights are off now =) damm new cars!!! so sensitive lol

 

Mine is 7 lbs and I think the stock one was somewhere around 13-16 lbs. I weighed it then but can't remember now.

~30k miles on it and no check engine light. I didn't think a lightweight flywheel would throw a CEL.

 

Ah ..... no the Fit is internally balanced so changing the flywheel will not make the engine "rotate less smoothly" (really?? not rotate smoothly?)

 

.........

 

hondata tells me there is a harmonic vibration at that rpm that sends a false misfire signal to the computer shutting the engine down. kinda learned to drive around it, engine just needs a slight load or no throttle at all. drove from Pittsburgh to mid ohio last wkend and only set it off once. hondata says there is NO damage being caused to the engine. the reflash for the 06-08 fits will not work on 09 and up fits. petition hondata to offer a reflash. they have one for the crz, odd.

 

If there is a "Harmonic vibration" then your new flywheel is faulty and you should get a refund. The Fit engine is internally balanced and ran fine until you put the flywheel on therefore the flywheel is out of balance.

 

ok I'll bite: why does Honda use a 13lb flywheel rather than one with less mass? Why bother with one at all?

As misfires are attributed to small changes in crank speed, could this have something to do with it?

 

The flywheel is not there to 'balance' the engine but to counteract the forces from the explosiuon in each cylinder. There are only 2 applied impulses to the engine every revolution of a 4 cylinder engine so at lower rpm the rotation of the crankshaft is blasted twice per revolution, easily observed even at 2400 rpm. That jerkiness of the rotation causes devices that measure revs to go crazy. That in turn drives the ECU into unstable directions. A flywheel reduces the jerkiness of the rotation and makes it more uniform. Just more uniform, not easlly smotth but that changes the rotation into smooth enough that the measuring and controlling devices can handle it.
The weight of the flywheel naturally is very critical to smooth ooperation. Typically, small 4 cylinder engines need a flywheel weight at least 10 pounds and of course the weight is more useful at the tip of the flywheel and indeed may not be balanced like a wheel. Its not unusual for the flywheel to be weighted so the weight locations are appropriate to better counter the impulses. Then its also important that the ftywheel diameter be considxered as the smaller the diameter the less restriction to increasing the energy required to increase revs.
Once rpm gets much above 3300 rpm the crankshaft has enough rotating mass to not need the flywheel; in fact there have been experiments with flywheels that electronically reduce diameter with increasing rpm and shown sigficant gains in max power at higher rpm. Thats a 'product' you can work on for the aftermarket that really works. Any fhywheel that reduces weight from OEM more than 20% is not a good choice for street engines but OK for com engines that idle at 3000 rpm.
Incidently those engines with counterrotating crankshfts dont really need a flywheel but are penalized by a lot of weight to be overcome by the engine. And yes as the capacity of each cylinder is reduced and the number of cylinders increased the weight of the flywheel is less needed. The flywheel of a 12 cylinder Ferrari is not much different from a Honda 4 cylinder.
cheers.
PS your 'bite' was the same as every fledgling ME; it's not intuitive to very many. Hope it described the reason well enough for you. Holler if it doesn't.

 

The harmonic imbalance is due to the uneven impulses from the two cylinders that fire each revolution that aren't counteracted by the flywheel because its too light. Add 4 lb to the periphery of your 7 lb flywheel and see if it goes away.

 

Yes, the engine parts are balanced but the impulses from the cylinders 'firing' twice per revolution are the reason for the flywheel. It smooths out the rotation so the mesuring and directed devices can be smooth too. A counter rotating crankshaft can replace the flywheel when ultra smoothness is important. If you remove the flywheel the engine is pretty easy to rotate with spark plugs removed but install the plugs and see how goofy the engine idles, if at all.

 

heh, my bite was to elicit a response such as yours. Thx.

 

The GE is known to have issues with a lightened flywheel. This is the reason why when I was about to purchase the one from JUN, they said they pulled it out of production because of the same issues causing CEL. The GE and GD really are different animals.

 

Ah no .... those pulses cancel out each other. A Fit or any other engine that is internally balanced will run with no flywheel (if you could pull start it LOL) or front pully.

 

Everybody is forgetting about all those automatic transmission Fits that run just fine with a flimsy flex plate and no flywheel at all.

And ignoring all the member cars that have a lightened flywheel installed and have been running them for carefree miles and miles.

 

The "torque converter assembly" provides the same function as a flywheel. Both for engaging the starter motor and providing rotational mass. The diagram at the link shows both the manual clutch and the torque converter.

 

I wonder when people will just ignore this thread, as a flywheel has NEVER set off any CEL or EVER caused any sort of negative effect.

The only thing you even need to do with a super light flywheel is learn to feather the clutch a bit more starting from a complete stop



I must be lucky that my filled engine mounts' extra vibration havent done anything bad!

 

I think this is the heart of the problem and the L15A7 is too smart for it's own good.

All the people I've found in links, etc that are running light flywheels have GDs...

 

You think both cylinders fire simultaneously ? And just where is the connecting rod 'fastened' to the flywheel? If they cancelled out the flywheel doesn't move unless the force is applied to only one side of the crankshaft.
And no, the Honda 4 cylinder engine doesn't run at idle without a flywheel, auto or manual.
The successful lightened street flywheel reduces weight by 10%. More than that regardless of engine the low rpm goes to pot. And care must be taken just how much the radius is reduced.

 

No close but no cigar. Starter motor engagement yep for sure. But rotational mass nope as the liquid is NOT CONNECTED physically to the crank. Yes it rotates and is under pressure and has mass but with no physical connection the effect is negligible.