Lighter Flywheel for Manual Transmission?

[thisisntjared]

Originally Posted by MetroMPG

Honda attributed a 2.65 mpg (US) improvement in highway fuel economy from cylinder deactivation in its V6 Accord hybrid over the non-hybrid (but only accounting for that technology, not any of the other hybrid tech).

http://www.hondanews.com/CatID2131?m...46959&mime=asc

The non-hybrid hwy figure was 30 mpg, so that's an 8.8% claim.

awesome! thats what i am looking for. i was definitely wrong, thats a very decent gain.

[SVOboy]

Anyway, the topic begs and answer. I have a lighter flywheel. My theory?

1. Honda made two high efficiency cars from 92-95, the cx, and the vx.
2. Honda shaved 3 pounds off the flywheel for each of these models.
3. It did not for the performance models or the standard models.
4. The vx has an aluminum alternator bracket that saves something like 8 ounces for efficiency.
5. Therefore, the lighter flywheel has something to do with better efficiency.

Sounds crazy to me too.

[psyshack]

I use to shave weight off rotating mass on motorcycles. It was a sure fire way to increase the speed at which rpm's climbed. Could make a throttle very snappy.

Shave to much and you ended up with a jerky motor at steady speeds.

MPG was never a concern at the time. The name of the game was rack the tach. Huge carbs, porting and extreme exhaust systems were.

psy

[GasSavers_Ryland]

Fasinating bit about the flywheel weight of the vx/cx, what are the numbers on those? I keep hearing things about them being lighter, but people never seem to weigh them, I did some checking on 2nd gen crx hf's have the same flywheel at the vx/cx...
when would you want a heavier fly wheel then?

[budomove]

psy, agreed. on a bike/bicycle a lighter wheelset is so much more important than shaving weight from anywhere else. In cycling it is much more noticable since it is your body not gasoline that drives it.

[Ted Hart]

Originally Posted by psyshack

I use to shave weight off rotating mass on motorcycles. It was a sure fire way to increase the speed at which rpm's climbed. Could make a throttle very snappy.

Shave to much and you ended up with a jerky motor at steady speeds.



psy

To get this message on post (so everyone can see / comment) I picked "psyshack" to respond to ... since he was "right on".

Flywheels are energy storage devices ; much like a rechargeable battery (in electrical counterparts). Take energy out...and RPMs will drop... drop RPMs...and less energy is available to tap(take out). No RPMs, no energy stored...or available. Dead battery!

Both sides of the energy storage picture must be considered : Most discussions about flywheels are concerned with the tendency to resist slowing in RPMs (damping?)... there is the other side of energy storage, increasing RPMs ( storing input energy)! This takes power... and MPG goes down. Use gas to put energy in, tap this stored energy to reduce gas consumption. As an energy storage unit cycle , nothing is 100% efficient... E in = E out + losses! There are always losses! It takes gasoline to spin up...it saves gas to tap into the spin down release. But the losses nibble at your gas consumption! The real world intrudes (friction of oil shear in the bearings, air resistance from the turbulence in the bellhousing) and the FE will always suffer...to one degree or another.

[SVOboy]

Originally Posted by Ryland

Fasinating bit about the flywheel weight of the vx/cx, what are the numbers on those? I keep hearing things about them being lighter, but people never seem to weigh them, I did some checking on 2nd gen crx hf's have the same flywheel at the vx/cx...
when would you want a heavier fly wheel then?

I weighed them, actually, with a scale. The difference is 15/18lbs.

Heavier flywheel makes it easier to shift, rpms don't drop as quickly.

[MetroMPG]

Ben: which one is lighter? The VX?

[SVOboy]

Yes, I am use the 15 pound cx/vx flywheel in my crx.

[thisisntjared]

Originally Posted by SVOboy

Heavier flywheel makes it easier to shift, rpms don't drop as quickly.

i disagree, but i do shift very differently than you. i think going to 1st from a stop becomes harder though.