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Lighter flywheel


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15 replies to this topic

#1 HATCHY

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Posted 23 November 2006 - 01:17 PM

Im geting a 19 lb flywhell.. Will I notice a big dif

#2 4x4_Welder

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Posted 23 November 2006 - 02:09 PM

Easier to stall on takeoff, but it will rev faster.

#3 GeneralDisorder

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Posted 23 November 2006 - 02:21 PM

The engine will free-rev better, and decelerate quicker, but you will lose torque, so accelerating up hills will be more difficult, and you will lose effective gearing due to the torque loss. The engine may also idle less smoothly, but that's not a huge weight loss so you may not notice much.

Basically it's really not worth the time and effort to lighten the flywheel of a 73 HP N/A engine built for a 4WD D/R vehicle - in fact it's counter-productive because torque is the engine's best and most useful attribute. There are plenty of more productive changes that could be made to the engine - just having the distributor recurved is good for around 10 or more ft/lbs of torque and doesn't even require the engine to be pulled. I'm saying your money is better spent on other things.

GD

#4 NorthWet

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Posted 23 November 2006 - 04:18 PM

Engines produce torque, flywheels just effect the delivery. As stated earlier, the lower rotating mass may effect idle smoothness but may allow the engine to free-accelerate/-decelerate quicker. It also depends on where the lightening occurred. Also, we are really talking about "polar moment of inertia", where an once on the rim has much greater effect than an once at the mounting flange.

I am with GD regarding money generally being better spent elsewhere.

#5 GeneralDisorder

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Posted 23 November 2006 - 04:42 PM

Yeah - it won't change the torque directly (it will change the torque curve), but it changes the engines ability to apply that torque to the drivetrain under some circumstances - such as acceleration up a hill. It also changes effective gearing when you add in the clutch action - slipping the clutch to multiply your gearing will be more difficult with a lighter flywheel as it will be easier for the drivetrain to change the engine speed. Crawling slowly over obsticles will be much more difficult as the engine will have to be kept at a higher RPM - clutch wear will accelerate, and the clutch will fade from heating as the RPM is increased to offset the loss of inertia. The net result of which is the "feel" of lost torque.

It can be useful to improve shifting speed on race engines to lighten the flywheel - it improves the engine's "response" but does not by itself assist in making power - in fact if not coupled with other changes to the engine to improve power it will generally be a detriment to overall vehicle performance. It's a very specific enhancement done for specific race uses. I personally think it's entirely unappropriate for the EA81. Turbo engines and "street" engines such as the ER27 are another story.

GD

#6 NorthWet

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Posted 23 November 2006 - 05:25 PM

...It can be useful to improve shifting speed on race engines to lighten the flywheel - it improves the engine's "response" but does not by itself assist in making power - in fact if not coupled with other changes to the engine to improve power it will generally be a detriment to overall vehicle performance. It's a very specific enhancement done for specific race uses. I personally think it's entirely unappropriate for the EA81. Turbo engines and "street" engines such as the ER27 are another story.

GD

Totally agree. These engines were given their flywheel's weight for a reason, and that reason wasn't because FHI was given a terrific deal on the cast iron. Street driveability can be greatly compromised by too low of a rotating mass, and offroad even much more so. For an offroad-only, rock-crawling vehicle I would rather have a flywheel with twice the PMI of stock.

Lightened flywheels can feel like lots of fun in the fast and twisties, but a pain in the posterior in day-to-day driving. My thinking is that lightened flywheels go with proportionally lightened vehicles.

#7 NoahDL88

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Posted 23 November 2006 - 05:52 PM

A lightened flywheel does not loose torque, it looses inertia:rolleyes:

#8 Qman

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Posted 23 November 2006 - 06:13 PM

All these points are reasonable. Not completely accurate but without knowing what he is doing with said vehicle all this means nothing.

So, what vehicle are you installing this flywheel into? What will the primary use be?

And for the record, all my vehicles have lighter flywheels. Including my big Brat. Never seemed to have any problems with the bottom end torque or pulling people's stuck butts out of the goo!

#9 baccaruda

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Posted 23 November 2006 - 07:08 PM

You might also try and find a deal on an XT6 flywheel. It's a little lighter than the EA82 cars' flywheels, and it would possibly be cheaper to get an XT6 FW instead of paying to have yours lightened and rebalanced.

My EJ wagon has an XT6 flywheel that I was fortunate enough to find at the parts yard (stock would have been fine with me but i found the flywheel at the right time). I haven't finished the car yet though so I have no idea how it runs :P

#10 dixracing

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Posted 24 November 2006 - 10:05 AM

i raced 4 cycle karts for years....these alcohol briggs engines are way under powered like the soobies.......so i would opt for the heavier flywheels for the momentum advantage coming out of the corners......don't kid yourself it works.......ask the guys that were looking down my header tube how it worked......hehe :burnout:

#11 Jerry DeMoss

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Posted 24 November 2006 - 10:13 AM

There is one on ebay for ea81 right now. I have tried a lighter flywheel before on a truck and I know for sure that it wouldn't be the best idea for offroad unless you are quick on the throttle.

#12 beataru

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Posted 24 November 2006 - 08:29 PM

Whered you get your Flywheel?? or did you just have yours lightend?

#13 carfreak85

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Posted 25 November 2006 - 01:26 AM

A lightened flywheel does not loose torque, it looses inertia:rolleyes:


AMEN!!! I'm shocked that that it took five posts to get the truth out. A lightened flywheel will:

NOT reduce torque
NOT change the torque curve for the worse (WILL look better)
make it easier to stall
make your clutch easier to overheat (You are lightening your heat sink)
NOT change your gearing
NOT make it harder to accelerate up hill

#14 HATCHY

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Posted 26 November 2006 - 08:08 PM

Thanks guys. Forget the flywheel. I dont offroad my hatch anymore. I driver it on street or gravel now thats it. Where can I curve the disty? Im going to do that for sure. Any iea on the price of that as well.... So a lighter flywheel not a good move?

#15 NoahDL88

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Posted 26 November 2006 - 08:53 PM

Philbin, a place in oregon will recurve for i believe around 40-60 bucks, provided your disty can be used.

I thought i had their phone number, but it turns out i don't

#16 GeneralDisorder

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Posted 27 November 2006 - 04:44 AM

Very good guys:

http://www.philbingroup.com/

GD




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