Lightweight FlyWheel - myth?

[D-UNIT]

This has been bothering me for some time. Is there an actually documented performance gain from Using a lightweight flywheel. All I hear is that it takes away torque especially going up hill. I think that is bad , especially on an I-4. Why would you want to lose torque without gaining HP. Everyone says it revs quicker and feels faster. Does anyone have actual proof ( dyno runs , 1/4 mile times , hear say).

My friend put one on his car and lost 1.3 sec on the 1/4 , but he immediatly went turbo and gained 2.7 sec back. So he attributed his weak 16.3 sec 1/4 mile to a cam/ ignition problem , but he didn't touch either when he changed his clucth. I say it was the flywheel , but he won't take it off. I need more proof.

[KDashy]

Lightenend flywheels make your car gain and lose RPM's quicker because there is less weight on the crankshaft, which makes shifting quicker.

The only problem is for the cars with narrow powerbands (high revving cars), the revs can drop off the powerband before you release the clutch, so you'd need to work on your shifting.

Modified by KDashy at 8:42 PM 2/8/2005
Modified by KDashy at 8:50 PM 2/8/2005

[dal2kvvisp]

It has had to be installed SEVERLY wrong if that was the cause of your buddy losing a whole 1.3 seconds in the quarter, thats a lot of time... its less rotational mass, and correct me if im wrong but i think i remember it being 1lb of rotational mass = roughly 50 lbs of dead weight added to the car am i right?

[Axel Grungy]

i drove my freinds civic with a lightened flywheel, shifting was funny. you pretty much had to keep your foot on the gas when shifting cuz it dropped revs that quickly. it didnt seem any faster tho. i didnt like it

[getnrowdy23]

umm... if it drops revs that fast it means it would rev up equally as fast, thus getting to the next gear is quicker, thus a quicker car. atleat that is how it works on my sr with fidanza flywheel. i like it. but it does drop revs in a hurry, so i just shift from 2nd to 4th a lot =) in the city goofing around of course

[w1ngzer0]

i don't understand this "drops to fast" thing. I figured droping fast would be a good thing. I meen it still drops to a certain rpm when you shift right? usually ni my ka24e if i shift at 3k it droped to 2.4

Does it drop lower or what>?

[getnrowdy23]

if your car stock drops to 2.4 then with lightened flywheel it could drop to 2.0 or lower if you suck at shifting

[w1ngzer0]

lol wow .... obviously not ment for daily driving.

[colies97~240sx]

I have a lightend flywheel and it is fine for daily driving. However I learned to drive manual with the lightend flywheel, (did the transmission swap back in aug.) So I cant tell you what the differences are between stock and the lightend flywheel, just that i personally have had no problems with it on my 240.

[MinisterofDOOM]

i don't understand this "drops to fast" thing. I figured droping fast would be a good thing. I meen it still drops to a certain rpm when you shift right? usually ni my ka24e if i shift at 3k it droped to 2.4

Does it drop lower or what>?

The KA has a fairly wide powerband for a L4. The negative effects of a lighter flywheel would not be as evident in a KA as in a higher revving, narrow powerband engine. If I lightened the flywheel on my '04 Maxima, which has a very wide powerband (from about 2 clear up to 6.5) I would hardly notice the negative effects.

There's a wording error in saying "a lightened flywheel makes more horsepower." While it can, and usually does, FREE UP additional horsepower, much like a more free flowing exhaust or aftermarket underdrive pulley, it does nothing to add to the power produced by the engine. What it does is help to get more of that power to the wheels.

Another downside to a lightened flywheel is less comfortable daily driving conditions, as letting off the throttle will more quickly cause deceleration, which in a manual can cause jerkiness.

[hatebobbarker]

lightened flywheels are really good on a roadcourse,

[Nismo_Freak]

Lightweight flywheels can make launching a tad bit awkward. If it was his first time out to the track with the flywheel then that could account for a few tenths but not 1.3 seconds. That sounds like a problem with the car.

[Toddles82]

i don't understand this "drops to fast" thing. I figured droping fast would be a good thing. I meen it still drops to a certain rpm when you shift right? usually ni my ka24e if i shift at 3k it droped to 2.4

Does it drop lower or what>?

That form of dropping when shifting gears is function of gears not a flywheel. The dropping they are talking about is best illustrated in neutral. If you reved a stock flywheel car and it takes 1 sec to go from 7K-5K then a lightened flywheel car might take .5 secs or something.

[nsrZ32]

lol

Nothing bad about a light weight flywheel. Anything that can reduce strain on the crank and reduce rotational mass is only a plus. Remember that the flywheel and the damper are the two external bolt ons to the crank at each end and heavy pieces can cause parasitic drain. Same basic idea with an aluminum driveshaft or a lighter crank.

Definately not a bad thing.

[themadscientist]

I can testify that a TODA flywheel made my Silvia scream on the top end but I lost a ton on the line, CA18DEs are not exactly torquey.

[cnickk]

yeah well there is no lag between my paddle shifters in the Enzo...

id rather drive the jcar

[hatebobbarker]

lol

Nothing bad about a light weight flywheel. Anything that can reduce strain on the crank and reduce rotational mass is only a plus. Remember that the flywheel and the damper are the two external bolt ons to the crank at each end and heavy pieces can cause parasitic drain. Same basic idea with an aluminum driveshaft or a lighter crank.

Definately not a bad thing.

dude its all abotu the carbon driveshaft!

[fangt317]

hey where can i get a mini s14?

[Axel Grungy]

hey where can i get a mini s14?

in photoshop

[240marcuSX]

are the effects of a lightweight driveshaft as noticeable as the effects of a lightweight flywheel??

[Jeff Williams]

I would think, since the dirveshaft does not "freewheel" when you push in the clutch, that the "effect" of engine RPM dropping fast during shifts, would not be the same.

Now, lightening any rotational mass of the dirveline will net more HP from the engine making it to the pavement.

Because of the efficiency of the transmission, the net "effect" would vary, based on what gear the car was in.

Lighter wheels, rotors, driveshafts, hubs, flywheel, harmonic balancer, pulleys,...they all affect the ammount of HP that gets to the pavement.

When the car is in gear, and you are using the rotational mass of the drivetrain to slow the car, any reduction in mass will affect the outcome.

[Dattebayo]

I have one on the KA and it's not really a big change for the bottom end as ive noticed.

Maybe your 1/4 mile track where you live is actually uphill, i know for sure that 75 & 80 track here in MD is uphill (an import vs american bias these rednecks have around here).

[crzycav86]

are the effects of a lightweight driveshaft as noticeable as the effects of a lightweight flywheel??

This is a classic physics-type question.

You can use physics formulas to determine which mod is more beneficial. I can do it if you supply me the diameter, thickness, and weight of the flywheel; and the diameter, length, weight of the driveshaft. It's a piece of cake.

[Onizuka]

I have an aluminum flywheel and aluminum driveshaft, makes for a very sporty ride. I also drive it with a ACT street clutch about 2.5 hours every day in stop and go traffic. Its a pain in the ***, but I dont think they flywheel makes it any worse.

[nametakennow]

are the effects of a lightweight driveshaft as noticeable as the effects of a lightweight flywheel??

In terms of performance gains, yeah, you'd have to run the numbers (or get two cars and race, of course).

However, in terms of driveability, the driveshaft would be just like driving a stock car, since the driveshaft is connected to the engine via the transmission, and thus the driveshaft would spin at the same rate as the transmission, rather than the engine (as with the flywheel).

Personally, I go back and forth on whether or not to get one (later). I guess it depends on if I go N/A or turbo, something I'm working out now. Boost (low boost, in my case, high boost + 2 litres + FWD = lag + burnouts, and lag/dead tires suck) = flywheel unless I hear really bad stuff. I guess it really is something you have to try on one car and see if it's something you want to do to future cars and/or your own (if tried on a friend's).

[240marcuSX]

ive always figured that a lightened driveshaft would be just as beneficial but less detrimental (sp?) of course ive never calculated anything, just figured it as common sense, but i was just looking for others input on it.

[Onizuka]

Definatly.

Aluminum driveshaft vs aluminum flywheel: I'd pick the driveshaft every time.

-Cost: Driveshaft only $75-150 more -Installation: Driveshaft is a piece of cake, flywheel is a major pain in the arse. Driveshaft is litterally a 10 minute install with basic tools (although a torque wrench is highly recommended for the 4 differential plate bolts)

-Driveablility: as mention before, flywheel will make things worse, driveshaft has no negative effects other than some noise.

-Performance: the flywheel will make for faster shifting, better clutch engagement due to new friction surface, and reduce rotational mass. Driveshaft only reduces rotational mass

-Weight: With either one you are shaving alot of weight off the car, driveshaft is more though

-Other: with a one peice driveshaft, the bearing hoop your old two peice used to sit in is now a driveshaft hoop safety device, required in certain motorsports, higher level drag racing in particular.

[hatebobbarker]

ive got a carbon driveshaft, but it came that way so i dont know what its like without it.

[EZcheese15]

The reason you lost time on a 1/4 mile is because the lighter flywheel has a lower moment of inertia. When the car is revved at the start, you increase the inertia. A lighter flywheel has less of an increase, while a heavier one would have more of an increase.

When the car is launched, with a HIGH moment of inertia, the inertia of the flywheel actually helps to accelerate the vehicle faster because the engine has to do less work to get the car moving. With a lighter flywheel, and LOWER moment of inertia, the engine has to work harder to accelerate the car. For this reason, a Pro Drag racer will opt for a HEAVIER than stock flywheel.

The reason lightweight flywheels are so popular is because of road racing, not drag racing. During a road race, many gear changes take place, including many downshifts. When heel-toeing, the idea is to rev-match a gear before shifting. It is easier to rev-match a gear when the time it takes for the engine to speed up or down is minimal.

So bottom line is this:If you do a lot of road racing, lapping days, even autoX, then a lightweight flywheel is what you want.

If you do a lot of drag racing, you actually want a heavier flywheel. Because these are unpopular, your best choice is usually the stock one.

[D-UNIT]

Good info. That is why I need "proof'' ( actual numbers), everybody just gets one because they are changing their clucth. My friend's stock flywheel weighed 22 lbs. The racing one he bought was 6.5 pounds. I swear I can upshift and downshift it like an auto trans ( faster even). It's great till your revving a little high and coming to a stop. Stall city. Better get your foot back on the gas.

So EZcheese15 your are saying if my friend puts the stock flywheel back on he should hit high 12's. Sounds good , but I thought turbo engines were supposed to benefit from light flywheels. Also if you lose that much on the 1/4 I'm sure you would see it on the road course. I still don't see how losing torque and not gaining any HP, is a benefit. Sounds like an oxymoron to me. "Feels faster" and "is faster" is different to me.