Big Debate on Lightening (Flywheel, underdrive, etc.)(not stupid ricer post)

[undrcroft]

i Knew there was some debate on lightening stuff but not to the extent i have seen recently. If this has been posted b4 i appologize, but i searched and couldn't find where an open debate had occured. I'm going to be driving long distances pretty soon, so i am looking for not only performance, but to make performance easier.
First: lightened flywheel
From what ive seen, shop can take it from about 20lbs to 12(taking 3rdcamry 4cyl here). Fidanza can do it up aluminum to 11lbs for quite a bit more than a shop. Someone recently mentioned a problem with it being balanced. If you get the shop to balance it, how could this be a prob? and do fidanza and other comp's not balance it? Now if balancing isn't a prob. then what iz? From what i hear it rev's easier/ faster but since it is no longer as heavy it's own wieght doesn't keep it moving which causes the car to drop rev's/gears alot faster when you let off the pedal. Now in a drag who cares what happens once you are letting off the gas, but does it really cause a loss in timing in a rally( going into turns etc) and what about daily driving? is it really that annoying. I would prefer if i want the car to slow down/drop gears for it to do so as fast as possible. Save a little wear and tear, save a little gas, and make the brakes' job easier. Am i right or way off?
Second: Underdrive crank pulley
basically works the same way, except makes the crank work less. Same problem apparently with balance though, but isn't that only a problem with cars that have a balance on the outside on the crankshaft. You have to take the balance off to put the underdrive pulley on(camaro's etc. whos cranks shafts aren't even and balanced) but with the camry the crankshaft isn't balanced but is balanced from the inside by the two balance shafts on each side. If it's balanced from the inside, then the crank pulley shouldnt be balancing anything. Hence replacing it with a lighter/smaller one wouldnt' effect anything. right? Does underdriving the crank pulley cause the same effect of dropping speed real fast as much as the flywheel, or not noticable?

I know it's alot of questions but I'm sure you "hardcore" techie freaks have alot of opinions. share them with the rest of the class.

[rezzle]

Simple ..

Lightened flywheel.

Advantage:
Removing weight from the flywheel enables faster rev upand adds a couple of horsepower.

Cons ...
Engine has to be rebalanced or there is a possiblity of extreme Crank wear and or worn front seal..
Shifting may be difficult with a standard causing premature wear on the synchros because flywheel and transmission gear selection from the factory are matched.

Increasing the crank pully size.

Pros
Can save a couple of HP becasue the alternator and water pump do not need to be run at the speeds they attain at redline.

Cons
They do need to maintain a certain speed at idle and serious engine damage can result in traffic.


My opinion:
Is it worth damaging my engine for a measly 15 HP gained for $1200 worth of modification? .. NO
Could it be worth it for someone who is going to do nothing but race their car? Probably.
Would I reccommend these mods to anyone who drives their ride on the street? Hell no.

[undrcroft]

ok well on the first one why would the engine need to be rebalanced if the flywheel has already been balanced?

second part: first $1200? what have you been pricing?
second i'm not talking about underdriving the alternator, or any pumps, im talking about just the crank. everyone knows about the problem with underdriving the alternator especially me. I'm running a system, i need the power for the subs.
what would cause problems with just underdriving the crank? no balance issues right?

[Nick]

the whole thing needs to be rebalanced cuz the weight isn't even on either end, so the end pistons move the ends more, eat bearing

like rezzle said, if you get the whole thing rebalanced with pulley and flywheel, then go nuts, but its expensive, not jsut bolt on

[Tony the Tiger]

Since undrcroft requested my advice on his thread, I will therefore, write a novel... It will be a good read for most folks too

Lightening Flywheel:

There is no set perfect weight for all cars, and lighter is definitely NOT better. For the street, you need your car to idle and not stall on you as you clutch in, so choose the weight wisely. If you are boosted, you would want to opt for a flywheel that has some mass (ie: shaving off 4-5 lbs depending on engine) that can carry the rotional weight before the turbo spools. If the flywheel is too light, the engine revs up too easily and there will be almost no load on the engine. No load = no exhaust gases = late spool.

Almost all of the aftermarket flywheels comes balance, but a lighter flywheel also has less mass to withstand the drivetrain shock during both normal driving and racing. A heavier pressure plate requires a flywheel that can take the abuse. I am sure you guys have heard of race cars shattering flywheels during launches, and most of time it is due to bad flywheel selection. When the flywheel is light, the ability to take the impact of a heavy PP is drastically decreased. So when choosing a flywheel, you will also have to look at what clutch you are planning to run.

For the Camry, I would suggest a 10-12 lb flywheel because our motors makes the most power during mid RPM's. A flywheel that's too light will end up with a weak midrange because the engine is still trying to "out-accelerate" itself before its torque peak. You would want a flywheel to be able to carry the engine's momentum just a bit before the torque peak so there will be no loss of power and response. The best way however, is to ask Camry owners with lightened/aftermarket flywheels because "streetability" is an issue that is based on people's feedbacks and opinions. Some might like all top-end performance, and some might like beefy midranges. It's all preference.


Crank Pulley:

For crank pulley, very little weight isn't really the cause of problems. For engine crank pulleys, the lighter is better, but it can only get so light before you encounter harmonic problems. There are physical balance and harmonic balance (dampening). Physical balance being fully balanced as the pulley spins, and harmonics are about dampening the engine's vibration and "odd forces". Odd forces are what we get from the power stroke as the fuel/air ignites, and detonation is also one of the forces you wouldn't want to "shock" the engine's internals. If the engine runs without being dampened by the stock crank pulley, it will eventually cause premature bearing wear and also a lost of power because the energy is being hit back to the engine crankshaft. I believe some of you have heard about the ATI super dampers/pulley, and the ATI pulley is not really lighter than stock actually. It was designed to only absorb the vibrations better than stock, and they achieve this through a liquid-filled dampener/pulley. The fact that it absorbed more vibration resulted in noticeable power gains and longer engine life (for race motors especially).

Most of our factory crank pulleys are filled with very solid rubber/plastic-like material in the centre. These rubber absorbs the engine's vibrations and keep our engines happy. The rubber might be heavy, but it serves a purpose. We have people making aftermarket lightweight crank pulleys, BUT the only way to lighten them more than stock is to completely eliminate the rubber centres and CNC a lightweight crank pulley. These are physcally balanced, but they lack the harmonic dampening properties and can't absorb the vibrations.

So all in all, I do not recommend changing out the factory crank pulley. One alternative way to getting a lighter crank pulley is to swap to another lighter factory pulley from another car. Sort of like Honda guys swapping to the ITR crank pulley. If you want to free power from the PS and alternator, get a set of accessory underdrive pulleys and leave the crank pulley alone.

[rezzle]

Every part of the engine weighs slightly different from car to car. The harmonic balancer on your car is for .. your car .. changing the flywheel will in no other terms fuck this up. Even worse, The more you lighten the flywheel the greater the chance of any internal imblance being noticable or damaging becomes. I don't even know if there are many automotive shops around that would have the right equipment to check and repair and imbalanced engine. I think perhaps a millwright shop or HVAC balancer would have the right stuff.

Where I work (an OEM HVAC company) we use CSI balancers they cost about 20,000 a piece not incuding sensors and software. We use them to balance all air blowers in excess of 13" diameter. Auto shops are not likely to shell out 20 grand for something they would do maybe once every year or two.

Like I said I wouldn't reccomend it for the street because there are plenty of ways to gain a HELL of a lot *more* than a 15 measly HP for 1200 dollars. When I am done my car I will have at least a 60 HP gain .. at the wheels and I will have less than $500 in mods.

Am I stopping anyone from doing it nawww ... whatever floats your boat man. If you really really need those extra ponies then ya I would do it. I had done both mods on a couple of road race cars I had built, a 240Z and a '72 corolla. However those cars never saw any time in traffic.

'Luck.


EDIT:
I type flappin slow Both of the above posts never existed when I started this one ... That is why I don't write novels ... Thanks for filling in the gaps Tony.

[undrcroft]

well i was manily asking about crank pulley and not the ps and alt. because not only is it bad on them but because i haven't seen pulleys to underdrive them anywhere anyway after quite a bit of looking. if there is a good pulley(not necessarily(sp?) lightened)for the crank, then where from? what company or what cars have one that would convert.
also something about the crank that i forgot to mention. my cousin mentioned something to me with a bit of caution. what about taking out the balance shafts? they obviously take power away from the crank, but obviously make it a bit rougher on the engine. BUT, how much rougher. didn't sound like a good idea to me, but is the camry crankshaft balanced enough on its own already or does it need the shafts?

[Nick]

stock engine with nothing broken or too worn down should be perfectly balanced

[undrcroft]

oldman, without the balance shafts or just in general?

[rezzle]

Originally posted by undrcroft

also something about the crank that i forgot to mention. my cousin mentioned something to me with a bit of caution. what about taking out the balance shafts? they obviously take power away from the crank, but obviously make it a bit rougher on the engine. BUT, how much rougher. didn't sound like a good idea to me, but is the camry crankshaft balanced enough on its own already or does it need the shafts?

Shafts?
Extra shafts?
I don't understand.

[undrcroft]

rezzle the crank shaft has two balance shafts on each side to keep it balanced as it turns

[Nick]

i can't picture this either

[undrcroft]

you can't picture the shafts or you can't picture taking them out? just check a chilton or haynes. its in there. theres two shafts on each side of the crank shaft to keep it balanced. hence there name. balance shafts

[warlock]

how about the flywheels with most of the weight in the center.
same weight but lighter to rotate?

[Nick]

as long as I the coefficient of rotational inertia is the same, then its ok, but then i think it the rest would have to be too thin