Hello people,

I know questions have already been posted aboutl lighter flywheels, but my question is...if i were to put on a 11-12 pound flywheel, wouldn't i have to balance the crank shaft? If so, how much effort would that take, and any ideas as to how much i can expect to spend?

 

I really dont think there would be a need to balance the crank, but if you really wanted you could get the crank micropolished/balanced for 150 or less. Take into consideration that you have to pay someone to take off the header, drop the oil pan, remove the windage tray and pickup, and remove the crank etc. before you send it out

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DJP &raquo;</TD></TR><TR><TD CLASS="quote">if i were to put on a 11-12 pound flywheel, wouldn't i have to balance the crank shaft?</TD></TR></TABLE>

No, you can just bolt it on.

 

When would be a scenario where you would have to rebalance the crankshaft? How light of a flywheel would you have to have in order to do so?

 

its not about how light you go. the flywheel you get should be balanced when you buy it.

 

honda cranks are zero balanced from the factory so it shouldnt matter how light a flywheel you pick as long as its correctly balanced when you buy it

 

Three question. How would i know whether the flywheel l buy is balanced.. where did you read the hond cranks are zero balanced straight out of the factory?...and.. if i WERE to put a 9 lbs flywheel, i know i would notice an increased acceleration from a stand still, but would i notice a dramatic difference in acceleration if i were to try and do it from a steady cruise?


Modified by DJP at 12:36 PM 7/12/2007

 

can't remember where i read it but going by the fact that the motors are revving to over 8000 rpm if they werent balanced they would shake themselves to bits!

as long as the flywheel is made by a decent company like act or fidanza it will be balanced

last question, since the moment of inertia is less with a lightened flywheel any acceleration will be quicker whether fromn a standing start of a rolling run

 

Like I've said in numerous threads like this before, a lightened flywheel is no good for a street car, there is a reason they weigh 18lbs, and its not because Honda wants to slow you down, if they wanted that they would take your VTEC.

The crankshaft and rotating parts depend on the flywheel to take combustion stress off of them by introducing an inertial weight. (the flywheel) By using a heavier flywheel, it takes considerable stress off the rods/pistons because instead of allowing combustion to force them down, the flywheels rotating weight helps pull them out of TDC, reducing the stresses induced on them, and providing reliability as a result.

Light weight flywheels will provide a snappier response, but at the cost of reliability of the internals. 14lbs would be the lightest I would safely go, as there are much better ways to add power and response to an engine, such as cams.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">there is a reason they weigh 18lbs, and its not because Honda wants to slow you down</TD></TR></TABLE>

No, it's because the average consumer doesn't want a lightweight flywheel.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">Light weight flywheels will provide a snappier response, but at the cost of reliability of the internals.</TD></TR></TABLE>

If you're going to make claims such as this, support them with some actual direct proof.

 

And why would they not want a lightweight flywheel? because it vibrates, caused by undampened pulses in the rotating assembly. The same reason applies when reciprocation becomes a major factor and balance shafts are used to also null the vibration of the engine (mainly in inline configurations because of the unbalanced nature of the power stroke, it is present in V type engines as well, but it is not as obvious because the pistons are fighting control over the crank at an angle to each other.)

Crank dampers are also used for the same reason, and I will post this as well so you can see the effects of unbalanced reciprocation and the vibration it produces, if that does not show the loss of reliability, I don't know what will...

https://honda-tech.com/zerothread?id=2038319

http://en.wikipedia.org/wiki/Flywheel

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">And why would they not want a lightweight flywheel? because it vibrates, caused by undampened pulses in the rotating assembly.</TD></TR></TABLE>

Your posts give the impression that you've never actually driven a car with a lightweight flywheel. There is no excess vibration. The reason that the average consumer prefers a heavier flywheel is because he does not want to experience the rapid drop in revs or the lack of momentum that requires a bit more attention and skill when driving.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">The same reason applies when reciprocation becomes a major factor and balance shafts are used to also null the vibration of the engine (mainly in inline configurations because of the unbalanced nature of the power stroke</TD></TR></TABLE>

Most Honda I4's don't have any balance shafts, and the B18C5 or B16B will happily spin at 8000+ RPM with their stock ~15 lbs flywheels (only 1 pound above your arbitrary safety limit) and not experience any adverse issues.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">Crank dampers are also used for the same reason, and I will post this as well so you can see the effects of unbalanced reciprocation and the vibration it produces, if that does not show the loss of reliability, I don't know what will...

https://honda-tech.com/zerothread?id=2038319</TD></TR></TABLE>

All I see in that photo is a broken oil pump. I could likewise post a photo of a broken camshaft, but it certainly wouldn't be direct proof that a lightweight flywheel will cause any "loss of reliability".

 

If course the 1.6 and 1.8 Honda engines don't have balance shafts, they are still too small in displacement for that, look at the 4g63, h22, k24 or any other large displacement 4 cylinder, I was simply stating a fact that is relevant to all cars, not just Honda.


Taken from Wikipedia.org:

A flywheel is a rotating disk used as a storage device for kinetic energy. Flywheels resist changes in their rotational speed, which helps steady the rotation of the shaft when a fluctuating torque is exerted on it by its power source such as a piston-based (reciprocating) engine, or when the load placed on it is intermittent (such as a piston pump).

Therefor, the heavier the flywheel, the steadier to rotation, and the smoother the engine operates. It also stores potential energy. (which translates to much better initial torque and torque during shifts) I highly doubt that car manufacturers put heavy flywheels in a car just so people do not have to shift fast. Obviously the Type R appeals to a younger crowd. So why not throw a 6 pounder on there? That is a lot of material/money wasted in creating a huge flywheel and I'm sure manufacturers know the game better than we do.

Like I said, drivability and reliability should be a big issue. No one wants their project car to explode, so reliability where you can get it and keep it is a good thing. Initial torque and smoother operation are a plus side. By reducing this weight you give up initial torque and smooth operation for faster engine RPM and a slightly higher peak toque, so in effect it will be beneficial to a redline Honda owner, but there are better ways to go about making power as I said before without the need to sacrifice driveability.

 

i agree with slow. You shouldnt go much lower then 14 pounds on a street car. i think most race cars are in the 11-12 pound range.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">It also stores potential energy. (which translates to much better initial torque and torque during shifts) I highly doubt that car manufacturers put heavy flywheels in a car just so people do not have to shift fast. Obviously the Type R appeals to a younger crowd. So why not throw a 6 pounder on there?</TD></TR></TABLE>

A heavier flywheel is not going to create more torque, it will simply allow for a greater margin of error while driving. As I said, if you had experience with a very lightweight flywheel, you'd understand that it isn't something that the average consumer (even some enthusiasts) would likely appreciate, just as most consumers would not appreciate the trade-off in ride quality that a race-ready suspension setup offers, or the high NVH levels generated by solid poly engine mounts. Auto manufacturers are constantly seeking the best possible compromise, even in high-performance models.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Amped &raquo;</TD></TR><TR><TD CLASS="quote">i agree with slow. You shouldnt go much lower then 14 pounds on a street car. i think most race cars are in the 11-12 pound range.</TD></TR></TABLE>

Again, have you driven a car with a very lightweight flywheel for any length of time, or are you simply choosing an arbitrary number? Even a 7 lb. flywheel is perfectly daily-driveable on a Honda, and in fact I (and others) greatly prefer it.

 

Do you have a flywheel that's less than 10lbs currently installed in you car? If so, did you notice a great gain in terms of off the line acceleration as well as from a constant speed acceleration?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DJP &raquo;</TD></TR><TR><TD CLASS="quote">Do you have a flywheel that's less than 10lbs currently installed in you car? If so, did you notice a great gain in terms of off the line acceleration as well as from a constant speed acceleration?</TD></TR></TABLE>

It's my brother's car, and it's 7.5 lbs.

What is most noticeable is the engine's willingness to rev, and the fact that the revs will drop more quickly with the clutch in. I would not say that there is a "great gain" in acceleration, but that isn't really the purpose of the part.

 

what would be a part that i would be interested in if i would like to see the gains that i have previously mentioned?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">

A heavier flywheel is not going to create more torque, it will simply allow for a greater margin of error while driving. As I said, if you had experience with a very lightweight flywheel, you'd understand that it isn't something that the average consumer (even some enthusiasts) would likely appreciate, just as most consumers would not appreciate the trade-off in ride quality that a race-ready suspension setup offers, or the high NVH levels generated by solid poly engine mounts. Auto manufacturers are constantly seeking the best possible compromise, even in high-performance models.</TD></TR></TABLE>


Again, from Wikipedia:

A flywheel is a rotating disk used as a storage device for kinetic energy.

I guess that energy just disappears into nowhere. If they are striving for the best possible compromise, why bother changing it, you would be doing yourself a disservice if that holds true.

I have driven an ITR with a act streetlite flywheel and exedy stage 1 clutch, and it takes substantially more gas and playing with the clutch than a stocker, personally I don't like it because I drive my car all the time, and playing with the gas and clutch to get going is just another inconvenience I would rather not have.

I prefer driveability, and after experiencing that ITR, I think 14ish would be an ideal weight for performance and driveability.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">Again, from Wikipedia:

A flywheel is a rotating disk used as a storage device for kinetic energy.

I guess that energy just disappears into nowhere.</TD></TR></TABLE>

"Store" does not equal "create".

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">If they are striving for the best possible compromise, why bother changing it, you would be doing yourself a disservice if that holds true.</TD></TR></TABLE>

Because I, and others, am willing to accept different degrees of certain attributes than what the general public might prefer. When you tune your car, you tailor it to your own personal preferences, thus allowing you to eliminate or reduce many of the compromises that the original manufacturer had to make in order to satisfy the public at large and sell cars.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote">I have driven an ITR with a act streetlite flywheel and exedy stage 1 clutch, and it takes substantially more gas and playing with the clutch than a stocker, personally I don't like it because I drive my car all the time, and playing with the gas and clutch to get going is just another inconvenience I would rather not have.</TD></TR></TABLE>

That's your preference, which you're entitled too. Not everyone shares that preference.

However, you've strayed from your original comments regarding potential engine damage, and turned the discussion into one of personal preference. The fact that you prefer the driving experience provided by a heavier flywheel is perfectly fine. The fact that you were previously trying to convince people that using a lightweight flywheel would somehow damage their engines while providing no factual evidence, isn't.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DJP &raquo;</TD></TR><TR><TD CLASS="quote">what would be a part that i would be interested in if i would like to see the gains that i have previously mentioned?</TD></TR></TABLE>

Anything that will increase the power output of your engine, or installing a different final drive in your transmission.

 

Engine creates it, engine stores it through centrifical movement and mass, objects in motion will stay in motion unless acted upon by an outside force. (clutch)

Your very true there, personal preference does have something to do with it.

The weight of the flywheel helps dampen the power pulse as to not shock the crankshaft as severely, which reduces vibrations in the rotating parts, just as balance shafts and dampened crank pulleys do. The smoother the operation the better, and that is really dependent on the engine itself. The 3.5L Nissan 350Z uses a 23lb light flywheel, which is ungodly for a Honda, but helps the engine rotate smoothly. In a 4 cylinder engine, there are two power pulses per revolution as you know, and this rotating weight helps maintain a constant speed, which reduces vibration and absorbs the pulse, creating stored energy, which like I said is only very useful during shifting and launches.

Like wheel hop, parts don't like to be started and stopped because it breaks them, and in the wheel hop department it is axles, the same rule would apply there. I've never seen one fail, but physics do not lie, and I would like to make that point because it is a factor to consider, and auto manufacturers obviously have. I should not have came off so hard on it, because I have not personally seen any drastic failures of a flywheel, but that does not mean that it can't happen.

 

of what relevance is a nissan 350z in this topic?
if you choose not to install a lightweight flywheel in case your engine spontaneously combusts then thats your choice but all i see is internet scaremongering here....

 

io went from a stock gsr flywheel to a honda lightened 9lbs fly wheel and noticed that i get wheel hop. never had the wheel hop before til the install. should i go back to the gsr flywheel?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pimpinblackcivic &raquo;</TD></TR><TR><TD CLASS="quote">of what relevance is a nissan 350z in this topic?
if you choose not to install a lightweight flywheel in case your engine spontaneously combusts then thats your choice but all i see is internet scaremongering here....
</TD></TR></TABLE>

You must realize that a 4 cylinder engine only has two power pulses, that at MOST last for about 35 degrees of crankshaft rotation, the rest of the time it is slowing down, until the next power stroke, and it happens all over again. This causes vibration due to changes in the flywheels speed, if you take the weight away, you are taking away the engines ability to coast into the next power stroke, and will accelerate the speed fluctuation of the rotating assembly/flywheel because the weight is less, which causes driveline vibration, and engine vibration as well. Physics don't lie.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSRpoweredSI &raquo;</TD></TR><TR><TD CLASS="quote">io went from a stock gsr flywheel to a honda lightened 9lbs fly wheel and noticed that i get wheel hop. never had the wheel hop before til the install. should i go back to the gsr flywheel?</TD></TR></TABLE>

That is completely up to you, if you don't want to deal with it, go back. Both sides have their ups and downs and driveability is more important for me right now.

 

yeah i think i will go back to my gsr one. i really didnt feel that much of a difference in acceleration. should i have it resurfaced before putting the old one back in.