Lightweight flywheels ?

Kompressor · #1 04-17-2006, 11:51 AM

Ok i have a my custom unorthedox lightwieght flywheel that I believe is half the weight of the original, this is the second one ive owned, this one for my mercedes my first one for my focus, i have yet to get one on one of my cars though. the one i just was gifted for the mercedes a friend of mine had made special but he sold his car and now I have all his old parts.

the flywheel is pretty new only like 10k miles on it. a few questions should i have it resurfaced if so then why and if not also why not.

now some general questions, per my friend having the flywheel on the car freed up 8hp and 9tq per dyno testing, this sounds good to me but I am also more interested in faster revs, and crisper shifts with the clutch im going to buy. what i want to know is the benifits/risks of using lightend flywheels, or in this case manufactured lighter to begin with its all aluminum except for the friction surface. the stocker is all steel. I believe this flywheel is half the weight of the stock piece, stock is like 27 pounds this one is closer to 16 pounds, the only drawback i can think of is faster revs mean i loose rpm's faster too but i can learn how to drive it.

heres what i have been told about lightwheight flywheels

benifts=
-faster revs
-less rotating mass= more usable power
-less weight on bearings=longer bearing life

problems=
-if its too light uphill travel or maintaining speed can be a problem
-revs can fall off too quickly while shifting if its too light for proper power band usage

I assume this one is not too light, Im guessing someplace in the 9 pound range or lighter id have the negative effects. so who has em who likes em and who knows the details about them.

Stack · #2 04-17-2006, 01:48 PM

Here's my 2 cents worth...

The biggest factor is clutch choice. Certain types of clutches don't work well with lightweight flywheels. Chances are your stock clutch will not be ideal for the lightened weight of the flywheel. I don't know the physics behind it, but the flywheel and clutch certainly have to work together properly, so find out the specs of the clutch you will be using and make sure it won't cause problems.

I think its usually a matter of learning the pros and cons of a lightened flywheel as it pertains to your car. On track, you really have to be pretty decent at heel/toe rev-matching - and if you're not used to the flywheel, that will take some practice. Upshifting will also take practice, since you'll have to be quick so as not to lose engine momentum during the gear change... but I've found thats not a big deal (at least in my car). Once the clutch is engaged, there should be no ill-effects other than getting used to the quicker revs (both up and down).

My guess is a lightweight flywheel is more beneficial to low horsepower, lightweight cars. My Z is a straight 6, approx 130 wheel horsepower, weighs about 2500lbs with me in it. It has a 9.5 lb Tilton flywheel with a Centerforce II clutch - I drive it every day, and its silky smooth. It revs VERY quickly (sometimes too quickly on upshifts if my timing is a bit off with engaging the clutch and getting back on the gas.) Stock I think, is about 23 lbs.

I don't buy into the idea of problems with going up hill... anything where you reduce the amount of weight the engine has to spin will help in all aspects of performance. Lightweight flywheel are similar to lightweight wheels in terms of needed less power to turn them.

Most of the drawbacks have to do with street driveability - on the track, you should only see positive effects.

Kompressor · #3 04-17-2006, 02:08 PM

thanks that was helpful I was going to go with an unorthedox stage 2 or stage 2+ clutch, both have substantially more clamping pressure then the stock clutch is that what im looking for in a clutch ?

Stack · #4 04-17-2006, 02:42 PM

Quote:

Originally Posted by Kompressor

thanks that was helpful I was going to go with an unorthedox stage 2 or stage 2+ clutch, both have substantially more clamping pressure then the stock clutch is that what im looking for in a clutch ?

Well... like I said, I'm not sure about the WHY ... but again, its more of a street driving issue. Here's my theory, and it is a completely un-educated theory... based mostly on what I've read on clutch and flywheel manufacturer's websites, so please, if anyone has any more technical knowledge, let us know... but here goes:

A clutch works similar to a brake - a friction material being clamped onto a metal surface. The faster that surface is spinning, the more heat will be generated when its clamped. The more a clutch is 'slipped', the more heat will be generated. The more heat that's generated, the shorter the life of the clutch. Street driving produces the most heat for a clutch, since to keep things comfortable, you'll be 'slipping' the clutch on purpose quite a bit. On track, not so much as up and down shifts tend to be much crisper.

The most common problem with a lightweight flywheel is bogging the engine down when trying to pull away from a stop... after that, its really not much different that a stock flywheel

Kompressor · #5 04-17-2006, 03:01 PM

well i need more clamping pressure then the stock clutch because a 3k rpm launch the clutch will just slip and ill have to get out of the gas for it to stop slipping, so i need more clamping pressure, mercedes has the clutch so cushy for that luxury ride i dont need that crap, i need a faster stronger clutch.

also will the car bog if i stay in my power band ? or only if i mess up, bogging on launch is the last thing i need lol, my car is pretty slow as it is.

Stack · #6 04-17-2006, 03:16 PM

Quote:

Originally Posted by Kompressor

also will the car bog if i stay in my power band ? or only if i mess up, bogging on launch is the last thing i need lol, my car is pretty slow as it is.

This is where the momentum of the flywheel comes into play... a heavier flywheel, once you get it spinning, will not want to stop - so starting a car in motion doesn't require paying as much attention to the throttle as a lightweight flywheel will. You have to be conscious of keeping the revs a little higher than normal for street driving.

As far as 'launching' a car... since I don't drag race, I'm afraid I won't be able to help you out too much there... but my guess is that is where the stronger clutch clamping force will help you out

Kompressor · #7 04-17-2006, 03:34 PM

well i dont drag race really either but i do like to have good acceleration, though im still smooth with my shifts, its still fun to take off fast sorta like you do out of the pits you go as fast as you can which is kind of the same thing as dragging, i like a balance in the car good acceleration better cornering and the best brakes. horsepower isnt king to me but id like to use as much of 162rwhp as i can

.

Conan · #8 04-17-2006, 06:23 PM

Quote:

Originally Posted by Kompressor

also will the car bog if i stay in my power band ? or only if i mess up, bogging on launch is the last thing i need lol, my car is pretty slow as it is.

I'm not sure what you mean by bogging on launch. A lighter flywheel will cause launches to feel different, but once you adapt to the feel, you should be able to launch it just as you did before. All that changes is the timing and revs.

I have a lighter flywheel in my car (14 lbs vs the 32 lbs stock one). It is a little trickier to launch "perfectly", but it's a lot better overall.

Kompressor · #9 04-17-2006, 06:27 PM

how would you say the experience is with the lighter flywheel ? is it night and day , is the car alot peppier, and easier to drive, my revs stock are very slow put it in nuetral and rev it and its a good long time to get to redline, my theory is that the lightweight flywheel will make the engine respond more to my liking.

Conan · #10 04-17-2006, 06:36 PM

Quote:

Originally Posted by Kompressor

how would you say the experience is with the lighter flywheel ? is it night and day , is the car alot peppier, and easier to drive, my revs stock are very slow put it in nuetral and rev it and its a good long time to get to redline, my theory is that the lightweight flywheel will make the engine respond more to my liking.

Actually, I'm a little dissapointed. I thought it would make a bigger difference. There IS a difference, but it's fairly small. In first and second gear she pulls a bit harder, and it revs quicker. Probably the biggest difference is braking. If I leave the clutch engaged while braking, it stops quite a bit quicker.