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Old 01-13-2013, 12:17 PM   #21
felixthecat
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Originally Posted by Lscman View Post
I have concluded from reading threads that any Focus that vibrates with over 50K miles has a bad motor mount. My '07 car felt like a buzzy old pinto that was ready to blow. After I replaced the $75 upper passenger mount it felt like a mercedes. However I was unable to visually determine that it was bad through looking touching lifting or pinching the mount. The original mount looked perfect on the car and even after I removed it.

I don't see any purpose to removing counterbalance assemblies on a street car because the parasitic fractional horsepower losses are well below any threshold that you could notice or even measure on a dyno. Stored energy from this rotating mass is good. It results in better launches and stronger tire-barking upshifts.
18.50 lbs of static & 10lbs of rotational weight is a lot plus it holds 6qtrs of oil= win win.
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Old 01-14-2013, 01:17 AM   #22
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I forgot which famed pro-stock drag racer said it, but when asked how heavy of a flywheel a motor should have:

"If the motor idles, the flywheel is heavy enough"

You can't decrease rotational mass enough, it all adds up. One of the most noticeable improvements for a manual transmission car is a lighter flywheel, honestly one of the bangs for the buck. (on V8 cars, I haven't played with racing a Focus)
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Old 01-15-2013, 12:52 AM   #23
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I forgot which famed pro-stock drag racer said it, but when asked how heavy of a flywheel a motor should have:

"If the motor idles, the flywheel is heavy enough"

You can't decrease rotational mass enough, it all adds up. One of the most noticeable improvements for a manual transmission car is a lighter flywheel, honestly one of the bangs for the buck. (on V8 cars, I haven't played with racing a Focus)
I definitely have more track miles under my belt than any famed pro stock drag racer and that would include Glidden or Garlits. That is, unless they have over 200K passes which would be a difficult feat for anyone under 100 years old who does not own their own track.

Anyway, I am talking about improving track lap times in a street legal car of the sort here, not a 8 second trailered drag car with powerglide. Rotational kinetic energy is good and can be used to a driver's advantage, especially with a manual transmission with conventional synchros that can't be powershifted. Drag racers don't launch at idle. Lighter flywheels provide a tremendous psycological boost to newbie rookies who equate quicker revs in neutral to better acceleration or more tractible power delivery under load. For me, a lighter flywheel just reduces drivability and leads to more wheelspin. The difference on the track is hardly measurable, as has been proven time and again by amateur racers in A-B control tests. A gifted driver can squeeze a tiny bit out of featherweight flywheel but the typical driver will see no improvement or be SLOWER due to the reduced traction. Flywheels help a vehicle maintain traction at the threshold of grip by resisting abrupt changes in wheel speed. It does not matter if it's a Corvette on concrete or John Deere in mud. The flywheel will not have a significant effect on PERFORMANCE unless your car is capable of a standing 1/4 mile in under 10 seconds. Yes, you WILL feel the engine rev's more freely and the tires will break traction more easily. However this is not the goal of a road racer...drifter, maybe.
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Old 01-15-2013, 01:54 AM   #24
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powerglides don't run a flywheel, they use a flexplate
Pro-stock doesn't run automatics anyhow, they have a clutch and flywheel
Reducing the rotating mass in an automatic is important, but they do it with aluminum drum, which has even less difference because the diameter is so small.

If heavy flywheels are so great, why does everybody run a 7.25" or smaller clutch on circle track cars? The 5.5" is becoming much more popular nowadays. Why not the 10.5" with a steel flywheel? Why so much money spent on lightweight crankshafts, gun drilled mains don't change the reciprocating mass at all, just the rotating. It's basic physics, whether or not that helps the driver get around the track quicker is dependent upon the driver's skill, but you don't leave parasitic losses sitting on the table if you can help it. Even a hobby stock, short track dirt racer will pick up a noticeable gain going to a lightweight clutch and flywheel.

I don't road race street cars, so I claim 100% ignorance of what is popular with that crowd. I only have experience working in a machine shop building drag and circle track motors. Nobody that is winning any races is ignoring the moment of inertia of their clutch setup.

Don't see why the laws of physics would change for a street car, but I can see how it would be the least important thing for the average weekend warrior doing a track day or taking driving lessons.
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Old 01-18-2013, 11:36 PM   #25
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Quote:
Originally Posted by elsolo View Post
powerglides don't run a flywheel, they use a flexplate
Pro-stock doesn't run automatics anyhow, they have a clutch and flywheel
Reducing the rotating mass in an automatic is important, but they do it with aluminum drum, which has even less difference because the diameter is so small.

If heavy flywheels are so great, why does everybody run a 7.25" or smaller clutch on circle track cars? The 5.5" is becoming much more popular nowadays. Why not the 10.5" with a steel flywheel? Why so much money spent on lightweight crankshafts, gun drilled mains don't change the reciprocating mass at all, just the rotating. It's basic physics, whether or not that helps the driver get around the track quicker is dependent upon the driver's skill, but you don't leave parasitic losses sitting on the table if you can help it. Even a hobby stock, short track dirt racer will pick up a noticeable gain going to a lightweight clutch and flywheel.

I don't road race street cars, so I claim 100% ignorance of what is popular with that crowd. I only have experience working in a machine shop building drag and circle track motors. Nobody that is winning any races is ignoring the moment of inertia of their clutch setup.

Don't see why the laws of physics would change for a street car, but I can see how it would be the least important thing for the average weekend warrior doing a track day or taking driving lessons.
I was just pointing out that a lighter flywheel will not help a Focus much in a street racing environment which is not much different than road track racing. Kinetic energy that can be wisely released upon clutch engagement is not described as a parasitic or frictional loss in my physics book. My bearings are well oiled and show little friction, even with a balanced rotating mass attached.

The majority of your post focuses on dirt/mud racing where max acceleration (power transfer) is achieved through incredibly high wheel slip rates which serve to clear tread, shear soil and create heat. Soil shear tire friction phenomenon is an interesting subject that has nothing to do with asphalt or concrete surfaces. High slip rates are used for dirt circle track, mud swamp buggy or dirt sled pulls by a tractor or truck. These engines need lower rotating mass to help initiate, encourage and maintain a high tire slip condition. Participants that fail to spin tires in dirt come in last place. The higher the slip rate the merrier, so multidisc clutches with smaller diameter are the hot ticket. Greater wheelspeed wins independent of forward velocity, so long as the chassis doesn't go into an underdampened oscillation and begin hopping. However in asphalt road racing where corners and braking is involved, just the opposite is true. Traction suffers when a very modest tire slip rate under accel, decel or cornering is exceeded. The fastest racers avoid wheelspin and they can dance on the edge of traction and manage slip rate. Heavy flywheels aid in this effort, although they do not benefit folks with highest skill levels. Rapid changes in engine speed will lead to tire smoke, loss of grip and reduced acceleration. Again, I'm not talking about drifting or some sport where sustained wheelspin on asphalt is being evaluated as a skill from a controlled skid standpoint. In drag racing, lower rotating mass is good and shifts are almost instantaneous, whether the tranny is considered to be a manual or automatic. These technologies become blurred once technologies merge. Sequential manual transmissions with dry clutches work quite well.
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Old 01-19-2013, 12:48 AM   #26
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That is a great and very detailed description, thanks.
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