How a LWF works...(if you don't read the other forums)
11-09-2005, 08:14 AM
#1
Race Car
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How a LWF works...(if you don't read the other forums)
11-10-2005, 06:03 AM
#5
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But isn't one of the drawbacks of LWF to make a car a bit more "edgy" to drive at low speed? great for "full attack" mode but not so for a more leisurely drive?
any comments from the one who drove with both
any comments from the one who drove with both
11-10-2005, 07:06 AM
#6
Instructor
At city drive, up shift is a bit jerky, as engine rev drops too quick, especially with AC on. Down shift is smooth, I guess it's because it has less engine brake effect due to lighter flywheel. Overall no major problem for city drive, only thing to concern is ocassionally stall when you come to a stop. Need to pay more attention on rev and control the throttle carefully.
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11-10-2005, 10:22 AM
#8
RL Community Team
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Having just installed a LWF in my coupe race car and no other mods to cloud the issue - the car is a hell of a lot faster in gears 1-3! 4th and 5th I can't tell much difference, but boy - it's wonderful!! 
11-10-2005, 10:36 AM
#9
Race Car
Thread Starter
I would guess that with those figures for a BMW that it might shave off a tenth or 2 in a 0-60 dash, but we have to consider that those figures are *not* for a 964. My guess is that you wouldn't realyl notice it in the real world, side-by-side with a DMF car....maybe half a car length to 60...maybe...?
11-10-2005, 11:24 AM
#10
Three Wheelin'
In my car especially I have no idea why the previous owner went from the stock flywheel to a lwf. In '89 the stock one was only 19lbs, vs the 30 lb dmf's used in later years.
I am expecting to see virtually no change in performance when I get a stock setup back in the car.
Overall I think they are great on a track car, but in regular city traffic the idle issues, etc get tedious. (I realise these issues differ in severity between owners, perhaps between years and models. And certainly show up most if you are a regular user of your cars A/C)
Kirk
I am expecting to see virtually no change in performance when I get a stock setup back in the car.
Overall I think they are great on a track car, but in regular city traffic the idle issues, etc get tedious. (I realise these issues differ in severity between owners, perhaps between years and models. And certainly show up most if you are a regular user of your cars A/C)
Kirk
11-10-2005, 02:18 PM
#12
Nordschleife Master
"So basically, a car does accelerate faster with a LWF right?"
Yes and no , depends how you drive the car .
If you are at a stop , the car with the heavy flywheel will move off the line faster .
The energy stored in the flywheel when spun up before the launch can be used to launch the car .
More rotating mass stores more energy .
If you have 100 hp motor and a flywheel that can store 20 hp , by spinning up the flywheel to max rpm before letting out the clutch you have in effect about 120 hp to launch the car .
If you have 100hp with a 5 hp flywheel you have about 105 hp to launch the car .
The 15 hp advantage will be gone in a flash when its turned into forward motion .
If you are exiting a corner and are not touching the clutch at all , the light weight flywheel car will accelerate faster .
The lwf has less mass to spin up .
Brakeing into a corner the driver/car with the lwf can go into it farther , less rotating mass and less mass moveing forward to de accelerate , before jumping on the brakes .
As the mass of the flywheel goes down , the talent of the driver has to go up .
A real light weight flywheel takes real talent , it makes the car easy to stall .
Most people will need to slip the clutch more with a lwf , that causes the disc life to shorten .
The atvantages of a lwf are mostly seen at wide open throttle driveing .
If your car makes 250 hp and you drive around without useing all 250 the lwf isn't really going to do much for you , if you come out of a corner using half the hp that your motor has , its not going to be faster or slower , you can press down the gas pedal just a little more to make up for the flywheel weight differance
Yes and no , depends how you drive the car .
If you are at a stop , the car with the heavy flywheel will move off the line faster .
The energy stored in the flywheel when spun up before the launch can be used to launch the car .
More rotating mass stores more energy .
If you have 100 hp motor and a flywheel that can store 20 hp , by spinning up the flywheel to max rpm before letting out the clutch you have in effect about 120 hp to launch the car .
If you have 100hp with a 5 hp flywheel you have about 105 hp to launch the car .
The 15 hp advantage will be gone in a flash when its turned into forward motion .
If you are exiting a corner and are not touching the clutch at all , the light weight flywheel car will accelerate faster .
The lwf has less mass to spin up .
Brakeing into a corner the driver/car with the lwf can go into it farther , less rotating mass and less mass moveing forward to de accelerate , before jumping on the brakes .
As the mass of the flywheel goes down , the talent of the driver has to go up .
A real light weight flywheel takes real talent , it makes the car easy to stall .
Most people will need to slip the clutch more with a lwf , that causes the disc life to shorten .
The atvantages of a lwf are mostly seen at wide open throttle driveing .
If your car makes 250 hp and you drive around without useing all 250 the lwf isn't really going to do much for you , if you come out of a corner using half the hp that your motor has , its not going to be faster or slower , you can press down the gas pedal just a little more to make up for the flywheel weight differance
11-12-2005, 02:30 PM
#13
Instructor
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I think a lot of people were easily convinced to convert to a LWF when they had problems with the stock DMF. This was the case with my C4. The PO had it done... it seems a bit gnarlier off the line, but it drops RPM VERY fast. It also took the wrench a bit of tweaking to keep the idle happy and prevent it from stalling during rapid deceleration.
11-13-2005, 12:01 PM
#14
Rennlist Member
I think the assumption that the weight of 10 pounds=10 HP is a little optimistic for a lot of cars, since the real value would be the actual HP to weight ratio of the car in question. For the typical 964 this is around 12 to 13 pounds/ HP. If you correct for that then the perceived change at one's butts more matches the theoretical power advantage number.
I think Indycam makes a good point about the stored energy effects vs the inertial effects. It would be interesting to figure if the stored energy effect lost during a drag race launch would be made up for by the lower inertial effect gained in the successive gears by a lighter flywheel.
I think the rule of thumb is whether the car has enough power and or stored energy to break the tires loose during a drag race launch. If you can still do that with the light flywheel, then effectively not much was lost, and the car is probably faster with the LWF.
I think Indycam makes a good point about the stored energy effects vs the inertial effects. It would be interesting to figure if the stored energy effect lost during a drag race launch would be made up for by the lower inertial effect gained in the successive gears by a lighter flywheel.
I think the rule of thumb is whether the car has enough power and or stored energy to break the tires loose during a drag race launch. If you can still do that with the light flywheel, then effectively not much was lost, and the car is probably faster with the LWF.