Lighter wheel benefits
09-12-2011, 12:57 AM
#50
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Manthey MM410 996 GT3 package was unlikely faster or stronger than a build someone did on a Seal Grey 996 GT3.
Have them deliver Car A with a Pro driver to Sebring, I will drive Car B and bring enough bet money too.
09-12-2011, 01:45 AM
#51
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Wheels, tires, flywheel etc.. are already light weight. On certain components on the car unsprung weight will affect the car but not in every situations.
Compare you 997 with your 997 and nothing else.
Take off 90 pounds of unsprung weight and see your lap times at the track.
Take off 90 pounds of sprung weight and see your lap times at the track.
Your comparisions don't make any senses with two different cars.
6:1 ratio is just not working the way you think.
09-12-2011, 03:08 AM
#52
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I think as someone already mentioned, the 6:1 ratio works the other way round... its more like 1:6, a 50lbs wheel will, in being accelerated, feel like 300lbs of sprung mass to the car. A 40lbs wheel will feel like 240lbs.
So, looking at NJ-GT's example:
Car A, 3000 lbs, 2900 spring & 100 unsprung = dynamic weight of 3500 lbs
Car B, 2000 lbs, 1600 sprung & 400 unprung = dynamic weight of 4000 lbs
Hmm, Car B would be slower. But 1000 lbs lighter in static? Seems impossible. But then again a car with 25% of its weight in unsprung mass also seems impossible.. .
As jfl91 says, need a like-to-like comparison.
I will post after I mount the new wheels.
So, looking at NJ-GT's example:
Car A, 3000 lbs, 2900 spring & 100 unsprung = dynamic weight of 3500 lbs
Car B, 2000 lbs, 1600 sprung & 400 unprung = dynamic weight of 4000 lbs
Hmm, Car B would be slower. But 1000 lbs lighter in static? Seems impossible. But then again a car with 25% of its weight in unsprung mass also seems impossible.. .
As jfl91 says, need a like-to-like comparison.
I will post after I mount the new wheels.
09-12-2011, 03:44 AM
#53
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I think as someone already mentioned, the 6:1 ratio works the other way round... its more like 1:6, a 50lbs wheel will, in being accelerated, feel like 300lbs of sprung mass to the car. A 40lbs wheel will feel like 240lbs.
So, looking at NJ-GT's example:
Car A, 3000 lbs, 2900 spring & 100 unsprung = dynamic weight of 3500 lbs
Car B, 2000 lbs, 1600 sprung & 400 unprung = dynamic weight of 4000 lbs
Hmm, Car B would be slower. But 1000 lbs lighter in static? Seems impossible. But then again a car with 25% of its weight in unsprung mass also seems impossible.. .
As jfl91 says, need a like-to-like comparison.
I will post after I mount the new wheels.
So, looking at NJ-GT's example:
Car A, 3000 lbs, 2900 spring & 100 unsprung = dynamic weight of 3500 lbs
Car B, 2000 lbs, 1600 sprung & 400 unprung = dynamic weight of 4000 lbs
Hmm, Car B would be slower. But 1000 lbs lighter in static? Seems impossible. But then again a car with 25% of its weight in unsprung mass also seems impossible.. .
As jfl91 says, need a like-to-like comparison.
I will post after I mount the new wheels.
The 6:1 ratio says Car A should be faster.
In my book, the 2,000 lbs car B would be massively faster.
On my 2007 GT3 RS, reducing unsprung weight by 92 lbs did not make the car feel 550 lbs lighter (or the stock car feel 550 lbs heavier).
But given that most of the experts here agree to the 6:1 ratio, here is my challenge to you all (and Manthey and Porsche).
Get a Porsche 997 GT3 RS with 996 PCCB and BBS Magnesium wheels. Add three passengers for a weight of 550 lbs, do same laps and see if you can match the laps from the same 997 GT3 RS on steel brakes and stock wheels. Both cars using the same tire width and compound.
Even easier challenge, 2010 GT3 RS with PCCB + 200 lbs passenger vs. 2010 GT3 RS on steel brakes. Hint: the PCCB save 42 lbs on the 2010 GT3 RS.
09-12-2011, 05:02 AM
#54
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Right, and that's where the 6:1 (or 1:6 ratio) is a flaw. Let's say that both cars are the same, Car B with carbon fiber panels and stripped, heavy iron hubs/brakes/wheels, while Car A uses carbon hubs, brakes, wheels and a standard body.
The 6:1 ratio says Car A should be faster.
In my book, the 2,000 lbs car B would be massively faster.
On my 2007 GT3 RS, reducing unsprung weight by 92 lbs did not make the car feel 550 lbs lighter (or the stock car feel 550 lbs heavier).
But given that most of the experts here agree to the 6:1 ratio, here is my challenge to you all (and Manthey and Porsche).
Get a Porsche 997 GT3 RS with 996 PCCB and BBS Magnesium wheels. Add three passengers for a weight of 550 lbs, do same laps and see if you can match the laps from the same 997 GT3 RS on steel brakes and stock wheels. Both cars using the same tire width and compound.
Even easier challenge, 2010 GT3 RS with PCCB + 200 lbs passenger vs. 2010 GT3 RS on steel brakes. Hint: the PCCB save 42 lbs on the 2010 GT3 RS.
The 6:1 ratio says Car A should be faster.
In my book, the 2,000 lbs car B would be massively faster.
On my 2007 GT3 RS, reducing unsprung weight by 92 lbs did not make the car feel 550 lbs lighter (or the stock car feel 550 lbs heavier).
But given that most of the experts here agree to the 6:1 ratio, here is my challenge to you all (and Manthey and Porsche).
Get a Porsche 997 GT3 RS with 996 PCCB and BBS Magnesium wheels. Add three passengers for a weight of 550 lbs, do same laps and see if you can match the laps from the same 997 GT3 RS on steel brakes and stock wheels. Both cars using the same tire width and compound.
Even easier challenge, 2010 GT3 RS with PCCB + 200 lbs passenger vs. 2010 GT3 RS on steel brakes. Hint: the PCCB save 42 lbs on the 2010 GT3 RS.
But they wouldn't be because in the corners unsprung mass doesn't come into play as much...
And how would you add three passengers into a GT3RS?
That would be a sight... We need an engineer from an F1 or Lemans teams or something to weigh in...
I am inclined to agree with the 1:6 or whatever but I believe this applies in small windows of time, I would say acceleration out of low speed corners (where GT3's are torque-limited) and not much else. As soon as you are into 4th gear you'd need to be an F1 driver to notice the difference.. Maybe steering response improves as some are saying...
The shop I'm working with says they've seen a 0.5s-1.0s laptime improvement on a 3 mile track.
09-12-2011, 03:10 PM
#56
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This thread got interesting. I too don't believe that it is a 6:1 ratio, atleast not on these cars, I just thought that you have to do an apples to apples comparison in order quantify how much it does help on porker street cars.
I remember a race engineer at a FSAE event describing it in such a way. Imagine strapping 10# lead weights to your feet and going for a jog, and then imagine strapping a 20# backpack and going for a jog. I'll take the backpack any day.
The problem here though I think is that, on a heavy flexible street car (GT3) vs. a 1300# formula car, it is much more difficult to realize the performance benefits of unsprung weight. There are too many other weak links in the system.
I remember a race engineer at a FSAE event describing it in such a way. Imagine strapping 10# lead weights to your feet and going for a jog, and then imagine strapping a 20# backpack and going for a jog. I'll take the backpack any day.
The problem here though I think is that, on a heavy flexible street car (GT3) vs. a 1300# formula car, it is much more difficult to realize the performance benefits of unsprung weight. There are too many other weak links in the system.
09-13-2011, 01:25 AM
#58
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the manthey car in my pic is a full blown race car, 600hp naturally aspirated 4.0l, 9800rpm, sequential box, 2200lbs of down force, ABS, traction control. I engineer this car while it stays in the USA this is the car the manthey blipper was designed for in 2004.
09-13-2011, 08:23 AM
#59
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This thread got interesting. I too don't believe that it is a 6:1 ratio, atleast not on these cars, I just thought that you have to do an apples to apples comparison in order quantify how much it does help on porker street cars.
I remember a race engineer at a FSAE event describing it in such a way. Imagine strapping 10# lead weights to your feet and going for a jog, and then imagine strapping a 20# backpack and going for a jog. I'll take the backpack any day.
The problem here though I think is that, on a heavy flexible street car (GT3) vs. a 1300# formula car, it is much more difficult to realize the performance benefits of unsprung weight. There are too many other weak links in the system.
I remember a race engineer at a FSAE event describing it in such a way. Imagine strapping 10# lead weights to your feet and going for a jog, and then imagine strapping a 20# backpack and going for a jog. I'll take the backpack any day.
The problem here though I think is that, on a heavy flexible street car (GT3) vs. a 1300# formula car, it is much more difficult to realize the performance benefits of unsprung weight. There are too many other weak links in the system.
09-13-2011, 08:33 AM
#60
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