Mind Candy--Possible 545i Weight Savings
09-18-2005, 04:18 PM
#1
Contributors
Thread Starter
Join Date: Aug 2005
Location: Austin TX
Posts: 6,554
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2014 X5 xDrive 5.0 M Package Carbon Black Metallic/2008 M Roadster Imola Red
If you have read this post before, then skip down to the edit--assuming you are interested in saving weight. Also, way over on page 5, I indicate were I think I ended up in terms of flywheel-equivalent HP gain.
New info on where I ended up on page 5
Hi All (I just noticed after all this time--Esthetic = Aesthetic ~0{:^)):
First, here is a question. How many miles would an average driver get on the 545i?s Dunlop run flats? The answer affects the economics of my/our individual weight-savings thoughts. You?ll have to factor in your particular circumstances. Also, note that I am not working with package pricing below--just with per wheel/tire prices. Forgive me for any mistakes; please let me know if you see any or question anything in the calculations. I?ll adjust or clarify.
1. By buying, for example, Michelin Pilot Sport PS2's, one can save the following (all weights below in lbs.) over the Dunlop run flats.
2(32 - 25) + 2(29 - 24) = 24 lbs. Given that unsprung weight is being saved, the sprung-weight equivalent is about 2(24) = 48 lbs.
2. By buying, for example, BBS RGR's, one can save the following over the stock sports package wheels.
2(34(?) - 21.2) + 2(32(?) - 19.4) = (approx.) 51 lbs. Given again that unsprung weight is being saved, the sprung-weight equivalent is about 1.5(51) = (approx.) 77 lbs.
3. The donut tire and jack weight about 37 lbs., together, while an after-market exhaust is likely to be about 30 lbs. lighter than the stock behemoth.
So, in sprung-weight terms, one can save about 48 + 77 + 37 + 30 = 192 lbs. with ease and without hurting the aesthetics any if at all.
4. Given use of the lbs./Flywheel HP ratio, 192 pounds translates into about 192 / 10 = about 19 flywheel HP--or (48 + 77) / 10 = 125 / 10 = about 13 flywheel HP from the wheels/tires alone.
So, the first question is how about the economics of obtaining, for example, the portion of the increase in flywheel ?HP? attributable to the wheels/tires alone? Suppose that one will need to replace his or her run flats before disposing of the 545i. If so, then the cost of the extra tires is pretty much nil and is ignored below for ease. And, given a US$ price of 2($702) + 2($731) = $2,866 for the RGR?s and that one could sell the wheels, plus what's left of the Michelins, when disposing of the 545i for half the cost of the wheels ($1,433), then the cost of the wheels is $1,433.
5. So, the extra 13 "HP" from the wheels/tires alone cost about $1,433 / 13 = about $110.23 per HP--which is somewhat economical given, for example, that a Dinan trottle body, when installed by a Dinan certified shop, will cost, with a 10% discount on the part, about $685--which yields a cost per flywheel HP of about $685 / (8 / .85) = $685 / 9.4 = about $72.78. And, the wheel/tire package also will result in more that just an increase in HP?specifically, it will improve handling and some might say the aesthetics. Finally, the run flats and factory wheels would be available for use?say on trips. I am assuming that the throttle body will not be sold when the 545i is disposed of.
6. Similarly, consider the cost, for example, of a B&B exhaust. The cost if installed by a BMW dealer, after a 10% discount on the part, is about $1,063. The related flywheel HP gain is about (10 RWHP / .85) + (30 lb. weight savings / 10) = about 15 HP. The cost per HP is ($1,063 / 2 / 15 = about $35.44 assuming the exhaust can be sold net eventually for half of its cost (about $532).
7. Together, all the costly weight savings, plus actual HP gains from the related items, gives a net cost of ($1,433 + $685 + $532) = $2,650. The cost per HP is $2,650 / (13 + 9.4 +15) = $2,650 / 37.4 = $71?which is similar to the per HP cost of the throttle body, itself.
8. So, the 545i ends up with 325 + 37.4 = about 362.5 flywheel ?HP.? If one throws in the 37 / 10 lb. saving from removing the spare tire, then the 545i?s flywheel HP is about 366?which is not too shabby. Thus, either way, one ends up with performance in the 550i range and is much better off not buying a comparable 550i if he or she already owns a 545i (i.e., consider loss on 545i and probably non-discounted or higher discounted price of 550i, price increase on 550i, etc., etc., and etc.) (ignoring the other new features of the 550i--which mean nothing to me).
The final cost per flywheel HP is $2,650 / (37.4 + 3.7) = $2,650 / about 41 = about $65?but no spare in the car.
I?ll keep checking my calculations?later. Any thoughts?
Edit 10/25/05: I might as well put all my serious weight-reduction thoughts in one place. Have you ever thought about how much 545i weight you might save on average, in relation to the "competition," if you add only 5 gallons of gas each time your running-on-reserve warning comes on?--i.e., when about 2 1/2 gallons remains. I used to use 7 lbs. a gallon when doing gasoline calculations. I have been told that a gallon of premium weights about 6.35 lbs. So, I am going to use this value until told otherwise by a higher authority.
One average, in relation to the "competition," you can save:
6.35*{[(18.5 - 2.5)/2]-[(7.5 - 2.5)/2]} = very close to 35 lbs. = 35 / 10 = about 3.5 HP assuming the competition fills up at the on-reserve warning.
Then, of course, some of us could go on a diet. I weight 160 and wouldn't want to lose more than 5 lbs. So, let's say I don't lose weight. Our BMW demographics suggest, as I recall, that we weight 180 lbs on average. I wonder if that includes women. Most women don't count because women usually are not the "competition." Well, anyway, I am going to assume that the average "competition"-pertinent male driver weights 190 lbs. If so, then on average, I am about 3 HP lighter than the "competition." So, let's all, well not me, get on the treadmill more. ~{;^) Then, we would have more goal congurence--auto "fitness" and personal fitness.
In total, on the basis of what's above, we 160 pounders can have about 6.5 HP for "free" on average. That's .06 in the quarter mile--enough of a margin to beat some of the "competition."
New info on where I ended up on page 5
Hi All (I just noticed after all this time--Esthetic = Aesthetic ~0{:^)):
First, here is a question. How many miles would an average driver get on the 545i?s Dunlop run flats? The answer affects the economics of my/our individual weight-savings thoughts. You?ll have to factor in your particular circumstances. Also, note that I am not working with package pricing below--just with per wheel/tire prices. Forgive me for any mistakes; please let me know if you see any or question anything in the calculations. I?ll adjust or clarify.
1. By buying, for example, Michelin Pilot Sport PS2's, one can save the following (all weights below in lbs.) over the Dunlop run flats.
2(32 - 25) + 2(29 - 24) = 24 lbs. Given that unsprung weight is being saved, the sprung-weight equivalent is about 2(24) = 48 lbs.
2. By buying, for example, BBS RGR's, one can save the following over the stock sports package wheels.
2(34(?) - 21.2) + 2(32(?) - 19.4) = (approx.) 51 lbs. Given again that unsprung weight is being saved, the sprung-weight equivalent is about 1.5(51) = (approx.) 77 lbs.
3. The donut tire and jack weight about 37 lbs., together, while an after-market exhaust is likely to be about 30 lbs. lighter than the stock behemoth.
So, in sprung-weight terms, one can save about 48 + 77 + 37 + 30 = 192 lbs. with ease and without hurting the aesthetics any if at all.
4. Given use of the lbs./Flywheel HP ratio, 192 pounds translates into about 192 / 10 = about 19 flywheel HP--or (48 + 77) / 10 = 125 / 10 = about 13 flywheel HP from the wheels/tires alone.
So, the first question is how about the economics of obtaining, for example, the portion of the increase in flywheel ?HP? attributable to the wheels/tires alone? Suppose that one will need to replace his or her run flats before disposing of the 545i. If so, then the cost of the extra tires is pretty much nil and is ignored below for ease. And, given a US$ price of 2($702) + 2($731) = $2,866 for the RGR?s and that one could sell the wheels, plus what's left of the Michelins, when disposing of the 545i for half the cost of the wheels ($1,433), then the cost of the wheels is $1,433.
5. So, the extra 13 "HP" from the wheels/tires alone cost about $1,433 / 13 = about $110.23 per HP--which is somewhat economical given, for example, that a Dinan trottle body, when installed by a Dinan certified shop, will cost, with a 10% discount on the part, about $685--which yields a cost per flywheel HP of about $685 / (8 / .85) = $685 / 9.4 = about $72.78. And, the wheel/tire package also will result in more that just an increase in HP?specifically, it will improve handling and some might say the aesthetics. Finally, the run flats and factory wheels would be available for use?say on trips. I am assuming that the throttle body will not be sold when the 545i is disposed of.
6. Similarly, consider the cost, for example, of a B&B exhaust. The cost if installed by a BMW dealer, after a 10% discount on the part, is about $1,063. The related flywheel HP gain is about (10 RWHP / .85) + (30 lb. weight savings / 10) = about 15 HP. The cost per HP is ($1,063 / 2 / 15 = about $35.44 assuming the exhaust can be sold net eventually for half of its cost (about $532).
7. Together, all the costly weight savings, plus actual HP gains from the related items, gives a net cost of ($1,433 + $685 + $532) = $2,650. The cost per HP is $2,650 / (13 + 9.4 +15) = $2,650 / 37.4 = $71?which is similar to the per HP cost of the throttle body, itself.
8. So, the 545i ends up with 325 + 37.4 = about 362.5 flywheel ?HP.? If one throws in the 37 / 10 lb. saving from removing the spare tire, then the 545i?s flywheel HP is about 366?which is not too shabby. Thus, either way, one ends up with performance in the 550i range and is much better off not buying a comparable 550i if he or she already owns a 545i (i.e., consider loss on 545i and probably non-discounted or higher discounted price of 550i, price increase on 550i, etc., etc., and etc.) (ignoring the other new features of the 550i--which mean nothing to me).
The final cost per flywheel HP is $2,650 / (37.4 + 3.7) = $2,650 / about 41 = about $65?but no spare in the car.
I?ll keep checking my calculations?later. Any thoughts?
Edit 10/25/05: I might as well put all my serious weight-reduction thoughts in one place. Have you ever thought about how much 545i weight you might save on average, in relation to the "competition," if you add only 5 gallons of gas each time your running-on-reserve warning comes on?--i.e., when about 2 1/2 gallons remains. I used to use 7 lbs. a gallon when doing gasoline calculations. I have been told that a gallon of premium weights about 6.35 lbs. So, I am going to use this value until told otherwise by a higher authority.
One average, in relation to the "competition," you can save:
6.35*{[(18.5 - 2.5)/2]-[(7.5 - 2.5)/2]} = very close to 35 lbs. = 35 / 10 = about 3.5 HP assuming the competition fills up at the on-reserve warning.
Then, of course, some of us could go on a diet. I weight 160 and wouldn't want to lose more than 5 lbs. So, let's say I don't lose weight. Our BMW demographics suggest, as I recall, that we weight 180 lbs on average. I wonder if that includes women. Most women don't count because women usually are not the "competition." Well, anyway, I am going to assume that the average "competition"-pertinent male driver weights 190 lbs. If so, then on average, I am about 3 HP lighter than the "competition." So, let's all, well not me, get on the treadmill more. ~{;^) Then, we would have more goal congurence--auto "fitness" and personal fitness.
In total, on the basis of what's above, we 160 pounders can have about 6.5 HP for "free" on average. That's .06 in the quarter mile--enough of a margin to beat some of the "competition."
09-18-2005, 05:17 PM
#4
Contributors
Thread Starter
Join Date: Aug 2005
Location: Austin TX
Posts: 6,554
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2014 X5 xDrive 5.0 M Package Carbon Black Metallic/2008 M Roadster Imola Red
Originally Posted by UPENN545' date='Sep 18 2005, 07:48 PM
I now have a Headache.? 
[snapback]172131[/snapback]
09-18-2005, 05:20 PM
#5
Contributors
Thread Starter
Join Date: Aug 2005
Location: Austin TX
Posts: 6,554
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2014 X5 xDrive 5.0 M Package Carbon Black Metallic/2008 M Roadster Imola Red
Originally Posted by UPENN545' date='Sep 18 2005, 07:48 PM
I now have a Headache.?
[snapback]172131[/snapback]
09-18-2005, 05:23 PM
#6
Senior Members
Join Date: Jun 2004
Location: Cincinnati, Ohio
Posts: 1,169
Likes: 0
Received 0 Likes
on
0 Posts
You're definitely on the right track. I substituted lightweight wheels and tires (albeit 19 rather than 18 inch) and noticed considerably better acelleration. With your suggested mod's, you may approach the 550 performance. Your reasoning sounds solid - the theoretical numbers for your HP gains may not be quite what you're predicting, but you'll be in the ballpark.
Also remember that 360 'aftermarket claimed' horsepower is probably not the same as 360 horsepower specified by BMW. I'd be very surprised if you were as fast as a 550, but you'll be close.
Also remember that 360 'aftermarket claimed' horsepower is probably not the same as 360 horsepower specified by BMW. I'd be very surprised if you were as fast as a 550, but you'll be close.
09-18-2005, 05:31 PM
#7
Contributors
Thread Starter
Join Date: Aug 2005
Location: Austin TX
Posts: 6,554
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2014 X5 xDrive 5.0 M Package Carbon Black Metallic/2008 M Roadster Imola Red
Originally Posted by wolverine' date='Sep 18 2005, 08:23 PM
Also remember that 360 'aftermarket claimed' horsepower is probably not the same as 360 horsepower specified by BMW.? I'd be very surprised if you were as fast as a 550, but you'll be close.
[snapback]172142[/snapback]
09-18-2005, 05:31 PM
#8
Contributors
Join Date: Aug 2005
Location: Westlake Hills - Austin,TX
Posts: 172
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: V8 beast!
Originally Posted by donv' date='Sep 18 2005, 08:17 PM
[quote name='UPENN545' date='Sep 18 2005, 07:48 PM']I now have a Headache.?
[snapback]172131[/snapback]
[snapback]172139[/snapback]
[/quote]I love austin I migrated from Devon P.A. I recently Built a house in West Lake Hills ..Horns are doing Awesome. My Grad ALMA MATER.
09-18-2005, 05:33 PM
#9
Contributors
Thread Starter
Join Date: Aug 2005
Location: Austin TX
Posts: 6,554
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: 2014 X5 xDrive 5.0 M Package Carbon Black Metallic/2008 M Roadster Imola Red
Originally Posted by UPENN545' date='Sep 18 2005, 08:31 PM
[quote name='donv' date='Sep 18 2005, 08:17 PM'][quote name='UPENN545' date='Sep 18 2005, 07:48 PM']I now have a Headache.?
[snapback]172131[/snapback]
[snapback]172139[/snapback]
[/quote]I love austin I migrated from Devon P.A. I recently Built a house in West Lake Hills ..Horns are doing Awesome. My Grad ALMA MATER.
[snapback]172144[/snapback]
[/quote]My grad degrees too. I love WLH's-although I haven't seen much of it in many years.
09-18-2005, 05:35 PM
#10
Contributors
Join Date: Aug 2005
Location: Westlake Hills - Austin,TX
Posts: 172
Likes: 0
Received 0 Likes
on
0 Posts
My Ride: V8 beast!
Originally Posted by donv' date='Sep 18 2005, 08:33 PM
[quote name='UPENN545' date='Sep 18 2005, 08:31 PM'][quote name='donv' date='Sep 18 2005, 08:17 PM'][quote name='UPENN545' date='Sep 18 2005, 07:48 PM']I now have a Headache.?
[snapback]172131[/snapback]
[snapback]172139[/snapback]
[/quote]I love austin I migrated from Devon P.A. I recently Built a house in West Lake Hills ..Horns are doing Awesome. My Grad ALMA MATER.
[snapback]172144[/snapback]
[/quote]My grad degrees too. I love WLH's-although I haven't seen much of it in many years.
[snapback]172146[/snapback]
[/quote]Oh yeah! I went to McCombs...The views in WLH are spectacular.One of the main things that sold me.