Crown

Forum - Thread

    Apr 23, 2009 6:07:14 AM

    reginos
    Rennteam VIP
    reginos
    Loc: Nicosia , Cyprus
    Posts: 12130, Gallery
    Registered on: Mar 20, 2005
    Reply to: fritz

    Re: Incoming GT2

    fritz:
    TB993tt:

    Just the Maha dyno test to see what the Cargraphic/RS stuff actually did. Frankly the sales guy Jan was IMO completely clueless but that is probably because he is not used to selling to anoraks like me - my BS detector was off the scale !

    FWIW, I don't think that your use of the noun "anoraks" in this context will be understood as you intended it to be anywhere outside of the UK.  Smiley

    There is always wikipedia:

    Do a search under Anorak(slang)

    en.wikipedia.org/wiki/Anorak_(slang)



    --
    It's not where you're going, it's how you get there that counts

    Apr 23, 2009 7:06:19 AM

    Enmanuel
    Rennteam VIP
    Enmanuel
    Loc: Boston , United States
    Posts: 8845, Gallery
    Registered on: Mar 7, 2008
    Reply to: reginos

    Re: Incoming GT2

     TB, could you please post some more pics of the wheels. thanx.

    Apr 23, 2009 8:51:14 AM

    Alcyon Offline
    Junior
    Alcyon
    Loc: Madrid , Spain
    Posts: 83, Gallery
    Registered on: Oct 12, 2005
    Reply to: Enmanuel

    Re: Incoming GT2

    I have saved some pics in my pc, could be from TB not sure.

    DYMAG09 new.jpg

     

    DYMAG006.jpg

     

    DYMAG005.jpg

    Apr 23, 2009 9:13:15 AM

    TB993tt
    Rennteam Pro
    TB993tt
    Loc: manchester , United Kingdom
    Posts: 2280, Gallery
    Registered on: Jul 22, 2002
    Reply to: Alcyon

    Re: Incoming GT2

    Here is some tech info someone (I forget who so no credit I'm afraid) shared with me about the benefits of these wheels:


    Determination of moment of inertia for a wheel is very difficult because the “normal” calculations are for a thin wall cylinder or solid rod, the calculation being a function of the mass multiplied by the square of the radius. With the Dymag carbon / magnesium wheel being of different materials and different masses as you radiate out from the hub, then the calculation needs to take on some assumptions.

    Therefore if we take the whole wheel, then the basic formula is: 

    MOI = ½ mr²

    If the carbon barrel alone is measured versus a metal rim it would be:

    MOI = mr²

    So because of the radius being squared in each calculation, the greater the diameter of any wheel then the greater the effect of reducing the MOI.

    As you can see if we use the generally accepted first formula then we are very conservative in our result, especially if we compare the Dymag wheel with an aluminium centred wheel where we could be as much as 50% greater on MOI than in reality! Hence the importance of measuring MOI of 2 wheels accurately on the same machine to make any comparison.

    Porsche 997 rear wheel comparison

    Comparing a 19x11.5” Porsche 997 Carrera S wheel with a Dymag carbon/magnesium 19x12” wheel.

    Porsche: 30lb x19” M=30lb, R=9.5”

    Therefore: ½ x 30 x 9.5² = 1,353.75 lb/in² MOI

    Dymag: 19lb x 19” M=19lb, R=9.5”

    Therefore: ½ x 19 x 9.5² = 857.375 lb/in² MOI which is 63% of the MOI of the Porsche wheel.


    Why is this important?

    Consider 2 factors of the wheel in use, rotating and steering.

    To rotate the wheel, the work energy required is calculated as force of net angular position change = ½ MOI x angular velocity², strictly speaking it is Force net θ = Δ( ½ MOI ω²)

    Which in English means that the energy consumption goes up as a function of the moment of inertia x the square of the speed, or as you go quicker it takes much more energy! This equation also shows that both acceleration and braking are both effected significantly by a reduction in MOI

    Steering changes are even easier to understand. The change in direction is governed by the momentum of the wheel which is calculated as the MOI x angular velocity, so in the above example, the Porsche on the Dymag wheel will use 47% less energy input to steer the car, either driver or power steering input, this is why the car feels “lighter” to drive and more responsive to steering input.

    Rule of thumb calculations

    This is a minefield of assumptions!! 2 of the old tuning rules of thumb were that 6lb weight saved on a car was equal to 1 bhp and that 1lb of rotating weight was worth 10lb of static weight, so in the Porsche example above, we are saving 11lb per wheel, x 10 = 110lb x 4 = 440lb ÷6 = 73.33 bhp we think this is probably excessive as the 10 factor does not take into account the diameter of the rotating part. A carbon propshaft would not have the same effect for example. 

    We have been stating that the rotating/static weight factor is about 6:1, this would give a result as above of 44bhp, which is roughly the gain effect that Parr Porsche said about the original tests of the carbon car wheels on the 996 GT3 RS!!

    Power to weight calculation

    Now if we take the Porsche wheels, the 997 Carrera S weighs 3131lbs and has 355 bhp, which gives it a power to weight ratio of 8.82:1 or, if you lose 8.82 lbs it is equivalent to 1bhp equivalent gained.

    So if we take the Dymag 6x factor for the carbon wheels then saving11lb per wheel x 6, x 4 wheels ÷ 8.82 lb/bhp = 29.93 bhp an important 8.43% power gain simply by bolting on different wheels. 

    But if we take the sometimes accepted10x rotating to static weight factor this figure comes to 49.88 bhp 

    Obviously using this type of formula, the more power to weight ratio, the bigger the wheel effect on performance – not too surprising really!

    Fuel saving and emissions reduction

    The best estimates available for fuel and emissions savings by using carbon wheels are between 3.0% and 8.0% fuel savings. The increased % would be with stop – start driving for the obvious reasons of overcoming inertia and momentum. Also air drag factors mask the wheels performance at higher & more consistent speeds.

    Emissions are much more difficult to calculate, especially when taking into account warm up and urban type cycles of car use. However as gasoline produces an average of 2.35kg per litre of fuel at the tailpipe, then it is safe to assume an initial saving of emissions to match fuel consumption. Again urban cycles will show a greater effect from the carbon wheel. So if the average car produces 165g of CO2 per km (at 7litres per 100km) the carbon wheels may reduce this to nearly 151g, a 9% improvement. 

    The fuel and emissions savings/reductions caused by carbon wheels need much more work. It is not possible to calculate these effects due to the other rotating components of the car which contribute to the overall moment of inertia, plus there are effects on non-rotating parts such as suspension where lighter wheels would give softer settings which require less energy to use the car in normal road conditions due to the reduction in energy losses with tyre deflections. 

    Conclusion

    Carbon rims have a noticeable effect on a car’s performance and handling, the variations in moment of inertia of the complete system are not well enough researched to give absolute figures of the improvements that the wheels give. That the improvement is significant is beyond doubt, the independent testing and standards agencies now need to make these evaluations, equally condemning many of the very heavy aftermarket products.

    Some bad pics I had on my computer - note the spokes are on Platinum Silver, the ones posted earlier are the darker smoked version I think.

    dymag4 002.jpgdymagnew.jpg


    --


    2009 997 GT2 RS Tuning 542PS/736NM

    Apr 23, 2009 11:06:16 AM

    Jay Offline
    Pilot
    Jay
    Loc: Earth , Eritrea
    Posts: 346, Gallery
    Registered on: Sep 6, 2002
    Reply to: TB993tt

    Re: Incoming GT2

    beautiful wheels and great write-up.   It'll make me think of PCCB's again too!

    Apr 23, 2009 2:19:21 PM

    andrea
    Rennteam Master
    andrea
    Loc: Italy, Pordenone , Italy
    Posts: 3569, Gallery
    Registered on: Sep 24, 2003
    Reply to: TB993tt

    Re: Incoming GT2

    TB993tt:

    Just the Maha dyno test to see what the Cargraphic/RS stuff actually did. Frankly the sales guy Jan was IMO completely clueless but that is probably because he is not used to selling to anoraks like me - my BS detector was off the scale !

    thanks for the info and the tech-links about your wheels!I appreciated a lot!


    --
    Dedi La vita è troppo corta per non guidare italiano.....

    Apr 23, 2009 9:08:25 PM

    fritz
    Rennteam VIP
    fritz
    Loc: BaWü , Germany
    Posts: 10248, Gallery
    Registered on: Jul 23, 2003
    Reply to: TB993tt

    Re: Incoming GT2

    TB993tt:

    Here is some tech info someone (I forget who so no credit I'm afraid) shared with me about the benefits of these wheels:
    Fuel saving and emissions reduction

    The best estimates available for fuel and emissions savings by using carbon wheels are between 3.0% and 8.0% fuel savings. The increased % would be with stop – start driving for the obvious reasons of overcoming inertia and momentum. Also air drag factors mask the wheels performance at higher & more consistent speeds.

    Emissions are much more difficult to calculate, especially when taking into account warm up and urban type cycles of car use. However as gasoline produces an average of 2.35kg per litre of fuel at the tailpipe, then it is safe to assume an initial saving of emissions to match fuel consumption. Again urban cycles will show a greater effect from the carbon wheel. So if the average car produces 165g of CO2 per km (at 7litres per 100km) the carbon wheels may reduce this to nearly 151g, a 9% improvement. 

    CO2 emissions are directly related to fuel consumption, so be suspicious of anyone who claims a 9% reduction in CO2 after suggesting that the best estimates of fuel consumption reduction are somewhere between 3 and 8%. Smiley


    --

    fritz

    Apr 27, 2009 9:55:51 AM

    Jay Offline
    Pilot
    Jay
    Loc: Earth , Eritrea
    Posts: 346, Gallery
    Registered on: Sep 6, 2002
    Reply to: Jay

    Re: Incoming GT2

    An 'obvious' question maybe regarding the implied HP increase using these wheels - or PCCB's for that matter.   Assuming the above math is ~correct, then you should be able to need a 'noticeable' 0-100 time difference etc.  

    I'm guessing that something like 0.3, on par with a FL model's power upgrade etc.  

     

    If the above is the case, then Porsche seem to have been quiet marketing it for their PCCB's

    Jan 7, 2010 11:18:54 AM

    scud
    Co-Pilot
    scud
    Loc: here , United Kingdom
    Posts: 201, Gallery
    Registered on: Aug 1, 2004
    Reply to: Jay

    Re: Incoming GT2

    If the above is the case, then Porsche seem to have been quiet marketing it for their PCCB's


    i have a question about the carbon rotors on the GT2. i have been told they are not a true full carbon rotor, but a steel rotor with a carbon coating?

    Jan 8, 2010 6:57:30 PM

    DaveGordon
    Rennteam Pro
    DaveGordon
    Loc: Zürich , Switzerland
    Posts: 2774, Gallery
    Registered on: Aug 20, 2007
    Reply to: scud

    Re: Incoming GT2

     I love the idea of removing rotating, unsprung mass - and mailed Dymag for a quote - they never even replied 


    --

    2007 987S, KW v3 1964 Type 1

    Jan 8, 2010 7:16:29 PM

    Porker
    Rennteam VIP
    Porker
    Loc: SZ , Switzerland
    Posts: 7062, Gallery
    Registered on: Jan 17, 2005
    Reply to: DaveGordon

    Re: Incoming GT2

    DaveGordon:

     I love the idea of removing rotating, unsprung mass - and mailed Dymag for a quote - they never even replied 

    They have gone bankrupt as far as I know...

     

    http://thekneeslider.com/archives/2009/11/30/dymag-racing-uk-ltd-in-bankruptcy-machinery-available-in-online-auction/

    Jan 8, 2010 7:21:27 PM

    FFaust Offline
    Senior
    FFaust
    Loc: Toronto'ish , Canada
    Posts: 736, Gallery
    Registered on: Nov 15, 2009
    Reply to: Porker

    Re: Incoming GT2

    Porker:
    DaveGordon:

     I love the idea of removing rotating, unsprung mass - and mailed Dymag for a quote - they never even replied 

    They have gone bankrupt as far as I know...

     

    http://thekneeslider.com/archives/2009/11/30/dymag-racing-uk-ltd-in-bankruptcy-machinery-available-in-online-auction/


    Wow, what a shame Smiley


    --

    Slow In, Fast Out

    Jan 8, 2010 7:23:56 PM

    fritz
    Rennteam VIP
    fritz
    Loc: BaWü , Germany
    Posts: 10248, Gallery
    Registered on: Jul 23, 2003
    Reply to: Porker

    Re: Incoming GT2

    Porker:
    DaveGordon:

     I love the idea of removing rotating, unsprung mass - and mailed Dymag for a quote - they never even replied 

    They have gone bankrupt as far as I know...

     Hmmm, I thought that selling carbon-rimmed wheels for road use would have to end in tears.  Smiley


    --

    fritz

    Jan 9, 2010 1:11:58 AM

    GT Offline
    Senior
    GT
    Loc: london , United Kingdom
    Posts: 618, Gallery
    Registered on: Jan 14, 2006
    Reply to: fritz

    Re: Incoming GT2

     They will be back trading in the next few months. Spoke to someone in the management team. They will focus on certain applications, car wheels will be one of those. So dont despair, you might still be able to get some. This was probably the best mod i did to this car todate..

    Jan 9, 2010 1:36:11 AM

    964C2
    Expert
    964C2
    Loc: Dallas, TX , United States
    Posts: 1825, Gallery
    Registered on: May 11, 2004
    Reply to: Porker

    Re: Incoming GT2

    HRE is now selling a line of wheels using the Dymag carbon rims.

    http://www.hrewheels.com/wheels/series.php?q=/CARBON/CF43/

     

    Jan 9, 2010 6:51:54 PM

    Leblanc
    Junior
    Leblanc
    Loc: Porto , Portugal
    Posts: 136, Gallery
    Registered on: Aug 4, 2009
    Reply to: 964C2

    Re: Incoming GT2

    Source: autogespot

     

     

    Jan 9, 2010 8:28:02 PM

    c4c
    Co-Pilot
    c4c
    Loc: North , Portugal
    Posts: 223, Gallery
    Registered on: Jul 14, 2004
    Reply to: Leblanc

    Re: Incoming GT2

    Fixed  Smiley

    1.jpg12630687232273.jpg12630687323835.jpg12630688345522.jpg 

     

     

     

    Jan 10, 2010 1:23:54 AM

    artur777 Offline
    Senior
    artur777
    Loc: Europe , Russia
    Posts: 774, Gallery
    Registered on: Dec 8, 2008
    Reply to: c4c

    Re: Incoming GT2

     nice pics

    Jan 10, 2010 5:48:15 PM

    Leblanc
    Junior
    Leblanc
    Loc: Porto , Portugal
    Posts: 136, Gallery
    Registered on: Aug 4, 2009
    Reply to: artur777

    Re: Incoming GT2

    Obrigado c4c.

    Thanks.

     

    Jan 10, 2010 5:50:54 PM

    c4c
    Co-Pilot
    c4c
    Loc: North , Portugal
    Posts: 223, Gallery
    Registered on: Jul 14, 2004
    Reply to: Leblanc

    Re: Incoming GT2

    Smiley 

     
    Edit

    Forum

    1. All 

    Boards

     
    Board Subject Last post Rating Views Replies
    Porsche Sticky SUN'S LAST RUN TO WILSON, WY - 991 C2S CAB LIFE, END OF AN ERA (Part II) 4/17/24 7:16 AM
    GnilM     		774669 1798
    Porsche Sticky Welcome to Rennteam: Cars and Coffee... (photos) 4/7/24 11:48 AM
    Boxster Coupe GTS     		440243 565
    Porsche Sticky OFFICIAL: Cayman GT4 RS (2021) 5/12/23 12:11 PM
    W8MM     		262017 288
    Porsche Sticky OFFICIAL: Porsche 911 (992) GT3 RS - 2022 3/12/24 8:28 AM
    DJM48     		260284 323
    Porsche Sticky The new Macan: the first all-electric SUV from Porsche 1/30/24 9:18 AM
    RCA     		84822 45
    Porsche Sticky OFFICIAL: Taycan 2024 Facelift 3/15/24 1:23 PM
    CGX car nut     		5442 50
    Porsche The moment I've been waiting for... 2/1/24 7:01 PM
    Pilot
     
     
     
     
     
    		 879314 1364
    Porsche 992 GT3 7/23/23 7:01 PM
    Grant     		814120 3868
    Porsche Welcome to the new Taycan Forum! 2/10/24 4:43 PM
    nberry     		389748 1526
    Porsche GT4RS 4/21/24 11:50 AM
    mcdelaug     		389056 1454
    Others Tesla 2 the new thread 12/13/23 2:48 PM
    CGX car nut     		371274 2401
    Porsche Donor vehicle for Singer Vehicle Design 7/3/23 12:30 PM
    Porker     		368031 797
    Porsche Red Nipples 991.2 GT3 Touring on tour 4/11/24 12:32 PM
    Ferdie     		288460 668
    Porsche Collected my 997 GTS today 10/19/23 7:06 PM
    CGX car nut
     
     
     
     
     
    		 260987 812
    Lambo Huracán EVO STO 7/30/23 6:59 PM
    mcdelaug     		239538 346
    Lotus Lotus Emira 6/25/23 2:53 PM
    Enmanuel     		229699 101
    Others Corvette C8 10/16/23 3:24 PM
    Enmanuel     		220702 488
    Others Gordon Murray - T.50 11/22/23 10:27 AM
    mcdelaug     		168836 387
    Porsche Back to basics - 996 GT3 RS 6/11/23 5:13 PM
    CGX car nut     		140736 144
    BMW M 2024 BMW M3 CS Official Now 12/29/23 9:04 AM
    RCA     		117222 303
    Motor Sp. 2023 Formula One 12/19/23 5:38 AM
    WhoopsyM     		108391 685
    Others Valkyrie final design? 4/28/23 2:45 AM
    Rossi     		99569 219
    Porsche 2022 992 Safari Model 3/7/24 4:22 PM
    WhoopsyM     		84023 239
    AMG Mercedes-Benz W124 500E aka Porsche typ 2758 2/23/24 10:03 PM
    blueflame     		75011 297
    Porsche 992 GT3 RS 3/3/24 7:22 PM
    WhoopsyM     		53418 314
    Motor Sp. Porsche 963 3/16/24 9:27 PM
    WhoopsyM     		24931 237
    Ferrari Ferrari 296 GTB (830PS, Hybrid V6) 1/21/24 4:29 PM
    GT-Boy     		21143 103
    BMW M 2022 BMW M5 CS 4/8/24 1:43 PM
    Ferdie     		19441 140
    AMG G63 sold out 9/15/23 7:38 PM
    Nico997     		16567 120
    AMG [2022] Mercedes-AMG SL 4/23/24 1:24 PM
    RCA     		13575 225
    128 items found, displaying 1 to 30.