.cd for the 928
04-02-2010, 11:39 PM
#2
Rennlist Member
From Theo
I found a list by Markus (MG) from the list put together by the 911 meeting that is quite interesting and contains a lot of Cd values:
Air resistance factor (Cd) x Front surface (A) m2 = air resistance index
356/1 GMÜND 1948 (open with 2 persons): 0.45 x 1.41 = 0.648
356/2 GMÜND Coupé and Cabrio 1948 to 1950: 0.29 x 1.62 = 0.469
356 to MJ 1952: 0.296 x 1.677 = 0.496
356 to MJ 1955: 0.365 x 1.692 = 0.618
356 Speedster to MJ 1958. Convertible D 1959: 0.377 x 1.640 = 0.618
356 A: 0.365 x 1.692 = 0.618
356 B: 0.398 x 1.611 = 0.641
356 B roadster: 0.386 x 1.599 = 0.617
356 B 1600 GS Carrera GTL (Abarth): 0.389 x 1.495 = 0.581
356 C: 0.398 x 1.611 = 0.641
550 R-S Spyder: ?
904 Carrera GTS: 0.383 x 1.401 = 0.536
914.1.7 (also 914/6, 914/8, 914/8 SII) MJ 1970 to MJ 1973: 0.38 x 1.60 = 0.608
914.2.0 MJ 1973 and 1974: 0.38 x 1.60 = 0.608
914.2.0 MJ 1975 and 1976: 0.377 x 1.60 = 0.603
924 (MJ 1976 to 1979): 0.36 x 1.76 = 0.634
924 (starting from MJ 1980): 0.33 x 1.79 = 0.591
924 turbo (931): 0.34 x 1.79 = 0.609
924 Carrera GT (937): 0.34 x 1.82 = 0.619
924S (946): 0.33 x 1.81 = 0.597
944 (also S) MJ 1982 to 1989: 0.35 x 1.82 = 0.637
944 turbo (951) (also S2, turbo S, 968 CS, 968 turbo S): 0.33 x 1.89 = 0.624
944 S2 Cabrio MJ 1989 to 1991 (also S2 Cabrio, turbo Cabrio, 968 Cabrio): 0.36 x 1.87 = 0.673
928 MJ 1978 to 1982: 0.41 x 1.95 = 0.799
928 S MJ 1980 to 1986: 0.38 x 1.95 = 0.741
928 S4 MJ 1987 to 1991 (also CS. GT): 0.34 x 1.98 = 0.673
928 GTS MJ 1992 to 1995: 0.35 x 2.02 = 0.707
986 Boxster: 0.31 x 1.93 = 0.598
986 Boxster S MJ 2000 to 2002: 0.32 x 1.93 = 0.617
987 Boxster: 0.29 x 1.96 = 0.57
987 Boxster S: 0.30 x 1.97 = 0.59
987 Cayman S: 0.29 x 1.98 = 0.57
955 Cayenne (V6) MJ 2004: 0.38 x 2.78 = 1.056
955 Cayenne S (and turbo) MJ 2003 + 2004: 0.39 x 2.78 = 1.084
901 1964: 0.363 x 1.685 = 0.612
911 MJ 1965 to 1967 all types (also Targa and S): 0.363 x 1.685 = 0.612
911 MJ ' 68 (all types): CD x A (m2) = 0.381 x 1.6853 = 0.642
912: Similar to 911 of respective model years
911 MJ ' 69-'73: Cd x A (m2) = 0.408 x 1.71 = 0.697
911 RS MJ 1973: 0.397 x 1.73 = 0.686
911 MJ 1974 to MJ 1977 (also S. Targa): 0.39 x 1.76 = 0.686
911 SC MJ 1978 to MJ 1983 (also Targa and Cabrio) and Carrera MJ 1974 to MJ 1977: 0.40 x 1.77 = 0.708
911 Carrera 3.2 MJ 1984 to MJ 1989: 0.39 x 1.77 = 0.690
911 Carrera 3.2 MJ 1984 to MJ 1989 with front and tail spoiler (also Clubsport):0.38 x 1.77 = 0.672
911 turbo (930) (also WTL, SC/RS, turbo slant nose): 0.39 x 1.86 = 0.725
959: 0.31 x 1.92 = 0.595
964 (also R-S. R-S America, R-S N/GT): Cd x A (m2) = 0.32 x 1.79 = 0.573
964 turbo (994). (Frere): Cd x A (m2) = 0.35 x 1.88 = 0.658
964 turbo (994) (also WTL, Jubi) (Bongers): 0.36 x 1.89 = 0.680
964 turbo S lightweight construction (994) (also R-S 3.8. turbo 3.6, turbo 3.6 low rise building): 0.35 x 1.89 = 0.662
993 (also R-S): 0.33 x 1.86 = 0.614
993 R-S Clubsport (with rear wing 0 Angle of incidence): 0.34 x 1.86 = 0.632
993 R-S Clubsport (with rear wing 9 Angle of incidence): 0.36 x 1.86 = 0.669
993 GT 2: 0.34 x 2.04 = 0.684
993 turbo (also 2S. 4S, turbo Cabrio): CD x A (m2) = 0.34 x 1.93 = 0.656
996: Cd x A (m2) = 0.30 x 1.94 = 0.582
996 4S: 0.30 x 2.00 = 0.60
996 GT 2: 0.34 x 1.96 = 0.666
996 GT 3 MJ 1999 to 2001: 0.30 x 1.95 = 0.585
996 turbo: 0.31 x 2.0 = 0.62
997: 0.28 x 2.00 = 0.56
997 Cabrio: 0.29
997S: 0.29 x 2.00 = 0.58
997S Cabrio: 0.29
980 Carrera GT: 0.396 x 1.94 = 0.768
Theo
1988 928S4 cherry talk
The Netherlands
Air resistance factor (Cd) x Front surface (A) m2 = air resistance index
356/1 GMÜND 1948 (open with 2 persons): 0.45 x 1.41 = 0.648
356/2 GMÜND Coupé and Cabrio 1948 to 1950: 0.29 x 1.62 = 0.469
356 to MJ 1952: 0.296 x 1.677 = 0.496
356 to MJ 1955: 0.365 x 1.692 = 0.618
356 Speedster to MJ 1958. Convertible D 1959: 0.377 x 1.640 = 0.618
356 A: 0.365 x 1.692 = 0.618
356 B: 0.398 x 1.611 = 0.641
356 B roadster: 0.386 x 1.599 = 0.617
356 B 1600 GS Carrera GTL (Abarth): 0.389 x 1.495 = 0.581
356 C: 0.398 x 1.611 = 0.641
550 R-S Spyder: ?
904 Carrera GTS: 0.383 x 1.401 = 0.536
914.1.7 (also 914/6, 914/8, 914/8 SII) MJ 1970 to MJ 1973: 0.38 x 1.60 = 0.608
914.2.0 MJ 1973 and 1974: 0.38 x 1.60 = 0.608
914.2.0 MJ 1975 and 1976: 0.377 x 1.60 = 0.603
924 (MJ 1976 to 1979): 0.36 x 1.76 = 0.634
924 (starting from MJ 1980): 0.33 x 1.79 = 0.591
924 turbo (931): 0.34 x 1.79 = 0.609
924 Carrera GT (937): 0.34 x 1.82 = 0.619
924S (946): 0.33 x 1.81 = 0.597
944 (also S) MJ 1982 to 1989: 0.35 x 1.82 = 0.637
944 turbo (951) (also S2, turbo S, 968 CS, 968 turbo S): 0.33 x 1.89 = 0.624
944 S2 Cabrio MJ 1989 to 1991 (also S2 Cabrio, turbo Cabrio, 968 Cabrio): 0.36 x 1.87 = 0.673
928 MJ 1978 to 1982: 0.41 x 1.95 = 0.799
928 S MJ 1980 to 1986: 0.38 x 1.95 = 0.741
928 S4 MJ 1987 to 1991 (also CS. GT): 0.34 x 1.98 = 0.673
928 GTS MJ 1992 to 1995: 0.35 x 2.02 = 0.707
986 Boxster: 0.31 x 1.93 = 0.598
986 Boxster S MJ 2000 to 2002: 0.32 x 1.93 = 0.617
987 Boxster: 0.29 x 1.96 = 0.57
987 Boxster S: 0.30 x 1.97 = 0.59
987 Cayman S: 0.29 x 1.98 = 0.57
955 Cayenne (V6) MJ 2004: 0.38 x 2.78 = 1.056
955 Cayenne S (and turbo) MJ 2003 + 2004: 0.39 x 2.78 = 1.084
901 1964: 0.363 x 1.685 = 0.612
911 MJ 1965 to 1967 all types (also Targa and S): 0.363 x 1.685 = 0.612
911 MJ ' 68 (all types): CD x A (m2) = 0.381 x 1.6853 = 0.642
912: Similar to 911 of respective model years
911 MJ ' 69-'73: Cd x A (m2) = 0.408 x 1.71 = 0.697
911 RS MJ 1973: 0.397 x 1.73 = 0.686
911 MJ 1974 to MJ 1977 (also S. Targa): 0.39 x 1.76 = 0.686
911 SC MJ 1978 to MJ 1983 (also Targa and Cabrio) and Carrera MJ 1974 to MJ 1977: 0.40 x 1.77 = 0.708
911 Carrera 3.2 MJ 1984 to MJ 1989: 0.39 x 1.77 = 0.690
911 Carrera 3.2 MJ 1984 to MJ 1989 with front and tail spoiler (also Clubsport):0.38 x 1.77 = 0.672
911 turbo (930) (also WTL, SC/RS, turbo slant nose): 0.39 x 1.86 = 0.725
959: 0.31 x 1.92 = 0.595
964 (also R-S. R-S America, R-S N/GT): Cd x A (m2) = 0.32 x 1.79 = 0.573
964 turbo (994). (Frere): Cd x A (m2) = 0.35 x 1.88 = 0.658
964 turbo (994) (also WTL, Jubi) (Bongers): 0.36 x 1.89 = 0.680
964 turbo S lightweight construction (994) (also R-S 3.8. turbo 3.6, turbo 3.6 low rise building): 0.35 x 1.89 = 0.662
993 (also R-S): 0.33 x 1.86 = 0.614
993 R-S Clubsport (with rear wing 0 Angle of incidence): 0.34 x 1.86 = 0.632
993 R-S Clubsport (with rear wing 9 Angle of incidence): 0.36 x 1.86 = 0.669
993 GT 2: 0.34 x 2.04 = 0.684
993 turbo (also 2S. 4S, turbo Cabrio): CD x A (m2) = 0.34 x 1.93 = 0.656
996: Cd x A (m2) = 0.30 x 1.94 = 0.582
996 4S: 0.30 x 2.00 = 0.60
996 GT 2: 0.34 x 1.96 = 0.666
996 GT 3 MJ 1999 to 2001: 0.30 x 1.95 = 0.585
996 turbo: 0.31 x 2.0 = 0.62
997: 0.28 x 2.00 = 0.56
997 Cabrio: 0.29
997S: 0.29 x 2.00 = 0.58
997S Cabrio: 0.29
980 Carrera GT: 0.396 x 1.94 = 0.768
Theo
1988 928S4 cherry talk
The Netherlands
04-03-2010, 01:08 AM
#3
Rennlist Member
Very interesting, and thanks for posting, Rick!
I find it fascinating that the earliest 356's were Cd=0.29, a figure not bettered until the 997...
The problem of course was the bumper-height requirements, and what to do with all the air below the bumper...
It is also pretty interesting that the Cd for the 928 was the same or better than 911's of the same vintage, in spite of needing to accommodate the engine within the front-end sheet metal.
(Of course if the engine were 8" taller then the sump and intake design would be simpler... but then it wouldn't look the way it does...).
I find it fascinating that the earliest 356's were Cd=0.29, a figure not bettered until the 997...
356/2 GMÜND Coupé and Cabrio 1948 to 1950: 0.29 x 1.62 = 0.469
356 to MJ 1952: 0.296 x 1.677 = 0.496
...
997: 0.28 x 2.00 = 0.56
356 to MJ 1952: 0.296 x 1.677 = 0.496
...
997: 0.28 x 2.00 = 0.56
It is also pretty interesting that the Cd for the 928 was the same or better than 911's of the same vintage, in spite of needing to accommodate the engine within the front-end sheet metal.
(Of course if the engine were 8" taller then the sump and intake design would be simpler... but then it wouldn't look the way it does...).
04-03-2010, 05:37 PM
#5
Race Director
WOW... .41 for the early 928's.....I know all narrow body 928's are 21.28 sq ft frontal area..probably a bit more for the GTS..... I thought S4's were .36 with the nose vents open and .34 with the vents closed?
Whats even more funny....the 1.5 million Veyron is .41 with 22.3 frontal area.....or 9.143 effective frontal area...even in top speed mode it drops to .36 or 8.03...still considerably worse than a 928 which ranges from 7.23 to 8.7......... not too bad considering it mid 70's design
Whats even more funny....the 1.5 million Veyron is .41 with 22.3 frontal area.....or 9.143 effective frontal area...even in top speed mode it drops to .36 or 8.03...still considerably worse than a 928 which ranges from 7.23 to 8.7......... not too bad considering it mid 70's design
04-03-2010, 08:31 PM
#6
Addict
Rennlist Member
Rennlist Member
Aren't aerodynamics often adjusted upwards in favor of stability at high speed? That would certainly explain the Veyron.
Were aerodynamics a big factor in the 70's when the 928 was designed?
Were aerodynamics a big factor in the 70's when the 928 was designed?
11-04-2010, 01:54 AM
#7
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Member
This is an interesting reference for the Mythbuster story...
https://rennlist.com/forums/928-foru...n-reverse.html
https://rennlist.com/forums/928-foru...n-reverse.html
https://rennlist.com/forums/928-foru...h-busters.html
https://rennlist.com/forums/928-foru...n-reverse.html
https://rennlist.com/forums/928-foru...n-reverse.html
https://rennlist.com/forums/928-foru...h-busters.html
