Top speed calculator
04-03-2008, 12:14 PM
#16
Rennlist Member
04-03-2008, 12:20 PM
#17
Rennlist Member
slippage on a dyno vs slippage on the street are two different things.
Slippage on the Salt Flats was due to running on salt, basic grip and aero.
the reason it went 180mph, was due to there being no slip.
I think when the devek car went 209, the rpms were right in line with the ground speed. meaning, there wasnt any slip. 10% would mean that instead of 5500rpm at 210mph you would be at 6100rpm, and that just wasnt the case.
mk
Slippage on the Salt Flats was due to running on salt, basic grip and aero.
the reason it went 180mph, was due to there being no slip.
I think when the devek car went 209, the rpms were right in line with the ground speed. meaning, there wasnt any slip. 10% would mean that instead of 5500rpm at 210mph you would be at 6100rpm, and that just wasnt the case.
mk
Brian:
One additional factor for top speed calcs is percent tire slippage. From the ORR runs I did in my 951, it's real and effects not only RPM needed but how effective the HP can be put to the ground. BAck in '97 when we were testing a 200+ SC 928, we figured about 10 percent slip at 200 given the slippage we saw on a rolling drum dyno. From my own observations in the 951, it was around 5-8 percent depending on conditions. Perhaps some of the other ORR folks can comment on their observations of this.
Back on the AEM / Mugen gig... definately glue a "R" on the back of any car and gain 100HP and 20+ MPH of top speed. Also, the sewer pipe exhaust is another must....
One additional factor for top speed calcs is percent tire slippage. From the ORR runs I did in my 951, it's real and effects not only RPM needed but how effective the HP can be put to the ground. BAck in '97 when we were testing a 200+ SC 928, we figured about 10 percent slip at 200 given the slippage we saw on a rolling drum dyno. From my own observations in the 951, it was around 5-8 percent depending on conditions. Perhaps some of the other ORR folks can comment on their observations of this.
Back on the AEM / Mugen gig... definately glue a "R" on the back of any car and gain 100HP and 20+ MPH of top speed. Also, the sewer pipe exhaust is another must....
04-03-2008, 08:52 PM
#18
Instructor
I have always suspected that running 60psi in the tyres for those runs exacerbated the traction problem on salt by reducing the area of the tyre contact patches.
04-03-2008, 09:06 PM
#19
Three Wheelin'
Join Date: Jun 2005
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Hi
Thats a VERY good point and still not sure which way to go on my 200 plus runs...
Do I run say...32 psi for grip...
Or....50 psi for increased rolling radius and higher top speed...
Rear tyre size = 275/40/18
I am inclined to go higher pressures but not certain yet...
All the best Brett
04-03-2008, 11:22 PM
#20
Drifting
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Isn't it "220 minus your age" the theoretical max?
Add 20 if you are a cop, 15 if you are a lawyer, and if you have IQ over 100, take away the additional in mph.
Theory and actual are always different.
Add 20 if you are a cop, 15 if you are a lawyer, and if you have IQ over 100, take away the additional in mph.
Theory and actual are always different.
