Top speed calculator
#1
Race Director
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While surfing today I found this
http://www.rbracing-rsr.com/aerohpcalc.html
yes it was designed intially for motorcycles, but the principles remain the same....(this doesn't account for rolling resistance or gearing limitations)... I entered the following for 928's
Cd of .36
Frontal area 21.28
weight of 3750lbs (with driver)
200mph: 448hp is needed (it doesn't say if its wheel or crank HP?)
210mph: 517hp
220mph: 593hp
230mph: 676hp
250mph: 866hp
So a 1000whp 928 in theory could go almost 262mph.....for some reason I really doubt it....
So guessing its wheel horsepower that means that Louie Ott could hit almost 220mph....the beast can do 210mph (thats pretty close really) & Todd's crazy SC will hit nearly 230mph.....
http://www.rbracing-rsr.com/aerohpcalc.html
yes it was designed intially for motorcycles, but the principles remain the same....(this doesn't account for rolling resistance or gearing limitations)... I entered the following for 928's
Cd of .36
Frontal area 21.28
weight of 3750lbs (with driver)
200mph: 448hp is needed (it doesn't say if its wheel or crank HP?)
210mph: 517hp
220mph: 593hp
230mph: 676hp
250mph: 866hp
So a 1000whp 928 in theory could go almost 262mph.....for some reason I really doubt it....
So guessing its wheel horsepower that means that Louie Ott could hit almost 220mph....the beast can do 210mph (thats pretty close really) & Todd's crazy SC will hit nearly 230mph.....
#4
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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....
#5
Rennlist Member
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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....
#6
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Hi ![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
I worked out that "in theory" with normal rear tyres and my diff , mine is "theoretically" capable of 235 mph...with the oversize tyres its now "theoretically" capable of 251 mph....
The above assumes that I have enough hp to push it that fast....which I just might but will be happy with over 212![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
Although if I hit my 212, I wont take my boot out until I figure even with my chute ,I wont stop in time![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
All the best Brett
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
I worked out that "in theory" with normal rear tyres and my diff , mine is "theoretically" capable of 235 mph...with the oversize tyres its now "theoretically" capable of 251 mph....
The above assumes that I have enough hp to push it that fast....which I just might but will be happy with over 212
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
Although if I hit my 212, I wont take my boot out until I figure even with my chute ,I wont stop in time
![Wink](https://rennlist.com/forums/images/smilies/wink.gif)
All the best Brett
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
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#9
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One more dumbass thing to live to tell about, but never do again on a bike!
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Jim
#10
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This is fairly good software to predict actual top speed:
http://www.cartestsoftware.com/cartest4.5/index.html
Or at least it works in predicting real stock model top speeds accurately once correct data is given for it. It might fail on high above 200 mph though same as it doesn't work too accurately on very fast acceleration numbers from standstill.
http://www.cartestsoftware.com/cartest4.5/index.html
Or at least it works in predicting real stock model top speeds accurately once correct data is given for it. It might fail on high above 200 mph though same as it doesn't work too accurately on very fast acceleration numbers from standstill.
#14
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There's no input for Kp (pucker factor) at higher speeds.
IIRC, about 8% wheel slip is the max you'd ever consider safe on even a straight run with no crosswind. This may be a major limiting factor in Brett's top-speed challenge run, judging by the drag-strip results posted previously.
IIRC, about 8% wheel slip is the max you'd ever consider safe on even a straight run with no crosswind. This may be a major limiting factor in Brett's top-speed challenge run, judging by the drag-strip results posted previously.
#15
Instructor
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The hp figures you have calculated are at the rear wheels and include rolling resistance.
While surfing today I found this
http://www.rbracing-rsr.com/aerohpcalc.html
yes it was designed intially for motorcycles, but the principles remain the same....(this doesn't account for rolling resistance or gearing limitations)... I entered the following for 928's
Cd of .36
Frontal area 21.28
weight of 3750lbs (with driver)
200mph: 448hp is needed (it doesn't say if its wheel or crank HP?)
210mph: 517hp
220mph: 593hp
230mph: 676hp
250mph: 866hp
So a 1000whp 928 in theory could go almost 262mph.....for some reason I really doubt it....
So guessing its wheel horsepower that means that Louie Ott could hit almost 220mph....the beast can do 210mph (thats pretty close really) & Todd's crazy SC will hit nearly 230mph.....
http://www.rbracing-rsr.com/aerohpcalc.html
yes it was designed intially for motorcycles, but the principles remain the same....(this doesn't account for rolling resistance or gearing limitations)... I entered the following for 928's
Cd of .36
Frontal area 21.28
weight of 3750lbs (with driver)
200mph: 448hp is needed (it doesn't say if its wheel or crank HP?)
210mph: 517hp
220mph: 593hp
230mph: 676hp
250mph: 866hp
So a 1000whp 928 in theory could go almost 262mph.....for some reason I really doubt it....
So guessing its wheel horsepower that means that Louie Ott could hit almost 220mph....the beast can do 210mph (thats pretty close really) & Todd's crazy SC will hit nearly 230mph.....