theoretical top speed
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18" wheels 40 tires and a 6 speed box from a st170 car will have around 400bhp and its front wheel drive with 8k rev limit
Last edited by jacko; 29-12-2008 at 03:54 PM.
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Well, i worked out with my 225/40/18 tyres and a 9k rev limit in 6th it would theoretically be doing 225mph...
I fear that even with aero/power mods you'd struggle to get past the high 170s/low 180s...
I fear that even with aero/power mods you'd struggle to get past the high 170s/low 180s...
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WHY !!!
you only lengthen the gearing if you can hit the limiter in Top gear with the 17's.
Seen 225mph quoted thats longer gearing than mine & I will have over twice the Power of this car & I could not pull that or even close.
Bit of advice gear short cos once moving it will pull past peak Power & accleration will benefit , your limiter will be on a dying Power curve so forget all about 9k
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Sounds as if doing the run in 5th is your best bet, 6th sounds a total waste of time.
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see this is why im asking i know verry little about all the top speed bolox but i want to lern
one thing though how fast was suny,s fieasta with what wheels power and geering
one thing though how fast was suny,s fieasta with what wheels power and geering
#20
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drive ratios for the st 170 box
1st 4.46 1 2.88 12.7
2nd 2.71 1 2.88 7.7
3rd 1.33 2 4.25 5.7
4th 1.09 2 4.25 4.6
5th 1.33 1 2.88 3.8
6th 1.09 1 2.88 3.1
Reverse 2.82 2 4.25 12.0
spoke to karl ( the owner ) eairler , dosent have any plans to rev to 9 k ,
the cars going to be a 2.1 , ze-vh , big valve head , newman , gt 30 - 35 ( undecided , )
obviously custom inlet , exhaust , big cooler , cossie management ,
not what power it will make in the end , but torque is whast hes going for and plenty of it ,
so on the final drive of 5th gear ( above ), 18s and say a poss 7.5 k rev limit ,
what you think it will make speed wise ,
beef ,
Focus ST170 Close-Ratio Gear Configuration
Gear Gear Ratio Layshaft Final Drive Ratio Overall Ratio1st 4.46 1 2.88 12.7
2nd 2.71 1 2.88 7.7
3rd 1.33 2 4.25 5.7
4th 1.09 2 4.25 4.6
5th 1.33 1 2.88 3.8
6th 1.09 1 2.88 3.1
Reverse 2.82 2 4.25 12.0
spoke to karl ( the owner ) eairler , dosent have any plans to rev to 9 k ,
the cars going to be a 2.1 , ze-vh , big valve head , newman , gt 30 - 35 ( undecided , )
obviously custom inlet , exhaust , big cooler , cossie management ,
not what power it will make in the end , but torque is whast hes going for and plenty of it ,
so on the final drive of 5th gear ( above ), 18s and say a poss 7.5 k rev limit ,
what you think it will make speed wise ,
beef ,
Last edited by -beefy-; 29-12-2008 at 09:35 PM.
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Force = Pressure x Area
Power = Force x Velocity
therefore
Power = (Pressure x Area) x Velocity
The Pressure is air resistance created from moving through a fluid.
Pressure = 0.5 x Density x Velocity^2 x Area Bernoullis
Pressure = 0.5 x Density x Velocity x Velocity x Area
Power therefore
Power = (0.5 x Density x Velocity x Velocity) x Velocity x Area
The area of a S2 is 1.834m x 1.349m = 2.474m2
There is a measured drag coefficient (Cd) , which is the effective area (how areodyamic it is).
The S2 Cd = 0.36
The area is then 2.474 x 0.36 = 0.891m2 (known as CdA)
going back
Power = (0.5 x Density x Velocity x Velocity) x Velocity x Area
Power = 0.5 x Density x Velocity^3 x CdA
Density of air is about 1.2kg/m3
Power = 0.5 x 1.2 x Velocity^3 x 0.891
To make 180mph = 290km/h = 81ms (meters per second)
Power = 0.5 x 1.2 x 81^3 x 0.891
Power = 284108Watts
Power = 284.1kW
Power = 284/0.746 = 380bhp AT THE WHEELS
The best gearbox will be about 80% eff, proberly less at those speeds
Power= 380bhp / 0.8 = 476bhp
Thats without the resistance of rolling the tyres at 180mph.
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drive ratios for the st 170 box
1st 4.46 1 2.88 12.7
2nd 2.71 1 2.88 7.7
3rd 1.33 2 4.25 5.7
4th 1.09 2 4.25 4.6
5th 1.33 1 2.88 3.8
6th 1.09 1 2.88 3.1
Reverse 2.82 2 4.25 12.0
spoke to karl ( the owner ) eairler , dosent have any plans to rev to 9 k ,
the cars going to be a 2.1 , ze-vh , big valve head , newman , gt 30 - 35 ( undecided , )
obviously custom inlet , exhaust , big cooler , cossie management ,
not what power it will make in the end , but torque is whast hes going for and plenty of it ,
so on the final drive of 5th gear ( above ), 18s and say a poss 7.5 k rev limit ,
what you think it will make speed wise ,
beef ,
Focus ST170 Close-Ratio Gear Configuration
Gear Gear Ratio Layshaft Final Drive Ratio Overall Ratio1st 4.46 1 2.88 12.7
2nd 2.71 1 2.88 7.7
3rd 1.33 2 4.25 5.7
4th 1.09 2 4.25 4.6
5th 1.33 1 2.88 3.8
6th 1.09 1 2.88 3.1
Reverse 2.82 2 4.25 12.0
spoke to karl ( the owner ) eairler , dosent have any plans to rev to 9 k ,
the cars going to be a 2.1 , ze-vh , big valve head , newman , gt 30 - 35 ( undecided , )
obviously custom inlet , exhaust , big cooler , cossie management ,
not what power it will make in the end , but torque is whast hes going for and plenty of it ,
so on the final drive of 5th gear ( above ), 18s and say a poss 7.5 k rev limit ,
what you think it will make speed wise ,
beef ,
#31
formerly beefy-rst-2
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look guys ,
all know is what ive mentioned above ,
thats roughly the spec the car is going to run , ill will be running the 6 speed st box ,
what were trying to work out is with say a 400 hp engine , whats his best way to reach his highest poss top speed ,
,
beef
all know is what ive mentioned above ,
thats roughly the spec the car is going to run , ill will be running the 6 speed st box ,
what were trying to work out is with say a 400 hp engine , whats his best way to reach his highest poss top speed ,
,
beef
#32
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i am no expert, alot of my knowledge is secondhand information, but i believe a CVH for example has has a very similar bore to rod length ratio, where as a ZVH doesnt to detrimental effect, meaning it struggles to make the power at increased revs?
Hopefully one of the the techy guy will be able to clear this up?
Hopefully one of the the techy guy will be able to clear this up?
#33
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There's a formula to work out topspeed from power and CdA if you know CdA. Then sort your gearing so that you can reach that speed at the revs your max power occurs at. So for example if 400bhp(at 7500rpm) will do 175mph, then you want to hit 175mph at 7500rpm in 5th for example.
(or I may be talking alcohol induced shite)
Found it. V = cube root of(2P/pCdA) where P=power in watts, p(roe) is air density, Cd is coefficient of drag, A is frontal area.
1 BHP = 745.7 Watts
Last edited by Fast Guy; 29-12-2008 at 11:05 PM.
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nowt ta do with the "top speed crack" but a gt35 on owt less than a 2.5-3.0ltr will be a shite road car.......laaaagg.............probably not going to make boost till 5k,rpm.....think u need to sort out ur engine/ power figure, then sort a turbo that will still pull to the red line....maybe use a "cossie" box that people know will do 170+ mph.....
#36
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nowt ta do with the "top speed crack" but a gt35 on owt less than a 2.5-3.0ltr will be a shite road car.......laaaagg.............probably not going to make boost till 5k,rpm.....think u need to sort out ur engine/ power figure, then sort a turbo that will still pull to the red line....maybe use a "cossie" box that people know will do 170+ mph.....
cant use a cossie box mate , , karls running fwd ,
imo this whole threads completely pointless and shouldnt even have been started till the engines built , mapped and we know its making x amount of power ,
cos till thats determined ,
everything else is bollocks ,
beef ,
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