jacko

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

Lee_R21Turbo

iTrader: (1)

Or perhaps even theoretical!!??

jacko

cant spell dont care

richard_syko

What car?

jacko

s2 but the airodynamics will be changed as much as posible to make it easier through the air and more stable

richard_syko

What width tyre?

jacko

7.5
wide

Big Will_

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...

-beefy-

iTrader: (6)

hes got 17s jack ?

jacko

with 9k


9k should be doable

jacko

there for everyday use seen asthough it wont need a good lock 18s will be going on
for speed attempts

this is still all theory at the mo

richard_syko

I get just over 202mph without worrying about power.

9000 rpm, 18/40/225

2 secs..

jacko

you need the power to get you through the air mate or it just wont rev that high

Rod-Tarry

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 , however you must gear for your Power with 400bhp around 170/175 I guess, gear longer & you wont pull anywhere near the cars potential cos accleration will be so badly blunted.

Sounds as if doing the run in 5th is your best bet, 6th sounds a total waste of time.

richard_syko

With 85% eff gearbox 400bhp will only give you 173mph what ever the gearing

-beefy-

iTrader: (6)

sounds like the 9 k limt aint the problem ,

its the extra 100 hp hes going to need then


beef

Big Will_

Need more than that to pull 9000rpm in 6th

richard_syko

I calc that you would need at least 650hp, about 550 at the wheels

jacko

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

-beefy-

iTrader: (6)

drive ratios for the st 170 box
Gear Gear Ratio Layshaft Final Drive Ratio Overall Ratio
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 ,

pa_sjo

160mph

-beefy-

iTrader: (6)

how did you come to that figure mate ?

also what would it make in 6th ,


- think we should change this thread to ,

what is needed to make a series two hit 180 ???




lol beef

pa_sjo

About 600bhp i'd say unless you were willing to do a lot of work on aero.

-beefy-

iTrader: (6)

ouch , sure the owner will be more than happy to hear that



beef

richard_syko

5th gear on the above ratios at 7500 is 135mph :S

richard_syko

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.

Twellsie

iTrader: (1)

i would love to see a zvh rev to that and still make the power, i am not saying it cant be done but would be suprised if that was the chosen unit to perform this task

Big Will_

To be honest if he goes for a GT35R he'll need big revs to get a decent powerband!

-beefy-

iTrader: (6)

so we saying a st 170 box is not good for a top speed attempt ,

or them final drive figures wrong ?

cant c why a zvh wont rev to 7.5 ?

im sure SAS is running at that rev limit ,


beef

Fast Guy

Top Speed Calculator

That will show you the top speed in each gear, but not what 400bhp will get you.

-beefy-

iTrader: (6)

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

Twellsie

iTrader: (1)

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?

Fast Guy

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

pete mcrash

iTrader: (1)

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.....

-beefy-

iTrader: (6)

well im sure the likes of turboboss and si etc are making over 350 + on 2.1's


were confident about making the power ,

and wont be no where near 9 k revs lol ,

just wanna know how fast it should go lol ,

beef ,

-beefy-

iTrader: (6)

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 ,

pa_sjo

It's all bollocks until you go run it and time it

pete mcrash

iTrader: (1)

........yes mate..........but u need to choose ur turbo, so it'll pull at peak revs............

-beefy-

iTrader: (6)

yeah deffo agree with you there pete ,

even karl aint sure what hes goin to go for yet ,

time will tell i suppose ,

me , in glad ive got a cossie engine lol,

seems soo much eaiser to get 400 out of that lol ,

beef

Twellsie

iTrader: (1)

they may well be, but they will certainly not have the broad power spread like Tims CVH for example as ZVH do not rev, FACT!