S2 won't go faster than 265 km/h

[quattrostyle]

5-speed and the Dutch members I told about had the same, chipped 3B with 5-speed

[UrS4boy]

Your top speed is determined by the gearbox ratios, Have you got a 5 speed of 6 speed?

Aren't the fifth gear of a five speed and the 6th gear of the 6 speed the same ratio? They are for the AAN transmissions.

Anyway, your statement only is true as it effects the point on the power band. Certainly, you cannot go faster with a 7 spd transmission just because you have 7th gear.

But maybe you've been listening to too much music at "11".

[UrS4boy]

5-speed and the Dutch members I told about had the same, chipped 3B with 5-speed

Perhaps those Dutch members were het vertellen ligt?

[Jonas_R]

What kinda tires are you running? Since this will have a effect on your speedo readings, and on your friends speedo as well.

In my opinion top speed readings are only accurate if they are from a GPS.

Your speedo could be spot on, so in fact your are close to 265 km/t, I think we have clocked a couple of chipped s2 Coupe's in Denmark to around 260 km/t with GPS.

[kwlw]

anybody got an idea what could stop my S2 from reaching 280 km/h like it should?

Check you tire pressure (hot), witdth, bearing wear (how easily you can push your car with your hand), antenas, spoilers and other stuff making air swirls. At the limit each tiny thing counts.

And BTW - maybe your friend is just running smaller diameter tires...

Sau

[S2central.net]

By my calcs - you need ~280bhp to hit 165mph (265kph) in an S2. This 265kph versus 280kph going by speedos is a bit irrelevant IMHO - its only 10% difference - tyre sizes and pressures could explain some of that - never mind speedo inaccuracy.

The same calcs show that 230bhp is appropriate for factory Vmax of 154mph. This is all a wee bit imperfect as Vmax doesn't necessarily align with peak point of power band. These are calcs that I found on some US website for drag strip racers - its all in imperial units. Haven't tried to rationalise them with quattrostyle's calcs.

As to the whole gearing thing - setting up a gearbox for theoretical limit of 200mph is fine - as long as you remember that you need something well in excess of ~500bhp to carry the car thru the aero resistance to that speed.

[quattrostyle]

Perhaps those Dutch members were het vertellen ligt?

the last 3 words are Dutch but wtf. are you trying to say?

I'm running Conti's in 225-45/17 on all corners, tyre pressure is 2.5 bar.

[S2central.net]

I have found an independent physics site that backs up this formula from quattrostyle - I rather like it - couldn't see how 'rho' came into it - rho being density of air in kg per cubic meter (at sea level).
Its nice to have a metric formula.

I use same Cd = 0.32 but for frontal area I have used 19.2sqft (somewhat measured) which is 1.78sqm - slightly different.

Don't forget that the ~215bhp resulting from the quattrostyle calcs is power at the wheels required to overcome aero losses at 265kph... Using ~25% quattro drivetrain losses gets us into 280bhp territory at the flywheel. And also don't forget we have not accounted for rolling resistance (which is maybe a tenth of aero losses at this speed so its not that big a deal).

I still say ~265kph for a chipped S2 is on the money.

[quattrostyle]

the calcs were from quattro84 mate will have another run with GPS in the car then, hopefully the speedo won't deviate 10% cause then it would still be a silly top speed.

[Rusty]

Take teh Dumbo wing mirrors off, gotta be work 1 km/h

[S2central.net]

LOL - I like this 'new' formula... Resolving it the other way to say flywheel power of X bhp to estimate Vmax is quite fun...

Using total drivetrain loss of 25% (includes rolling resistance) and Cd=0.32 and Area of 1.85sqm we get the following data

169kW (~230bhp) yields 155mph - claimed / measured / official Vmax is 154mph so a pretty good baseline

250bhp yields 160mph
280 --> 166
300 --> 171
400 --> 188
500bhp --> 202mph
1000 -> 256

See how need another 500bhp to go another 50mph faster than 200 !!!!!!!!!!! Bonkers...

[quattrostyle]

okay okay, I'll take the elephants ears off and cut 10 cm. of the springs on all corners

My car has 298 hp so according to your calcs it should do 170 mph, right?

[S2central.net]

This stuff is no exact science - it is called estimation my good man... Plus don't forget there is mixture of measurements and estimates to get your claimed flywheel power of 298bhp. Even it that is 5% high you are actually on 283bhp - if you see where I am going here...

Surely you aren't upset if you only reach 165mph ?
Thats bonkers fast enough for anyone IMO...

[Sonic]

I dont know how you take your eyes off the road to look at the speedo when your doing 165mph

There are loads of things that can account for the "lost power" - a head wind, fuel mixture, uphill gradient..

[quattrostyle]

ow well I may be a little upset in this

I have a couple of friends with some fast cars that reach 260+ quite easy with less hp. There is one with 80 Avant 2.8 30V with about 200 hp, another with a 325 E36 coupe they both do 260 km/h and there is one with a E36 M3 286 hp. that does 280+

It's not that hard to see how fast your going at that speed but in this case I had a camera attached to my steering wheel.