160+ mph S2 Avant

[Bibby]

Not bad for a 1.6....

[T2Andy]

Some young lads at work were bragging the other day about a mates CALIBRA doing 167 mph wot aload of ********!!!!!!!!!!!!!!!

[Martynf]

it is a 20 valve 1.6!

Not bad for a 1.6....

[T2Andy]

Its a valver with a power band and neons

[philS2]

Si,

I think the point I was trying to make is that indicated speed doesn't mean anything.

Neither does a one way run.

I've seen 160mph on my speedo too but it was downhill. I doubt the car would have managed much more than 130mph the other way up the strip.

My bike speedo error is ~8%. At 100mph, in absolute terms the error is therefore...errr 8mph. But at 200mph, the error is ....errr 16mph.

Its pretty consistent against the GPS.

At the end of the day, knowing the C_d of the car and its frontal area, with a RR plot of max power, one can easily calculate the theoretical top speed of the vehicle.

My contention is that it is not possible for a 230hp S2 to hit 160mph.

If you happen to blast down your local drag strip and see your speedo indicating 160, there are two explanations:

1) Whatever your speedo is reading its wrong because your tyres are bald, the speedo is shagged, you're going downhill, there is a 20mph wind behind you and you're being generous with the parallax error...

2) Your car is making more than 230hp!

If, however, someone comes along and shows me a GPS read-out from a stock S2 reading 160mph, I'll eat my hat. Get that Etrex out!

I know they're pretty accurate as I've used them to back up the readings at the strip myself when on my 12R.

The notion that a 2.8 Coupe can also do 160mph is also beyond me. Sure there wasn't a bottle of NOS in the back? Or it wasn't a 3.8?

i've seen 160 on the speedo.with standard boost,a blowing exhaust,three boost leaks and going up a slight incline.i only backed off because the boot sounded like it was going to fly open and i hate having a car full throttle in fifth for ages.i don't think it had too much left though.

[charlie]

Si,

I think the point I was trying to make is that indicated speed doesn't mean anything.

Neither does a one way run.

I've seen 160mph on my speedo too but it was downhill. I doubt the car would have managed much more than 130mph the other way up the strip.

My bike speedo error is ~8%. At 100mph, in absolute terms the error is therefore...errr 8mph. But at 200mph, the error is ....errr 16mph.

Its pretty consistent against the GPS.

At the end of the day, knowing the C_d of the car and its frontal area, with a RR plot of max power, one can easily calculate the theoretical top speed of the vehicle.

My contention is that it is not possible for a 230hp S2 to hit 160mph.

If you happen to blast down your local drag strip and see your speedo indicating 160, there are two explanations:

1) Whatever your speedo is reading its wrong because your tyres are bald, the speedo is shagged, you're going downhill, there is a 20mph wind behind you and you're being generous with the parallax error...

2) Your car is making more than 230hp!

If, however, someone comes along and shows me a GPS read-out from a stock S2 reading 160mph, I'll eat my hat. Get that Etrex out!

I know they're pretty accurate as I've used them to back up the readings at the strip myself when on my 12R.

The notion that a 2.8 Coupe can also do 160mph is also beyond me. Sure there wasn't a bottle of NOS in the back? Or it wasn't a 3.8?

I totally agree with you.

[Fat Audi 80]

I have always calculated my speed off the rev counter to try and elliminate speedo error. I have seen 145mph ish calculated off the rev counter with a little bit left to go.

I suspect my 280 bhp chipped S2 will run out of puff at the 150 -155 mark personally....

[flossymeister]

don't know if this helps or not, but i have tried to apply some maths to this one. I only have some of the data, and its for an RS2 NOT S2....

according to Performance Car October 1994, the following is true:

6th Gear ratio: 0.71:1
Final Drive ratio 4.11:1
Redline is 7100 rpm

Therefore, i calculate that if you were redlining in top gear the wheels revolve:

(7100/0.71)/4.11 = 2433.1 times per minute

Now, I don't have an RS2 (yet), so I don't know the precise wheel circumference. However, my dad's Saab 95 runs 17inch 225/45s - which happen to be the modern-day recommended tyres for an RS2 (used to be 245/40s but Dunlop don't make the right ones etc etc etc). Therefore, I have measured the diameter of my dad's wheels including tyres and they are almost exactly 60 cm.

Therefore, using circumference = Pi (the greek letter) multiplied by diameter

it follows that circumference = 3.142 * 0.6 = 1.885 metres

Therefore, in 1 minute at redline in 6th, the car travels:

2433.1 * 1.885 = 4586.285 metres

So, in 1 hour it travels 4586.285 * 60 = 275177 metres.

Now, there are 1.09 yards in a metre so it does 300937.23 yards per hour

And there are 1760 yards in a mile.

Therefore, theoretical max speed of a delimited RS2 is (300937.23)/1760

= 171 mph

However, as said above, that does assume you hit the redline, on perfectly flat road and that my estimation of wheel circumference is accurate.

[Fat Audi 80]

Only slight floor to that argument is:

Does it have the power at the redline to propel the car though the air at that speed????

Remember the power tails off at 5800 or whatever.

I did some maths at uni that could work out the power required at any given speed dependent on the coefficient of drag of the car and a couple of other small parameters.

I think SR71 was refering to this too....

Cheers,

Steve

[flossymeister]

Only slight floor to that argument is:

Does it have the power at the redline to propel the car though the air at that speed????

Remember the power tails off at 5800 or whatever.

Yeah, exactly - that's the darn problem . As i said in the maths, this assumes it CAN hit the redline . I reckon the RS2 might be able to (though that's up to you and J since fluid mechanics is something i left behind a LONG time ago!), but i don't know about an S2... I reckon J's 3bhp per mph (or whatever it was) could do for an S2 up there....

[Fat Audi 80]

Yeah, exactly - that's the darn problem . As i said in the maths, this assumes it CAN hit the redline . I reckon the RS2 might be able to (though that's up to you and J since fluid mechanics is something i left behind a LONG time ago!), but i don't know about an S2... I reckon J's 3bhp per mph (or whatever it was) could do for an S2 up there....

Oops, read all the mathsy bit and did not read your assumption at the bottom!

Speed reading is fault of mine!

Cheers

Steve.

[Ian Simmonds]

I know this has nothing to do with S2's but my old (modified) GT was timed on Millbrook testing bowl at 146.2mph for a flying lap (almost literally!) but altitude and barometric pressure, together with 'angle of attack' into the banking all had a bearing on this figure.

At sea level and on a flat surface with good air density it could 'theoretically' pull 150...before you ask; the gearbox wasn't standard either....but the 'variable' will be the same for a 'stock' S2 Estate....IMHO At sea level, on a flat road with ideal air density (Misty morning, say air temp of +5 deg) and the gearing provided, the car will be 'within the ballpark' of 150/160mph.

By the way - flossymeister - I love the maths, top man!

[flossymeister]

cheers Ian!

still waiting with my flame suit on for the engineers, though....

Tim

[Baldy]

nice maths

could also work it out a bit further for testing without doing the speed

171/7.1 = 24.1 gives you the speed per 1000rpm

so at 3000rpm you should be doing 72.3mph (almost legal)
how far is is your speedo from this??

[SR71]

The 3hp/mph applies only for my 12R at ~200mph.

We can work out the figure for the S2 if we have a frontal area figure, bearing in mind I believe the C_d=0.31?

Whilst I concur with your calcs Flossymeister, the major problem will be losses through the clutch which reduce the theoretical max.

When racing my bike, as some posters have suggested, the rpm counter is a better device.

I know that max power on my 12R is 10500rpm so I need to cross the line with a gearing that means I hit 10500rpm as I cross the line. If I'm low on the rpm I'm not using all the bikes power. Reasons: 1) Being a pussy. 2) Gearing too high and bike can't pull it. If I'm high on the rpm, I'm on the back side of the power curve and I can probably afford to change the gearing up again to extract a few more mph.

Of course the next problem is how accurate is your rpm counter and is your clutch fubar?

The geeks amongst you might like the following bit of software that calculates the performance of your vehicle:

Car Test Software

That would settle it if backed up with a GPS run.



Personally, my vehicle does not like going above 5900rpm in top (silly bitch). Funnily enough thats what I'd expect, because like Steve says, thats where max power is.