Vauxhall SRI V6 did 105 in 3rd gear!!!

dam!! 80 in 2nd i cant even get 60 in second :(

Pretty sure no-one on MIG has ever reached 200mph dude

Theres a big debate on there atm about calibra top speed, it's pretty confuseing now because there are over 250 posts and people keep mentioning other cars and crap, here's the link, pretty interesting reading.

I think that T.F.S dude has done 200 mph+ in a cali (says on first page) along with another guy, but tbh you would have to read it all and I only started reading it once it had gone past the 8th page!

It's trivial to work out.

Grab the formula for BHP:Speed

It's something like the speed increase is equal to the cube of the power increase - but I can't be bothered to remember right now. Take stock Calibra power and top speed, and then do the maths. You can find an exact bhp figure required, to hit 200mph.

Albert might come along and do it for you if you're lucky :)

It's an easy calculation if everything is constant but it's not, one c20let engine of the exact same spec will not make the same power as another one due to its age. Also you can no longer calculate the mechanical drag of these machines because many use aftermarket transmission mods for higher endurance and longer gearing ratios to make 200 mph such as Quafie. Also many of the internal items of the engine are changed for specialist forged items, so Nom you can't work it out except to race+time them.

Trivial.... my ass.

in news: snipped-for-privacy@news2.newsguy.com, "Nom" slurred :

*cough* Yup, power goes as V cubed. IIRC, top speed of 200BHP calibra is 150mph (?), so you need 474BHp (ignoring trans. losses and so on).

Taking tranmission losses into account, you might be looking at more like

470Hp.

That fantasticlly low drag figure seems to be just the early 8V ones. Maybe they don't need a radiator and under bonnet airflow as they don't make any power? Output power = power to make exhaust noise = power to heat rad and engine bay etc. No power = no heat = no need for drag inducing cooling airflow. But almost everybody quotes that figure as gospel for all Calibras.

drag coefficients2.0i 8v : CD 0.26

2.0i 16v/2.0i 16v 4x4/V6/Turbo 4x4 : CD 0.29

How the F did the 8v get down to 0.26 while the rest had 0.29? My 200SX is 0.3 and I can't see much difference in shape. If anything it should be better as 200SX has one piece door glass so there is no drag inducing guide strip up the door window. The pop up headlamps go completely flush easily matches low profile Calibra lights. The Calibra rear quarter glass has a joint line to the C pilliar, yes it's a real nice close fit but it's there. While the 200SX glass wraps smoothly round the C pilliar with no join. Windscreen and tailgate glass don't appear to be any more flush than 200SX. My 200SX is the '91 on model without the fake grill slots in the bumper. Cali is 1" taller and taking 2"rear bumper overhang off the 200SX body is just about the same length. Could it all be down to internal engine bay, smoother underside or smoother disc wheels? Or just a mistake that's been propagated for all time? I have seen one claim to 0.2629 someone could have got it transposed. Or did someone just helpfully tape over all the panel join lines for wind tunnel testing the 8V? Could it have been the smooth clay model with no internal air passages and just shallow scribed grooves for panel joints with no drag causing openning behind them?

very odd how they got it down so low to start with and then theythrew it all away on later ones while the other makers have taken 10years to catch up. I smell something from the farmyard. It's also shows how people take the best claims for one special model and apply to all others in the range. Like all Sierra Cosworths are just as special as the image making BTCC winning RS500. Truth is that it was 3 door and didn't have power sapping 4WD while the road car version most people raved about and bought was the 4x4 saloon version. All Impreza's are chips off the WRC winning and reputation making coupes. While truth is very few road models are coupes and the 4 door WRC has had a fortune spent on it for years and still not had as much success.

See his other post it's an auto.

Fortunately, you don't need to care about that because the speed you can make will depend on the power of the engine. If a given particular car has an engine with less power, it will merely travel more slowly flat out.

The top speed of the standard model will of course be based on the engine when in perfect condition, not when worn out.

Mechanical drag is only really significant at low speeds (many of the internal items of the engine are changed for specialist forged

What is trivial, the shape of the car and the skin friction basically define the aerodynamic drag forces acting on the car for a given speed. This is defined by the air, not by the engine, or by the car, and the air doesn't change greatly with place and time.

The drag force, at top speed, will essentially match the power of the engine at the wheels.

It varies with speed, and follows a cube law, double the speed and you have to multiply the power by a factor of eight.

Actually, if memory serves correctly the relationship is not cubed, it is more like to the power of 2.6 but to the power 3 is good enough for ballpark figures.

Now there is a *tiny* bit of a problem with that simplification in the real world. You can't just bolt eight times the power into the engine bay and get double the speed. First of all, the gearbox will be wrong.

The standard car will deliver peak power at particular RPM. When you know what the drag force at a given speed will be, you can arrange that the car will be traveling at this speed when, in the fastest gear, it reaches the RPM at which the power peaks and balances that drag force. If you arrange the gearing a little higher, the car will never be able to reach peak revs in the fastest gear (which might be fourth if the car is geared to also run overdrive).

Conversely, if you gear it a little lower, the car will reach a lower top speed, but when conditions aren't quite as favourable or the engine is a little tired, the car will still reach the top speed.

Increase the power output, changing the shape of the power curve and the car will peak at the wrong speed.

Ok, so you work out the gearing ratio from the power output and knowing what the drag forces will be at a given speed, and adjust the gearing to suit.

Next problem. The shape of the vehicle does more than merely minimise aerodynamic drag. To travel faster, you can reduce aerodynamic drag factors but as you achieve this, you are necessarily also reducing aerodynamic downforce and this starts to be very much more significant for your purposes.

If you have insufficient downforce at a given speed, the aerodynamic lift will cause the front of the car to lift and attempt to take off, and as the wheels lose touch with the ground, it will topple back and cartwheel off down the road. Slightly more realistically, you will find the steering goes lighter and lighter, and stops working altogether at some speed or other and the whole thing is undrivable, veers off into the central reservation or whatever. You need four wheels on the road to go in a straight line, basically.

It's not going to be too shocking to realise that the shape of a car is a compromise between aerodynamic downforce, and aerodynamic drag, among other things.

So the actual shape of a car is not just a fashion statement, it is a compromise. Put simply, the shape of a car defines what its maximum speed is, and will deliver the least aerodynamic drag consistent with delivering the necessary downforce at that speed.

You can put 5000 BHP into a Model T Ford, and it *will not* reach 200 mph because it will have crashed before it reaches it. Power isn't the problem, shape is.

Modern, highly refined cars, well oddly enough, if you design a car to reach

150 mph, you are not going to sacrifice 2mpg in order that someone else can upgrade it to reach 170 or 175. You are going to give it a safety margin and then minimise drag for maximum mpg.

So you can't go faster than the aerodynamic design permits, however it has been modified under the skin.

Adding spoilers? Well yes, but aerodynamics is a complex subject and it's a poor strategy to just bolt on downforce devices without extensive wind tunnel testing and similar - you can end up needing twice the power to get to a properly designed 200 mph and cars like the F1 and the Bugatti and whatnot are designed from the outset to do this, so you have something gobbling twice the fuel, which won't corner, and which will have some very poor road manners. It'll cost more to build, most likely.

I'm not saying people don't get some very respectable speeds out of all sorts of specials, they do, but it isn't done with trick pistons and most of the people who say they regularly do 200 mph are basing this on nothing more than a really, really badly over-reading speedo or just wishful thinking.

(There are more issues than just these two characteristics.)

Hope this was informative.

in news: snipped-for-privacy@4ax.com, snipped-for-privacy@quickwatchsales.com slurred :

I agree with pretty much everything you said (including all the stuff I snipped :) In actual fact the drag _force_ varies as the square of speed (and it actually is a power of 2, _IF_ you have a turbulent flow - which almost every car ever made has above a speed of a few mph).

Energy=force x dist, so power=force x velocity, and so it's the power required that scales as v^3 (and again, it actually is a power of 3, for turbulent flow).

:)

Er, yes it is.

You need X bhp to reach a speed of Y, in car Z. It's that simple.

Albert has kindly worked it out for you here :

(?), so you need 474BHp (ignoring trans. losses and so on). Taking tranmission losses into account, you might be looking at more like

470Hp.

Basically, you need 470bhp-ish to hit 200mph in a Calibra.

Er, see above. We're trying to work out the power required to hit 200mph. How it's made, isn't really relevent !

It's very trivial - I suggest you go and get some books, and do some learning !

Agreed with all that.

Assuming the gearing is appropriate though, the "power goes as V cubed" thing works fine in "simplified world" :)