Actually you can work out the top speed quite accurately, given the power curve and gearing (or just the BHP, if you assume "perfect" gearing), for a given car in still air. It's simple physics - the engine can stick out a certain amount of power .. or torque .. or, to be simple, force .. to move the car along, and the wind resistance creates a drag force in the opposite direction to that movement, which is a function of (air)speed and the drag coefficient (based on the shape and cross-sectional area) - which for a given, unmodded car, should be fairly constant.
You can do the maths on it with a range of cars knowing these numbers and the results are fairly accurate. In fact for low powers, it holds fairly true even just taking as a given that most modern cars are roughly as aerodynamic as each other, and have near-optimal gearing; 20hp is all you need to "cruise" with the trucks; 35hp will see you troubling but not breaking the continental speed limits. 45hp is kissing 90mph; 55 high 90s; you have to have just over that to break the ton on the flat in still air. 70 is about 110 constant, 75 is about 115 (seen it in a punto). (The magic number, i found, from about 7.5 to 75hp, is the square root of (180 x power)). ... Differences from this can usually be explained by crazy gearing (hard to define without driving it) or aerodynamic benefits / penalties (quite obvious by looking, a lot of the time - e.g. Lotus Elan vs a Grand Move)
Beyond that fluid dynamics of air starts to get a bit more complex and shifts from a square-rule law to a cube one, and then higher powers... In fact beyond 100mph it's a little tricky, but you can bend the facts a little to suit yourself (that's around where it starts changing noticably - 70 is more like 108, 75 more like 112)
BUT .... You're on the right lines just the wrong side of the track. What you CAN'T reliably do is work out the power output simply by the engine size, or even rely on it to be the same from one engine of the same type off the same production line on the same day to the next. You get good ones and you get bad ones. Even just the difference from CL to GT to G40 should show that. Same block. But quite a range of power.
You get 1100cc class motors (for arguments sake lets put the 1043 there) with about 30hp, like some Morris Minors were; some with mid 40s, like the polo; some with 55 or 60, like on Puntos. Or even reasonably recent 1200cc's with a poor low 40s hp (nova merits)... put the variability onto this wide range of bhp-per-litre and you see the typical differences that are spread amongst owners on this board. Could be that mk3dave's engine is simply an underperformer, the way the block, pistons, head, valve, inlet & exhaust piping, basic distributor timing etc came off the line has combined to give him only about 41hp instead of 45...... and yours are overacheivers, giving quite a spunky and high level of horsepower.
(personally i think mine was nearer 50 when i got it and has slowly worn down during it's hard-thrashed tenure.. i can only guess why
)
Which is why I think you should take it (and the 1272 if it's around) on a rolling road day. See if it's trousers match your mouth, so to speak. It'd be cool to see a 55hp 1043 after all (not sure if it could be more than that unmodified - you sure it wasn't a following wind?), just as it's neat to see Karl's 1.3 SPi putting down 62 horses and two welly boots full of torque.
Of
course it
IS all to do with how well the engine's been looked after and how well it's working - because those things will influence the power output! A knackered engine will put out far less of it's potential than one that's been mollycoddled and pampered all it's life.
120mph requires far more power than you think. Hell, 108 does. Those are some damn fine working engines you have there.
I've driven a 1043 myself, very, very f***ing hard most of the time, for the past 2 and a half years. I've done 150 mile motorway jaunts on mixed gradients without lifting my foot from W.O.T. for more than a culmulative minute. Kept the oil (fairly) fresh and always topped up, the air filter clean, airways unobstructed, exhaust ok, tyres pumped, leads, plugs and contacts all clean and in good condition.. even chipped it. The most i've seen out of it, downhill, on an over-reading speedo, giving it
absolute death, is 106mph. I thought the engine was going to blow. The revcounter needle was just into the red and I was glad when the road levelled out and that speed ebbed away again. Might have gone quicker with a 5-speed, but only 1 or 2mph more... there's no way in this world it would have done that on the flat in any gear, or sustained it in 4th without blowing up. Plus the real speed was probably not significantly over the ton.
Best 0-60 in it ever was about 16.5 seconds, and i dont think that was particularly accurate, though consistently it would be about 19 rather than the 20 in the book (i got the off-the-line starts and 1-2, 2-3 gearchanges down to a science).
Which again is why I'd be eager to see the test results...
