Wouldn't mind knocking up a simulation of my Rotax V-twin, just to give me some rough idea of bhp v throttle opening, if thats at all possible?

Ricardo's WAVE software is good, though certainly not free, and certainly not quick. How accurate do you want it to be? How much information do you know about the engine, like cam profiles, intake and exhaust tracts, cylinder and head volumes etc?

Not that accurate really, just some idea of how the throttle openings change the bhp/torque, as for info, I am sure I could find a fair bit of info out about it, there is a heck of a lot of info pertaining to the Rotax V60 on the net.

BTW, way, way off topic, I was sitting in the doctors waiting room this morning, thumbing through a copy of Autosport, and low and behold, I stumbled upon a letter regarding CO2 in tyres by none other than our very own T.Cliffe, what are the chances!!!!

If you know the wide open throttle torque/power curve then you could almost say that throttle is a linear metering device between zero and whatever for a given RPM. So 50% throttle is close enough 50% power for any given rpm. Of course, it isn't really as efficiencies and blockages aren't totally linear. Why do you want to know? Just curiosity or a way of improving the bike?

It was rather heavily edited. I think I ended up with every sentence starting with And, which wasn't quite how I sent it. But how else am I going to get in Autosport - they don't really bother with sub-par club racing reports

Might be easier to shove it on a dyno for 30 mins really then?.

Just want to get some idea how much hp it takes to break rear traction.

Yeah, it would be a lot easier. It's not just about power/torque either, but about tyre traction, and you of all people will be aware how complex even simple tyre modelling is!!!!!

Last trackday, big high-side, only just managed to save it, I remember the rough amount of lean, and the rough throttle position, so I just wondered how much bhp it took to cause a high side

Isn't a highside not caused by excess throttle (that starts a slide), but how the throttle is closed, or the bike brought upright? In other words this analysis won't help much, and you'd be much better off getting a bit smoother with the throttle in scary situations. Which I know is a lot easier written than done!

I was just curious how much power it takes to initiate the intial slide.

Of course, the high side is cause by the brain's saftey reaction of coming off the throttle when the rear starts to slide, and causing it to flip back into line, cue arse 3ft in the air!!!!, would be better off, like you say, coming off the throttle smoother, or maybe not at all, but it's one of those immediate fight or flight reactions that are hard to "train" your brain out of, heck even the pros can't stop it happening!!

The trouble is that the power required to initiate the slide depends on lean angle, speed, camber, throttle, load transfer... Applying more power to get more rearward weight transfer means that tyre can make more power than it did on neutral throttle etc etc.

I think even on a dyno you'll be no better off, because you can't lean over and experiement. If you wanted to learn from highsiding, I'd suggest fitting a datalogger with lean angle, throttle, GPS speed and wheel speeds (and a clever equation to take wheel speed variations with lean angle into account) Then you can see how much throttle causes wheelspin at various lean angles.

Quote from tristancliffe :

If you know the wide open throttle torque/power curve then you could almost say that throttle is a linear metering device between zero and whatever for a given RPM. So 50% throttle is close enough 50% power for any given rpm.

That's not taking engine braking into account. The way I do it in VHPA is to model a curve for 100% throttle and another (or rather a straight line) for 0% throttle, then linearly scale between those two extremes. This also nicely causes the peak power to drop in rpm with reducing throttle, which doesn't happen if you scale to zero.

Good point, well made.

Quote from tristancliffe :

It was rather heavily edited. I think I ended up with every sentence starting with And, which wasn't quite how I sent it. But how else am I going to get in Autosport - they don't really bother with sub-par club racing reports

It's perfectly possible to get a nice picture of yourself in the front of the national section, especially if there's another car flying over you at the time.

Have you got a copy of your letter or are we going to have to go and buy Autosport this week

I still have the copy of Autosport that I made it into (only the letters section, don't get excited)... good fun.

It was two or three weeks ago actually, and it turns out I wasn't that correct anyway (although closer than the letter I was writing in response to).