how much power to pull a wheelie? (vid clip)

I assume you mean this one,

Strange looking 'yank tanks'

It's Wheeeeeelie Gweaaaaaaaaat. Anyone else remember Tiswas, and Sally James with leather thigh boots.

Just get the weight near the arse end.

WTF!!!???? confused What has a remote controller got to do with wheelies?

Wheelie off line from rest needs NO power.

Take moments acting around rear wheel for condition where front wheels carry no load.

m x a x h = m x g x lr

m is Mass a is acceleration g is accel due to gravity = 9.81m/s^2 h is height of CofG lr is horizontal distance from rear axle to CofG

Mass cancels out, so limiting acceleration is.

a = g x lr / h - (equation 1)

So if you stick the CofG way back making lx small and/or high up making h big it will wheelie like a 0.5bhp 16 year old on a pedal cycle. Limits and reduces acceleration so wheelies lose races - including drag races.

Once you have enough acceleration to lift the front wheels it's a no return trip. As the front lifts h gets bigger and lr shorter, reducing the limiting acceleration, results in lifting the CofG higher and rotating the car on to it's roof, hence the need for wheelie bars. Can't use body mass to balance a car and the foot throttle has poor control compared to a bike twist grip.

Newtons law Force = Mass x Accel - (equation 2)

x both sides by Velocity gives Force x Velocity = Mass x Accel x Velocity

Now Power = Force x Velocity so Power = Mass x Accel x Velocity

Rearrange Accel = Power / (Mass x Velocity) - (equation 3)

When going slow Velocity is small and 1/Velocity is large so at low speed it needs very little power for high acceleration [1]. You can't apply this at ZERO Velocity as the calc is really Accel = Force x Velocity / (Mass x Velocity) = 0 / 0 And 0/0 is not 0 nor 1 nor infinity but any and every value in the universe all at the same time. It's indeterminate.

From rest the power needed is Zero (again). Power = Torque v angular speed. The back wheels aren't going round at launch so power is Zero as 0 x anything is 0. Once moving equation 3 gives the acceleration, if it's greater than the result of equation 1 then it wheelies after launching.

So at rest it must be torque that make it accelerate and wheelie.

Torque at rear wheels = Force x rolling rad. Equation 2 in this gives Torque = Mass x Accel x rolling rad so Accel = Torque / (Mass x rolling rad).

and rear wheel torque = clutch torque x diff ratio x gear ratio. So using equation 1 with the above you can calculate how much of all that throbbing engine torque to allow though the clutch by slipping it to get enough accel for a wheelie.

slipping clutch torque for wheelie on launch from stationary = Mass x rolling rad x g x lr / (h x diff ratio x gear ratio)

Few feet or hands are clever enough to work this out and get the clutch just right. They need lots of training, which burns up expensive clutch plates, tyres and can wreck gearboxes. So people with brains use a slipper clutch which loads the plate using centrifugal weights, the faster they go, the less it slips and the greater the torque it transmits. If it's wrong on one run it will be wrong on all runs so you change the weights and it loads up differently. There is an art to getting the weights right but it gives nearly consistent results. And just when you have it right the plates burn out.

Usually the limiting factor is wheel spin occurring, preventing enough acceleration for a wheelie. But that's a whole lot more calc's and you didn't ask it.

For a FWD vehicle lr is negative so the calc gives a negative acceleration meaning you have to reverse to exceed the wheelie acceleration or in the forwards direction any acceleration is greater than the wheelie acceleration. So it could be viewed as already in wheelie mode but it has a long, sprung and well damped wheelie bar (the rear suspension) which it's "riding hard". This condition is the bane of drag racers as it results in wheel spin which causes the big expensive tyres to "light up" get hot, make smoke, lose grip and lose the race. Sad. Best thing is to get weight low and forwards to reduce lx. Most ot the better acceleration FWD cars have 75% weight on the front wheels. Logical conclusion for a FWD dragracer is to remove everything from behind the bulkhead and fit a heavy duty wheelie bar. Then put the driver in a cage IN FRONT of the engine. This could get lr down to Zero but then braking will tip the whole lot up on the drivers feet.

That will teach you ask simple questions!

[1] hence the apparent good "low down" power/torque. "I'm going slow so I accelerate better than when I'm going fast".

i still don't get it? wanna recap? :)

Mass = 1350Kg rolling rad = 0.307m g = 9.81 lr = 1.25m h = 0.8m diff ratio = 3.916 gear ratio (1st) = 3.592

torque at clutch for wheelie = 1350 x 0.307 x 9.81 x 1.25 / (0.8 x 3.916 x 3.592) = 58.6 Nm.

Not a lot of engine torque needed.

It's more a case of onset of wheel spin limiting the ability of most RWD cars to do wheelie's.

And POWER required is ZERO until it moves.