Separate names with a comma.
Interested in talking motorbikes with a terrific community of riders?Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.
Discussion in 'Multimedia' started by zmokin, Jan 31, 2007.
Because ducs being a twin and twins fire at every 720 degrees making the power going through the rear tyre in a power stop power stop fashion and an inline 4 fires every 360 degrees making constant delivery of power through the rear tyre, I wonder what the outcome would have been if say a GSXR 1000 K6 was used?
I suppose in the end its who has the fastest final lap speed.
Take that Mr Lamborghini :grin:
But i'll give credit where credits due as he sure can drive that thang.
wow, my money would have been on Lambo to win
That dude is a pretty awesome rider, coz I KNOW Tiff is a shit-hot driver.
Great vid - I think last one I saw some Porsche beat an R1 :?
Queensland raceway, R1 with slicks Vs a 600hp Gemballa GTR
(built off a porsche 911 turbo)
But the R1 won. close race though.
Yeah... Nurburg Ring wasn't it?
I think on a longer track with more slower corners a supercar will usually outstrip a bike.
zlIz3l6vZTQ[/media]]I think this is the vid?
edit: huh, watching... not the Nurburg
edit2: aha, wD-ySwO-PO0[/media]]here's the Nurburg ring one... I think... it looks familar from Project Gotham2
Thanks - haven't seen the Nurberg one before. Five laps cost about 60euro ($100) for five laps (plus car/bike) - gotta be a once in a lifetime trip
heres a clip of a porshe chasing a bike
^^ Better quality version (sound & video) of vid in OP
the facts you have here are quite wrong. Every individual cylinder has a firing interval of 720 degrees. So a 360 degree parallel twin would have a firing order of half the the individual cylinder firing interval (360 degrees).
A in-line 4 has a firing interval of 180 degrees.
A 90 degree v-twin has an odd firing interval of of 270 and 450 degrees.
Your question, however is an interesting one.
Which is better for better lap times, an even power delivery, or an intermittent one?
There is a theory that the intermittent one makes for better traction. This come about, because of the big bang two-strokes in the latter days of 500cc racing.
It certainly suited Mick Doohan, but whether it had any real merit is debatable.
how do you get a heavy fridge to move? Apply a constant load or give it a shove?
To me it seems logical that the v-twin will have poorer traction characteristics, when compared to an in-line 4. Others will argue otherwise.
The converse is, of course, physical fact that once initial inertia is overcome and an object starts to slide, that the co-efficient of friction drops. i.e. it requires more force to get an object to move/slide, than it does to keep it sliding.
V2's, having a longer stroke and revving lower than I4's, may be delivering close to twice the power per push, but the actual torque during the power stroke is only a little bit higher than the I4, but it lasts for longer.
Rubber, being elastic and all, can deal with amazing temporary loads, such as a power stroke from the engine, before breaking traction.
Now overall, I'd agree with you that given the characteristics above that we'd still expect a V2 to break traction more often than an I4 purely due to what's going on with the power stroke. The thing is though is that there's suspension involved. Bikes are not ridden around on the absolute edge of traction, and in fact given absolutely perfect suspension, could go still quite a deal quicker than they presently do.
So what really happens is that rarely are the twin nor the I4 are actually breaking traction through the power stroke overcoming the friction of the tyre with the road, but rather in conjunction with the suspension having to deal with bumps in the road. This loads and unloads the tyre, and means that the tyre will often slip just a little bit during the power stoke when it's unloaded then regain traction again.
Back to the first point though, if we continue to push and push rapidly, the tyre will have less of a chance to regain traction. We've overcome that initial inertia, and now the torque of the I4's rapid delivery will sustain the slide. Over to the V2, and while the tyre might have broken traction slightly sooner than the I4, the tyre also has 3x the time to recover between the twin pulses, as well as the suspension having more time to recover to get the tyre loaded up again. Once the tyre regrips, chances the circumstances are such that the next power pulse won't unhook the tyre again because we're back to the initial high-friction state. Meanwhile, the I4 keeps feeding pulses to the tyre, never allowing it to regrip properly.
So yes, in a perfect world (perfectly smooth road and/or perfect suspension) I would agree that an I4 would have less of a tendency to break traction than a V2. In an imperfect world however, the characteristics of the V2's power delivery does allow for greater traction during the rapid loading/unloading of the weight on the tyre due to pavement variances.
Actually I think it's all a bit of wankery.
A twin cylinder, revving at 9000rpm is producing 150 power pulses per second.
An equivalent I-4 at say 13000 rpm is producing around 433 power pulse per second.
So how either of those figures could be considered intermittent is beyond me.
Ever watched a super-slo-mo of a dragster accelerating from standstill. The twisting and recovery of the rubber per pulse can be clearly seen.
The valves in an engine are mechanical, and are opening and closing extremely rapidly, and you can bet your bottom dollar that they are doing so in an intermittent fashion.
Just because something happens quickly doesn't mean that it's not feasible.
Still, you say that the V2 is working at 150 power pulses per second, but really it's a pair of pulses 0.0017s apart, followed by nothing for 0.005 secs.
At 100kph, a bike is travelling at 27.8m/s. This means that the tyre will rotate by around 14cm between the twin pulses. This is longer than the span of an entire rear tyre contact patch length. When talking about getting new unloaded & unstretched rubber into full contact with the road, that really is quite significant. You had better believe that the rubber is doing an awful lot of moving over that time/distance.
funny I thought you were wrong, because your time between pulses is incorrect, but your final figure of 140mm is right.
It's then 230mm to the next fire.
I suppose the thing to be remembered is that a cylinder firing is not a one off explosion, but an expansion of gas that lasts for around 2/3rd of one of those figures and around 2/5th of the other and then there's a thing called a flywheel.
Pure fluke. I had forgotten to divide the effective rpm by 2 since it's a 4-stroke engine. The times should be twice what I stated.
Yeah there was a vid up on the forums a little while back of that and it was truely awsome to see the twisting and buckling effect that the tyre under goes.
Top Gear needs to do more bike stuff. They've got 2 presenters who ride already, it's just a pity that JC would be such a pillock about it that it'd be pointless.