Big Bang Bumkum?

[Berlin]

From the moment we get on a bike we are told that being smooth is good. Smooth breaking, smooth lines, smooth braking, smooth throttle action, smooth body movement.

Smooth is good.

... Until, that is, it comes to power delivery, it seems.

I keep reading more and more about " ... a tyre having a chance to regain grip between power pulses" with V twin and big bang engines.

So it seems that smooth is not a good thing at all in this case.

Now, if the power keeps coming in pulses this should technically put more stress on the tyre and the smoother the application of power of a straight four *should* be better (becasue it's smoother)?

Surely, for every "pause, allowing the tyre to regain grip" there is a following surge at half the frequency of a straigth four that's trying to break that grip that's just been regained?

Surely the difference is that the twin has (relatively) more torque at the point of peak power than the same size straight four and it is this that allows for more grip.

Torque equals drive and so you get more drive at a lower level of revs with a big bang or V twin and so if things do start to go wrong it's easier to back off to regain grip. This is even more applicable for a single.

Or have I got it all wrong? :confused:

Carl

[Tim in Belgium]

Well PB have done a scientific test:

1. Test a standard GSXR.... in January on a cold track.

2. Do a BB conversion & BORE IT OUT at the same time.

3. Test the bike produced in step 2 in summer, and if it blows up test again in later summer.

4. Surprise surprise the bigger displacement bike in warmer conditions laps quicker, which proves naff all. It might sound good, it may have extra traction but they proved naff all. Where is the control? Bike journalists doing science? No, never, luckily my bag of salt split all over the magazine on the way home from the supermarket (getting extra traction from my 4wd system which being a boxer is semi big bang) before I could shower it with a pinch...

5. I quite like PB normally until they spout sh1te! Just read 80% of the mag.

[Berlin]

Hi Tim,

Granted with PB, but this is now starting to spread to other mags such as Fast Bikes and even Bike magazine.

And I endorse your point about a control. If we were to use a control we'd actually need to produce two different engines as well as a different bike.

In producing a big bang/V twin engine that allows for the tyre to regain grip we would also need a second Big Bang/V twin engine tuned to give the same torque and power graph as the original engine (i.e. high power, low torque).

We'd then need to test all three engines in the same frame on the same day. This is the only way we can test one change at a time.

My money would be on the big bang engine that hadn't been remapped to reduce torque and increase power.

My money would be on the increased torque for the corresponding power that was allowing for more traction.

I see this as a new urban Myth taking form. Its a big bang engine/V twin therefore, ergo, QED it must be the pause between power pulses increasing traction. When in fact, there's a far greater probability of it being the higher torque to power ratio.

If we look at the Dyno graphs of a Curvy 650 versus a K1 GSXR 600 K1 (helpfully overlayed on page 148 of May's Bike mag) we see that they have a fairly similar curves until the SV runs out of puff. The Gixer then goes on to rev through to 107 bhp maintaining the same torque as the SV has. The SV runs out at 68 bhp. So the Gixer is producing about 40% more power for the same torque. I belive it is this that is causing the difference and not a relaxation of power between pulses allowing for grip.

If you rode the Gixer round at no more than 8000 RPM (where the power graphs diverge) what do you think would be the chances of spinning out the rear?The SV and Gixer are developing similar torque and power at 8000 rpm (surprisingly)(~70bhp and ~40 lb.ft. torque. Also surprising is that from 5,500 they are producing about the same. It's only below 4000 where there's a significant advantage to the SV.)

So there is the control. Electronically limit a GSXR 600 K1 to 8000 RPM, fit a 160 profile rear tyre and see which is easier to lose the rear end on. My bet would be the gixer would be better than the SV.(as a straight four)

If we increase the torque for the Gixer by making it a big bang engine (so it produces the same power and torque graph as that of a 1000 V twin, We'd have a higher ratio or torque to power and most probably better traction. Or the same traction as a 1000 V twin.

Attributing this to "... allowing the tyre to regain grip in between pulses" seems to me to be smoke and mirrors.

I'd be happy to be proved wrong though.


Cheers,
Carl

[Pedrosa]

Big Bang is a way of extracting more useable power from an IL4 donk. The real alternative to what is sought is the V4.

Rumour has it that the 2008 Fireblade will be the last of the iconic machine, it will be replaced in 2009 by a V4....bring it on!:cool:

[RhythmJunkie]

Hi Carl.
I have thought about this weird problem for ages too. Power pulses causing more grip? Uh? Doesn't make logical human type sense until you think ABS, which I suppose is the exact opposite of not losing friction through forward traction!? It all happens too fast for the human mind to comprehend. :)
Slipper clutch anyone? ;)
If a slipper clutch can't fully control it then I guess it must be down to power pulses.

[yorkie_chris]

I wouldn't say its got much to do with ABS, all that does is find out how much grip there is by locking the wheel.
Instictively I'd say that the smoother engine would be able to use more traction, as dynamic friction is usually less than static.

I'd say they're talking nonsense and its simply a matter of having more useable low down power.

All IMO and I know nothing about racing...

[northwind]

I can see how it could make sense... If you think about pushing a heavy box, what makes it slide better- not the occasional big push, but getting it going and keeping it going through constant gentler pushing. So I suppose an occasional large pulse could be better than frequent small pulses, since the tyre has more recovery time. But what do I know? :)

[chakraist]

In superbike magazine this month, there's an article about the end of racing twins, about how boring out a 1098 to 1200 for the 1000 series is ridiculously hard. Anyone else read this?

[johnnyrod]

My ass tells me it works...

Do you think the GP teams with pots of money and only one thing on their mind (winning) are going to chase an urban myth?

[RhythmJunkie]

I wouldn't say its got much to do with ABS

Hmmmmm.... I should have known this would happen!

ABS = lots of little blobs of high friction interspersed with little spaces/rests/cooling periods with less friction! "(to slow you down)"

>It prevents the tyres losing grip and breaking away< (sliding)

V-twin pulses = lots of little blobs of high friction interspersed with little spaces/rets/cooling periods with less friction! "(to speed you up)"

>It prevents the tyres losing grip and breaking away< (sliding)

Geddit?? :smt039

The rear ends of Ducati's on track certainly seem more planted (in general) than their 4 pot counterparts! I'm not saying it's all down to this single reason but its one of the only "big" differences there are! Weight can't be a factor as less weight means less grip!

Is that why lots of race car drivers say that the V8 cars are easier to drive out of corners than the V10's and V12's??

Is this the reason dirt bikes are invariably single cylinder?? Power pulses?? There's lots of dirt biking where the extra weight and width of a 4 pot engine is of no consequence and more power would be welcomed but.....

.......anyone know if V-twins and singles are better for hill-climbing?? The lighter weight here would be very negative as high grip is paramount but hard acceleration out of greasy, muddy hairpins is a damned good test for power pulse theory!!!!

[yorkie_chris]

I get what you're saying, however ABS isn't meant to slide, its just an iterative way to keep the tyre close to its maximum amount of grip int he conditions.

And just to be pedantic, the weight arguement doesn't stand as with less weight you also need less force to accelerate at a given rate, its all down to the friction given by the tyres.

I reckon its all down to the BB engines giving more torque lower down and getting better drive out of corners.

[RhythmJunkie]

I know ABS isn't meant to make the tyres slide Chris 'cor blimey guvnor'! ;)

....but..but..but... if you accelerate with a pillion squashing your rear into the tarmac you will get better tyre wear due to less slippage innit? You would require more power to overcome the extra weight yes but the extra grip/friction would still be a factor. Whats known as the coeficient of friction, all to do with forces keeping surfaces in contact with each other....hey...my brain is working today....I think....or was that yesterday....hello?

I reckon its all down to the BB engines giving more torque lower down and getting better drive out of corners

...but what if you lower the gearing for the corner Chris? You would get the same net effect surely? Better torque out of a given corner.....but.....the tyre breaking away is a factor of too much torque isn't it? How that torque is applied is what the V-twin argument is about...?

[yorkie_chris]

Lowering the gearing would, for an instantaneos part of it, increase torque, but you still have a narrower powerband which is going to be harder to use well.
And just to throw another factor in, using one gear and getting drive all the way through is going to get more power down than having 'breaks' in the power delivery to shift gears.

And as soon as you add more mass, then there is more grip, but you need to apply more force, the mass basically cancels from both sides of the equation, you end up with acceleration (max possible) being proportional to the coeffiecient of friction. Mass isn't a factor.

[northwind]

Personally I think they're all hanging about WSB.org, chatting about the weather and the Red Arrows and whatnot, then a new guy turns up and says "LOL my kwaks got big bang and its got loads more grip why u noobs still got standard cranks1!!1!. LOLFLROPROPFC" And stung by the new guy, everyone else runs out and gets big bang engines and custom management systems. Eventually, someone will say "Do you have any dynos of the engine" and Mr Kwak will say "No I bot it on ebay but I read on Visordown its the fastest".

But, I could be wrong.

[Berlin]

Some interesting replies above.

I see the analogy between the theory and ABS but the opposite of ABS in this case is traction control. This cuts the power in the same way as ABS cuts the breaking until a sensor tells it it's save to feed it back in again.

But this isn't as I see the Big Bang theory.

Going back to my earlier posts, the higher torque per unit power means that the engine is spinning at a lower RPM for any given torque. It also means that a straight four producing a certain level of torque is a lot more "committed" to producing that torque than the equivalent Big Bang or V twin which is running a lower RPM for the same amount of torque..

If traction does break, because the straight four engine is more committed, it's harder to reign it in in the fraction of a second required before losing it. The Big bang/V twin is producing the same drive at a less committed, lower RPM and hence is easier to reign in should it break traction. It's easier to catch a slide on a Straight four at 8000 rpm than it is at 14,500 rpm due to the lesser commitment of the engine.

Explaining this lesser commitment with Power Pulses might just be looking for the sexier explanation rather than the more obvious one. I deal with this on a daily basis in my trade. It's far easier to use the sexy explanation than the one that actually describes what is going on. Two things are different in a V twin/Big bang engine and until they are tested in isolation, I suppose we will never know which is actually the hero and which is the hanger on.

But in the mean time, I'll go for higher torque per RPM

Carl

[RhythmJunkie]

it's harder to reign it in in the fraction of a second required before losing it

I don't see how the rider can possibly react that quickly Carl...at 8000 rpm the pistons are going up and down 133 times a second so a V-twin will be firing that many times a second also. Those power pulses are very, very close together when you think about it!

So although I can see the mechanical logic at a tyre meets road level, I just don't see a rider being able to take advantage of something which takes only a tiny fraction of a second to occur. For instance, how many times do we see a rider 'react' just before he high-sides into the gravel???

By the time the signal has gotten from the riders buttocks to their brain, taking into account the delay between the tyre starting to break loose and the rider receiving the sensation, the pistons will have gone up and down about 20 times. By the time the riders subconcious auto-pilot sends the signal to panic to the muscles its too late.....and another high-side is born. :)

There are too many unknown variables here. Do the big bang motors use slipper clutches? If they do maybe the combination of clutch and pulses gives them the none-slip ability?

I'm sticking with the Occams principle here before I get a head ache....simplest explanation....it just does it! :)

...alternative... cos that bloke on the telly said so! :)

http://www.youtube.com/watch?v=i6K2CUdqURg&mode=related&search=

[Berlin]

Sooooo! It turns out that Yamaha have different ideas on What the Big bang engine configuration gives in the way of traction.

It turns out that they don't think it's the time that the firing order gives the rear tyre to "regrip" between power pulses.

Its actually due to the mismatch between combustion torque and inertial torque and nothing to do with the tyre regaining grip between pulses!

That (for me) is a lot more believable and based on actual science instead of vague gesswork. After all, they won the world championship using it.

a Big bang engine minimises inertial torque and actually spreads the power *more* smoothly, not less.

Thank you Yamaha. :)

[arenalife]

There's nothing so dangerous as a plausible theory, most people still think that if you drop a cannonball and golf ball at the same time the cannonball will drop faster.

Anyway, isn't the new R1 firing order supposed to improve throttle feel by evening out combustion and inertial crank energy, they're not claiming the higher grip scenario. Sounds plausible :)

[muffles]

And the new R1 isn't technically big bang, is it? Thought it had to fire all cylinders at the same time for that. Mr Greek will be along some time to comment on that :D

[ThEGr33k]

Well PB have done a scientific test:

1. Test a standard GSXR.... in January on a cold track.

2. Do a BB conversion & BORE IT OUT at the same time.

3. Test the bike produced in step 2 in summer, and if it blows up test again in later summer.

4. Surprise surprise the bigger displacement bike in warmer conditions laps quicker, which proves naff all. It might sound good, it may have extra traction but they proved naff all. Where is the control? Bike journalists doing science? No, never, luckily my bag of salt split all over the magazine on the way home from the supermarket (getting extra traction from my 4wd system which being a boxer is semi big bang) before I could shower it with a pinch...

5. I quite like PB normally until they spout sh1te! Just read 80% of the mag.

Aye they do compair the two but they never say look the big bang is more powerful... as you said it should be with the tuning. It was the mad tuning (comp ration of 14:1) and a valve being too slow that caused the blow up.



If we look at the Dyno graphs of a Curvy 650 versus a K1 GSXR 600 K1 (helpfully overlayed on page 148 of May's Bike mag) we see that they have a fairly similar curves until the SV runs out of puff. The Gixer then goes on to rev through to 107 bhp maintaining the same torque as the SV has. The SV runs out at 68 bhp. So the Gixer is producing about 40% more power for the same torque. I belive it is this that is causing the difference and not a relaxation of power between pulses allowing for grip.

If you rode the Gixer round at no more than 8000 RPM (where the power graphs diverge) what do you think would be the chances of spinning out the rear?The SV and Gixer are developing similar torque and power at 8000 rpm (surprisingly)(~70bhp and ~40 lb.ft. torque. Also surprising is that from 5,500 they are producing about the same. It's only below 4000 where there's a significant advantage to the SV.)
Cheers,
Carl

I dont think most people would be able to tell the difference in grip...



If we increase the torque for the Gixer by making it a big bang engine so it produces the same power and torque graph as that of a 1000 V twin, We'd have a higher ratio or torque to power and most probably better traction. Or the same traction as a 1000 V twin.

I'd be happy to be proved wrong though.

Cheers,
Carl

You couldnt make a 600 have the same torque/power characteristics as a 1000cc V-twin. Power = torque x revs /5252... basically its the big torque that is the reason a V2 revs less but produces more power than a 600. A 600 revs more as it needs to chase the revs to get the power (as shown with the sum). If you could (simplistic this is) make the SV650 rev like a IL4 600 you'd have the same/more power with the SV.

*Edit* Forgot to mention that making a big bang engine doesnt increase torque by its self.

Also a gixxer 1000 vs a V2 1000cc is like compairing a Sv650 to a IL4 600. A 1000cc V2 has a little more power u until 8K rpm then the IL4 1000 takes off... this is again because the IL4 can rev more easily and so takes off with the power. V2's have more issues with reving... big pistons = more wight to keep stopping and also valve area vs piston area is worse. Very complicated. But thats going off topic.


Big Bang is a way of extracting more useable power from an IL4 donk. The real alternative to what is sought is the V4.

Rumour has it that the 2008 Fireblade will be the last of the iconic machine, it will be replaced in 2009 by a V4....bring it on!:cool:

I hope so!!! :mrgreen:

Lowering the gearing would, for an instantaneos part of it, increase torque, but you still have a narrower powerband which is going to be harder to use well.
And just to throw another factor in, using one gear and getting drive all the way through is going to get more power down than having 'breaks' in the power delivery to shift gears.


Doesnt increase torque, the engine still produces the same goods, its the drive force that is felt. That is explained well here (http://www.geocities.com/SL_mille/df.html).

Sooooo! It turns out that Yamaha have different ideas on What the Big bang engine configuration gives in the way of traction.

It turns out that they don't think it's the time that the firing order gives the rear tyre to "regrip" between power pulses.

Its actually due to the mismatch between combustion torque and inertial torque and nothing to do with the tyre regaining grip between pulses!

That (for me) is a lot more believable and based on actual science instead of vague gesswork. After all, they won the world championship using it.

a Big bang engine minimises inertial torque and actually spreads the power *more* smoothly, not less.

Thank you Yamaha. :)

Indeed... Basically they made it fire like a VFR 750/800 to get rid of the inertial torque.

And the new R1 isn't technically big bang, is it? Thought it had to fire all cylinders at the same time for that. Mr Greek will be along some time to comment on that :D

Indeed your right. It isnt. A true big bang has TINY times seperating pairs of the firing of the cylinders.

Here is a question for you. Ducati went from a screamer to a big bang V4, why is that? V4's dont suffer from the same problems that a IL4 does with inertial torque, so why change it if it doesnt make a difference?

Ive also noticed that the Yams dont have the best drive out of corners, the Honda and the Ducati have it beat on that. Maybe that is the big bang thing vs the inertial torque theory?

All I know is that a M1 Yamaha sounds Ace so does a VFR 750/800 and so will the new R1. :cool:

[Dangerous Dave]

Rumour has it that the 2008 Fireblade will be the last of the iconic machine, it will be replaced in 2009 by a V4....bring it on!:cool:
Unlikely as the 2008 model is only a year old, plus that rumour has been floating about in our dodgy weekly papaer for the past few years (although the model has changed every year, Blade, Bird, VFR, Bird, Blade, VFR, Bird, Blade....).