Screamer v. Big Bang (Redux?)

<div class='quotetop'>QUOTE (xx CURVE xx @ Feb 13 2008, 08:47 AM) <{POST_SNAPBACK}><div class='quotemain'>and another turd floats to the top..

I was talking about Mekizo, if i wanted .... from you, i'd scape it off my boot...piss off.


way to go ad hominem there. your kung fu is sharp. gimme some time to recover.

<div class='quotetop'>QUOTE (drumfu @ Feb 13 2008, 08:50 AM) <{POST_SNAPBACK}><div class='quotemain'>way to go ad hominem there. your kung fu is sharp. gimme some time to recover.


sorry.

here ya go:

definition

Impressive...you know how to use the world wide web... good for you!


Enough with the handbags at dawn ladies...Back on topic...

Point being they just slammed the door on an option to find more horse power...(that they obviously need) I find that odd...just like when they said they would not build a V-4...

<div class='quotetop'>QUOTE (xx CURVE xx @ Feb 13 2008, 03:57 PM) <{POST_SNAPBACK}><div class='quotemain'>Impressive...you know how to use the world wide web... good for you!


Enough with the handbags at dawn ladies...Back on topic...

Point being they just slammed the door on an option to find more horse power...(that they obviously need) I find that odd...just like when they said they would not build a V-4...
As I said before the handbagging, do you think it would require more electronics/tc etc which rossi might not like?

<div class='quotetop'>QUOTE (michaelm @ Feb 13 2008, 03:48 PM) <{POST_SNAPBACK}><div class='quotemain'>I don't know whether it is an urban myth, but I always liked the story that mick doohan was supposed to have favoured the development of the screamer 500 2-stroke honda engine not so much because it made the bike faster but more because he thought no-one other than him could ride a honda so equipped .it's all true mickeyboy, honda went big bang, everybody followed, doohan went back to screamer, everybody followed but fell off lots. then 500's went unleaded and the screamer lost it's edge, doohan said that robbed him of an advantage. read his biog, the thunder from down under, top stuff.

<div class='quotetop'>QUOTE (michaelm @ Feb 13 2008, 11:04 AM) <{POST_SNAPBACK}><div class='quotemain'>As I said before the handbagging, do you think it would require more electronics/tc etc which rossi might not like?

i don't know, ask drumfu and mekiza, our forum engineers

It's only common sense, I don't need to have engineering degree to know...
"hey we need more HP" that being said as an engineer why would you not leave your options open?
V4, screamer, whatever it takes......you just don't, say NAAA, i don't wanna try that....thats a .... attitude to have i think...

Well Looky here LINKY

Now tell me NOT trying the screamer or a V-4 isn't f'ing stupid......like i said, he might be an engineer, but has no common sense.

<div class='quotetop'>QUOTE (skid @ Feb 13 2008, 03:17 PM) <{POST_SNAPBACK}><div class='quotemain'>put him out of his misery fish, don't bait the guy.

But I'm soooo bored.

I don't think Rossi has much input on the engineering of the bike (may be chasis and suspension feel) For example, he has been asking for a V configuration, and Yamaha has stuck to the inline. The Big Bang firing order also APPEARS to be Yamaha's decision.

I would like to restate my original question, does the screamer configuration work better (from a rider's perspective) on a V configuration (as opposed to an inline)? Ducati and Honda, who have Vs, have switched back to screamer and have moved forward. Yamaha, who have an inline, cannot seem to make the screamer work better than their big bang.

Personally, I don't understand Yamaha's explanation of "noise" related to screamers at high revs. Theortically, it should be smoother than big bang. To me, the Big Bang just seemed to be a way to compensate for lack of sufficient tire grip.

<div class='quotetop'>QUOTE (crvlvr @ Feb 14 2008, 05:41 AM) <{POST_SNAPBACK}><div class='quotemain'>Personally, I don't understand Yamaha's explanation of "noise" related to screamers at high revs. Theortically, it should be smoother than big bang. To me, the Big Bang just seemed to be a way to compensate for lack of sufficient tire grip.

I don't think Furusawa has gone into enough detail as to just what vibration is their main concern, but one inherent vibration with a straight 4 ie. the rocking motion along the shaft has to be cured with balancer shafts, bit of a bummer in modern GP really as the more the vibration the bigger the shafts/drive required hence it take more wasted energy just to get rid of that vibration.

One big bang firing order ... two outside fired then two insides fired gets rid of a lot of that rocking motion.

Inline 4's have long shafts, compared to say a V four which can be made very slim ( short shaft ) by placing two nearby conrods on one close bearing surface ( side by side if need be ), You can still play with firing order plus you have the benefit of palying with the cylinder angles. So in thinking that all engines can play with firing orders and the only diference is the crankshaft length ( and Yamaha don't have the cylinder angle option ), perhaps it indicates that that rocking motion is the one that worries them the most. V4's would stil have it but depending on how close to the centre they place the conrod bearing points it must be greatly reduced in a V4.

It seems the cure is to go V4, but I think Yam,s production favourite is the inline 4 so I guess they are at least doing the honourable thing in terms of developing there bikes via GP. It would seem "odd" to produce V4 gp bikes but then not produce production bikes in that configuration. Perhaps the equivalent of marketting "Seppuku". Same applies to Kawasaki really.




Edit: Add.

On whether Valentino is better suited to the Yam's inline straight 4 or a V configuration ..... perhaps all the Rossi fans who blame the Yamaha are colloquially onto something here!!??:

"Valentino" .... starts with a "V"

What with Uccio allways hanging around perhaps folk wonder if he is a "straight kinda guy"

The fans allways say he has "big balls" ..... but what about the shaft!!? is he a short shaft or long shaft kinda guy?

Cue the "twilight zone" music here

Thanks for the explanation Barry. It makes a lot more sense now.

That's probably why Rossi wants a V engine.. must be hard trying to catch Stoner while he is vibrating his b@lls off..

<div class='quotetop'>QUOTE (BarryMachine @ Feb 13 2008, 10:46 PM) <{POST_SNAPBACK}><div class='quotemain'>It seems the cure is to go V4, but I think Yam,s production favourite is the inline 4 so I guess they are at least doing the honourable thing in terms of developing there bikes via GP. It would seem "odd" to produce V4 gp bikes but then not produce production bikes in that configuration. Perhaps the equivalent of marketting "Seppuku". Same applies to Kawasaki really.
This is also my view on why they are sticking with the in-line 4, and I guess it is in some ways admirable, although it doesn't help rossi much as curve implies. Who knows, maybe with bridgestone tyres that will go the distance the great handling of the yamaha which some have theorized is helped by the in-line 4 may be enough for rossi.

<div class='quotetop'>QUOTE (crvlvr @ Feb 13 2008, 07:41 PM) <{POST_SNAPBACK}><div class='quotemain'>I don't think Rossi has much input on the engineering of the bike (may be chasis and suspension feel) For example, he has been asking for a V configuration, and Yamaha has stuck to the inline. The Big Bang firing order also APPEARS to be Yamaha's decision.

I would like to restate my original question, does the screamer configuration work better (from a rider's perspective) on a V configuration (as opposed to an inline)? Ducati and Honda, who have Vs, have switched back to screamer and have moved forward. Yamaha, who have an inline, cannot seem to make the screamer work better than their big bang.

Personally, I don't understand Yamaha's explanation of "noise" related to screamers at high revs. Theortically, it should be smoother than big bang. To me, the Big Bang just seemed to be a way to compensate for lack of sufficient tire grip.

I had problems fully understaning the explanation too. First of all I would need a technical dictionary, but I think I got the idea that many small pulses with a high background noise are harder to "see" compared to fewer much higher pulses, as they more clearly rising high above the noise. Don't know if that made any sense but that's about as much I got out of it.

<div class='quotetop'>QUOTE (crvlvr @ Feb 13 2008, 07:41 PM) <{POST_SNAPBACK}><div class='quotemain'>I would like to restate my original question, does the screamer configuration work better (from a rider's perspective) on a V configuration (as opposed to an inline)? Ducati and Honda, who have Vs, have switched back to screamer and have moved forward. Yamaha, who have an inline, cannot seem to make the screamer work better than their big bang.
The 990 Ducati tried both twin pulse (cylinders firing in pairs) and screamer configurations. The screamer made more power but was a ..... to ride so they used the twin pulse. With the arrival of the 800s and more complex electronics they can access this power and still have rideability. For pure rideability therefore the twin pulse is softer and hence more rideable.

<div class='quotetop'>QUOTE (crvlvr @ Feb 13 2008, 07:41 PM) <{POST_SNAPBACK}><div class='quotemain'>Personally, I don't understand Yamaha's explanation of "noise" related to screamers at high revs. Theortically, it should be smoother than big bang. To me, the Big Bang just seemed to be a way to compensate for lack of sufficient tire grip.
As far as Furusawa's explanation of noise, this article on how he believes the big bang engine operates is interesting. His basic premise is that at high revs the signal (the rider's feeling of connection between the throttle and the rear tyre) is distorted by the noise (stuff reducing the rider's ability to feel the connection). He reckons that the noise is caused by 'inertia torque', (torque due to the motion of the crankshaft, con rods and pistons). At high revs the torque produced by the combustion process drops off, but the inertial torque keeps on increasing as rpm squared, so at about 16,000 revs inertial torque is (according to Furusawa) about double the combustion torque. The article goes on to explain why an I4 screamer makes significantly more inertial torque than a big bang I4 engine. This theory of Furusawa's is why, as Yamaha are sticking with the inline four, he believes that the only way forward is the irregular firing order crank.

Julian Rider explains Big Bang

Another interesting article on why Kawasaki have decided to try the screamer configuration.

Kawa Screamer

I guess time will tell who is correct.

The Kawasaki link makes a lot of sense and I can see the rational that they use -- giving tires time to recover.

But with Yamaha's explanation of noise and feel -- vven of the theory is true (and it probably is) the frequency of these noise (torque pulses, intertia torque, whatever) is so high that it is difficult for me to fathom that rider will be able to tell the difference.

For example, at 16,000 rpm the number of torque pulses for a screamer would be 533/sec and that for twin pulse would be 266/sec. Think about that -- 266 time per SECOND. That's just too fast for regular human to comprehend. That's like trying to catch a slow bullet v. a fast one

Why don't they just use a flywheel to even out this noise?

It looks like Ducati is able to manage their screamer beacuse of their "fly by wire" throttle control. ie. The race course is preprogrammed and their fuel management system knows to adjust the fuel ahead of time. (Apparently the system is reset after each lap). The other bikes use reactive systems which mean then sense that the tire is slipping and then try to adjust the fuel. Apparently, these TC systems are not reacting quicky enough -- my slow v. fast bullet analogy.

Not sure I'd enter too much into the fixing it with electronics idea first ..... they have a mechanical problem to solve and I believe they want to get that sorted first then enhance with whatever they can electronically. Ducati would not have as hard a task mechanically as v's have more scope for balance experimentation. Plus that short shaft really is a benefit.

Adding flywheels ( counterbalance shafts ) costs energy ( power ) therefore not the best fix. A " stopgap" at best.

This may be a dumb question, but here goes...

Why go big bang 4 and not go for twin cylinders instead (i2/v2) ?

is it harder to optimize the 'breathing' of a big bore/short stroke twin, than to compensate for the extra weight (extra conrods, extra valves, longer crank) of a 4 big banger?

how about the extra kgs off the minimum weight of the bikes running twins?

just curious...

<div class='quotetop'>QUOTE (wise_mumu @ Feb 15 2008, 05:07 PM) <{POST_SNAPBACK}><div class='quotemain'>This may be a dumb question, but here goes...

Why go big bang 4 and not go for twin cylinders instead (i2/v2) ?

is it harder to optimize the 'breathing' of a big bore/short stroke twin, than to compensate for the extra weight (extra conrods, extra valves, longer crank) of a 4 big banger?

how about the extra kgs off the minimum weight of the bikes running twins?

just curious...

Great question ..... in the 500cc days Honda ran both a 4 and a twin ..... the twins never really seemed to perform as well as the 4's but they must have felt it was worth looking into, and had some faith in.

Friction? .... not sure as the piston friction would be too dependent on the piston wall surface profile. .... so ?


Also it really only compares to a 180 degree engine.

But .... the firing order is one side then the other alternately ..... again why I wonder if that longitudinal vibration along the shaft is not the worst vibration they encounter. Hence big bang 4's cure this over a twin. A benefit the V twin also had was the very short shaft.

Also, something that is probably pure fancy on my behalf, but .... maybe they like the idea of keeping their options open ... so if they have the the engine infrastructure allready in place for a 4 they can experiment with far more than just a twin eg. if they got "creative" they could use a staggered firing order like 90-180-90 etc. etc. etc.

Also valve trains and shafts would be better for high revs .... and these days revs = HP.

maybe its the revs thing and the rocking shaft vibration thing.?

Not sure what the final outcome was with two strokes it seemed it should work on paper ... but in reality V4's won.

<div class='quotetop'>QUOTE (wise_mumu @ Feb 15 2008, 07:07 AM) <{POST_SNAPBACK}><div class='quotemain'>This may be a dumb question, but here goes...

Why go big bang 4 and not go for twin cylinders instead (i2/v2) ?

is it harder to optimize the 'breathing' of a big bore/short stroke twin, than to compensate for the extra weight (extra conrods, extra valves, longer crank) of a 4 big banger?

how about the extra kgs off the minimum weight of the bikes running twins?

just curious...
You see the issue at play in WSB. There are mainly two issues where the twin loose out: Max RPM due to limited by piston speed/ecceleration and valve area. You loose RPM and you loose valve area when going from 4 to 2 and both are almost proportional to the HP produced. So 10% lost on both give you almost 20% loss in power. They are both really tied to the same main factor of HP produces: How much O2 can you get into the combustion chamber over time. That is the overall deciding factor of power. Then again you gain some torque in the twin so the calc isn't that easy, but for HP only it's really quite easy: O2/min = HP
Besides, the extra conrods, valves, crank legth aren't that much added weight. While it's more in numbers the twin has longer rods, beefier crank heavier pistons, longer and fater valves and springs....
All in all you gain much more than you loose. The original theoretical calculation was a 25% loss on a twin. Hence the old SBK 1000cc twins vs 750cc fours. That didn't take into consideration the extra torque on the twin and Ducatis determination to win. And you got some years with Ducati/Honda domination.

<div class='quotetop'>QUOTE (BarryMachine @ Feb 15 2008, 10:27 AM) <{POST_SNAPBACK}><div class='quotemain'>Great question ..... in the 500cc days Honda ran both a 4 and a twin ..... the twins never really seemed to perform as well as the 4's but they must have felt it was worth looking into, and had some faith in.

Friction? .... not sure as the piston friction would be too dependent on the piston wall surface profile. .... so ?


Also it really only compares to a 180 degree engine.

But .... the firing order is one side then the other alternately ..... again why I wonder if that longitudinal vibration along the shaft is not the worst vibration they encounter. Hence big bang 4's cure this over a twin. A benefit the V twin also had was the very short shaft.

Also, something that is probably pure fancy on my behalf, but .... maybe they like the idea of keeping their options open ... so if they have the the engine infrastructure allready in place for a 4 they can experiment with far more than just a twin eg. if they got "creative" they could use a staggered firing order like 90-180-90 etc. etc. etc.

Also valve trains and shafts would be better for high revs .... and these days revs = HP.

maybe its the revs thing and the rocking shaft vibration thing.?

Not sure what the final outcome was with two strokes it seemed it should work on paper ... but in reality V4's won.

Without having seen any white papers on the 2 stroke I assume the same apply there as on 4-strokes, the rpm and (for the 2 stroke) the channel opening area are both better on fours. On 2-stroke I don't know if rpm is that much of an issue. They have a much lower rev limit due to the nature of 2-stroke, doesn't they? I don't know how that change with regard to the size of the cylinder.