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Offline TheBear

Re: MotoGP 2018.
« Reply #1200 on: October 11, 2018, 10:14:41 am »
These engines are updated and modified every year. Pre seaon testing early last year on the 2018 spec engine which Yamaha proudly annouced was on different Tyres Yamaha was the fastest, I believe they were caught out by the tyre change Thailand seemed to prove what a good bike it really is when the tyres grip. The FACT is both Yamaha engineers and Rossi now state it is an engine problem and Yamaha have developed a new motor for next year I am sure it will still be an in line 4 Cylinder..

Just the fact that the 2018 spec engine was the fastest when announced, and now struggle so, seems to prove that it's not the engine. It could do it before, why not again, the very same engine?
I think the problem is the clutch on the Yamaha, it bites more than the other bikes and thus the spin ;) :peepwall: >:D
I wish they would sort it out because I'd like to see Rossi ride like he can for the last bit before he retires. :thumleft:

Matt Birt, who has been with the MGP as a journalist for decades wrote a great story a few weeks ago.  He makes the point that VR46 is the best he has even been this year and we are robbed of seeing that, due to the Yamadog he needs to ride.
.#BRADICAL!
 
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Offline 2StrokeDan

Re: MotoGP 2018.
« Reply #1201 on: October 11, 2018, 01:17:37 pm »
Apart from reading about who has the bigger knob.......lots has been said about horsepower and torque. Very interesting.
In the day when i raced off-road nationals (on 2 strokes) we would add weights to the flywheel (something like 10 ounces) to give the bike more tractable power when negotiating more technical sections and for those perpetual rock sections. Heavier flywheel on a 2 stroke gives it 4 stroke type grunt.

Exactly Converting stored energy to torque. I am over it if Yamaha say it is the engine thats good enough for me.

How did Rossi cope on the NSR500, where all the torque and HP were at the top end of the revs?
 

Offline Sonny

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Re: MotoGP 2018.
« Reply #1202 on: October 11, 2018, 05:59:41 pm »
He won a world championship on the bike in 2001.
 

Offline Sonny

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Re: MotoGP 2018.
« Reply #1203 on: October 11, 2018, 06:00:41 pm »
Guess he coped ok.
 

Offline 2StrokeDan

Re: MotoGP 2018.
« Reply #1204 on: October 11, 2018, 09:36:57 pm »
Guess he coped ok.

But now he can't, for the same reason.....
 

Offline OomD

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Re: MotoGP 2018.
« Reply #1205 on: October 12, 2018, 06:20:55 am »
Guess he coped ok.

But now he can't, for the same reason.....
Don't make it Rossi's fault, Dan, we all know it's the Yamaha...  :pot:
 

Offline OomD

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Re: MotoGP 2018.
« Reply #1206 on: October 12, 2018, 06:23:03 am »
Guess he coped ok.

But now he can't, for the same reason.....
Well, back then, everyone else was also on the 500 2-strokes, and everyone presumably had the same struggles. Now everyone is on the 4-strokes, and Rossi's 4-stroke is at a disadvantage to the others, it seems. In all this he's still 2nd in the championship. I'd hardly call that “not coping”.
 

Offline 2StrokeDan

Re: MotoGP 2018.
« Reply #1207 on: October 12, 2018, 06:28:37 am »
Guess he coped ok.

But now he can't, for the same reason.....
Well, back then, everyone else was also on the 500 2-strokes, and everyone presumably had the same struggles. Now everyone is on the 4-strokes, and Rossi's 4-stroke is at a disadvantage to the others, it seems. In all this he's still 2nd in the championship. I'd hardly call that “not coping”.

Well, much has been made of how MM would not be able to ride a 500 2stroke like Rossi could, and now Rossi is failing to ride a bike with similar power characteristics.

But yes, whether it is the engine, or the electronics, he is at a huge disadvantage, as is Vinhales.
 

Offline Altie7deLaan

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Re: MotoGP 2018.
« Reply #1208 on: October 12, 2018, 07:05:30 am »
Een van die dae gaan Rossi se racing nommer sy ouderdom weerspieel..... ;)
xl185  cb750f  gsx600f  fz750  gsxr750  cbr600f2  cbr900rr cbr929rr  cbr954rr  vtr1000f  fzr1000exup  650dakkie gsxr1000k4  lc4 supermoto  bandit1200s   project fartblood (fireblade streetfighter)  f800gs


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Offline Bwana

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Re: MotoGP 2018.
« Reply #1209 on: October 12, 2018, 09:28:11 am »
Bore size is capped at 81mm and therefore by implication so is stroke
 
This is interesting I was entirely unaware of this. As it turns my argument 1/2 way upside down. However volumetric effeciency of the engine still plays a part. Simply put as I was taught
volumetric effeciency is the amount of air that an engine can draw in and (or burn) on its combustion stroke. In the old days at sea level the maximium was about 50%  hence turbo Charging an engine where it could be increased to 100% had to be half the size. However when advances in Turbo Charging started to over boost or compress air into the cylinder increaseing the Volumetric effeciecy to over 100% the rules changed and also a pop off valve was introduced. There are many other aspects that affect volumetric effeciency ie heat,atmospheric pressure valve timing etc. However Volumetric effeciency is a variable on all naturally aspirated engines and decreases as RPM increases. Simply put the higher the volume of air(Volumetric effeciency) you can burn the bigger the bang( the more powerful your engine)you also need to add a bit of Fuel to the equation. Quote from the internet:The increase of rpm helps in increasing the mass flow rate which is much higher than the drop caused by the decrease in volumetric efficiency. So there is another equation the Engineers have to work out.

Even though now not relevant. Due to the fact that a long stroke engine revs slower and the Valves are open slightly longer and it also generates less heat. The Volumetric effeciency is higher than a short stroke engine. Generating more torque but less HP as the the explanation above explains.The increase of rpm helps in increasing the mass flow rate which is much higher than the drop caused by the decrease in volumetric efficiency
 
« Last Edit: October 12, 2018, 09:38:48 am by Bwana »
 

Offline TheBear

Re: MotoGP 2018.
« Reply #1210 on: October 12, 2018, 11:54:52 am »
Guess he coped ok.

But now he can't, for the same reason.....
Well, back then, everyone else was also on the 500 2-strokes, and everyone presumably had the same struggles. Now everyone is on the 4-strokes, and Rossi's 4-stroke is at a disadvantage to the others, it seems. In all this he's still 2nd in the championship. I'd hardly call that “not coping”.

Well, much has been made of how MM would not be able to ride a 500 2stroke like Rossi could, and now Rossi is failing to ride a bike with similar power characteristics.

But yes, whether it is the engine, or the electronics, he is at a huge disadvantage, as is Vinhales.

I doubt that they Yamaha and Honda have similar power characteristics.  V4 versus Inline 4 cross plane, may be close, though.  Anyway, even if identical, after ECU interference, they are nowhere near similar.  Look at some of the new records set by this particular M1.

-  Longest losing streak by Yamaha ever.
-  First time since new qualifying that all 4 Yamahas have to come through Q1.
-  Worst ever qualification position for Rossi.
-  Worst ever qualification position for a factory Yamaha.

SIES Yamaha!   :biggrin:


Guess he coped ok.

But now he can't, for the same reason.....
Well, back then, everyone else was also on the 500 2-strokes, and everyone presumably had the same struggles. Now everyone is on the 4-strokes, and Rossi's 4-stroke is at a disadvantage to the others, it seems. In all this he's still 2nd in the championship. I'd hardly call that “not coping”.

3rd my Omie!   :lol8:

Anyway, not bad for an old codger on a slow bike.   :ricky:
« Last Edit: October 12, 2018, 11:57:30 am by TheBear »
.#BRADICAL!
 

Offline 2StrokeDan

Re: MotoGP 2018.
« Reply #1211 on: October 12, 2018, 01:32:00 pm »
Ek het niks om voor te lewe nie. :xxbah:
 

Offline TheBear

Re: MotoGP 2018.
« Reply #1212 on: October 12, 2018, 02:26:37 pm »
Ek het niks om voor te lewe nie. :xxbah:

Ek weet hoe jy voel.  Ek wil al my 1976 Yamaha RD50 se fotos opskeur.   :'(
.#BRADICAL!
 

Offline 2StrokeDan

Re: MotoGP 2018.
« Reply #1213 on: October 12, 2018, 03:26:54 pm »
Ek het niks om voor te lewe nie. :xxbah:

Ek weet hoe jy voel.  Ek wil al my 1976 Yamaha RD50 se fotos opskeur.   :'(

Ek steek sommer my DT's aan die brand.....
 

Offline OomD

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Re: MotoGP 2018.
« Reply #1214 on: October 12, 2018, 04:44:14 pm »

3rd my Omie!   :lol8:

Anyway, not bad for an old codger on a slow bike.   :ricky:
Soos my wifey altyd vir my sę, “Aag man, jy weet wat ek bedoel”.  :biggrin:
 

Offline Bensien

Re: MotoGP 2018.
« Reply #1215 on: October 12, 2018, 05:39:24 pm »
Just to clear up a few things. A heavier flywheel does not increase torque. What it does can be expressed in different ways, eg. it stores more rotational energy, increases angular momentum, or increases rotational inertia, which is the measure of the amount of torque needed to accelerate or decelerate a rotating object. That’s why if everything else is equal, the bike with the heavier flywheel will accelerate slower, but is also less likely to stall at low revs, especially with regard to single cylinder bikes.

It hardly bears mentioning that if you increase the bore diameter of the cylinder you have to decrease the stroke length in order to keep the displacement the same. The stroke length is determined by the vertical distance between the centre of the main journal on the crankshaft and the big end. Torque is directly proportional to the product of the downward force created by the combustion process and the length of the stroke. The longer the stroke, the longer the lever that the force acts upon. But because the crankshaft rotates, the lever gets shorter and longer in relation to the direction of piston travel. At 90 degrees (halfway through the stroke) it is at its longest, and at the top and bottom it has zero length. Think of riding a bicycle without cleats on the pedals. It is very much like a two cylinder engine with a 180 degree crank. You generate maximum torque while the pedals are horizontal and nothing while they are vertical.
A long stroke engine produces less downward force, but has a longer lever for the force to work on. The longer lever also has more mass and because the piston travels further, the piston has to accelerate faster, reach higher speeds and decelerate faster that a short stroke engine turning at the same revs, which creates a lot more stress and limits how high it can rev. Power output (KW or hp) is intrinsically linked to torque and revs. An engine producing 100 N.m of torque at 2000 rpm will always produce 21Kw at 2000rpm. And with 100 N.M at 10 000 rpm it will produce 105Kw. If it produces 50 N.m at 10000 rpm it will produce 52Kw. That is why diesel engines produce less maximum Kw than comparable petrol engines even if they produce more maximum torque. The torque is generated at much lower rpm.

As stated,  a piston generates maximum torque halfway through the power stroke and nothing  during the other half cycle in two strokes, or one and a half cycles in four strokes. That is why a single cylinder stalls easier. There are longer intervals between the torque pulses.

 So here is my hypothesis about the Yamaha. With a flat plane crank in a 4 cylinder bike, there is a phase in the cycle where two big ends are at the bottom and two at the top and where the engine produces zero torque. With a cross plane engine the big ends are staggered round the centre line, so there is never a phase where the crank has zero effective length

.Now think of ABS on a car.  It works by pulsing the brakes on and off. A cross plane engine doesn’t pulse the torque but produces a steady flow, so that is maybe while the Yamahas are more prone to spinning their wheels, and why their traction control is less effective.
« Last Edit: October 13, 2018, 03:58:19 pm by Bensien »
Why do things that only happen to stupid people always happen to me?
 
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Offline Az

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Re: MotoGP 2018.
« Reply #1216 on: October 12, 2018, 10:03:30 pm »
[Matt Birt, who has been with the MGP as a journalist for decades wrote a great story a few weeks ago.  He makes the point that VR46 is the best he has even been this year and we are robbed of seeing that, due to the Yamadog he needs to ride.
I read that, it was a good logical article.

I saw today that the WSBK are moving to a 3 race format and it made me grateful for MotoGP, I'd hate to watch Marquez win 3 times a weekend  :lol8:
 

Offline 2StrokeDan

Re: MotoGP 2018.
« Reply #1217 on: October 13, 2018, 08:59:21 am »
Did Matt Birt imply that Rossi was the best he has ever been, over his whole career, or just the best he's been this season?

If the former, Matt must be smoking fried banana peels.

The old Rossi would have won, even on this bike.
 

Offline KiLRoy

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Re: MotoGP 2018.
« Reply #1218 on: October 13, 2018, 12:40:59 pm »
Not even jc can win on this donkey.   Yamaha fucked up good riders careers the past few seasons...

Not a VR46 fan, but credit to him with the points he have managed to steal on this donkey..
 

Offline TheBear

Re: MotoGP 2018.
« Reply #1219 on: October 13, 2018, 01:52:38 pm »
Did Matt Birt imply that Rossi was the best he has ever been, over his whole career, or just the best he's been this season?

If the former, Matt must be smoking fried banana peels.

The old Rossi would have won, even on this bike.

He meant over his whole career and I differ from you.  Not even the old  young Rossi, could have won on a bike that will wheel spin in 6th gear going down the main straight while competing against similarly talented riders without that problem.
.#BRADICAL!