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zadok
19th February 2006, 11:55
I just read a short article that says That Yamaha may be fitting VVT to the forthcoming V-Max (more advanced than VTEC apparently).
Excuse my ignorance, but has VVT been around on bikes for a while? I was under the impression that the BMW 'brick' had it. Have there been any others? If not, could this be the next big thing with bikes?
It has been a good system on my car. Good power and economy.

onearmedbandit
19th February 2006, 12:17
Honda pioneered (I think) their vtec system on one of their bikes in the early 80's. Not that I've had any personal experience with their late model bikes with vtec it gives better economy but no more power (bikes already having reasonably aggressive cam profiles so the option to honda was to give a milder cam profile at lower revs for better economy). Now variable inlet tract length is someting worth looking into.

TwoSeven
19th February 2006, 12:52
Why would you want variable inlet tracts on a FI bike ?

onearmedbandit
19th February 2006, 13:21
Um same reason BMW etc put them on their fuel-injected cars. Better response etc.

imdying
19th February 2006, 14:18
Cylinder filling is optimised at different RPMS by different length runners. I guess bikes having such vast rev range means they'd benefit even more than cars do?

onearmedbandit
19th February 2006, 14:23
Stands to reason.

TwoSeven
19th February 2006, 14:58
But FI uses an injector pulse which has a variable length and timing.

I found this (http://world.honda.com/motorcycle-technology/pgm-fi/index.html) as a useful article. Its a few pages long, but gives a good idea how things all hang together these days.

imdying
19th February 2006, 15:31
The cylinder filling is the amount of mixture getting in, not the metering of the fuel. The injector pulse just controls how much fuel is going in, not how much air (mixture) is getting into the cylinder.

Hitcher
19th February 2006, 16:01
But FI uses an injector pulse
FI? F1 surely to goodness?

onearmedbandit
19th February 2006, 16:09
Hitcher, are you taking the piss mate? FI = Fuel Injection.

onearmedbandit
19th February 2006, 16:12
But FI uses an injector pulse which has a variable length and timing.

I found this (http://world.honda.com/motorcycle-technology/pgm-fi/index.html) as a useful article. Its a few pages long, but gives a good idea how things all hang together these days.

So pray tell why major auto companies (BMW, Toyota, etc) are employing this on their newest vehicles. If what you are trying to say is correct then obviously they are wasting millions of dollars developing these 'improvements'. Different length/diameter inlet tracts change the speed that the air fuel mixture travels at etc. Different then fuel metering.

cowpoos
19th February 2006, 16:33
So pray tell why major auto companies (BMW, Toyota, etc) are employing this on their newest vehicles. If what you are trying to say is correct then obviously they are wasting millions of dollars developing these 'improvements'. Different length/diameter inlet tracts change the speed that the air fuel mixture travels at etc. Different then fuel metering.
yes your completely right OAB....I have no idea where twoseven is coming from... differing lenght inlet tracts [and diameter] change the flow of air at different RPM's by manipulating air speed to optimise burn and cyclinder fulling....even to the point that you can develop a supercharging effect at high RPM...

and this was about variable valve timing this thread I think...and honda's system on the vfr800 isn't real vtec...its a 4 valve per cyclinder head that only uses 2 valves up until a certain RPM and then employs the other two for high RPM running... but the varible valve timing yamaha are playing with alters valve lift and duration...so as to alter timing completely...so it can run high performance cam profile at high RPM for increased power over a middle of the road camshaft profile to suit drivability at all rpm like most bikes...while retaining low rpm and medium rpm performance aswell.... Expect one hell of a flat torque curve!!!!! and one very flexable motor....

TwoSeven
19th February 2006, 18:19
I made my original post because to elicit out the reasons behind the original statement. Asking questions to get people to explain themselves when they make generic statements is a good way of finding out what they really mean and I can learn stuff. :)

My original question was why would you want a variable inlet tract on a modern FI bike, when they often have two injectors set at specific heights (to clarify the question a bit more).

I understood the reason why two injectors were used on a motorcycle engine was that the first injector works at low speed rpm being situated close to the engine and the second injector works at high rpm. A butterfly valve is used to vary the air speed is it not - I would have thought this was similar to a variable inlet tract - unless I have it wrong which is highly likely :)

Anyhow, i-vtec I think is what the original question was about. The latest version alters lift,duration and timing so as to get optimum volumetric efficiency at different rpm. It would be sensible to do this I suspect if you have two injectors set at different heights - As I understand how it works

zadok
19th February 2006, 18:46
Getting back to the original question, forgetting about VTEC......do then, any of todays bikes employ VVT and if not why not? Make it in the real world, not motogp etc. Many car manufacturers seem to be employing it.

Ixion
19th February 2006, 18:51
One of the main reasons car manufactures are using such devices is to meet US emission and noise requirements. These are (I believe) not so "tough" for bikes,so bike manufacturers have not yet had to resort to such clever trickery.

Sketchy_Racer
19th February 2006, 18:55
yes Badit 250s have VVT. i believe.

i dont know how their system works

zadok
19th February 2006, 19:01
One of the main reasons car manufactures are using such devices is to meet US emission and noise requirements. These are (I believe) not so "tough" for bikes,so bike manufacturers have not yet had to resort to such clever trickery.
I'm sure you're right, but that asside, I thought that it would make the motor run at it's optimum performance (forgive me if I'm wrong, I don't know about these things).

onearmedbandit
19th February 2006, 19:06
'infinite' variable valve timing would be the go as far as optimum performance, doing away with the camshaft would have to be the first improvement. Pnuematic valvetrain anyone? (Has to have a constant supply of pressuriesd air though!)

Ixion
19th February 2006, 19:13
'infinite' variable valve timing would be the go as far as optimum performance, doing away with the camshaft would have to be the first improvement. Pnuematic valvetrain anyone? (Has to have a constant supply of pressuriesd air though!)

Meh, just do away with the camshaft. Full stop. And the silly valves and all the rest of the silly stuff. Real engines don't need them anywa.y

Ixion
19th February 2006, 19:14
I'm sure you're right, but that asside, I thought that it would make the motor run at it's optimum performance (forgive me if I'm wrong, I don't know about these things).

Probably does, but the cost in dollars, complexity, reliability etc , it's not worth it unless there's something else (like emissions) to sweeten the deal.

Kickaha
19th February 2006, 19:49
Pnuematic valvetrain anyone?

old technology mate :lol: they're trying electromagnetic systems now

SPman
19th February 2006, 20:13
Suzuki and Honda 400's have had VTEC since the early 90's, on some of the CB400's and The Bandit and RF400's -(the ones with the red brake hubs). And ,of course, the VFR800 - and what a retrograde step that was......
I think MV augusta has variable intakes....

Jamezo
19th February 2006, 22:03
Probably does, but the cost in dollars, complexity, reliability etc , it's not worth it unless there's something else (like emissions) to sweeten the deal.

Well, your "real engine" more than makes up in that regard! Emissions for Africa!



mumble mumble blardy power sapping fiddly camshaft thingie wotzits..... who needzem?

Ixion
19th February 2006, 22:12
Yeah, two smokers are anti social, ain't they. Noisy, smokey things - heh heh heh :devil2: :msn-wink: :nya: :violin:

imdying
19th February 2006, 23:00
I understood the reason why two injectors were used on a motorcycle engine was that the first injector works at low speed rpm being situated close to the engine and the second injector works at high rpm. A butterfly valve is used to vary the air speed is it not - I would have thought this was similar to a variable inlet tract - unless I have it wrong which is highly likely :)If you open up a throttle body all the way before it's required to be, you'll slow the airflow down, reducing cylinder filling. Twin butterflys allow the computer to essentially close the butterfly (pretty much overriding the riders right hand), without having to close the butterfly the rider is controlling. Variable length inlet tracts allow the pulses inside the tracts to be harnessed to improve cylinder filling. They're working towards the same end, but they're different in their approach. I'm not sure why you want to know why a bike with two injectors wouldn't want variable length inlet tracts? They're not really related in the way I suspect you're thinking. There are many good books on the subject, I could recommend some on Amazon if it interests you.

Ixion may be fishing to be sure, but the concept of no poppet style valves and cams is quite inviting for manufacturers. Valves are very restrictive, no matter how small the stems are. They're also very heavy when opening and closing (and thus accelerating and deaccelerating) no matter what they're made of. Doing away with poppet valves (pnuematic, electromagnetic or whatever, they're still teh ghey) altogether is seemingly the way forward. There's a motor in this mornings press with some sort of rotary valve, didn't get a chance to more than skim it tonight though.

So anyway, VVT coming to bikes. Cams and valves are very reliable and cheap to manufacture. VVT has proven itself reliable, but it adds components, which increases costs. It also adds valve train weight, which reduces a motors ability to rev. Doesn't matter so much on a relatively low revving car, but that's why it's relegated to either small bike motors (with their lightweight valvetrains), or gutless pieces of crap like the VFR800 that don't require super high revs. Rest assured though, when they can build high revving ones for not too much coin, you'll see em on the R6/R1.

Ixion
19th February 2006, 23:09
..

Ixion may be fishing to be sure, but the concept of no poppet style valves and cams is quite inviting for manufacturers. Valves are very restrictive, no matter how small the stems are. They're also very heavy when opening and closing (and thus accelerating and deaccelerating) no matter what they're made of. Doing away with poppet valves (pnuematic, electromagnetic or whatever, they're still teh ghey) altogether is seemingly the way forward. There's a motor in this mornings press with some sort of rotary valve, didn't get a chance to more than skim it tonight though.

..

Come back Charles Yale Knight - all is forgiven. Even the smoke ! (My two smokers may have competitors ).

Elimination of the poppet valve has been a Holy Grail of 4 stroke engine designers for more than a century. No-one has managed it yet (Though Mr Knight came close at one point)

All valves are the devil's work - abolish 'em altogether !

imdying
19th February 2006, 23:14
2 stroke 4 lyfe, uh huh :) Ringa ding ding, nothing like a bike that sounds flock a swarm of pissed off wasps..

<-- this man misses his race piped rz500 :'(

Motu
19th February 2006, 23:17
Get a hold of the book on Ralph Watson - The Lycoming Special is what he is famous for,but what he did to his BSA Special was more impressive.He worked on it for decades,like Munro,and in it's final form the motor was completely built by Watson - and has rotary valve heads,something often tried,but seldom sucessful.

stanko
20th February 2006, 20:58
All valves are the devil's work - abolish 'em altogether !

Power valves are Gods work on earth !

Pixie
22nd February 2006, 00:12
'infinite' variable valve timing would be the go as far as optimum performance, doing away with the camshaft would have to be the first improvement. Pnuematic valvetrain anyone? (Has to have a constant supply of pressuriesd air though!)
Lotus and Eaton have been working together on a electro-hydraulic valve train for some time.
No camshafts and allows valve timing to follow complex maps as ignitions do already.
When this is possible it will allow the removal of butterfly valves to control airflow,giving an efficiency boost to the engine.
The BMW Valvetronic doesn't have butterfy valves,but still uses cam shafts.

Pixie
22nd February 2006, 00:16
Come back Charles Yale Knight - all is forgiven. Even the smoke ! (My two smokers may have competitors ).

Elimination of the poppet valve has been a Holy Grail of 4 stroke engine designers for more than a century. No-one has managed it yet (Though Mr Knight came close at one point)

All valves are the devil's work - abolish 'em altogether !
Aircraft engines had sleeve valves.The cylinder liners were moved to uncover fixed ports
http://www.classiccarclub.org/knightsleevevalvekb.htm
http://www.enginehistory.org/bristol_aquila.htm

avrflr
22nd February 2006, 11:46
'infinite' variable valve timing would be the go as far as optimum performance, doing away with the camshaft would have to be the first improvement. Pnuematic valvetrain anyone? (Has to have a constant supply of pressuriesd air though!)

Formula one engines still have cams, only the valve spring is replaced by a cylinder filled with compressed nitrogen. (If air was used there is the potential for detonation....)

IMHO VVT isn't in the current crop of sportsbikes because they manage to fairly high specific power and a linear power curve using other, simpler and cheaper technologies. Like carefully designed inlets, airboxes, and a valve in the exhaust to help fill in the mid range flat spot you would otherwise get with a cam that delivers you 170hp/litre.

Of course, as the horsepower wars rage on, no doubt manufacturers will have to resort to more tricks like variable length inlet tracts and VVT to deliver more peak power without compromising civility.

Motu
22nd February 2006, 11:53
As Ixion mentioned at the very begining of this thread - VVT is used to meet emmission standards,they have to meet those,power is just an added bonus.Bikes need to comply with few standards so any systems are basic and just marketing ploys.Electromagnetic valve actuation is not capable of high speed use at this stage,if ever,even a modern diesel revs too high for it.

avrflr
22nd February 2006, 12:00
Motu, you seem so be saying that VVT is just about reducing emissions, which I would disagree with. I would say VVT (in any of it's forms) is simply a way of using a hotter cam and making it driveable. This applies to bikes as much as cars. Manufacturers just like to say that it reduces emissions because we all love the environment, don't we?

Pixie
22nd February 2006, 16:34
As Ixion mentioned at the very begining of this thread - VVT is used to meet emmission standards,they have to meet those,power is just an added bonus.Bikes need to comply with few standards so any systems are basic and just marketing ploys.Electromagnetic valve actuation is not capable of high speed use at this stage,if ever,even a modern diesel revs too high for it.
Never say never.
http://www.grouplotus.com/mediactr/pr_download.php?pid=110

Motu
22nd February 2006, 17:08
But that blurb says exactly nothing...although they do say electro hydraulic,which could be the answer.Solenoids can't opperate the valves fast enough,but if they opperate a hydraulic system that could be a way around it.Like a fuel injector,that's electronic control of a hydraulic system,and it works very well.

And I will defend my position of all engine advances in the last 30 years being driven by California Emmission regulations.The fact that combustion chamber design,camshaft profiles and electronic fuel injection and ign systems have offered a big increase in power is just the iceing on a rather messy cake.

avrflr
22nd February 2006, 18:25
I hear what you're saying Motu, if oil was plentiful and nobody cared about pollution, to get more power manufacturers could just keep making bigger engines. For cars that is. Given that bikes need to be small, light, simple and cheap, a bigger engine might not be a good answer. So I think there are reasons bike manufacturers would look to things like combustion chamber design, cams, EFI, electronic ignition and VVT to pack more power in a small space without considering emissions.

Ixion
22nd February 2006, 18:31
Why? (bike light and cheap I mean) Apart from aberrations like the NZ 250cc thing, it's still easier to just increase the engine size. Nothing beats cubes. Works for Harley. I don't see a massive rush of people buying things like the VTEC Honda fours. It's much cheaper just to have bigger holes than complicated whaddjamoogoos.

SixPackBack
22nd February 2006, 18:45
Why? (bike light and cheap I mean) Apart from aberrations like the NZ 250cc thing, it's still easier to just increase the engine size. Nothing beats cubes. Works for Harley. I don't see a massive rush of people buying things like the VTEC Honda fours. It's much cheaper just to have bigger holes than complicated whaddjamoogoos.

Weight is the last thing you want to increase, reducing engine size whilst increasing performance produces superior motorcycles in every way.
Personally I can see Electronic linear actuators being the ultimate development for valve control...could be a while though.
Contemplate the advantages of controlling valve lift, opening and closing speed with continous adjustment, petrol engines would be so much closer to full torque at zero revs [a la electric mtr].

SPman
22nd February 2006, 19:01
. Given that bikes need to be small, light, simple and cheap, a bigger engine might not be a good answer. .
Seems to have worked over the last 30 yrs..........

avrflr
22nd February 2006, 19:17
OK I admit I am thinking more of the sports bike market (which forum is this again?). I don't really want a 190kg GSX-R2000 and I think the reason is obvious. I don't honestly need more power than I already have, if I used full throttle on the road much I wouldn't last long. A lighter bike on the other hand is always a good thing - better handling, less tyre wear, less fuel consumption, less emissions.

Scouse
22nd February 2006, 19:40
yes your completely right OAB....I have no idea where twoseven is coming from... differing lenght inlet tracts [and diameter] change the flow of air at different RPM's by manipulating air speed to optimise burn and cyclinder fulling....even to the point that you can develop a supercharging effect at high RPM...

and this was about variable valve timing this thread I think...and honda's system on the vfr800 isn't real vtec...its a 4 valve per cyclinder head that only uses 2 valves up until a certain RPM and then employs the other two for high RPM running... but the varible valve timing yamaha are playing with alters valve lift and duration...so as to alter timing completely...so it can run high performance cam profile at high RPM for increased power over a middle of the road camshaft profile to suit drivability at all rpm like most bikes...while retaining low rpm and medium rpm performance aswell.... Expect one hell of a flat torque curve!!!!! and one very flexable motor....
Youv'e just disapointed me poo's Im not used to seeing such sensible posts coming form you

Pixie
23rd February 2006, 15:01
But that blurb says exactly nothing...although they do say electro hydraulic,which could be the answer.Solenoids can't opperate the valves fast enough,but if they opperate a hydraulic system that could be a way around it.Like a fuel injector,that's electronic control of a hydraulic system,and it works very well.

And I will defend my position of all engine advances in the last 30 years being driven by California Emmission regulations.The fact that combustion chamber design,camshaft profiles and electronic fuel injection and ign systems have offered a big increase in power is just the iceing on a rather messy cake.
The blurb was dated 2003 and there have been pics of the test engine in the media,including bike media.
As you have noted it is electro-hydraulic,as there are solenoid valves fast enough for high speed engines.A fuel injector is a solenoid valve.
I'm sure we will see these around 2008.
Btw the unamed european manufacturer which signed up for the technology is Renault

Motu
23rd February 2006, 15:39
The poppet valve is the stumbling block - like telescopic forks they are rude and crude,but work so well the high tech alternatives are a no show.I think electro/hydraulic control of some sort of window valve would be the go,kinda like rotary valves without the mechanical drive...

Pixie
24th February 2006, 23:53
The poppet valve is the stumbling block - like telescopic forks they are rude and crude,but work so well the high tech alternatives are a no show.I think electro/hydraulic control of some sort of window valve would be the go,kinda like rotary valves without the mechanical drive...
Poppet valves are easy to seal.Which is the problem with most other designs.

I was looking for a sleeve valve engine I saw in a model aircraft mag.Where the bore rotated around the piston and in the cylinder and the prop was attached to the rotating cylinder.
I found the website and it seems they are applying the technology to more than just models...

http://www.rcvengines.com/corporate/rcv_company_profile.htm
http://www.rcvengines.com/rcv120sp.htm
http://www.rcvengines.com/corporate/motorcycle_applications.htm



* How it Works




The engine operates on a simple but elegant principle; the cylinder, incorporating the combustion chamber port, is rotated around a conventional piston and crank at 1/2 crank speed via a 2:1 gear reduction. A fixed timing ring completes this efficient rotating valve arrangement and removes the need for any complex overhead valves, cams or electronic servo cartridges. RCV have the following engine capacities in various stages of development:- 9.5cc, 10cc, 15cc, 20cc, 25cc, 33cc, 49cc, 90cc, 110cc, 125cc and 250cc.