Variable Valve Timing

[Sketchy_Racer]

yes Badit 250s have VVT. i believe.

i dont know how their system works

[zadok]

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]

'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]

'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]

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]

Pnuematic valvetrain anyone?

old technology mate they're trying electromagnetic systems now

[SPman]

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]

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]

Yeah, two smokers are anti social, ain't they. Noisy, smokey things - heh heh heh

[imdying]

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]

..

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]

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]

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]

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

Power valves are Gods work on earth !

[Pixie]

'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.