Royal Enfield Motorcycles > Bullet with the UCE engine

How do Hydralic Lifters work. ?

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chinoy:
Since our new UCE engines come with Hydralic Lifters.
And my expoure to them is limited.
The only engine Ive worked on which used them was the Huyndai open wheel formula class.

It would make intresting readings if somebody like Bob or Ace.
Explained it to us.

I think its safe to say we all know the basics. i.e. why they are used
a. Reduce Valve train noise.
b.Allow better power output as you dont loose any lift to valve lash.


Bob could you explain how they work.
I know there is a spring. And I know oil gets pumped into it. And this moves a piston up. The piston moves the lifter which the push rod sits on.
It also has a lock which prevents the oil from poping the lifter out.

My doubts are as the RPM climbs so will the oil pressure right ?
So why now use this to give you a V-tec type setup where you lift increases as the RPM climbs.

Ive tried google but really couldnt find much info on how these things work.
How do you set them up ?
i.e. how much should your push rod pre-load that sping when the engine is cold.
What happens when you start the engine.
And what happens as the RPM climbs.

ScooterBob:
The hydro-lifter consists of basically a low pressure (engine oil pressure) and a high pressure chamber (hydraulic lock, essentially). The engine oil fills the low pressure chamber which rides inside the lifter body, which is the high pressure chamber. There is a spring under this low pressure chamber within the high pressure chamber that takes up slack in the valvetrain and keeps the low pressure chamber form bottoming out in the lifter body. With the lifter pumped down and "at rest" the low pressure chamber is open to the oil galleries in the engine and is full of oil, as is the high pressure chamber. Upon valve lift, the low pressure chamber is pushed downward into the lifter body and the oil pressure feed hole is occluded, causing the lifter to be essentially solid during the lift cycle. Upon returning to the base circle of the cam, the high pressure chamber can leak off around its periphery and the low pressure chamber can equalise with the engine oil pressure - and the spring under the low pressure chamber takes up the valve lash until the next "fill and lock" cycle repeats again. That's pretty much it in a nutshell!

chinoy:
Still have doubts
a. Is the oil pressure in the engine related in any way to RPM ? You get where Im going with this i.e. if it is why cant we get the lifter to lift more when the RPM climbs.

b. At rest when coil. The spring is pushing up on the lifter till the point where its pressed up against a spring. Now we set the lash or check the lash by puting it all together and seeing if we can spin the rod with our fingers. You should just about be able to spin the rod it should not be something you could do easilly.

Say this point of easy spining is 60 Thou or the spring has depresed 1mm. Inside the lifter.
Now when the engine starts and the oil enters the lifter. how hard is the oil going to push up on the lifter will it push it out to its full locked position ? i.e. will the lifter be pressed up against the lock or not. If it is then what happend to that 1mm or 60 thou we set when it was cold.
What is confusing me is the comment that when it has oil in it. Its as good as solid.
But solid to what height ?

Lastlly what would happen if we set too little pre-load i.e. your valve train has worn a few thou. And now at rest the rod ends can be spun freely but you cant move the rod up and down.
And what would happen if we set too much pre-load i.e. you shave your head and dont adjust for the change in your rods or lifters.

How is setting the push rod length different between the UCE and the C5s in the process you follow.
As we know that no two bikes will be the same from the factory.

longstrokeclassic:
http://www.ducati.co.il/home/en_lessons_hydrauliq_valves_lifter.php

jayprashanth:
Ric450classic,

Terrific find. Thank you.

Cheers,

Jay

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