[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

[ace.cafe]

That's a good diagram of how typical hydraulic lifters work.

Basically, a hydraulic lifter is a self-adjusting type of lifter, that is designed to take up any lash in the valve train which might occur from heat expansion or for any other need.
This is set by "pre-loading" the lifter to be able to have enough distance to make the necessary length adjustments to cope with any lash changes during normal operation.

When I look at things like this, I don't only look at "how they work".
I look at what happens when they don't work.

One of the limitations of a hydraulic lifter design comes in high performance applications.
In theory, any amount of pre-load that you have adjusted into your hydraulic lifters can be "pumped-up", causing the lifter to be too long, if certain things occur during the higher rpms of your rev range.  If there is any pushrod flex, or momentary valve float in the valve springs, which can occur in high rpm conditions like racing, then the hydraulic lifter treats this the same way as it treats normal valve lash, and takes up the distance by becoming longer. This "pump-up" then makes the lifter longer than it should be, and it holds the valve off the valve seat, losing alot of power and potentially burning a valve.
As you reach near your limits of valve train stability, it doesn't all happen at once. You may start to see some pushrod flex or momentary valve spring float at rpms lower than your theoretical maximum rpm. And the hydraulic lifter will take up this distance and them become too long, and you'll then lose power from compression leakage at the valves.

Most people generally consider hydraulic lifters to be suitable to 5500-6500 rpms. Above those rpms, there are some "anti-pump-up" types of hydraulic lifters that can be used, or most people then switch to a solid tappet, and if they have roller tappets they switch to a solid roller tappet. This solves the rpm limitations that are seen at higher rpms in hydraulic tappets.

In the UCE, the rpm range is well within the ability of a hydraulic tappet to handle. it's a good quiet system, and is not going to have pump-up problems in this normal application.
For a racing application in which rpms higher than 6000 rpm are contemplated, it would be prudent to switch to a solid roller tappet to avoid "pump up" issues with the hydraulic ones.

This is a well-known issue that is discussed often in racing communities. The rule of thumb is hydraulics are ok under 6000 rpm, and use solids at higher rpms. There are ways to modify hydraulic tappets to "act" like solids, but that's another topic. At that point, you may as well just install solids.

[chinoy]

Thanks guys.
Good find there Ric.
With the Bullets 90MM stroke. I see no point in reving it out to more than 6000 RPM.
Unless you can somehow reduce the stroke.

[WKinNJ]

One of the limitations of a hydraulic lifter design comes in high performance applications.....
Most people generally consider hydraulic lifters to be suitable to 5500-6500 rpms. Above those rpms, there are some "anti-pump-up" types of hydraulic lifters that can be used, or most people then switch to a solid tappet, and if they have roller tappets they switch to a solid roller tappet. This solves the rpm limitations that are seen at higher rpms in hydraulic tappets....
... The rule of thumb is hydraulics are ok under 6000 rpm, and use solids at higher rpms. There are ways to modify hydraulic tappets to "act" like solids, but that's another topic. At that point, you may as well just install solids.

Honda Motorcycles has been using hydraulic lifters in their engines for years, granted they are Overhead Cam designs - but red-line is much higher than 6,000 RPM.  I have a 1985 Honda Nighthawk with hydraulic lifters that red-lines @ 9,000 RPM and has 25,000 miles on it with no issues.   Also in the "stable" is a Harley Davidson XR1200 with hydraulic lifters and push-rods that red-lines @7000 (HP / 67kW @ 7000 rpm).

[ace.cafe]

Honda Motorcycles has been using hydraulic lifters in their engines for years, granted they are Overhead Cam designs - but red-line is much higher than 6,000 RPM.  I have a 1985 Honda Nighthawk with hydraulic lifters that red-lines @ 9,000 RPM and has 25,000 miles on it with no issues.   Also in the "stable" is a Harley Davidson XR1200 with hydraulic lifters and push-rods that red-lines @7000 (HP / 67kW @ 7000 rpm).

Great!
Your Honda has anti-pump-up lifters. They have a rapid bleed-down feature.
Your Harley might too, being that it is a sport model which has a higher redline than a typical Harley would encounter.

That doesn't help engines which don't have them.
Most Harleys don't have them, and the UCE doesn't have them either.

[motomataya]

a 1985 Honda doesn't have hydraulic lifters they have hydraulic valve adjusters. Its very different.

[chinoy]

Since we have so many knowledgeable people on the subject here.
Can somebody explain how you setup Hydralic lifters i.e. how do you set the clearance.

[chinoy]

Here is an article than answered all my questions.
I esp. like the strip down on the lifter.

http://www.ratwell.com/technical/HydraulicLifters.html#operation

[ace.cafe]

Here is an article than answered all my questions.
I esp. like the strip down on the lifter.

http://www.ratwell.com/technical/HydraulicLifters.html#operation

Nice article!