OK, engineer here. What you are seeing in the video is not valve float - the title is wrong. Valve float is when the RPM of the valve train is so high that the spring does not have time to extend fully before the cam comes down again. IF this was valve float, you would see a video of a compressed spring that never seems to move back to its uncompressed state. What you ARE seeing is valve bounce, where the inertia developed by the cam is so high that the valve unseats itself slightly every stroke. Valve and spring rotation is normal at these RPMS. Finally, AlixHAF is correct - the reason it looks like the image is 'frozen' is because of the sampling rate of the video relative to the RPM of the vehicle, in the same manner that car rims sometimes look they're not moving in a video. It is based upon a part of signals theory called Nyquists Theorem, which I won't detail here but you can look it up if you're interested. Hope this clarifies things.
It is Nyquist if they have intentionally set the frame rate to be at least 2x the frequency of the information as Nyquist's theorem states that is how information can be recovered from a signal. In this case it's aliasing or intentional undersampling to recover the information. I won't detail it here but you can look it up.
So, a Honda engine isn't really designed for what they advertised, 8500rpm (JDM), 7800-8000RPM (USDM), right? Don't push your Honda past 5000rpm perhaps?
Amazing video!! Great job! I never thought there was that much flex in the valve stem itself! And the rotation is interesting also!! Thanks I really learned something and I will remember what I learned and apply it toward my next engine build!!!!!!!
Amazing Video!!!!! This should help many people understand what's going on with their Valvetrain. The use of fast ramp rates just exacerbate the valve float problem. Better springs and lighter parts ie Valves, Retainers, Locks etc should alleviate the problem Thanks for the great Video!!!!
Great Video. Its nice to see that of those that understand common performmance issues and have learnt how to fix these issues, still take the time to help the general public with excellent illustrations such as this. Well Done. another anomoly in the high revving valve train arena. Is the virtual elimination of the hi frequency resonance by balancing camshafts. It works so well every engine running in the NASCAR Cup Series uses the technique. an 60% reduction in valvetrain death.
Valve float happens when the cam profile is too aggressive for the valve spring rate. The higher the lift, the stiffer the spring you have to use. Some people have the misconception that roller lifters add power.. but in reality it's just to alleviate friction from running super stiff valve springs.
As I think I remember it, the Volvo P1800, according to a Car and Driver test article in the early 1960’s, was capable of valve float. The engine was incredibly strong with an actual five main crankshaft bearings. One 1966 P1800S holds the record for the highest mileage car of an original owner of non-commercial use at 3.2 million miles. Comments from any fellow old timers??? Interesting video!
Valves are supposed to rotate in operation. Some stock 3-piece valve retainers have funky spring washers to ensure they spin. Valve float is when the valve's inertia overcomes the spring pressure and the follower comes off the valve stem tip. In fact the entire valve train goes loosy-goosy. The side play is loose stem clearance and/or a too thin valve stem. Hard to fix since you need clearance to oil the stem. Double springs are a must for high seat pressures and to kill harmonics.
Another possible factor is a hydraulic lash adjuster, either in the lifter or bucket. A sad feature of e hyd adjuster is that when there is even a small amount of float (loft) the adjuster takes up the lash. The net result is that the valve does not seat when on base circle and you lose cylinder seal.
You are totally correct about the compression ratio dynamic vs. static. And to further add to 23607's total and utter failure to read what ever book he's been reading properly, dynamic cr. sure as hell does mean alot when you apply static cr. If you have a dynamic compression ratio of 11:1 and apply pressure even 0.5 bar/7.35 PSI, could be damaging on any engine, generally, don't get carried away trying to prove me wrong on this data.
The type of vavletrain makes a big difference. Pushrod engines are the worst because the spring has to arrest the inertia of the lifter, pushrod, rocker, retainer and valve. Next best would be the overhead cam with a follower pushing on the valve. The best is an overhead cam pushing directly on the valve via a valve spring cap. But they are a royal pain to set the lash. You have to measure all of the lashes, remove the cam, insert shims under every cap, then put it all together.
I believe there are some very normal things going on here, and that it is an over dramatization using worn parts, to promote their cylinder head service, as well the delays caused by raped frame rate changes deceiving the eye
I know this video is regarding valve float at high rpm, but.. Do the springs tend to still oscillate as much at say, half the rpm? Is oscillating only really an issue at very high rpms? I have an engine with ~.300" between full lift and bind. I'm seeing wear patterns on the lash caps that look like the stem is moving around like in this video. However, the engine is rarely at 7000. Spends most of it's time between 3000-4000.
so correct me if im wrong cause i no nothing about how your able to watch the valve. but from what it looks like, your using some sort of strob in timing with the valve so you can take almost still shots of it to see the placment and unwanted rotation of the valve spring. its really amazing that the quick flashes trick your mind into seeing it almost still when really its moving 7000 times a min.
its supposed to rotate along with the valve, to help keep the face seated. The rocker arm intentionally pushes on the valve tip at a slight angle to make it rotate. Float is uncontrolled up and down motion from spring resonance. Hi-perf engines have 2 springs per valve to raise the resonance higher than the engine can even go.
hmm thats weird thats not what I have been taught since high school. In fact its simply wrong..."Depending on valve train design, the valve rotation might be obtained by using the cam or rocker offset position or by using angled cam"
I see what you are saying, some designs don't have it, but to say NO designs have it is false. Honda tech school explained how they do it. In fact the last year CB750F suffered valve guide wear when they put the latest camshaft in it, the side load was beyond the original parameters.
Seat load of the spring is only part of the reason for valve bounce. Under extreme dynamic conditions, coil surge changes the seat load. If the valve seats when the coil surge is heading up the stem, it can unseat the valve if the acceleration and amplitude of coil vibration are high enough to overcome the static seat load.
Yes, The frequency of the valve was at or close to the resonant frequency of the spring. This condition is know as spring surge and can cause spring failure ie snap the spring.
I'm wondering if these tests are really done by just spinning up the valve train or actually running the engine,,especially with the underside of the valve view.. cylinder pressure also pushes valves closed but granted during intake and exhaust pressures are lower, but during the compression stroke would valves seat faster or more efficiently? I see no flame front on the compression chamber during these tests. and I'm actually surprised the float is not worse.. but this was still fascinating to see.
Also, they replaced the springs when I had the head decked and cleaned up. They used the OEM part. Still floats around 4100RPM, which coincidentally is Ford's recommended max RPM for my engine.
valves spinning is a regular occurance. bmw did tons of testing on their s1000 motor before going into production. valves spin regularly. and when harmonics come into play, manufacturers put in inner valve springs, which also raises overall spring pressure.
@novaracer1963 at the end the valve seems to go faster but in fact it goes almost the same speed. It's just because the strobe-light is not timed perfectly with the rpm... you can see the same thing with a timing light and a fan.
@FLSHBK1 The valves are supposed to rotate ok, one of the spring holders contain a "roto-cap" and causes the valve to rotate slightly each time it is pushed. A friend of mine once had a Ford V6 that sounded like it had a bad valve lash on one valve. Removed the valve covers and found that one of the valves didnt rotate. Gave it a squirt of 5-56 and knocked it with a hammer(yes it was running), and the sound disappeared.
What did you do to correct the side to side valve movement, I know how important the spring pressure is but did you tighten up the stem clearance? Was this an actual running engine or electric motor driven?
Hmm so what is it we are seeing here exactly, or rather more, how is it done? Is that a strobe light used in order to capture the motion? (assuming that at 8000 rpm the valve assembly couldn't been seen by the camera, letalone the naked eye)?
@mikem75 How do you think they adjust timing belts? A computer is used with a strobe light hooked to it and the computer is hooked up to the engine to calculate the engine's RPM. Then uses this RPM and tells the strobe light what frequency to flash with.
@JasonMann8 normal speed with a strobe light cycling just slightly less or more than the rpm of the engine. eg: 8000 rpm engine with a 7999 or 8001 flash per minute strobe. Very cool effect
Nicely done friend,no wonder my machine shop keep telling me ,vavle guide can wear quicks on Honda motor and Mitsubishi motor,but also they should have some way of making diff. kind of valves guide instead of brass material,prevent fro wear on valves and valve guide,wonder if double valves spring also cause the damage on valves and valves guide also.
Yeah, most have two rotors though, so generally people just cite the number as 3. Engines with 3 rotors are fairly rare and engines with 1 or 4 rotors are extremely rare (though in the case of 4, extremely cool, too!) Water/oil pumps, distributors, carburation/fuel injectors, etc. are all accessories of course, so they don't really count. Though as fun as it is to tote the simplicity of the engine, the sealing system is actually much much more complex than that of a piston engine, so...
Please help me to understand because I'm yet a student in this field. 10000 rpm means about 83 valve openings per second. How comes the rocker arm seems to rock very slowly. is it some optical illusion like "wagon wheel effect". Thanks in advance.
@FLSHBK1 I think the problem with valve float is that the valve doesn't make good contact with the valve seat and so not only causes a loss in engine power but the valve does not cool properly and the valve "burns" causing permanent power loss and valve cooling problems.
I think I might want to consider upgrading my valve springs and cams after seeing this O.O I redline my Subaru pretty much every day I drive it, and I have no idea if the stock valve springs would like it...
This video reminded me of how my wife and I conceived children our children for some odd reason. LOL! Seriously this video gives some really good insight to what might be taking place in some engines.
Im not arguing it. But wanted to know how valve spring rotation can be a good thing? And what is valve bounce exactly? Whwn the valve isnt quick enough to return to its position or whwn it wobbles? Or...? Thanks.
Wouldn't valve float mean that the valve spring can't co op with the rotation from the camshaft and by that way stays open? Here you can see it bouncing and thus closing on the seat. Never thought it rotated this much on a stroke.. Nice footage!
This just made me anxious and paranoid. I'm rebuilding my whole damn car from the ground up (seriously... in my garage, by myself) and I was already worried about bottom end bearings and piston rings. Looks like I'm just gonna replace all internals, go bigger, forged etc and hope my husband's at least kind enough to let me have a few blankets and a pillow in the doghouse. He's gonna have a damn canary and an aneurysm simultaneously when I spend what I'm bout to... he just got a new motorcycle tho so he'll be fine lol. Hopefully I will be too... hahaha
I remember when I was young and just learning about fixing cars ‘( 87, ) some guys said valve float was accelerating as fast as you can and when you reached max rpm let off and hit the breaks….i always questioned that and where as I never became some super race tech ( I prefer cars all factory, and I do refrigeration ) I could never believe that. I have rebuilt a few engines in the VW air cooled area and more in the Honda 96-2012 line and consider myself a decent tech, the valve float thing is real but rare from my view point
ok 6 years reply in the making. in laymen terms float is when the valve cannot close completely ( or floats) because spring cannot overcome centrifugal force applied .
This depends, I guess. The way I learned it is that a valve is considered to be floating when the lifter loses contact with the back side of the cam lobe, contributing to the valve slamming closed and the bouncing that you see. The back side of the cam lobe is "supposed" to be designed to permit a gradual closing of the valve. When a valve stays open long enough for almost 720 degrees of crankshaft rotation, (where it is about to be pushed open again) a piston is liable to make contact with that valve in the mean time. I would expect engine power to drop off to nothing at that point, thus the only way for this to happen is to jam it into low gear on the highway.
What you see there maybe it's not what really happens. Have you taken in mind Shannon's Sampling Theorem for this video capture? You may see frequencies that don't exist at all. Aliasing happens.
you are right in that b/c only one company deals w/ rotaries, they are inherently expensive, but they is a reason why everyone is doing piston engines and no one bothers w/ rotaries
The valves are supposed to rotate so the portion of the stem that the rocker arm contacts doesn't wear a a singular spot at the point of contact. The keepers and spring retainers and springs are all made to help induce this rotation.
