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!!!!! 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!!!!
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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!!!!!!!
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.
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.
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!
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.
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.
@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.
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.
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.
@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.
@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
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.
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...
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.
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.
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.
@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.
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.
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
Dr, I'm not talking about wire springs. Del West makes the gas spring used on many F1 cars. Using gas to actuate the valves would take an enormous pressure bottle. just imagine the amount of gas needed to operate the valves at this very high speed, and do it many times a second for a long time without refill. I don't think it's possible. I am familiar with a high pres. N2 tank. It is used in the gas spring setup that I described. Coates is right down the street. Been there.
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.
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 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...
Nice Spintron video, but correctly stated, the fix for spring resonance is not higher seat pressure directly, it is correcting the natural freq. of the spring to move it out of your operating range. IE. a change in wire dia, number of spring, windings, or a change in the cam profile.
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.
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
@combomaster99 ok, i get it, i didnt see any changes like how a wheel looks like its going backwards, the spring just compressed and decompressed at the same rate.
Frame rate seems to be screwy 'cause they're doing this with a regular video camera and a high-speed strobe light. When he changes engine RPM, he also has to tune to strobe light to the right speed to make the valvetrain appear like it's moving in slow motion.
Adding another spring doesn't eliminate valve float completely, whenever there are springs involved, there will always been some valve float in the peak rpm range.
People use heavier valve springs in order to try and alleviate valve float and/or valve bounce. By doing so, wouldn't that cause excessive wear and damage to the cam itself, with the more excessive spring pressure?
+TheProfessor936 Yes mate. Stiffer valve springs have pros and cons, like everything in engineering. Although strong springs can deal issues at high rpm band, especially when aggressive cam lobe geometries are introduced, like the ones mentioned (+higher lift capacity and seat pressure) they do introduce several stresses=friction=wear in the entire parts of the valve train [cam bearings, cam lobes, rocker arms+cam followers, rocker arm shaft (if it does exist - automotive engines=>rarely nowadays), lash adjusters, valve guides, etc.] On a carefully studied and builded engine stiffer springs will be taken into account and counterbalanced by the adoption of appropriate materials and geometries. (As for industrial concept)
For every lift of one "higher spring pressure" valve one is falling, meaning actually helping the cam around. I was amazed to read that pressures of 1200 lbs on the cam and 800 on the seat are common place in high perf engines today.
yeah exactly mate, the video is only capturing a shot probably 25 or 50 times a second, so it may capture 2 consecutive frames where the valve has done a cycle, or 1.1 cycles, or 5.2 cycles, or whatever, in between the two frames.
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.
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.
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!
Is this video taken with a strobe? Or a very fast fps vid camera, or both? The comment that said it would be difficult to set up a strobe for this isn't true. The strobes that I have used for this kind of stuff are really pretty simple. They have a dial and a digital readout on them. So you just have to jack around with the dial to get it "on". We use them all the time at my job. Thanks for sharing!!
You can tell. I have an inline six in a pickup, notorious for weak springs that has no RPM. I can feel valve float as low as 4,000RPM. Typically, on my engine, it manifests as a loss of power and a tone/pitch change in the exhaust note. Now, I don't let it float long enough to harm anything, and I know this for a fact as I had to change the head gasket and found none of the damage typically associated with valve float. Old valves and pistons were reused. Engine has 260K miles, BTW.
its not that it rotates buddy, its that the valve stem was obviously moving side to side at 1:00 that clearly indicates the valve isnt fully shut reducing compression and risking the piston slapping the valve resulting in a bent/broken valve or damaged piston depending on the cam profile and dome on the piston head, so yes valves and springs do rotate a bit rotate, but not as much, but especially not side to side
very right comments by some of the observers, I also personally thing there is no valve float, or the stroboscope is not catching the exact timing of valve float
Spring strength wouldnt be able to snap a valve. The spring pushes on a plate which is mounted to the swingarm from the cam which is also mounted to the valve. The spring isnt really pushing directly against a valve nor would the strength wreck it. And no, you dont need thicker springs to be stronger springs; there are materials that are thinner but harder to compress, all depends on the metal used. you are right about a weak spring not sealing properly but that would be catastrophic
Bouncing the valve on the seat is a sure way to kill the valve train. The spring pressure needs to be high enough (at speed) to overcome the valve's inertia so the cam follower (or rocker arm) can correctly lower the valve back onto its seat. Pounding the seats can loosen pressed in seats and recess the valves - loosen the clearances and exacerbating the problem, Severe situations can lead to smacking the valve with the rising piston. That will lead to a broken valve head and much noise.
I've always understood it as the entire valve train becoming out of sink with the cam. Whether you have push rods or rocker arms riding on the cam. the cam more or less throws the whole valve train so much that the valve spring cant bring it back to the closed position fast enough.
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
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)?
turbos don't change comp. ratio, as it is a mechanical limitation. they do technically change the static(or dynamic, can't remember) ratio, i.e. 10:1 is always 10:1, 180 lbs could be bumped up to say 220 lbs with boost, if thats the ratio you ment. but the main problem with rotaries is the same w/ diesels; their too expensive to build properly when compared to the average gas engine
I don't know. You tell me. Starting with your engine. It is undisputed physics that springs have resonant harmonics and two different springs allow creating a valvetrain that is less harmonically "peaky". Two thinner springs also allow more lift with less chance of binding the springs and ultimately more seat pressure. If you're OK with what you have then good for you. Run it all day long. I'm just stating a fact. But what do i know. I've only been building engines for 30+ years.
What ever you call it, isn't the valve train motion at some point not sufficiently controlled, so the valve train is operating in a fashion other than what it was intended or designed to function? Or is someone trying to say this valve train is still considered under control? Either way when you see this it makes you rethink what your valve train of choice is doing.
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.
Another internet engineer huh?
you are 100% correct... but you should have mentioned that you'll never see severe valve float on a rocker!
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.
Eric H You are absolutely right my friend. It is not valve floating, just spring bounce.
Correct sir.
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?
8000 RPM
4 Stroke: Shits getting real!
2 Stroke: I call this 'high idle'.
I have seen this one 2 stroke racing bike where the tacho started at 8k rpm lol
@@jamppa4693 What size engine was it?
@@conortobin6180 50cc :D
Why arnt F1 cars 2-stroke?
Why arnt F1 cars 2-stroke?
this video makes me feel like im watching a nuclear explosion about to take out a whole city the all the noise and music and flashes
There’s no music you idiot
@@WELLINGTON20 I wrote this comment 5 years ago and have absolutely no idea why I said any of it 😂
@@Joolian.r Legend 😂
There's gonna be an explosion alright, and real soon! Pistons are antisocial, and don't like meeting others, especially Mr. and Mrs. Valve!!!
@@milojanis4901 they’re not very good neighbors when brought together. They like to stay separate.
That valve at the end is rotating so much it could almost lap itself in - just add grinding paste.
davidrobert2007 You just made me spit coffee all over my keyboard!
Buelligan what are you even replying to? Like the guy said nothing about ignition LOL.
Lol
Wow! That was a random thread!
Buelligan88
Two live down the street here. Unfortunately.
god i feel like im watching a very old horror movie.
yeah at 1:23 XD
So amazing it stays together even for a minute or two!
Great video, love the shot of the valve! In addition to spring pressure, cam profile plays a large part to minimize valve bounce too. Nice job!
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!!!!
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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!!!!!!!
sloppy valve guide clearance
WOW!!! I've never seen an inside view of a running engine like that! Very informative!!
Sweet, now I'm having a seizure.
You got triggered.
@@godfreypoon5148 LOL
lol
Great, just after commenting somewhere that my drink went out through my nose you catch me off guard with this laconic remark
I love little Cesar’s!
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.
Agreed. To see it all in action, such as in cutaway, is always interesting.
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.
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!
1:32 How about an epilepsy warning for fullscreen viewers..wow lol
@Furio an engine stroke? or a stroke stroke?
I just had a full monic-clonic-tonique seizure after seeing that
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.
Worn out valves are awesome! I just love the pop and crackle sound when I let off the gas at high RPM.
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.
Extremly good Video!!! I've never seen suh a dynamic process before and it helps me to understand what happens in the motor.
Wow imagine seeing this in 2020 with modern cameras
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.
I'm guessing this was done with a Strobe Light?
Would explain the non-continuous movement.
Ouch, you can see the valve dancing back and forth, possably needs a set of guide's and obviously new springs xD sweet video!!!
@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.
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.
this clip could make a good dubstep video
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.
@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.
@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
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.
This video reminds me of VHS...
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...
@FLSHBK1 The rotation isn't bad, the jackhammer effect is... It's basically pounding on the valve seat.
Excellent video!
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.
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.
The direction of the valve spring coils cause the rotation. The rocker should theoretically be centered on the valve tip
they are offset, to keep the valve rotating and clean of carbon. Don't take my word for it, the truth is out there.
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.
Duke Nukem, makes a lot of sense,i never thought of it! After all,the spring is a torsion bar;
dude you need to go back to class that isn't float .. float is when the spring hasn't expanded all the way before the rocker start coming down again.
gswy ohhki
K. Thanks for explaining in the most easiest way possible. Thanks doood
fuzzy wuzzy hmm. I don't know. Should I?
IKR waste of my time
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.
Wow. iv been in those engines. those valve stems are pritty stiff... and they just wiggle. amazing
I couldn't really see any valve float, the spring always looked connected to the rocker to me?
the speed at the cam is the half of the crank
and when the intake valve works the exhaust doesn't
so it's not so high rpm that 8000 for the valves
the idea of rotary valves is a great one! while the seal does suck, it can be made to work, and the RPMs would be amazing, as are desmodesic valves
*1:15** SEIZURE WARNING*
or is it at 1:35? yes I see the time stamp
G Smith *AND IT CONTINUES TO **4:21**!?*
This should be in the title.
@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.
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.
@299special yeah it is correct,strobe lights was used for super slow motion before the invention of high fps cameras
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
Dr, I'm not talking about wire springs. Del West makes the gas spring used on many F1 cars. Using gas to actuate the valves would take an enormous pressure bottle. just imagine the amount of gas needed to operate the valves at this very high speed, and do it many times a second for a long time without refill. I don't think it's possible. I am familiar with a high pres. N2 tank. It is used in the gas spring setup that I described. Coates is right down the street. Been there.
good vid. I have a better understanding now of valve train components valve springs in particular. thanks
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.
3000 people had a seizure watching this i bet
No, 3000 people know the difference between valve float and valve bounce.
Seizures 2 years later.
Now you listen here, don joe...
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
That will teach him...go get em Cha Cha Muldowny!
I've seen push rods bend in diesels without the piston even contacting the valve. Due to harmonic weakening of the metal over time.
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...
@MrGizmo757 because some engines do have valves that are desinged to rotate, but most dont because of the desing of the valve seats
Congratulations on a FANTASTIC video!
0:53 when the acid hits
imagine if someone had an epileptic seizure watching a valve float video
Nice Spintron video, but correctly stated, the fix for spring resonance is not higher seat pressure directly, it is correcting the natural freq. of the spring to move it out of your operating range. IE. a change in wire dia, number of spring, windings, or a change in the cam profile.
I don't know which part I doubt more, the idea that you'd be in the movie, or that they'd let you use your accord in it too.
Its a cut up motor meant to test valve trains. It probably does not even have a piston in it. It is spun by a high speed electric motor
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.
Amazing how long valve spring last wonder how many million time they operate in life time ?
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.
This video is more like "equivalent time sampling". ie deliberate aliasing.
Very Kool video to see the reality of what 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
@combomaster99 ok, i get it, i didnt see any changes like how a wheel looks like its going backwards, the spring just compressed and decompressed at the same rate.
very cool video of the valvetrain at high rpms
Frame rate seems to be screwy 'cause they're doing this with a regular video camera and a high-speed strobe light. When he changes engine RPM, he also has to tune to strobe light to the right speed to make the valvetrain appear like it's moving in slow motion.
Adding another spring doesn't eliminate valve float completely, whenever there are springs involved, there will always been some valve float in the peak rpm range.
People use heavier valve springs in order to try and alleviate valve float and/or valve bounce. By doing so, wouldn't that cause excessive wear and damage to the cam itself, with the more excessive spring pressure?
+TheProfessor936 Yes mate. Stiffer valve springs have pros and cons, like everything in engineering. Although strong springs can deal issues at high rpm band, especially when aggressive cam lobe geometries are introduced, like the ones mentioned (+higher lift capacity and seat pressure) they do introduce several stresses=friction=wear in the entire parts of the valve train [cam bearings, cam lobes, rocker arms+cam followers, rocker arm shaft (if it does exist - automotive engines=>rarely nowadays), lash adjusters, valve guides, etc.]
On a carefully studied and builded engine stiffer springs will be taken into account and counterbalanced by the adoption of appropriate materials and geometries. (As for industrial concept)
For every lift of one "higher spring pressure" valve one is falling, meaning actually helping the cam around. I was amazed to read that pressures of 1200 lbs on the cam and 800 on the seat are common place in high perf engines today.
That was fantastic! Thank you for uploading this
yeah exactly mate, the video is only capturing a shot probably 25 or 50 times a second, so it may capture 2 consecutive frames where the valve has done a cycle, or 1.1 cycles, or 5.2 cycles, or whatever, in between the two frames.
@FLSHBK1 Yeah the valves ARE supposed to rotate, but not the springs also.
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.
Eric is correct. Valve float is when spring can’t keep up with the mechanical motion of the camshaft. This is from a 2nd engineer, BSME.
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.
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!
Is this video taken with a strobe? Or a very fast fps vid camera, or both?
The comment that said it would be difficult to set up a strobe for this isn't true. The strobes that I have used for this kind of stuff are really pretty simple. They have a dial and a digital readout on them. So you just have to jack around with the dial to get it "on".
We use them all the time at my job.
Thanks for sharing!!
You can tell. I have an inline six in a pickup, notorious for weak springs that has no RPM. I can feel valve float as low as 4,000RPM.
Typically, on my engine, it manifests as a loss of power and a tone/pitch change in the exhaust note. Now, I don't let it float long enough to harm anything, and I know this for a fact as I had to change the head gasket and found none of the damage typically associated with valve float. Old valves and pistons were reused.
Engine has 260K miles, BTW.
Curious as to valve seat run out/ valve run out. Concentric to one another? Looks like a bowl wobbling on a table. Cool old vid
its not that it rotates buddy, its that the valve stem was obviously moving side to side at 1:00 that clearly indicates the valve isnt fully shut reducing compression and risking the piston slapping the valve resulting in a bent/broken valve or damaged piston depending on the cam profile and dome on the piston head, so yes valves and springs do rotate a bit rotate, but not as much, but especially not side to side
Looks like it’s working perfectly fine
very right comments by some of the observers, I also personally thing there is no valve float, or the stroboscope is not catching the exact timing of valve float
Spring strength wouldnt be able to snap a valve. The spring pushes on a plate which is mounted to the swingarm from the cam which is also mounted to the valve. The spring isnt really pushing directly against a valve nor would the strength wreck it. And no, you dont need thicker springs to be stronger springs; there are materials that are thinner but harder to compress, all depends on the metal used. you are right about a weak spring not sealing properly but that would be catastrophic
Bouncing the valve on the seat is a sure way to kill the valve train. The spring pressure needs to be high enough (at speed) to overcome the valve's inertia so the cam follower (or rocker arm) can correctly lower the valve back onto its seat.
Pounding the seats can loosen pressed in seats and recess the valves - loosen the clearances and exacerbating the problem,
Severe situations can lead to smacking the valve with the rising piston. That will lead to a broken valve head and much noise.
Alternative title: "4 and a half minutes of epilepsy"
I've always understood it as the entire valve train becoming out of sink with the cam. Whether you have push rods or rocker arms riding on the cam.
the cam more or less throws the whole valve train so much that the valve spring cant bring it back to the closed position fast enough.
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
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)?
Can having the wrong spring pressure cause the engine to feel like it has a rev limiter?
Most rotary issues are from owners. A maintained and well reved rotary will run for a long time.
Excellent video! Thanks
How is this filmed? Its awesome!
dude !!! this is totally awesome video very nice!!!
Just use the correct valve train parts when building your engine for intended use, and you won't have to worry about shit like this!!
turbos don't change comp. ratio, as it is a mechanical limitation. they do technically change the static(or dynamic, can't remember) ratio, i.e. 10:1 is always 10:1, 180 lbs could be bumped up to say 220 lbs with boost, if thats the ratio you ment.
but the main problem with rotaries is the same w/ diesels; their too expensive to build properly when compared to the average gas engine
I don't know. You tell me. Starting with your engine.
It is undisputed physics that springs have resonant harmonics and two different springs allow creating a valvetrain that is less harmonically "peaky".
Two thinner springs also allow more lift with less chance of binding the springs and ultimately more seat pressure.
If you're OK with what you have then good for you. Run it all day long. I'm just stating a fact.
But what do i know. I've only been building engines for 30+ years.
What ever you call it, isn't the valve train motion at some point not sufficiently controlled, so the valve train is operating in a fashion other than what it was intended or designed to function? Or is someone trying to say this valve train is still considered under control? Either way when you see this it makes you rethink what your valve train of choice is doing.
one of the best videos i seen great job!