Wiped Cam :( - Page 3 - LotusTalk - The Lotus Cars Community
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post #41 of 121 (permalink) Old 02-18-2017, 08:44 AM
George B.
 
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Please add me to cylinder #3 Intake cam, high lobe failure. I bought the car in Denver and experienced a misfire code that shut me down on a very ugly stretch of highway in Wyoming. Of course turning the key off, and a restart allowed me to continue on my trip, and I didn't experience another event, but made an effort to stay off the high cam. Car is 2005, has 23K, car is very clean, but I have no idea how enthusiastically it was driven in the past.

There are certainly a lot of theories as per what causes these failures, and those that pattern to cylinder number three make me wish there was an on line database we could make entries in. One thing I wonder, do elise owners have more dry starts than others? The other day I started my off road RZR1K, and the dry clatter caused me to cringe, I will be sure to run it at least once a month from now on, and of course the Elise will be run monthly or more often as well.
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post #42 of 121 (permalink) Old 02-19-2017, 09:55 AM
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Originally Posted by gbrecke View Post
Please add me to cylinder #3 Intake cam, high lobe failure. I bought the car in Denver and experienced a misfire code that shut me down on a very ugly stretch of highway in Wyoming. Of course turning the key off, and a restart allowed me to continue on my trip, and I didn't experience another event, but made an effort to stay off the high cam. Car is 2005, has 23K, car is very clean, but I have no idea how enthusiastically it was driven in the past.

There are certainly a lot of theories as per what causes these failures, and those that pattern to cylinder number three make me wish there was an on line database we could make entries in. One thing I wonder, do elise owners have more dry starts than others? The other day I started my off road RZR1K, and the dry clatter caused me to cringe, I will be sure to run it at least once a month from now on, and of course the Elise will be run monthly or more often as well.


I don't believe driving it enthusiastically would prove to be a determining factor on wiped cams. There are people with cars that are babied that get it as well. As far as the dry clatter, it can happen to any car that sits for too long. I start mine up once every 2 weeks because of this.
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post #43 of 121 (permalink) Old 02-21-2017, 08:34 PM Thread Starter
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I checked my valve clearances.
#2 and #3 are on the tight side (0.0025 and 0 respectively). #1 and #4 are at 0.005 and 0.004.
Exhaust valves were fine (as was the cam...)


There is not a definitive correlation between the valve clearance and wear in my case (#1 looks like the most worn just by eyeball). BUT I think there is something to theory of valve lash being too tight and contributing to the wear.


I am going to loosen all these up, my target will be 0.010.
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post #44 of 121 (permalink) Old 02-22-2017, 06:17 PM
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at .010" or .279 millimeters you are still going to run the high risk of cam lobe wiping. There are a lot smarter people than me, on here recommending .012-.013". It is also important to note that the measurement is between the shim and the underside of the rocker arm. It is not between the cam lobe and the rocker arm (you can't check both of them).

Look at the cam lobes also. Look for impact on the high cam lobe about the center with the cam facing down. If it looks hammered, you will have severe/catastrophic engine problems in the future. (like a valve breaking, destroying your head, rocker arm breaking, etc.) That is what I found, among other things when I tore my engine apart last fall.

It is also important to note that with a dual oil cooler car and BOE oil pan, splitter, driving on the highway means your pan oil temperature is probably about in the 40deg C - 60degC (winter - summer in the Midwest). That is after an hour of driving. Traffic will raise it but once you start moving it is going to drop quickly.

I don't seem to get it to or above 100degC on track also. I am NA.
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post #45 of 121 (permalink) Old 02-22-2017, 07:17 PM Thread Starter
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This TSB states that the valve lash is measured between the roller and the lobe.
http://testroete.com/car/Toyota/celi.../Engine/10.pdf

Do you have a more recent document that shows otherwise?

I will go ahead and try out the 0.012 lash spec.


I have some plans for getting the oil temp up.
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post #46 of 121 (permalink) Old 02-22-2017, 08:56 PM
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TSB or not, measuring lash between the lobe and the rocker isn't a good way to do it as you're only getting a reference from the tallest valve...

I've written in detail about the oil temperature, etc... It's a reasonable theory.

The stock cams are considerably softer than the aftermarket variants, which are also much more resistant to wiping. So there's that.

You can try other strategies like enlarging the orifice that controls the oil flow to the shower system and experiment that way if you're wanting to expand the experiment with additional oiling- the 2ZZ sits more upright in the Lotus. Perhaps, there's a straw leaning against the camel's back there too...

As I've said before, the incidence of failure is far less on race cars than comparatively babied street cars...

-Phil


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post #47 of 121 (permalink) Old 02-23-2017, 10:12 AM
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If babied cars are seeing more wiping than track cars..... which I have heard several times - Is it possible that the wiping is occuring during low RPM use ??? - maybe the slipper is "bouncing" on the large camshaft because the slipper is not "engaged" and the spring is allowing the slipper plate to bounce on and off the large cam during low rpm use ????

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Originally Posted by turbophil View Post
TSB or not, measuring lash between the lobe and the rocker isn't a good way to do it as you're only getting a reference from the tallest valve...

I've written in detail about the oil temperature, etc... It's a reasonable theory.

The stock cams are considerably softer than the aftermarket variants, which are also much more resistant to wiping. So there's that.

You can try other strategies like enlarging the orifice that controls the oil flow to the shower system and experiment that way if you're wanting to expand the experiment with additional oiling- the 2ZZ sits more upright in the Lotus. Perhaps, there's a straw leaning against the camel's back there too...

As I've said before, the incidence of failure is far less on race cars than comparatively babied street cars...


-Phil
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post #48 of 121 (permalink) Old 02-23-2017, 10:16 AM
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Originally Posted by Familyman951 View Post
If babied cars are seeing more wiping than track cars..... which I have heard several times - Is it possible that the wiping is occuring during low RPM use ??? - maybe the slipper is "bouncing" on the large camshaft because the slipper is not "engaged" and the spring is allowing the slipper plate to bounce on and off the large cam during low rpm use ????
If that was what was going on, I'd fully expect the camshaft to grenade itself when the high cam is engaged. When it is just "along for the ride", it is both at a lower rpm and hugely reduced force. Being babied adds to Phil's temperature argument since the temps are even lower.

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post #49 of 121 (permalink) Old 02-23-2017, 10:30 AM
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My point was that at high rpm the slipper is locked in and will maintain steady contact with the cam - at low rpm the slipper is allowed to "float" and the spring could allow "bouncing" on the large cam. Many of the wiped cams also show an "Impact" wear pattern in addition to the top of the cam getting wiped out. Again, I'm just speculating.



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Originally Posted by cyow5 View Post
If that was what was going on, I'd fully expect the camshaft to grenade itself when the high cam is engaged. When it is just "along for the ride", it is both at a lower rpm and hugely reduced force. Being babied adds to Phil's temperature argument since the temps are even lower.
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post #50 of 121 (permalink) Old 02-23-2017, 10:43 AM
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Originally Posted by Familyman951 View Post
My point was that at high rpm the slipper is locked in and will maintain steady contact with the cam - at low rpm the slipper is allowed to "float" and the spring could allow "bouncing" on the large cam. Many of the wiped cams also show an "Impact" wear pattern in addition to the top of the cam getting wiped out. Again, I'm just speculating.
Yeah, I know what you are saying, I just would be surprised if that's the primary failure cause. There is a smaller spring inside the VVT rocker that (in theory) keeps the high cam in contact. Since that spring is small (but also much less inertial) then it could be a perfect storm where there is a low rpm that gets a unique case of valve float. I wouldn't bet on that though.
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post #51 of 121 (permalink) Old 02-23-2017, 10:53 AM
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Agreed - it is possible, but a reach. Could changing the lash change the vibrational resonance of that small spring and eliminate the "mini float" (if it exists) ???

Sorry, the mechanical engineer in me is coming out. I've been suppressing that guy for the last 20 years.
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post #52 of 121 (permalink) Old 02-23-2017, 11:05 AM
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Originally Posted by Familyman951 View Post
Agreed - it is possible, but a reach. Could changing the lash change the vibrational resonance of that small spring and eliminate the "mini float" (if it exists) ???

Sorry, the mechanical engineer in me is coming out. I've been suppressing that guy for the last 20 years.
The vibration frequency would be sqrt(k/m) where k is the spring stiffness and m is the mass of part of the spring and that vertical plunger thingy. You'd want to move the frequency up past 6k rpm, so you'd need to stiffen the spring or reduce the plunger mass. Lash could change the severity but not really the frequency unless the lash is noticeably changing the stiffness of that spring.

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post #53 of 121 (permalink) Old 02-23-2017, 12:05 PM Thread Starter
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I got the shims measured. Kind of a PITA compared to the shims in my motorcycle engine. But I cobbled together a rig to measure it up with an optical table, mag base, some optical jig pieces, and a nice little dial indicator.

Quote:
Originally Posted by turbophil View Post
TSB or not, measuring lash between the lobe and the rocker isn't a good way to do it as you're only getting a reference from the tallest valve...

I've written in detail about the oil temperature, etc... It's a reasonable theory.

The stock cams are considerably softer than the aftermarket variants, which are also much more resistant to wiping. So there's that.

You can try other strategies like enlarging the orifice that controls the oil flow to the shower system and experiment that way if you're wanting to expand the experiment with additional oiling- the 2ZZ sits more upright in the Lotus. Perhaps, there's a straw leaning against the camel's back there too...

As I've said before, the incidence of failure is far less on race cars than comparatively babied street cars...

-Phil
Well the proper procedure (per Toyota) is to first make sure there is no tallest valve. You are meant to balance out the clearance on the rockers first, and then check the lash between the cam and the rocker. I am sure you have seen it but I attached what I am referencing for clarity.

I suppose just measuring the lash at the rocker and valve tip from the get go accomplishes the same thing in one step.

I know the aftermarket cams are harder but does that not just move the wear point to the slipper pads? Also, I do not want to re-tune the car for a cam swap.
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post #54 of 121 (permalink) Old 02-23-2017, 03:37 PM
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Quote:
Originally Posted by 111Joe View Post

I suppose just measuring the lash at the rocker and valve tip from the get go accomplishes the same thing in one step.

I know the aftermarket cams are harder but does that not just move the wear point to the slipper pads? Also, I do not want to re-tune the car for a cam swap.
Correct. One step done right.

Re the cams. Not in my experience.

-Phil


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post #55 of 121 (permalink) Old 02-25-2017, 10:11 PM
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I found two high cam lobs wiped with the same pattern familyman shares, one of the rockers was broken off on the high cam side of the rocker. The broken piece trapped in the valley, and the valve shim got trapped in the allen head depression of that big plug!

Both slippers are severely worn with a 'deep' groove across the face of the slipper.

The exhaust side looks good except for one lobe on the roller side that has a scratch in line with one side of the roller.

I'm wondering how many would check the valves, springs, and more at this point? 23K miles...

Last edited by gbrecke; 02-26-2017 at 10:01 PM. Reason: On close inspection I see the lobes are very similar, this seen after the removal of the cam and studying it in better light.
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post #56 of 121 (permalink) Old 02-25-2017, 11:53 PM
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Originally Posted by cyow5 View Post
The vibration frequency would be sqrt(k/m) where k is the spring stiffness and m is the mass of part of the spring and that vertical plunger thingy. You'd want to move the frequency up past 6k rpm, so you'd need to stiffen the spring or reduce the plunger mass. Lash could change the severity but not really the frequency unless the lash is noticeably changing the stiffness of that spring.
Doesn't cam rotate at half the RPM the crank does? ...then past 3k for the frequency calculations...

Whoever said that island life is great was never committed to Alcatraz...
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post #57 of 121 (permalink) Old 02-26-2017, 12:02 AM
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Originally Posted by Familyman951 View Post
My point was that at high rpm the slipper is locked in and will maintain steady contact with the cam - at low rpm the slipper is allowed to "float" and the spring could allow "bouncing" on the large cam. Many of the wiped cams also show an "Impact" wear pattern in addition to the top of the cam getting wiped out. Again, I'm just speculating.
Isn't the so-called "impact" damage right at the start of the "ramp" of the cam? Then that would be just plain load wear due to inertia and spring load, where the rest of the lobe just has spring load wear. If your so-called "impact" damage is on the back side of the lobe, then I would tend to agree that that is impact damage.

Whoever said that island life is great was never committed to Alcatraz...
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post #58 of 121 (permalink) Old 02-26-2017, 10:48 AM
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I believe the impact marks are in the "back side" of the cam - when it is closing the valve.
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post #59 of 121 (permalink) Old 02-26-2017, 09:51 PM
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I haven't checked my cam yet either... What happens if a bad cam is left in? Is it just a loss of power or will it lead to more?
Expect Broken Rocker(s) and possibly a vertical mark across the cam after the top of the lobe that looks like it was hammered on.. well at least that's what happened to mine...
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post #60 of 121 (permalink) Old 02-26-2017, 10:11 PM
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My lobes are identical.

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Originally Posted by Familyman951 View Post
I believe the impact marks are in the "back side" of the cam - when it is closing the valve.
It's almost like the valve was stuck in the guide, and the slipper lost contact with the lobe, and then the valve slapped the rocker back into the cam with a hammer like blow. That vertical line across the face of the cam (on the back side) looks hammered in. Was that what happened my rocker? Hammered till it broke?
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