Disaster....
- Thread starter Gerard van Santen
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Yellow Rose
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- 22 November 2001
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Valve Cover Damage
I am not so sure - certainly can be wrong - that crankcase overpressure was the cause of the valve cover failure. For that much force to blast out a not-so-small piece of metal, the internal pressure would intuitively been great enough to cause a hose to come lose first, thus allowing the crankcase pressure to bleed down. Could it have been a mechanical event that not only allowed the valve head to let go, but also something in the valve train slapped against the inside if the valve cover to break it?
I am not so sure - certainly can be wrong - that crankcase overpressure was the cause of the valve cover failure. For that much force to blast out a not-so-small piece of metal, the internal pressure would intuitively been great enough to cause a hose to come lose first, thus allowing the crankcase pressure to bleed down. Could it have been a mechanical event that not only allowed the valve head to let go, but also something in the valve train slapped against the inside if the valve cover to break it?
Re: Valve Cover Damage
After thinking about this for the day, I agree—it seems overpressure would rupture the breather hose first, unless magnesium is not all that strong? When the valve broke, there might be enough clearance for the valve stem to be shot into the cover at a pretty high velocity when the valve spring sprung. It would have to move the rocker arm out of the way (this is a not a physical certainty in my mind), and it would have to have been an intake valve—seems there would be visible impact damage to the cover too. I guess we’ll all know the answer to this mystery pretty soon. I’m scared to see the next pictures.
BTW: if the number "02" is stamped on the bottom of the broken valve, then it's an intake (which would be surprising in this case). At least that's what's stamped on the bottom of the valves that serve as paper weights on my desk.
DanO
AndyVecsey said:
After thinking about this for the day, I agree—it seems overpressure would rupture the breather hose first, unless magnesium is not all that strong? When the valve broke, there might be enough clearance for the valve stem to be shot into the cover at a pretty high velocity when the valve spring sprung. It would have to move the rocker arm out of the way (this is a not a physical certainty in my mind), and it would have to have been an intake valve—seems there would be visible impact damage to the cover too. I guess we’ll all know the answer to this mystery pretty soon. I’m scared to see the next pictures.
BTW: if the number "02" is stamped on the bottom of the broken valve, then it's an intake (which would be surprising in this case). At least that's what's stamped on the bottom of the valves that serve as paper weights on my desk.
DanO
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I had a valve contact a piston with enough force to knock a section out of the cam shaft, that section caused some major damage to the aluminum vavle cover that was on that motor.
If that cover had been a cast piece it would have shattered as well.
Len
If that cover had been a cast piece it would have shattered as well.
Len
What is to be learned here:
Replace the damper as a preventitive measure? (Does Woodwork care?)
Pull the head and inspect any/every event in which the timing belt slips more than 3 teeth (more? less?)
I do like the idea of making a screen for the CSTC. Is it practible? What type of materials would be used and how fabricated? I'm guessing making a little tray that fits inside the hole and screw it in, but then I'd worried about a screw coming loose and dropping down into a piston.
Gerhard, I think you should buy some lottery tickets...you should some serious luck coming your way to offset this incredible and awful chain of events.
I'm also guessing that it is likely that your piston walls are not happy either. Gawd, what a mess.
Replace the damper as a preventitive measure? (Does Woodwork care?)
Pull the head and inspect any/every event in which the timing belt slips more than 3 teeth (more? less?)
I do like the idea of making a screen for the CSTC. Is it practible? What type of materials would be used and how fabricated? I'm guessing making a little tray that fits inside the hole and screw it in, but then I'd worried about a screw coming loose and dropping down into a piston.
Gerhard, I think you should buy some lottery tickets...you should some serious luck coming your way to offset this incredible and awful chain of events.
I'm also guessing that it is likely that your piston walls are not happy either. Gawd, what a mess.
Factory-X 3.5L engine anybody?
Hmm.
Looks like the timing belt skip did damage the valve. Not enough to fail the compression test but I'm guessing it broke shortly after the engine was started, hence the rough idle you were already loosing compression. It was either completely or partially broken, once broken on the compression stroke most of the air was being pushed out the intake port probably putting pressure on the SC. Eventually a compression stroke blows the valve head back up into the intake manifold and here we are. I doubt the valve went into the SC, but maybe just the air pushing back against it damaged it? Don't know the answer to that part. Anyways once the SC seized the crankcase breather isn't large enough to equalized that much pressure and blew the VC off.
Looks like the timing belt skip did damage the valve. Not enough to fail the compression test but I'm guessing it broke shortly after the engine was started, hence the rough idle you were already loosing compression. It was either completely or partially broken, once broken on the compression stroke most of the air was being pushed out the intake port probably putting pressure on the SC. Eventually a compression stroke blows the valve head back up into the intake manifold and here we are. I doubt the valve went into the SC, but maybe just the air pushing back against it damaged it? Don't know the answer to that part. Anyways once the SC seized the crankcase breather isn't large enough to equalized that much pressure and blew the VC off.
Fellow Primers,
Everybody thanks for your support and sympathy. At this moment I have to think over about a lot of things. This week I'll have a time out.
I'll keep you all informed.
Thanks,
Gerard
Everybody thanks for your support and sympathy. At this moment I have to think over about a lot of things. This week I'll have a time out.
I'll keep you all informed.
Thanks,
Gerard
satan_srv said:
I think you're right.
There is another thing to mention. As I said before, the car was incredible fast just before the supercharger seized. I think I know what was the reason.
Just guessing but I think only minutes before the SC seized, the valve was pushed into the intake manifold and closed the waste gate of the SC. I found the broken valve laying on the waste gate opening. If this truelly happened, a lot of pressure was building up in the manifold with the result I mentioned. An incredible fast car.
Isn't it a strange idea that the moment my NSX was as fast as never before only five cylinders were running
satan_srv said:
Isn't it possible that parts of the valve stem were pushed into the supercharger? The pulley can't be moved for even a fraction of an inch.
Gerard, you will find metal in the Supercharger, Either the bearing metal form the super charger (doubtful) or Metal from the valve material.. That is why you see the gouges all over the blades of the supercharger. after awhile a piece was larger enough the lodge between the blades of the supercharger, causing it to finally seize.. You can take the metal you find in the Super charger and have it analized if you really want to know where it's from.. I would bet on valve material. The damage was done when the timing belt seized most likely, during reversion, as I have been told, the valve material can work it's way upstream to the supercharger... If your blades on the supercharger were free of damage, and the blades had been sucked up into the housing on the pulley end of the supercharger, it could have been a bearing failure or incorrect lashing of the supercharger when it was assembled. However, everything is pointing to the timing belt jumping and damaging something, valves or otherwise, still giving your car the ability to run, all the while metal was dancing around inside your supercharger until it was able to lodge it and make it seize....
Just my opinion, and best guess.
Len
Just my opinion, and best guess.
Len
I've been following this thread and relay sympathy to you Gerard. Engines and the way they work are not my thing.
I think I'm getting the general impression that it was timing and or valve problem. I am contemplating getting a CTSC and am curious if this problem would have happened regardless of the SC?
In other words, is the reliability of the SC in question here or was it most likely damaged as a result of other issues?
(Not to hijack the thread in another direction, but) Is the reliability of the CTSC as good as comptech's site says? I only found one known CTSC failure in my 'Search.'
I think I'm getting the general impression that it was timing and or valve problem. I am contemplating getting a CTSC and am curious if this problem would have happened regardless of the SC?
In other words, is the reliability of the SC in question here or was it most likely damaged as a result of other issues?
(Not to hijack the thread in another direction, but) Is the reliability of the CTSC as good as comptech's site says? I only found one known CTSC failure in my 'Search.'
Bilulan said:
Hi Bilulan,
I don't think you have to worry about the SC. What happened to me was a chain of problems that started with a balancer that broke out of my crankpulley and pushed parts of the timing belt cover between the timing belt and the push pulley. The results are known.
The last 11/2 year I have had no problems with the engine in combination with the supercharger what so ever. Last year I did a complete NSX Trophy season (vijf race weekends with ten races and all the training). I drove 17k miles during that period. Most of them were high speed miles (races and Autobahn). The only mechanical thing I had to do was replacing my clutch last februari with an Exedy twin plate.
Hi Gerard,
I am very very sorry to read about this great misfortune of you and your car. I hope very much that the damage will not be too much and that repairs will not take too long. Also hope you already have all the parts you will need to fix it and make it as new again.
If you need any help (as far as I'm able to give) just give me a call.
I am very very sorry to read about this great misfortune of you and your car. I hope very much that the damage will not be too much and that repairs will not take too long. Also hope you already have all the parts you will need to fix it and make it as new again.
If you need any help (as far as I'm able to give) just give me a call.
len3.8 said:
I just looked at the pics again...now I see all the marks on the SC...perhaps the flying valve did get into the charger then...
But to your other points the valve didn't actually "break" until he after he started the car again...as he passed the compression test. Which is quite unfortunate as the whole thing could have been averted if the damaged valve or two were damaged enough to lose compression.
As for the pulley itself, do you think the SC contributed to the deterioration of the crank pulley?
I haven't seen a Comptech install but I'm assuming it's driven off the crank pulley. The SC adds a lot more drag to the pulley and could have caused some premature wear of the rubber internals.
Has your car had periods where it has sat for a long time? The rubber cracking/falling apart like that shouldn't usually happen on an often used engine.
I haven't seen a Comptech install but I'm assuming it's driven off the crank pulley. The SC adds a lot more drag to the pulley and could have caused some premature wear of the rubber internals.
Has your car had periods where it has sat for a long time? The rubber cracking/falling apart like that shouldn't usually happen on an often used engine.
satan_srv said:
I don't think so.
satan_srv said:
The rubber balancer sits fixed in the pulley and doesn't make contact with the crankshaft. I don't think the extra drag from the SC causes extra wear of the rubber. I have more concerns about the Exedy clutch, although I can not proof it. This clutch comes in with a such a force that the balancer has more to absorb than with a more smoother clutch (I think). It works like a torque absorber and I can tell you, a lot of torque has to be absorbed.
satan_srv said:
I have this car for five years now and I do more than 15k miles per year. Perhaps it is a combination of aging and the clutch and the SC.
Yikes! I’ve been almost totally out of circulation for a couple weeks so I’m just now catching up. Sorry about the misfortune Gerard. You certainly have an unusual case here.
Besides the fact that reversion seems to have blown an entire valve head back up through the intake, something blew a huge chunk out of one valve cover. Have you looked inside the cover and on that piece for a sign of something hitting it? I suspect that once the valve broke that cylinder still fired and the pressure of combustion was so great and rapid that it came up through the valve guide and blew the side out before it could escape through vents etc. It may even be that as the piston came up on a combustion stroke it forced air/fuel mixture up through the guide into the cover then ignited it with the sparkplug. Boom! Pretty wild. But that assumes the valve stem was not still in the guide. Have you pulled it down far enough to examine that?
As for the valve being broken before it felt so strong, I don’t it. I don’t think the CTSC is bleeding off any pressure normally as it is sized and “geared” for early boost then pretty much runs out of steam on it’s own at high RPM. I also doubt if the valve was partially broken for awhile. They are very hard and therefore brittle, so when that delicate stem cracks it just breaks. It may have been bent previously the self-straightened somewhat (as it slams shut each time), but you should still have easily detected that in a compression check. Of course being bent and straightened would probably weaken it so I guess that amounts to the same as being partially broken.
So why did it feel faster? Perhaps in part because you hadn’t driven it for awhile (that always fools me) but I suspect you may not have had the valve timing exactly right when you put it back together. It may also be that you reset all the long-term trims in the ECU (disconnected the battery), so ignition timing and fuel were suddenly different. If there was some global timing retard or a change to the A/F for closed loop operation (both very likely to at least some degree) then it might well be quicker for a bit. For example, the CTSC tends to be somewhat fat (rich) in the lower range and lean up top, so the ECU may be adjusting. Reset the trims and things are suddenly different, maybe better maybe worse. (We don’t really know if trims “learned” in closed loop are applied to open-loop, but it seems logical that they would.)
Back to the valve again. Did you say the guide as intact? If the valve had been bent for awhile you may see some wear from it inside the guide.
Well, those are just my rambling first thoughts. I’m anxious to hear what you find. BTW, check to be sure that the valve seat had not come loose and dropped down, causing the valve to fail.
Besides the fact that reversion seems to have blown an entire valve head back up through the intake, something blew a huge chunk out of one valve cover. Have you looked inside the cover and on that piece for a sign of something hitting it? I suspect that once the valve broke that cylinder still fired and the pressure of combustion was so great and rapid that it came up through the valve guide and blew the side out before it could escape through vents etc. It may even be that as the piston came up on a combustion stroke it forced air/fuel mixture up through the guide into the cover then ignited it with the sparkplug. Boom! Pretty wild. But that assumes the valve stem was not still in the guide. Have you pulled it down far enough to examine that?
As for the valve being broken before it felt so strong, I don’t it. I don’t think the CTSC is bleeding off any pressure normally as it is sized and “geared” for early boost then pretty much runs out of steam on it’s own at high RPM. I also doubt if the valve was partially broken for awhile. They are very hard and therefore brittle, so when that delicate stem cracks it just breaks. It may have been bent previously the self-straightened somewhat (as it slams shut each time), but you should still have easily detected that in a compression check. Of course being bent and straightened would probably weaken it so I guess that amounts to the same as being partially broken.
So why did it feel faster? Perhaps in part because you hadn’t driven it for awhile (that always fools me) but I suspect you may not have had the valve timing exactly right when you put it back together. It may also be that you reset all the long-term trims in the ECU (disconnected the battery), so ignition timing and fuel were suddenly different. If there was some global timing retard or a change to the A/F for closed loop operation (both very likely to at least some degree) then it might well be quicker for a bit. For example, the CTSC tends to be somewhat fat (rich) in the lower range and lean up top, so the ECU may be adjusting. Reset the trims and things are suddenly different, maybe better maybe worse. (We don’t really know if trims “learned” in closed loop are applied to open-loop, but it seems logical that they would.)
Back to the valve again. Did you say the guide as intact? If the valve had been bent for awhile you may see some wear from it inside the guide.
Well, those are just my rambling first thoughts. I’m anxious to hear what you find. BTW, check to be sure that the valve seat had not come loose and dropped down, causing the valve to fail.
sjs said:
Yes I think so. This week I don't have the motivation to look after the engine
Maybe this weekend.
I will keep you informed and make photos during the process.
Thank you all for the support.
Hello Gerard !
Saw you in Assen, Japanese Car Festival last weekend and you told me about what happened to your supercharged NSX ... I've been following this topic on Prime and I'll continue in the future. Hope everything works out and hope to see and meet all Dutch NSX drivers again soon. Greetings from Belgium ! www.nsx.be
Saw you in Assen, Japanese Car Festival last weekend and you told me about what happened to your supercharged NSX
... I've been following this topic on Prime and I'll continue in the future. Hope everything works out and hope to see and meet all Dutch NSX drivers again soon. Greetings from Belgium ! www.nsx.be
BlueEyes' NSX said:Hello Gerard !
Saw you in Assen, Japanese Car Festival last weekend and you told me about what happened to your supercharged NSX
Thanks Eric,
I hope I have my NSX repaired soon. Although I think soon won't be in the near future
Today I tried to open the supercharger, but that didn't work out the way I wanted to. I couldn't get the gears off the supercharger. Does anyone know how to do it?
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Gerard
Can't help you on disassembly, but I believe the SC is made by Whipple. You might need that small clue...
I'm also going to wager a guess that the lash on the screws is very close tolerance and that they might be ruined already, but doesn't hurt to disassemble and smooth out the imperfections. They are either going to spin or not and it is unlikely they will disintegrate and fall into your engine (but then again, what has happened to you...)
You can buy just the unit for a USD$2000 and used for less. There are several on ebay now.
Drew
And still nobody has commented on how to make a "catch screen/basket" to prevent this from happening. I must be on the global "ignore" list...
I'm about to install my CTSC and thinking about making a "basket" that fits down into to intake, but I don't know what type of materials and such, suggestions would be welcome.
Can't help you on disassembly, but I believe the SC is made by Whipple. You might need that small clue...
I'm also going to wager a guess that the lash on the screws is very close tolerance and that they might be ruined already, but doesn't hurt to disassemble and smooth out the imperfections. They are either going to spin or not and it is unlikely they will disintegrate and fall into your engine (but then again, what has happened to you...)
You can buy just the unit for a USD$2000 and used for less. There are several on ebay now.
Drew
And still nobody has commented on how to make a "catch screen/basket" to prevent this from happening. I must be on the global "ignore" list...
I'm about to install my CTSC and thinking about making a "basket" that fits down into to intake, but I don't know what type of materials and such, suggestions would be welcome.
drew said:
I don't think it would be a wise idea to place a "screen" or "baskett" in the flow stream of a pressurized air/fuel mixture. It is much more likely that, over time, a piece of the screen or basket would end up ruining your engine rather than protect your supercharger from a stray valve head.
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