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What is the most common cause for NSX engine failure and what happened to this one?
- Thread starter acuhon
- Start date
Perfect as in like new, meaning it was replaced after the damage?
Looks more like a dropped valve than a timing belt failure. The stock valve retainers have failed in a few engines that were run extremely hard
The timing belt was old but had no visible cracks. I'm not sure if the belt skipped causing the damage? I wasn't able to rotate the engine to #1 TDC to confirm timing.
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Retainers looked good.
Possibly. I guess debris from the middle cyl in the photo got up in the intake manifold and then went into the lower chamber in the photo. From all the metal that must have been flying around, I'm surprised that only one other chamber showed damage.
NSX engine failures are so rare that it's hard to suggest a "most common" cause. The engines are very well designed and most high mileage NSXs are running strong. A friend of mine has put about 320,000 miles on his NSX and when he had the compression and oil pressures checked recently, the tech said the engine still seemed to be in as new condition.
Whatever happened to your engine is not normal but that makes finding the cause all the more interesting. What do the valve guides look like? Broken intake valves remind me of this post by Kaz, one of the engineers who designed the NSX: http://nsxcb.co.uk/entry.php?72-Potential-C32B-Engine-failure-%96-Intake-Valve-guide.
Whatever happened to your engine is not normal but that makes finding the cause all the more interesting. What do the valve guides look like? Broken intake valves remind me of this post by Kaz, one of the engineers who designed the NSX: http://nsxcb.co.uk/entry.php?72-Potential-C32B-Engine-failure-%96-Intake-Valve-guide.
With the way the damage is isolated to that one clinder, it makes you wonder if someone dropped something metal into the one cylinder during a spark plug change. It happens somewhat frequently in the 3000GT world. People unknowingly drop something (washer or bolt usually) into one of the cylinders, button the car back up, and start it. Ouch.
Are the plugs in the engine new?
Are the plugs in the engine new?
I'm only guessing but I would say the #1 cause of NSX engine failure is engine modification, including addition of superchargers and turbochargers, especially if tuning is not not done well. I would guess that number 2 would be oil starvation, during track events. Number 3 would be overheating due to improper coolant maintenance. Not to say any one of those issues caused the damage shown in the OP.
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Dropped a screw from one of the VVIS butterflys ?
I'm not qualified
I'm not qualified
you beat me to it
That's my guess too.
Probably over rev cause it. I know a nsx locally that had at least 2 engine failures. One of the engine with a valve hitting the piston and the other failure was putting a hole on the block. That nsx ecu has no rev limiter.
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Which ECU is that? I'm pretty sure the OEM computer has a fuel cut at 8,200 rpm.
def looks like the head of a valve has come off bounced around, smashed everything it can before exiting to the sump or out the exhaust... a dropped valve, or hi rev valve float meaning the valve and piston try to defy the laws of physics by trying to occupy the same place!
my Boss's Hart 420R has often suffered from this exact damage that was overrevving. if it's stock NSX it'll probably be too many revs!
with time and effort and a good welder, the head could be saved!
my Boss's Hart 420R has often suffered from this exact damage that was overrevving. if it's stock NSX it'll probably be too many revs!
with time and effort and a good welder, the head could be saved!
With the way the damage is isolated to that one clinder, it makes you wonder if someone dropped something metal into the one cylinder during a spark plug change. It happens somewhat frequently in the 3000GT world. People unknowingly drop something (washer or bolt usually) into one of the cylinders, button the car back up, and start it. Ouch.
Are the plugs in the engine new?
Spark plugs were old.
Agree with Britlude.
Something caused a valve to break off (maybe two of them) and it only takes a second or two to cause that kind of damage.
The ECU cuts off fuel at 8200 as jwmelvin says so the likely cause of overreving is downshifting at too high an rpm for the next gear down.
That can drive the engine well over the fuel shutoff rpm.
Is the cylinder wall damaged?
Got my fingers crossed the cylinder wall is okay.
The head repacment/repair is not too onerous but if the cylinder wall is damaged it may mean a new/used or rebuilt engine.
Is this C30 or C32? Perhaps cylinder damage, if any, is not so bad and if a C30 then you can bore and hone.
VVIS screws are all in place.Stock engine and ECU.1991
a little more history may help the nsxperts http://www.nsxprime.com/forum/showt...one-I-finally-got-one-93-Red-NSX-Thanks-Santa
But that link is about a '93 and the subject car is a '91?
My 93 NSX is doing just fine.
This in my #2 NSX 1991 project bought from a guy working on new NSX . He complained about tight tolerances on the new NSX. That's all I was able to get from him. He said that he drove the car and it just died. He also said that the timing belt is broken and had scoped all cylinders and there was no damage. I didn't believe that, but didn't expect this much damage. I knew that it was 50/50 that I'll need new engine.
lol that is called lazy research on my part:redface:.....so you are becoming a nsx hoarder :wink: nothing wrong with that.My only advice is to keep your eyes peeled for any and all recently wrecked nsx for a used motor.Also pm Shawn and Larry B if they have any leads.
Are the chambers and pistons on the other bank undamaged? How much was left of the missing piston?You can get the bad cyl resleeved and find a replacement head, or look for a replacement engine...Or do the "J" swap. http://www.nsxprime.com/forum/showt.../176807-The-quot-J-quot-Swap?highlight=J-swap
NSX hoarder ? You sound like my wife.:smile: I'm just pulling an engine from wrecked 91 NSX I bought two weeks ago not to far from Shawn.
When I asked if there was an engine I was told that there is nothing in the front and trunk is full of junk. I asked if they can lift the rear glass...:biggrin:
I would still like to know why the engine got so much damage.
