Our theory on stock rod failure...
#41
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Originally Posted by georgec
That amount of fluid would tend to bend a rod not break a rod imo, I still believe that rod failure is due to the big end bearing spinning in most rod failures.
Do you have a pic of the failed rods, that would tell the story quickly.
George
Do you have a pic of the failed rods, that would tell the story quickly.
George
Originally Posted by thawk408
Did either one of these cars have cams? Or has the head ever been off the car before the rod went?
Originally Posted by taurran
MRC - It's a good though, but wouldn't this realistically bring you back to step one. What I mean by this is that by your theory, only one element in the string of circumstances must be present for failure to take place. For instance: Maxed out injectors > Lean Condition > Detonation > High Cylinder Pressure > Headlift > Liquid in Combustion Chamber > Increased Stress on Connecting Rods > Bent Rod. I'm just saying that while this theory may be entirely valid, it doesn't necessarily help determine the root cause of the failure as it could be a number of problems and the resulting chain of events.
Originally Posted by taurran
I also think that Sentry brought up a good point in questioning if either of these cars had displayed signs of headlift previous to failure. While its definitely possible that this was a sudden case of headlift due to other contributing factors, its hard to place blame when there is no physical evidence other than a bent rod.
Regardless of the outcome, it is good to see that you're actually willing to share your findings with the community. Thank you for that.
Regardless of the outcome, it is good to see that you're actually willing to share your findings with the community. Thank you for that.
Originally Posted by Cannysage
I'm running 14.5 A/F, but it's NA. Would it still be considered dangerous? I'm going with UTEC, but can't fork out the $ for the part and tuning right at this moment.
Originally Posted by DXB350Z
nice write up...good to see someone concerned
however...what would be an approperiate precaution to prevent this even of liquid "sneaking" into the combustion chamber? any solution for nonbuilt engines running ~8psi of boost?
however...what would be an approperiate precaution to prevent this even of liquid "sneaking" into the combustion chamber? any solution for nonbuilt engines running ~8psi of boost?
The below picture is a picture of what a spun rod bearing looks like..This was NOT from these two motors..
Last edited by Julian@MRC; 06-30-2006 at 08:25 PM.
#42
This motor seems to be a tough nut to crack.
Many people say the stock block isn't strong, can't reliably be tuned at 400whp. SOme blow under that, so many things seem to happen but there is no consistency and just a bunch of theories.
I start off by saying I have no clue what causes or prevents it.
I however have 28,600 something Forced Inducted miles at 440whp or more. I went with the APS TT in Jan05. I had 28k when I went FI. I have 56,6xx something miles. I drive it every single day. Why? Because its too much fun and you only live once. Im religious on maintenance and where I get my gas from. I think i have signs of headlift too. Or just really, really, really bad air in the system. Happened this morning. Getting on the freeway. Coolant temp surged then I applied moderate throttle temp falls, car runs normal. Anyhow, I think these are all theories and if all motors are built the same then there is no reason how some of us experience so many miles with no failure (knocks wood). I suspect and some others have, that many engines might have better tolerances and thats the only thing that can be contributed.
Many people say the stock block isn't strong, can't reliably be tuned at 400whp. SOme blow under that, so many things seem to happen but there is no consistency and just a bunch of theories.
I start off by saying I have no clue what causes or prevents it.
I however have 28,600 something Forced Inducted miles at 440whp or more. I went with the APS TT in Jan05. I had 28k when I went FI. I have 56,6xx something miles. I drive it every single day. Why? Because its too much fun and you only live once. Im religious on maintenance and where I get my gas from. I think i have signs of headlift too. Or just really, really, really bad air in the system. Happened this morning. Getting on the freeway. Coolant temp surged then I applied moderate throttle temp falls, car runs normal. Anyhow, I think these are all theories and if all motors are built the same then there is no reason how some of us experience so many miles with no failure (knocks wood). I suspect and some others have, that many engines might have better tolerances and thats the only thing that can be contributed.
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Originally Posted by overZealous1
how do those pistons look compared to the rest? they appear to be pretty clean, but if they match the other pistons, then i highly doubt there was water making it back into the cylinders.
on my first motor, when i pulled it apart, i had 5 bent rods and 4 pistons with broken ring lands. there was no indication of water making it back into the cylinder, especially enough to hydrolock like that. you would also hear a cylinder missing right before it happened, as the water would come in slow at first, then more and more.
the only possible way i could see this happening is if when the cylinder next to the problem cylinder lifted the head so far it pushed coolant into the cylinder next to it. if that was the case, the problem cylinder would then push water back into the other cylinder, and ultimately it should happen to the entire motor, not just end cylinders.
again, this is just my opinion, and i have seen some really weird stuff happen before. but i feel there may have been a split second timing glitch as the cylinders were right next to eachother in firing order.
on my first motor, when i pulled it apart, i had 5 bent rods and 4 pistons with broken ring lands. there was no indication of water making it back into the cylinder, especially enough to hydrolock like that. you would also hear a cylinder missing right before it happened, as the water would come in slow at first, then more and more.
the only possible way i could see this happening is if when the cylinder next to the problem cylinder lifted the head so far it pushed coolant into the cylinder next to it. if that was the case, the problem cylinder would then push water back into the other cylinder, and ultimately it should happen to the entire motor, not just end cylinders.
again, this is just my opinion, and i have seen some really weird stuff happen before. but i feel there may have been a split second timing glitch as the cylinders were right next to eachother in firing order.
The stock head studs do not offer superior clamping force over the L17's or L19's and are only TQ'd to 65ft lbs from the factory. It may have been an incident where the two motors were just weak motors. Like I said, after the dozens of TT installs we have done this was the first failure we have ever seen..
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Well, in our case, we have built many stock internals engines all in the 400-450. In my car I ran a year on 525hp stock internals with no problem. Now we HAVE had Rc injector stock before (actually 3 injectors). It would be intresting to know timming were these engines runnig, what engine managent?, what fuel? and what exhaust they had.
#45
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Originally Posted by taurran
Are you serious? Saying that is like saying you won't fly cause you read about a plane crash. I seriously think I can count the number of blown motors on stock Vortech kits on my fingers. In all reality, the actual number of blown FI stock motors is relatively small.
I'm a family man that can afford the car "as is" and could 'Splurge' on an FI kit for around $5K, but I simply cannot afford $10-12K without being out of my comfort zone. My Z is my Daily Driver (52K in 24 Months) and between the possiblity of being without it for a couple of months for repairs and the said cost of repairs I just can't chance it that much. If it was a 5-10% chance of the motor going out then I might... Its just a bit too risky financially for me.
I have already modded out one car that was and still is my wifes daily driver and doubled its horsepower. I could have afforded to replace the motor in it.. looking back, I got lucky.
Now if a Simple HG and Stud Kit will dimish the risk considerably it might be worth it..
Last edited by sq40; 05-31-2006 at 08:11 AM.
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Were either of these motors revups? I'm curious if there has ever been a case of a blown revup motor with FI. I know revups have stronger rod bolts but maybe they have tighter tolerances as well.
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Originally Posted by Nismo350ZRT
Were either of these motors revups? I'm curious if there has ever been a case of a blown revup motor with FI. I know revups have stronger rod bolts but maybe they have tighter tolerances as well.
#50
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Originally Posted by Nismo350ZRT
How aggressive was his tune? Any idea why it blew?
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Originally Posted by TK2005
Cuz Joke is a maniac on the streets, much like Gman. Joke was looking for more power the day after he got it back with the stock motor. I believe you can find Joke flying around the streets of Houston on his bike when he isn't flying the Z. Joke was tuned by SGP with E-manage Blue (I beleive) to the tune of 421rwhp (I believe).
Here is Jokestrap's blown thread.
https://my350z.com/forum/forced-induction/156949-blown-05-w-tt-going-for-550whp-now.html
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Originally Posted by TK2005
Cuz Joke is a maniac on the streets, much like Gman. Joke was looking for more power the day after he got it back with the stock motor. I believe you can find Joke flying around the streets of Houston on his bike when he isn't flying the Z. Joke was tuned by SGP with E-manage Blue (I beleive) to the tune of 421rwhp (I believe).
Last edited by paranormal; 05-31-2006 at 09:00 AM.
#57
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Originally Posted by doug
and the benefit of that would be? i am curious... do you N/A Owners come to the F/I forum to tell F/I owners that their cars are going to blow up?
I don't pretend to know more than what I know. I would never come in and tell F/I owners that their car is going to blow. I am sure most F/I guys on stock blocks (and there are quite a few) have a pretty reliable setup and like Taurran have done their homework and understand the risks involved. Am I talking to them? No.
But that doesn't mean I should not do my part to inform the misinformed that installing F/I is risky business. Just because my car does not have F/I does not mean I should not be allowed to post good (truthful) information in the F/I forum. My intention was never to make it sound like F/I on a stock block is UN-reliable.
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a built motor isn't all that much more $$ when you consider cost of install at a premier shop. for example SGP quoted me a price of 1800 for TN kit install alone but that install price pretty much stays the same if you throw in a built block so the block only costs 4 to 5k installed as opposed to 6 to 7 doing the turbo then later building the block.
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I think it unlikely that a cylinder could hydolock at high rpm from anything short of ingesting water through the intake tract.
A stuck injector won't do it as the fuel is ejected from the cylinder every other revolution. I've had a 380cc injector stick open on my 4 cylinder 1300cc turbo bike (325cc/cylinder) and even at idle it just resulted in a lot of white smoke.
If the head gasket is leaking it is from extreme pressure within the cylinder which results in combustion gases being forced into the water jacket under boost. While water could leak into the cylinder at rest I can't imagine it happening with the engine running at high rpm.
A stuck injector won't do it as the fuel is ejected from the cylinder every other revolution. I've had a 380cc injector stick open on my 4 cylinder 1300cc turbo bike (325cc/cylinder) and even at idle it just resulted in a lot of white smoke.
If the head gasket is leaking it is from extreme pressure within the cylinder which results in combustion gases being forced into the water jacket under boost. While water could leak into the cylinder at rest I can't imagine it happening with the engine running at high rpm.
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Originally Posted by Wired 24/7
Thank you for asking.
I don't pretend to know more than what I know. I would never come in and tell F/I owners that their car is going to blow. I am sure most F/I guys on stock blocks (and there are quite a few) have a pretty reliable setup and like Taurran have done their homework and understand the risks involved. Am I talking to them? No.
But that doesn't mean I should not do my part to inform the misinformed that installing F/I is risky business. Just because my car does not have F/I does not mean I should not be allowed to post good (truthful) information in the F/I forum. My intention was never to make it sound like F/I on a stock block is UN-reliable.
I don't pretend to know more than what I know. I would never come in and tell F/I owners that their car is going to blow. I am sure most F/I guys on stock blocks (and there are quite a few) have a pretty reliable setup and like Taurran have done their homework and understand the risks involved. Am I talking to them? No.
But that doesn't mean I should not do my part to inform the misinformed that installing F/I is risky business. Just because my car does not have F/I does not mean I should not be allowed to post good (truthful) information in the F/I forum. My intention was never to make it sound like F/I on a stock block is UN-reliable.