Our theory on stock rod failure...
05-31-2006, 08:55 PM
#101
i must say, i highly doubt that hydro-lock is the prob. it would not be an instant thing. it would happen slowly and that piston would look brand new on the top of it. i am gunna have to give it to less than normal strength on the rods based on what you are saying. rod bolts have nothing to do with a bent rod under compression. rod bolts only come into play for rpm, when the rod is trying to rip itself apart.
believe me, my motor was so bad with water loss, if hydrolocking was going to happen to anyone, it would have happened to me as my motor sounded worse than anyone elses.
believe me, my motor was so bad with water loss, if hydrolocking was going to happen to anyone, it would have happened to me as my motor sounded worse than anyone elses.
06-01-2006, 05:06 AM
#102
Registered User
iTrader: (7)
Join Date: Apr 2005
Location: Bradenton/Sarasota
Posts: 5,254
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by MRC Motorsports
It is actually the opposite..While the pistons are crap, the rods on these motors are pathetic when compared to a real high performance rod..
I also do not think the rod end bolts have anything to do with the failure considering the rods snapped and bent halfway up the rod at the thinnest portion of the rod.I have yet to see a rod bolt snap or contribute towards a VQ failure to date..
Pics....Stock rod VS Corillo "H" beam..The mother of all rods for the VQ motor..
I also do not think the rod end bolts have anything to do with the failure considering the rods snapped and bent halfway up the rod at the thinnest portion of the rod.I have yet to see a rod bolt snap or contribute towards a VQ failure to date..
Pics....Stock rod VS Corillo "H" beam..The mother of all rods for the VQ motor..
Give Clark at JWT a buzz about the rod bolt failures on Z's. Most of what he's seen has been attributable to high revving (7k+) a stock motor. While I know this increases the stress on the bolts multi-fold.......I have a tendency to think that an increased power level via forced induction will do the same thing.......this is all just my theory mind you. Of course, the ultimate test would be to yank out a stock drivetrain, cryo the whole shebang (pistons/rods) get some Hi-po rings, ARP rod bolts, and assemble it just to see what can be done. I know, I know, a PITA for basically not much......but to experiment and just see what exactly the limits could be...
as someone stated as well, optimal ignition timing tune. Maybe not optimal for power, but for fuel burn. This kind of makes me want to shy away from using 100 or so on the TN reflash simply because the ecu adds in quite a bit of timing for power with the higher octane. When stage 1.5 comes out, I'm going to take a good, hard look at the ignition timing and see what can be done to optimize it/how I can find that out haha.
06-01-2006, 06:31 AM
#103
Originally Posted by mchapman
But under the head lift condition the combustion gases are pushing outwards as they expand, resulting in the heads lifting when the pressure gets above a certain point. Doesnt the same expanding gas force any water away from the combustion chamber as the pressure tries to escape through the lifted head?
Or are you saying that its possible that when the gas is forced into the the water jacket some water could be pushed back into the combustion chamber as a result?
Did any of the blown motors have blown head gaskets inbetween the liners and the water jacket? Wouldnt this tell us if it was head lift as some of the head gasket material would be pushed away?
Or are you saying that its possible that when the gas is forced into the the water jacket some water could be pushed back into the combustion chamber as a result?
Did any of the blown motors have blown head gaskets inbetween the liners and the water jacket? Wouldnt this tell us if it was head lift as some of the head gasket material would be pushed away?
The way I understand it, as the gas from one cyl is pushed out, another cyl on intake stroke will vaccume water in when the head lifts. Correct?
06-01-2006, 06:40 AM
#104
So will a Simple Change out to Better rods and a better stud set decrease the likleyhood of engine failure significantly? If I read Right, a basic set of forged rods will run about $600 and Studs about $400.. Not counting install.
And the Pistons are not a likley point of failure?
How many hours of shop time would it take to change the rods and studs?
Sorry for the "Noobness" of my questions here..
And the Pistons are not a likley point of failure?
How many hours of shop time would it take to change the rods and studs?
Sorry for the "Noobness" of my questions here..
06-01-2006, 06:56 AM
#105
Former Sponsor
iTrader: (564)
Join Date: Feb 2003
Location: Long Island, New York
Posts: 19,266
Likes: 0
Received 5 Likes
on
5 Posts
my point was "just swapping rod bolts in" is not an easy job like "installing a boost controller" - it is a royal PIA, and given the time involved, and the fact that it is merely a bandaid, it's not worth it....either replace the rod (at which point, do pistons too), or, IMHO, it is not worth doing. The stock rods are not beefy at all, and as mentioned, are often a point of failure
06-01-2006, 06:56 AM
#106
Originally Posted by sq40
So will a Simple Change out to Better rods and a better stud set decrease the likleyhood of engine failure significantly? If I read Right, a basic set of forged rods will run about $600 and Studs about $400.. Not counting install.
And the Pistons are not a likley point of failure?
How many hours of shop time would it take to change the rods and studs?
Sorry for the "Noobness" of my questions here..
And the Pistons are not a likley point of failure?
How many hours of shop time would it take to change the rods and studs?
Sorry for the "Noobness" of my questions here..
06-01-2006, 07:08 AM
#107
Originally Posted by Weqster
Hey guys. I recently purcahses a 350z. I Have been apart of the forced induction Honda community for over 5yrs now. THis means i am quite accustomed to open decks and the associated downfalls.
There ar a few terms being thrown around here which are cuasing confusing.
Headlift: headlift is a common term used to desicribe combustion gases escaping into the water jackets during boost. People think boost pushes its way outside the cylinder. Sure this happens, but is is mearly an after-effect of another problem
90% of all headlift is the cylinders themselves SHIFTING or SINKING. Due to the open nature of the decks having less support around the cylinder walls, R/S ratio and revolutions causeing extreme sidewall loading of pistons - cylinders actually move around. The slightest movement will brech a headgasket.
So what can i do?
Tuning:
Reduce cylinder pressures. You must run optimal timing. This is not best timing for power, but best timing to minimise cylinder pressures during combustion. The key is timing. A motor can have an a-grade tune and still push coolant.
Mechanical:
Unlike popular beleif, ARP headstuds are not the be all and end all of preventitive mechanics. They will help to a certain point. I have personally pushed coolant 'headlifted' with ARP headstuds. Its in the tune.
Run ductile iron sleeves. This is the ONLY reliable way to save urself from cylinder movement. SIMPLE. In the honda community, stock sleeves only go so far. Get a set of aftermarket sleeves installed by a EXPERIENCED install. I must stress this - only use the best. It is very common to have sleeves sink if not done properly.
If u do decide to run stock sleeves on a built motor - look into o-ringing of the head of block. o-rings are compressable peices of metal installed around the top of the sleeve to help give it that extra tight seal. These do put extra stress on headgaskets, but they are work the risk IMO. They helped me solve my problems.
What shouldnt i do:
I havnt seen these used yet on the VQ motors, but a popular band-aid fox for cylinder movement is a 'block guard'. This is a alluminium support which os installed around the cylinders to give them more support. These CAN help, but mor then likely dont do anything at all. They can however cause overheating problems.
Other spin-off's are the block-gaurd is block filling and block posting. Google for more information on these. Some people swear by them, but the consensis is, these are all bandaid fix's to the real problem.
Once again, i must stress. The tune - correct timing maps - are vital to keeping ur cylinders from dancing around.
Re the original poster;
My opinion on these engine failures is fairly simple. I beleive everyone here, using large single turbos and twin turbo setups, are running the motors on the edge. Reliable and best whp are very different. I beleive these rods failed due to being over-stressed. The original poster commented that one motor blew at 4500rpm. This means it will of been developing a chunkload of torque (peak?) and putting alot of stress on the rods. Torque and/or RPMs kill rods.
To all the other posters thinking about pulling out of F/I after hearing these horror stories. I have no doubt the VQ would be a super reliable motor at 300-350whp. Why be greedy and go for 400whp which is on the edge of safety, and is the point were factory variation component reliability is put to the test.
There ar a few terms being thrown around here which are cuasing confusing.
Headlift: headlift is a common term used to desicribe combustion gases escaping into the water jackets during boost. People think boost pushes its way outside the cylinder. Sure this happens, but is is mearly an after-effect of another problem
90% of all headlift is the cylinders themselves SHIFTING or SINKING. Due to the open nature of the decks having less support around the cylinder walls, R/S ratio and revolutions causeing extreme sidewall loading of pistons - cylinders actually move around. The slightest movement will brech a headgasket.
So what can i do?
Tuning:
Reduce cylinder pressures. You must run optimal timing. This is not best timing for power, but best timing to minimise cylinder pressures during combustion. The key is timing. A motor can have an a-grade tune and still push coolant.
Mechanical:
Unlike popular beleif, ARP headstuds are not the be all and end all of preventitive mechanics. They will help to a certain point. I have personally pushed coolant 'headlifted' with ARP headstuds. Its in the tune.
Run ductile iron sleeves. This is the ONLY reliable way to save urself from cylinder movement. SIMPLE. In the honda community, stock sleeves only go so far. Get a set of aftermarket sleeves installed by a EXPERIENCED install. I must stress this - only use the best. It is very common to have sleeves sink if not done properly.
If u do decide to run stock sleeves on a built motor - look into o-ringing of the head of block. o-rings are compressable peices of metal installed around the top of the sleeve to help give it that extra tight seal. These do put extra stress on headgaskets, but they are work the risk IMO. They helped me solve my problems.
What shouldnt i do:
I havnt seen these used yet on the VQ motors, but a popular band-aid fox for cylinder movement is a 'block guard'. This is a alluminium support which os installed around the cylinders to give them more support. These CAN help, but mor then likely dont do anything at all. They can however cause overheating problems.
Other spin-off's are the block-gaurd is block filling and block posting. Google for more information on these. Some people swear by them, but the consensis is, these are all bandaid fix's to the real problem.
Once again, i must stress. The tune - correct timing maps - are vital to keeping ur cylinders from dancing around.
Re the original poster;
My opinion on these engine failures is fairly simple. I beleive everyone here, using large single turbos and twin turbo setups, are running the motors on the edge. Reliable and best whp are very different. I beleive these rods failed due to being over-stressed. The original poster commented that one motor blew at 4500rpm. This means it will of been developing a chunkload of torque (peak?) and putting alot of stress on the rods. Torque and/or RPMs kill rods.
To all the other posters thinking about pulling out of F/I after hearing these horror stories. I have no doubt the VQ would be a super reliable motor at 300-350whp. Why be greedy and go for 400whp which is on the edge of safety, and is the point were factory variation component reliability is put to the test.
quite possibly the best first post this sight has seen. i agree completely with all that is said here.
06-01-2006, 07:08 AM
#108
Registered User
iTrader: (7)
Join Date: Apr 2005
Location: Bradenton/Sarasota
Posts: 5,254
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Z1 Performance
my point was "just swapping rod bolts in" is not an easy job like "installing a boost controller" - it is a royal PIA, and given the time involved, and the fact that it is merely a bandaid, it's not worth it....either replace the rod (at which point, do pistons too), or, IMHO, it is not worth doing. The stock rods are not beefy at all, and as mentioned, are often a point of failure
shoot, technically, you can put in pistons and rods right from the bottom, if you're so inclined to pain and don't want to pull a motor, lol.
06-01-2006, 07:12 AM
#109
Originally Posted by chimmike
shoot, technically, you can put in pistons and rods right from the bottom, if you're so inclined to pain and don't want to pull a motor, lol.
06-01-2006, 07:15 AM
#110
Former Sponsor
iTrader: (564)
Join Date: Feb 2003
Location: Long Island, New York
Posts: 19,266
Likes: 0
Received 5 Likes
on
5 Posts
the twisting or bending of the rod is fairly simple to diagnose - and it stems from the fact that the rods simply do not have the "beefiness" or tensile strength, to withstand the rapid acceleration that boost introduces to a motor. This is why, very often, you'll see a motor where the pistons look like they could be eaten off of (no pit marks, holes, cracks, or other signs of detonation), but the rod is bent.
Having been around modded cars for the better part of 15 years I have
1. never seen an injector stick, either opened or closed
2. never seen a motor hydrolock due to fuel, only injested water
Weqster has it spot on, and I can tell he has experience in the pains involved in turbo'ing a non turbo car
Having been around modded cars for the better part of 15 years I have
1. never seen an injector stick, either opened or closed
2. never seen a motor hydrolock due to fuel, only injested water
Weqster has it spot on, and I can tell he has experience in the pains involved in turbo'ing a non turbo car
06-01-2006, 07:37 AM
#111
New Member
iTrader: (2)
Join Date: May 2005
Location: Tennessee
Posts: 434
Likes: 0
Received 0 Likes
on
0 Posts
I'm not FI'd, but from what is being said wouldn't stronger head studs help fight head lift at a relatively low-medium PSI, and have their functionality multiplied by using thicker head gaskets to lower cylinder pressures? Another question, would running the injectors at a lower Duty Cycle lower the risk of them sticking in the open or closed position and causing the lean or rich condition? I think this is a great finding due to some motors on here that have been blown off boost, crusing around town. In those cases I would think the injectors would come into play.
06-01-2006, 07:44 AM
#112
Former Sponsor
iTrader: (564)
Join Date: Feb 2003
Location: Long Island, New York
Posts: 19,266
Likes: 0
Received 5 Likes
on
5 Posts
head studs help...they are not a be all and end all solution, but merely another thing that should be done..just like adding the additional studs. Thicker headgaslets - not a fan personally, as you are better off having pistons of the proper CR to begin with, but again, it's a cheap solution that "may" help
Yes a lower IDC helps to prevent an injector from sticking open, but as I mentioned, I have never, in 15 years of building/owning/tuning cars, seen an injector stick open
Yes a lower IDC helps to prevent an injector from sticking open, but as I mentioned, I have never, in 15 years of building/owning/tuning cars, seen an injector stick open
06-01-2006, 07:52 AM
#113
Originally Posted by SilverJDMCoupe
I'm not FI'd, but from what is being said wouldn't stronger head studs help fight head lift at a relatively low-medium PSI, and have their functionality multiplied by using thicker head gaskets to lower cylinder pressures? Another question, would running the injectors at a lower Duty Cycle lower the risk of them sticking in the open or closed position and causing the lean or rich condition? I think this is a great finding due to some motors on here that have been blown off boost, crusing around town. In those cases I would think the injectors would come into play.
2. thicker head gaskets can lower cylinder pressures, but not in the instance being used here. later timing will lower peak cylinder pressures and won't have a huge effect on power output.
3. only way to run the injectors at a lower duty cycle is by running less boost, or getting larger injectors.
4 i have blown n/a motors at 1500rpm before. cause was a valve that hit kissed the piston at high rpm 3 days before. the valve was slightly bent and finally fatigued and the head snapped off. at that rpm and only making about 35-40hp, it took the block, crank, heads, cam,and most of the other smaller parts with it. my point is, as Z1 mentioned, sometimes it is hard to find the true basis that started a catastrophic failure.
06-01-2006, 07:58 AM
#114
Registered User
iTrader: (1)
Join Date: Mar 2005
Location: Room full of blood
Posts: 2,422
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by gatti-man
What car would that be?? Lets say I spend 20k on my car in mods and I paid 26k new for my z. That's 46K, what car sub 60k could compete with the FI z I would now own? none imo. the vette is the only thing that comes to mind and I'd far prefer a custom car to an oem fast ride.
Got 1 word for you, my friend:
SUPRA
06-01-2006, 08:50 AM
#117
Registered User
iTrader: (1)
Join Date: Mar 2005
Location: Room full of blood
Posts: 2,422
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by doug
Thank you. I will sign up for the supra forums and see what's up...
I should have done this back in '03.
For all that good looks of the Z and the power potential of the VQ35DE (once buckefulls of $$ are applied), it is still an underengineered POS as opposed to the 2JZ.
06-01-2006, 09:00 AM
#118
Registered User
iTrader: (6)
Join Date: Dec 2005
Location: Berkshires
Posts: 532
Likes: 0
Received 0 Likes
on
0 Posts
I'm interested in this topic and hope that it stays on-topic as this is something that could potentially affect my Z, since I'm FI on a non-built engine....
Thanks!
Thanks!
06-01-2006, 09:01 AM
#119
Registered User
iTrader: (8)
Join Date: Nov 2004
Location: Miami, FL
Posts: 4,328
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by doug
That car is 16 years old man!
Sorry dude, but I'll keep blowing motors and replacing them if I have to. Cars from 5 years ago looked dated to me. I gots to have the new!
Last edited by Gman2004; 06-01-2006 at 09:17 AM.
