chimmike

iTrader: (7)

since when? a stock b16 won't take that much boost. As he said, his motor was built.


I still think the stock rod bolts could be a big factor in premature rod failure. the stock rods aren't inherently weak, hell, the pistons are really the weaker link in the block, with the high ring lands lending themselves to crack more easily under detonation. I REALLY strongly believe rod bolt failure could be the culprit.

It'd be nice if someone threw in some ARP bolts and ran 550whp for a while just for shats n' giggles to see.

Z1 Performance

iTrader: (564)

but the thing is, why bother going through the time and expense to tear the motor apart to install rod bolts, when you could just go and install rods (which have the bolts as part of them)

BrianLG35C

iTrader: (2)

This all sounds very familiar. Pretty much the same thing happened to me while pulling away from a stoplight.

bsp

iTrader: (2)

Good point, I would say perhaps money could be an issue, but if you can afford to have the motor pulled you more than likely should be able to afford a new set of con rods.

taurran

iTrader: (18)

Right. Until someone has the excess time and money to REALLY break down this stock motor and play with it, we will never know the exact cause. Until then, people will continue to make power through brute force by replacing the bottom end with internals rated at over 1000whp and running 500whp.


About the failure on the single turbo kit -- I very much doubt that it was related to overboost on the kit if overboost did not visually occur on the dyno. Overboost on these kits does not take the form of a boost "spike", as much as "creep". Meaning it would hit full 8psi and creep up to 9-9.5psi. I ran my car at this level for over 8 months with no audible sign of detonation.

chimmike

iTrader: (7)

tear the motor apart? IIRC you can just drop the oil pan completely and install brand new rod bolts like that. BAM, no need to yank the motor, etc. At least that's what I've seen and what I've gathered from my convo's with JWT.

350zDCalb

iTrader: (21)

you could do it that way, dropping the upper oil pan, and turning the crank to get to each rod...

theking

iTrader: (3)

Even if you have another knock sensor installed it doesn't mean that is has the right resonant frequency or is looking for the correct order harmonics that a V6 like ours creates when knocking. John from J&S can't even find the magic bullet for knock in our cars and that is his expertise. Until we can take a stock motor and do something such as Ion sensing we won't know what is knock and isn't. Us built motor guys are in a totally different boat since the dynamics of the cylinder have changed and even the stock sensor won't pick up true knock.

chimmike

iTrader: (7)

......

If I were to want to rev higher, I'd install the ARP bolts anyways. Too much empirical data showing those stock bolts no likie the higher revvie for that long.

Sharif@Forged

iTrader: (92)

After quicklying scanning the thread, a couple of points came to mind. It's unlikely that headlift would cause a bent rod. We've intentionally and unintentionally lifted heads on my car, and the only thing that happens is coolant goes everywhere, and the engine overheats. It's not enough liquid to hydrolock the motor...at least from our experience.

In regards the injector theory, it's also unlikely that an injector, already running near 90-100% duty cycle near redline, would cause damage if it did stick open at WOT near redline. In essence, the injector is already near the point of continously being open.

More food for thought.

My theory has always been that some of these engines are built a little bit better than others. For those on the fence, and concerned about going FI, I would say that you have little to worry about, provided the kits are properly installed and tuned, and power levels and kept at a sane level. There will always be a few freak cases of engine failure, but it shouldnt discourage people from going FI, if that is their desire.

Julian@MRC

iTrader: (28)

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..

Julian@MRC

iTrader: (28)

Then how does his product detect knock to work??

Eagle1

iTrader: (2)

This is an interesting thread. I concur with Sharif's observations, and have a couple of my own, that are probably shared by others.
1. If you cannot afford to blow it up, don't do FI. End of story.
2. If you boost a stock motor, be conservative and careful with the tune, but also with how much power you seek. My personal view, and others may differ, is that 360rwhp is about the max of what you should go after if what you want is a daily driver with solid reliability. I got 23,000 miles on a Procharger with that tune, drove a bunch of track days with it too, and it was absolutely flawless. When the SC was taken down the compression and performance of the stock motor was outstanding. Some element of luck was probably there, but just reporting the facts.
3. Turbo is more violent on the motor than SC. Factor that into your tuning decisions.
4. If you build the motor, because you are going to run higher boost, then "overbuild" it.

theking

iTrader: (3)

I'll let him answer that. I'm no longer running his ultrasafeguard. If you know what I mean.

Julian@MRC

iTrader: (28)

This is what I thought also, but one motor did go at 4500 rpms, where there would be plenty of injector left.However I am not leaning towards the injector theory either...A blown headgasket or head lift can leak enough liquid into the cylinders to Hydrolic a rod, since it only takes 1/4 of a cup of liquid to bend the rod.Remember, liquid does not like to compress in any amount.
If the heads lifted or the head gasket leaked fluid in between layers into the cylinder this could happen..
However we are also leaning more towards the rods mechanical limits being reached on those respective engines. It is the only logical theory left to explain what happened, since there were no classic signs of detonation or pre-ignition...

tig488

iTrader: (18)

correct me if im wrong, but dont you have to pull the motor to take off the upper oil pan?

mchapman

iTrader: (1)

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?

Sharif@Forged

iTrader: (92)

You can remove the upper pan without removing the engine. However, its an extremely messy job.

tig488

iTrader: (18)

gotta be a real PITA too, i thought some of the bolts are impossible to get at without removing the motor. i guess if you undo the mounts and jack the motor up its possible. you would know more than me tho, youve taken out lots more VQs than i have, lol.

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.