Yeah you're correct in saying this though we have conducted plenty of real life road testing (not just dyno testing) and to date we have not experienced any engine drama.

I'm not suggesting that the stock engine will be reliable for 50-100k Miles..............there's simply no way of knowing this without accumulating the test mileage.

I believe that the con rod failure in this thread is most likely a fauly/weak factory con rod................it just maks no sense to me knowing the boost pressures that we have run on the stock engine during the development and testing phases.

I do appreciate and agree with your comments and we all need to be careful not to promote overly high boost pressure on low octane fuel and with stock engine internals.

Peter

APS

 

Here's some speculation as to why Gurgen threw a rod while being *very* safe whereas Slay and APS have run at high boost levels without blowing their engines.

When Intel manufactures a Pentium 4, all chips, regardless of clock speed, are manufactured from the same materials and by the same process. Because of tiny variances in the process and materials, not all of the chips will be able to reliably run at the highest clock speed. After all the chips are made, they are individually put through a series of stress tests to determine which clock speed they can handle and will ultimately be sold at.

Perhaps Nissan utilizes a similar system for manufacturing and installing VQ35 connecting rods? The toughest rods are put in the Z and the 6MT G35, where the power output is the highest and the timing is the most aggressive; lesser rods are installed in the 5AT G35C and the G35 sedan, where the tolerances are lower.

This sort of system would make sense, considering the number of cars Nissan installs the VQ in. Can anyone who knows more about Nissan's manufacturing process comment on this?

 

that would be an interesting finding.

 

There have been rod failures at low boost even on Zs @ <7psi. So the theory really doesnt' really hold water.

 

Yes... in fact most of the rod failures ARE on 350z's... Of course, there are far more Z's that are TT'd than G's.

 

This is most likely correct................more TT and supercharger systems on 350z's and the owners pushing the power boundaries.

I guess this entire con rod issue can be very confusing and I wonder how many of the engine failures have been diagnosed 100% correctly.

If you consider all of the possibilities with regard to engine failure it's quite conceivable that a piston may have failed prior to the con rod venting the cyl block...............equally a big end bearing may have spun causing the con rod failure due to a hammered big end bearing..............or just poor clearance between the big end bearing and crankshaft journal.............there are just so many different causes for con rod failure..........other than the obvious cause which may prove to be ultimately inadequate con rod structure.

I believe this entire con rod issue needs much more indepth investigtion before people just make the assumption that the con rod is simply weak and not up to the task.

Of couse it just may be that there are a number of poor quality/faulty con rods slipping through quality control..........food for thought.

Peter

APS

 

i think what he was saying was that there may be a difference in the rods in the 6MT and auto.

 

highly unlikely imo

 

The shortblock part numbers from Nissan are the same between the 350Z and G35 sedans and coupes.

 

Totally agree with Phunk and APS...the VQ35 cold coined vanadium rods are stronger then they look.

As said before, compressive loads from boost are not that hard on rods, however tensile stress from a long stroke/high piston speed is *HUGE*. Bumping up the RPM on the VQ35 especially when boosted is asking for weakening the rods OVER TIME until one time when you get on it at a low rpm/high crank angle or maybe with a little detonation and *SNAP*.

My question is, how many people that are blowing these engines, have TS ECUs and enjoy the extended rev-limiter?

 

I have purchased a long block that has "two" bent rods due to only a few miles @ 7psi (Greddy TT on Z). The block has been fully dismantled and inspected. Basically all bearing surfaces are undamaged. No upper cylinder or head damage whatsoever (indicates lack of any major detonation events).

So the only real damage was two bent rods , (and a commensurate oil squirter got squished).

This may not be the norm, but it appears to be that these rods were simply overstressed.

 

look at my post when you reply. i'm talking about 6MT to auto. not coupes to sedans to 350Z.

 

The shortblock part numbers between coupes , sedans , 6mts and autos are all exactly the same.

 

What he said No need to get snippy Damen.....just trying to help

 

I'm very sorry that this happened to you gurgen. Not a good time. I've grenaded motors before on other vehichles and know that it just plain s@*ks.

 

You know what I'm wondering.. What were everyones EGT's that threw a rod. With my car, it never ever has gone above 550 celcius, no matter how much boost I was pushing, street or track. Like tonight, I let my girl drive and told her to push it, we were running 12psi and it was right at 480c, with 100 octane, that was at the end of a 20 mile drive. I'm just wondering if high EGT's might have something to do with this... Just a thought.

 

i didn't mean for it to seem as if i was snippy. i was just trying to clearify the previous post. basically do 6MT's come with stronger rods than auto tranny cars.

 

High EGT can contribute to detonation, which Gurgen didn't have, and can melt pistons...which also didn't happen.

Again, I would urge you take at the factory rod design. It is not desigen for F/I, it is desiged to be light weight, which is great for higher reving N/A applications, but not for FI. I suppose nobody can EVER know what causes an engine failture..at least to 100% certainty. But clearly, a very strong trend of broken con-rods is accumulating in the TT world.

 

Whatever happened to the thread where we compiled information on all the blown FI motors? I guess there isn't as much interest in compiling this sort of data considering:

• So many people are getting their motors built anyway.
• It's pretty clear that the factory con rods are weak under boost.
• The 2005 Anniversary / Track Z is most likely going to come with stronger con rods.

 

ravaz: those EGTs you are posting are insanely low... that couldnt possibly be taken from the manifold? is that in the downpipe?

EGTs that low (in the manifold) would be sign of a LOT of ignition timing (advance) combined with a LOT of fuel (rich as hell) and probably some high octane fuel as well??