Phunk this random con rod failure seems very strange to me...............maybe there is a small % of under spec stock con rods..............it's really strange that a stock con rod would fail at such low positive pressure.................maybe some engines have a big end bearing clearance problem.............none of this makes any sense.

I've been as high as 12 PSI (on 94 octane fuel) in the APS TT Z and no problem to date with either stock con rods or pistons..............surely the stock rods should survive low boost.............5 to 6 PSI.

Don't be scared push your beast to 10 PSI.................you'll love the huge increase in torque.

Peter

APS

 

Guys...

Thanks very much for all your support, it's much appreciated.

I will definitely document absolutely everything to the best of my abilities. There are a few scenarios to consider here.. if I can find someone here in NorCal (I am up here for school now) that is reliable (any suggestions?, so far there is only 1 possibility) I will try to do it here; in this scenario, I will document every minute step. Otherwise, the car is getting shipped to TS in L.A., and documenting any evidence will be tougher.

Sharif....
I just do not see how this can be detonation related. In addition to what was already said, another point to mention is that 4200 is in the knock-control ergion of the stock ECu, which would pull another 4 degrees on all cylinders were the J&S to not detect the knock (which is extremely unlikely). So, detonation can't realistically be an issue here.

Also, the points that have been brought up about rods... I couldn't agree more.... Not all of the rods would fail, of course.. Otherwise, where is the engineered margin of error? Those stock rods are a joke for any serious power.

Now, I am agreeing 100% that any acceptable level of reliability with TTs, REQUIRES an engine build. The TTs, especially in high gears, have 0 lag and full boost come in instantly. So when I did gun it at 4000 rpm in 4th gear (1:1 ratio), this represented the worst case scenario for the rods... B/c of the tall gear ratio the engein stayed in that 4000-4500 rpm range a little too long, exposing the engine/rods to the stressing for a relatively prolonged period... This may not have happened in 2nd gear or even 3rd....

Gurgen

 

Jason

That scenario is also beign considered. Actually, I hae been researching the matter for a while now.... I will need a new EGI harness if i really want to do a clean install. This may be a far easier proposition since the engine will be pulled anyway.... So, I will be considering this seriosuly... We should talk sometime... Give me a call...

Also, this happened when I was solidly in 4th gear (i was using MM mode for shifting through the twisties).

Gurgen

 

Hey Guys

You can see the pictures here...

 

Could the factory plenum have anything to do with this?

 

Maybe we should start a thread that list the build date/compliance of each blown Z to see if there is a trend.

There could have been a revision that we are not aware of.

 

I don't hink so, as it was not a lean condition or anything.... No detonation, no warning... It's got to be a rod failure.

G

 

Peter, there is a big difference between running a dyno at 12psi, and reliably running at 12psi on the road for tens of thousands of miles. I am just concerned that your comments will be construed by others, that the stock bottom end is reliably capable of 10+PSI. I know you andPhunk have pushed the envelope on the dyno, but that doesn mean the engines will last for 50-100K miles.

Just my .02.....don't get lulled into a sense of complacency. The stock rods suck.

 

Gurgen,

I am So Sorry to hear this happend to you

--------
Charles and Peter, I don't get it either. I beat / abuse my z everytime I get in it.
I constantly do runs of 8.5 - 10 lbs runs on the street, back to back, datalogging, and testing different things.
Probably have well over 300 WOT runs
No problems...

So why do others who barely get on theirs, and at a much lower psi blow their engines ?

Only thing I can think of.
No fuel upgrade and low octane.
Charles and Bill (ravaz) run 100+ octane.
Peter 94, I am using 93.
And all have done fuel system upgrades

Seems most engines are failing on lower octance gas (like available in Cali)

Ofcoarse there is exceptions, but this seems to be the case...

 

I've been running 12psi and up to 13psi pretty often lately, that was on 112 Oct, sometimes C-16, but lately it's been just on 100 octane. I've got about 100 dyno runs on this motor (will do about 10-15 more this week), who knows how many runs in the track/street, over a few hundred WOT runs. I'm with you guys I beat on it everytime I get in it. I run never ever run lower then 8.5psi, that puts me over 450hp/440tq at the wheels. I had both a Procharger and now the Greddy TT on this car.

I don't get it either, but hopefully we can all get to the bottom of this. I know you all think these rods are real weak and they are for alot of boost and long term, but they seem to be taking 13psi and alot of abuse for me just fine.

 

Ok, you guys will forgive the dumb question I hope.

It seems like blown motors are only ever blamed on two things: (1) Detonation--i.e. not enough timing retard and/or not enough fuel or (2) weak parts in the stock engine.

Are those the *only* two possibilities? I mean could there be some other sort of electrical or ECU-related thing that is happening that could cause this?

--Steve

 

Bini2 had a full fuel system upgrade with FPR, return line, and Walbro 255. He was running 93 octane fuel and it blew at 8psi. He was professionally tuned and running ignition retard

Gurgen has running ignition timing retard, 5.7psi, and 11:1 A/F and 91 octane fuel, and fuel pump, FPR...assuming since he is in CA.

JoeNismo: 6psi, snapped con rod, 93 octane fuel, Walbro 255

Fernandino: Blew at 7psi, with fuel pump upgrade...tuner blew it up tuning.

I think these guys all had adequate fuel...

I am sticking to me theory on weak con rods. And I dont think it's a "random" failure. I believe its only a matter of time before the others will fail as well.

 

As much as I hate to say it, it looks as if I'll check into the rods & pistons quicker than I anticipated. Similar to other industries, product failure will occur when driven out of spec (turboed). Will it happen tomorrow, next month, or next year, we don't know. But for those who have been fortunate, it seems to be a toss of the coin.

In this particular case, having the auto tranny doesn't seem to be helping matters since you're stuck in the gear for a longer duration, which equates to longer exposure to boost. In any case, just be careful. These TTs are like tobacco . . . we know they are bad for you, but d@mn it, we love it

G

 

Gurgan I do remember when you swung by the shop that the intercooler being at a very hot temperature (too hot to touch for long). I am not sure if this hot intake charge temp would have to do with the failure, but it certainly wouldn't have been helpful.

 

there are other bizarre possibilities. Its hard to say. Cast compents will tend to be less consistent then forged which could be the sole problem tho.

every dyno graph I see with people pulling out timing with the E-Manage harness seems to get really bumpy on top... like something is not right.

HP itself really is not a lot more stress on the rods, depending on where thye are breaking. HP alone is no more stress what so ever on the rod bolts. if its a rod bolt failure someone had, its not from HP. power is a compressive force on the rod and if timed properly it doesnt take much of a rod to hold a lot of power, but it is definatly important to have everything timed correctly.

The compressive force on a connecting rod will be at its lowest with the right ignition timing. Fire your timing too advanced and the rod will have a lot of resistence to rotate the crank and there is great compressive force. Fire it too late and I would naturally have to assume that with your peak cylinder pressure happening wihle the rod is at such an extreme angle would not be healthy for a cast part.

They say your optimum peak cylinder pressure point is 14 degrees after top dead center. You only fire your plugs before that cause it takes time for the pressure to build. higher octane gas burns slower and thats why you can run more timing on it. You will actually loose HP from higher octane if you do not have the car tuned right for it. The longer burn of higher octane gives more time for detonation to occur, but since it offers more stable combustion you are still less likely to run into detonation or preignition.

This could also be as stupid as someone putting too much oil in the engine. This engine naturally takes about 5 quarts. Over fill it and the windage if the rod hitting the oil could be extreme. I have not looked aruond the crankcase much tho and I would have to assume that it would take a LOT of too much oil for that to happen, but maybe it only takes an extra quart I dunno. Being thta the dipstick can often be so hard to read in these cars I have often feared people over filling their oil.

It could really be a lot of things... but I am still not totaly convinced that the rods are total JUNK, i think they are just going to be more picky to correct tuning... not overly conservative or overly aggresive. It seems that the only people whos engine are holding high HP are those that are not being conservative at all... i took stock ignition timing all the way to 435rwhp. I am still running around 23 degrees of timing at 9 psi with my 100 octane. Those of you who arent into tuning know that even given the bore size of the engine... that is a lot of timing... its more like what you would run in a lower compression engine. THis is why my engine puts out such smooooth dyno graphs and high HP for boost.

 

I've ready the thirty or so posts on this thread so far. Really...nobody knows for sure what the stock internals can and can't handle. There is one thing I would like to point out however: HIGH PERFORMANCE ENGINES BREAK!!!! Even in "stock" form, high power, high tune motors break. Do you really think a Ferrari Modena motor is built to run reliably for 100,000 miles? It most certainly isn't. Stock M3's are blowing motors. The previous generation Audi S4 was plagued by turbo failures. The only possible exception to this rule is the Honda S2000, and that only succeeds at being reliable because it is such a low torque motor. The only really safe way of getting higher power is increased displacement. The fact is that most highly tuned motors are really not found on cars that are long term daily drivers. Most Ferrari Modenas, for instance, will never be driven more than several thousand miles in their entire lifetime. My HKS supercharger goes on next week, but my Z isn't driven more than 5000 miles per year at most. Metal fatigue will happen over time. There will always be a weak link somewhere in thes system when you tune a vehicle.

The key to some amount of longevity is to not abuse your motor. If you hammer it at every light every time, you will blow your engine. DRIVE NORMALLY MOST OF THE TIME. Use a throttle position that would not generate more torque than stock for a given rpm. Use your extra power ONCE IN A WHILE when you just can't resist and you'll be okay.

Finally, and this is just my opinion, but if this car is really your only means of transportation and is a true daily driver, I wouldn't put any type of FI system on it.

 

^^^^ yup

 

Yes,

I was running chevron 91 octane gas, 10.x-11.3 a/f, fpr (fuel return), J&S -5deg (that's about 17-18 total advance), and the knock based retard as needed, 5.7 psi

I did cec kthe oil level on tuesday before I drove into S.F. It was a 1/4" below max (in the morning - oil settled). So, I definitely did not have too much oil, and not too little, as a lot of oil both on the gorund, on the tow truck bed, and where it is parked now is spilling out. This was not an oil issue.

G

 

Bobby...

That was because I was sitting and idling for a long time. When I touch it after riving for a long time, it is hardly warn to the touch...

Gurgen

 

Thank you for making Clear - The Management is the Key..

Less Fluctuation on Dyno's (and Real Live run's) the less Stress on the Stock Rod's

Please now add your view of what a JS - Kit "might" do to a tune with E-Manage Fluctuations...

Thanks in advance..

Cheers Amy -