What is the reason for breaking rods. I'm boosting at 9psi and making only 380ish hp and 310ish ft/lbs torque. Guys with TT setups are making 400/400 with 6-7psi and they seem to break more frequently. So what gives? Boost or HP?

 

Generally the two go hand in hand....more boost=more hp/tq

In my opinion it's not one single thing that leads to an engine letting go, obviously if there is a ton of power they just wont be able to handle it. However, the quickest engine killer is detonation. If you're on the cusp of making too much power and don't have a really good tune...boom there goes your engine.

--wes

 

Most of the broken rods are happening with the TT setups or untuned S/C systems. This is probably because the 2 turbos are putting huge stress on the engine starting very early in the rpm band and staying all the way to redline. The TT's are TQ monsters compared to the other systems so I'm sure this goes in hand. Other systems such as the Vortech S/C and Single Turbo systems don't really get as much power until higher in the rpm band. S/C systems such as Stillen have a very linear power system.

Nitrous also creates huge amounts of TQ but the typical system doesn't engage until after 3k rpms and thus far it seems there haven't been many cases of damage from Nitrous.

 

That's the interesting thing about Stillen though.......the maximum torque comes in at around 1700 rpm's....long before any TT set-up. Yet they seem to be surviving with no failures as of yet. So maybe the amount of torque through the rpm band is not the issue......

 

I don't believe the Stillen is making 370+ ft lbs at low rpm like a TT will do.

So an additional question would be, does engine speed affect rod damage. It appears that answer is no.

 

It's simple, if your making too much power for the rods to handle they are gonna snap. The TT setups make a lot more power then most other systems so they are more likely to break a rod. But I don't believe their is any definitive point where the rods will break. Someone could make 450 rwhp all day, and someone else could put a window in their block at 400. It's hard to say, so If you wanna be safe stay well below the point where people are poping motors. If you guys have not see the stock rods I suggest you look them up. If that doesn't stop you from going crazy on the boost nothing will. They are weak.

 

I was making reference to the different amounts of stress the rods see through the rpm band with a TT vs Roots blower. With the Stage 3 there are a couple guys who have seen just as much torque as the TT's that have blown up.

 

The reason more Stillens havnt broke is beacuase there are only a handful of installations. The Greddy TT has 100+ installations, and the PE kit has less than a dozen....so the more installed units....the more likely you'll have more incidents of failure.

I agree with what everyone else here says. The rods with a TT are under extreme trq at very low RPM, and this puts the maximum load on the rods, at a point when you really don't want it there. It is kinda like lagging a motor...likely floorring it at 1500rpm...not good for the motor.

 

Detonation is the culprit . . . during detonation, the cylinder sees up to 3x the nominal pressure. Mark my words, in a few months we will see the light . . . and a reputable company will bring forth the solution

As in all industries, we sometimes focus on the end result (rods snapping) and not the source, but I will tell ya, detonation is the prob and the solution will be here shortly . . .

 

This would not seem to be the case for gurgen. He has a J & S and was experiencing no detonation when his rods let go. Perfect A/F ratio, reduced timing,etc. Let go at 4000 rpm's.

https://my350z.com/forum/forced-induction/92140-bad-day-pe-tt-blew-the-engine-at-5-7-psi.html

 

Gurgen is the reason I started this thread, because it came as such a shock to hear how his engine broke. I keep thinking of the obvious like bad gas, or oil leak, or FP failure, but he appears to be a smart enough guy to realize those things. I think it may just be the engine was tired of being forced around. That simple.

 

If a tree falls down a mile away and no one (human) has the capability of hearing it, did it really happen? If we had, lets say binoculars, we could actually see it to confirm, eh? . . .

More to follow

 

350G, my vote is that you should either contribute to this thread with *real* information (rather than smugly intimating that you know something we don't) or keep your trap shut.

--Steve

 

I vote Steve learns to spell

Translation: the issue has been accidentally found, addressed, and corrected, BUT won't be available for a month or two. I don't have any specific details since its proprietary info, but the problem has been unveiled. Hell, I'm in the same boat (waiting game) and choose not to turn up my boost or fine tune beyond the basic Greddy configuration (staying safe).

Regardless, there's nothing more to disclose, but if anyone wants, they could get a 30K device to measure the cylinder pressures in a tuned Z (while running) and take note of the nasty, mostly inaudible, spikes in cylinder pressure (over 3 times nominal) . . .

Until then, I'll keep my trap shut

 

Learn to spell?! Me?

Sounds like you are privy to the same information I've heard floating around. Either that or more than one company has come up with a solution.

I can't wait either

--Steve

 

Spill you're guts!!!

 

Has anyone considered heat as being the major issue in regards to detonation. It would seem somewhat logical depending on the quality of gas people have been using (with proper tuning) when their engines failed. I have heard some people using race fuel with successful boost levels a bit higher than many. With our stock compression ratio, the compact engine compartment (causing high temps in the engine compartment), and variabilities in pump gas one would think detonation would be very possible instead of the rods. It would be interesting to know just how hot things are getting. Also, people have been successful with fairly large nitrous injections on stock internals which makes me wonder again about the heat/detonation combo. Nitrous has a cooling effect much like higher octane racing fuels. Maybe the TT intercoolers are not efficient enough, or bigger oil pans are an absolute must, or vented hoods are needed, heck maybe all of the above are critical. Forged rods would add a nice piece of mind, no doubt about it, but is that really the issue???

 

Also, wouldn't it seem more logical that heat would be an issue with the TT setups? They have the turbos spinning causing heat and the large exhaust manifolds, that can not be as efficient at transferring heat as the stock manifolds or a set of headers.

 

Detonation is also apears to "not" be the cause of failure in Fernadito7's Z block.

I have bought it from, and had it fully dismantled and inspected. No signs of top cylinder ( that includes ring, head gasket and head) damage.

Just mainly two bent rods. One slightly , the other more so. And a smashed oil squirter + cracked skirt (= symptoms of the worst rod getting bent).

It appears that the these rods just couldn't handle the TQ of a Greddy TT @ ~7psi. Maybe a poor batch of rods?, But note it was 2 out of the 6.

 

I wish I could tell you more, but I'm simply not a mechanical engineer, nor did I really pay attention to the schematics during my session with the company (he didn't tell me until the end of our meeting). BUT, with the pressures that the cylinder was enduring, it could make the end of our rod split like sliced cheese.

Here's another tidbit: "Using finite element analysis, our rods appeared better than the rods in LS1s or 4.6L Cobras" (he said he would almost bet on it). This guy was by no means a marketing person, because he was so blunt with his information and rationales. I could have spent hours talking with him and I believe his company's reputation precedes him.

ZIMBO (Steve): Out of curiosity, where did you here your info from? From what I understand, I'm the 4th or 5th to hear it, but he also said that the engineers from other companies will eventually catch up and notice the minor problem with our NA gone TT engine. Just want to compare notes