Nightlife 0 compression found and cause.

Roberto, I am still very sorry to read this. I was wondering how you were getting on.

So, I guess I would look at both options and price them up. Do you know how bad the piston on that cylinder is? Can't hurt to pull the head and take a proper look, at least then you will be able to get a fair idea of the parts required and then price the job.

As far as the other engine, if you can verify the condition (leak down/compression) and the seller offers some sort of warranty then provided the $$ is less that is the way I would go. You will save a ton of labour and your old engine will be able to be sold.

But, then there is the fact that your current engine rebuilt is going to be a "fresh" engine where as the other one is 10k+ old.

She is a tough call mate....

 

Roberto:

I want to echo James' post above. I am really sorry this happened to you. It is a tough call. Although, from your posts, it seems that you are, and always will be, a 348-man. If this is the case, I would take a lesson from Sy and rebuild your original engine to perfection. Add some horsepower and torque, make it bulletprooof. In addition, it would be good to keep your original engine (matching numbers) for when the world recognizes the 348 is the best Ferrari ever built and its value climbs to 250GTO status.

Best of luck, whatever you decide.

BTW, you might want to contact Hyperflow..............

 

+1

 

Sorry to hear about this. I hope you get her straightened out.

360s (2000 and older cars) have been having a similar issue as the cars and cats have aged.

 

sorry to hear about your engine.. thats a real bummer..

i've read someone else mention cat debris getting sucked in to the piston.. How does this happen? What causes the suction? Aren't the cats downstream of the exhaust flow (positively pressurized)?!!? Wouldn't that prohibit exhaust reversion?!? should failed cat bits get expelled through the exhaust?!?

 

I wonder if the cat failure was due to manufacturing or you have a cyl or bank of cyl. running rich (i.e. an injector hanging open.. or having lazy response times).

 

I agree, I don't see how any cat material could flow backwards into a combustion chamber. I've read about failed headers causing fried pistons, but even so I'm not clear how reduced backpressure causes a lean condition.

I could envision the failed cat causing more backpressure, holding back excessive heat leading to piston failure. I still have my stock cats in but deleted the bypass cats...hmmm.

 

Absolutely if the cat failed from materials or something, it'll be replaced without question. Actually, Roberto call me anyway... I'll get you fixed up on that side.

BUT, I'd put good money on the problem being WAY upstream of that cat. A cat is reactive, and heats up based on the amount of gunk on the back end of a combustion cycle. Something is out of whack in your fuel load, and that cat was cooked by the tune of the car. Not the other way 'round.

I'm not a mechanic. But it sure seems like something's not kosher in front of the cat.

 

An owner's worst nightmare! I hope to never feel this pain. Please keep us updated as to further diagnosis.

 

No question about it. See it every week.

 

Not uncommon. There have been many engine failures due to this. One of the Japanese companies, I believe Honda had a recall due to the problem.

 

Headers work by harnessing the wave action of hot gasses. Basically (1) when an exhaust valve opens the high pressure in the cylinder (about 70-90 PSI) runs down the header pipe to the collector. (2) When this wave reches the collector and finds a lot bigger ares (3 other header pipes and the Cat) a moderate sized negative pressure pulse runs back up the header. (3) this negative pressure wave should be 'timed' by the header to arrive while both exhaust valve and intake valves are open (the overlap area). (4) This negative pressure wave cause fresh mixture to enter the cylinder even before it starts to decend.

Back at (1) a high pressure pulse slams into the Cat matrix and breaks little particles off.

Back at (2) This negative pressure pulse can carry particles from the decaying Cat up the header pipe and into the combustion chamber.

 

Thanks for the detailed reply; I understand this theory, I just didn't think the magnitude of flow reversal would be enough to move particles backward, especially at high revs.

As Daniel said and Brian sees weekly, makes sense it's a problem upstream that caused the cat failure.

Roberto - I would suggest sending the injectors out for flow test and clean; you might learn that one was blocked causing a lean condition and you'll have them cleaned and ready to go for your next engine. (of course label good what cylinder they came from)

 

It is made worse as a cat disintegrates. The broken cat substrate reduces flow and and creates an even greater desire for the gasses and particulates to follow the path of least resistance.....back to the combustion chamber, driven by the output gasses of the next cylinder in the firing order. 360 has something on the order of 60 degrees of exhaust overlap, cylinder to cylinder in firing order on the same bank. On 360's we have found large cat particles in the intake plenums.

 

That's what I was referring to earlier with the 360s. You are able to 'splain it much
gooder than me...

 

It can get so bad that it turns the affected bank into a 4 cylinder pump, pumping debris from cylinder to cylinder.

 

And to think that 355s get all the bad press...

 

Interesting, thanks

 

Bad luck Roberto.

Going to check them when we take teh engine out next month.

Still getting conflicting opinions regarding the exhaust residue. Someone again told me that a light grey powder is a sign that the engine is running well.

 

wouldnt the exhaust valve be closed by the time the low pressure reversion wave would be in the region (if there would be one at all)? Would the wave have enough velocity to carry debris? If the exhaust valve is open (and the combustion chamber open to the exhaust track) the cyl pressure seems like it would be flowing AWAY from the engine.. If I remember correctly I've seen cyl. pressure tests in the +/-170-180 psi range.. There is no pressure away from the engine when the valve is closed.. but at the same time I would think if the valve is closed contaminants from the exhaust wouldnt be able to get in to the combustion chamber. I seem to remember on 4-stroke engines when the cat is plugged enough to totally restrict airflow to an engine the engine stalls (no room for the intake air/fuel mixture for the combustion process)..

Its has always been my understanding header scavenging works by the timing of the exhaust pulse (tuned by length) in which the exhaust gases leaving one cyl going in to the collector cause a vaccum in the other exhaust tubes (upstream of the collector) to help DRAW out the exhaust gas.. (similar to the old siphon effect used to drain waterbeds back in the 70'-80s) It seems counter-intuitive for gas or liquids to want to make 180* turns..

thinking more as I type, would the exhaust gas pressure on the cat also keep debris pinned to it?

I know nothing about the particulars of Ferrari engines but really want to understand them.. Maybe this happens due to the 5 valve design.. then again.. isnt it the center intake valve that is 10* out of phase with the other two?!? meaning arent' both exhaust valves in phase with each other? The only way I can think the exhaust could suck anything is if the exhaust valve is open when the piston travels down the cyl bore (a syringe like action).. but that doesnt seem like something a performance engine would do.. as that would seem to be similar to EGR valves (and Exhaust gas recirculation emission concepts).

anyways, thanks for taking the time to read my questions and explain these things to me.. These engines are so fascinating!

 

With your Hyperflo cats, had the exhaust temperature thermocouples been eliminated from the system? Were your "slow down" warning lights no longer operational?

 

If this were true the headers would not be good for anything other than a low resistance flow from cyclinder to muffler. Note: Headers are typically tuned for all this resonating action at peak TQ or slightly higher, nowhere near redline.

The wave travels at the speed of sound:: about 1600 fps at the 1200dF temperatures of this gas (up from 1150 fps in normal air). At this speed there is plenty of time--especially at peak TQ.

On the back side of the negative pressure wave is a high pressure wave.

At cranking speeds, the compression process is isothermal--that is the compressed gass have plenty of time to shed heat into the cylinder, piston and head. This leads to a linear relation between compression ratio and pressure.

At peak TQ the compression process is adiabatic and leads to significantly higher pressures even if the mixture is not fired.

The release of the energy of the gasoline increases pressure somewhere in the 4X to 5X range from the compressed unburned value in the cylinder at TDC. The amount is dependent on the amount of energy in the gasoline with is dependent on the chemical make up. Tolulene+Xylene (race gas) are closer to 5X, non-ethanol pump gas is closer to 4.5X ethanol is lower at close to 4X.

Peak pressure in the fired cylinder at TDC is in the range of 800 PSI. This produces work as the piston decends until the exhaust valve is opende around 70-90 PSI (full throttle).

We are not talking about a plugged cat, but a cat whose matrix is decomposing.

This vacuum is the negative pressure pulse I have been writing about. But this negative pressure pulse goes back up the SAME header tube it comes down. The other tubes see a positive pressure pulse, as does the front side of the cat.

Pressure waves are more than happy to turn corners, a mass of flowing hot gasses is highly reluctant to turn a corner. Its a wave--to a first order it has no mass--the positive pressure wave travels down through the gas left over from the previous exhaust stroke. The mass of exhaust gas expands from the clinder into the header as this wave races down the tube. As the negative pressure wave races back up the tube it travels through the newly expent gasses.

A mass of hot gas flowing over the front of the cat would. A resonating set of pressure waves would not. You should also know that as this 1200dF gas goes through the first Cat matrix the gas is heated back up to some 2000dF and creating substantial backpressure to the inflowing gasses.

Has nothing to do with the number of valves.
Has nothing to do with the intake center vavle timing
The wave action is greatest near peak TQ not at peak HP
Has a lot to do with the RPM band of the engines--which necessitiate short headers.
Has a lot to do with the high specific outputs of these engines
Might have something to do with the variator timing in the 360
Most other high performance (stock) vehicles don't use real headers (including Z06/Z51)

 

Mitch:

Is there any area of automobiles you don't know about? Between Dave Helms, Brian Crall, you, all The Stooges and many others, I am getting a serious inferiority complex. Jesus, I wish I had 1/10th of the knowledge that you guys possess. You all are an incredibly valuable asset to the 348/F355 section, and FChat in general.

Many, many thanks,

Scott


EDIT: BTW, Brian, I had to go back and edit my post. I initially spelled your name "Brain" instead of "Brian". Do you think it may have been a Freudian slip?