Myth or Fact: Pre-Cat or Main Cat Failures

If the pre-cats are metallic honeycombs then what material is sucked into the engine that causes so much damage? All the posts I've read refer to the ceramic breaking up.
Alan

 

You are correct, it is not ceramic but the metal matrix is brittle and breaks up in a similar way.

 

I was a retained expert for a case involving this exact topic and did a great deal of research. I was not able to find a single verifiable incident of precat failure that was not attributable to a long term running issue exposing the cat to excessive HC and the resulting high temps.

I know there will shortly be a chorus saying "mine failed and my car ran perfectly". I researched many cars with the same claim only to find an undetected running issue. That alone further underscores having the car serviced by people that are really up to speed. In the cases I investigated the car didn't become a problem, incorrect servicing caused the problem. In other words it was a result of human interaction.


The problem with the Ferrari header is the precat is placed at the confluence of the 4 pipes and when a break up type of failure takes place it partially blocks the matrix causing the exhaust gas pulses to literally pump the debris laden gas from one cylinder to another. Due to the overlap inherent in valve timing the debris will find its way all the way to the intake manifold and the induction system.


In 2000 the emission output was reduced. Precats and air injection was added to make the cold start test cleaner.



Before people start throwing Ferrari under the bus for this, much larger and highly respected auto manufacturers have this exact problem and researching their issues helped greatly in the overall understanding. In that sense much of my work was done for me. Ansa or whoever designed these manifolds just copied others, it was not an original idea. The problem here is really not the design, it is the servicing and that is not Ferraris fault. I know it makes great internet lore to say Ferrari cats are junk. As a general rule that is not true. Blaming Ferrari for cat failure is no different than blaming guns for crime. The servicing in many cases is a disaster but we can't blame Ferrari for that now can we?

 

Brian,
Is there for a Ferrari tech to tell whether the pre-cat matrix is going bad even if the car is showing no signs of an issue. I recently purchased a 2000 306 with a Tubi exhaust that passed the PPI with flying colors. Car is running great, but for "peice of mind" I am wondering if there is any inspection that can be done of the precat (e.g., bore scope through a sensoring fitting) that might show the condition of the matrix material.

Ken

 

No, not really. After it has started you can if you know what to listen for.


What tests were run to assure the car is running great?

 

Brian,
My PPI was done at Norwood Auto Italia in Dallas (James Patterson & Mike Luongo). These guys really know their stuff. They did a full PPI, including road test, leakdown, compression and a full check on an SD2.
Ken

 

Rifledriver,

I understand your point and logic re "don't blame the manifolds" because they only fail "if the engine isn't tuned properly" (btw, is this what you are saying? I didn't know what you are inferring is causing the excessive HC and heat).

That said, there are a lot of failures here.

IMHO, isn't part of engineering any high quality system (cars, planes, dishwashers, phones, cameras, etc, etc) to build in enough quality/over-built/tolerance such that they don't fail because of a "seemingly common" (at least that's what I gather from your comments) failure (in this case to properly tune the cars)? I mean, every part/system has to deal with an imperfect environment. Some are designed with these imperfections considered and addressed. Some are not.

 

If you build it like a tank it will drive like a tank. The more performance you ask from anything the lower you make your safety margins.

And on top of that I guess you didn't read the part about other manufacturers?
Honda had such a problem it caused a recall.

Considering the fact that this almost always is caused by service related screw up it also stands to reason that cars that are far less service intensive will have a lower incidence of failure.


Ferrari pioneered the use of metallic cats. That was the best technology available.


Again, don't blame Ferrari, blame the dip **** mechanic you hired to work on the car.

 

I’m with Brian on this one.

I have a little Mazda Miata MX5 for daily driving on nice days. Read the forum on these cars (almost 1 million produced). Cat failure is common and it is almost always traced back to something else, bad coil pack, bad plug, camshaft sensor, throttle body etc etc. Something that creates an issue with the exhaust gas. People have replaced the Cat only to have it fail again in a short period of time. Once the root cause of the problem is resolved the Cat lasts a long time. Many of the Miata’s are out there with over 150,000 miles still running the original Cats.

Another entertaining fact is the Miata has a “cam belt” and calls for replacement at 60,000 miles or 6 years. Total cost for belt service with water pump is $800. The Miata is truly “cheap fun”.

 

between listening to the sound on start up carefully and a bore scope, mine would have been caught. Fortunately sound alone was enough to alert on a loose pre cat, there were some pieces loose but had not not entered the engine. Early detection is the key in a lot of stuff.

 

Thanks, I figured that was part of it (that getting high performance requires it to be less "tank like".)

What is it exactly that the "dip **** mechanic's" are doing wrong that is causing this problem?

 

As my old southern friend would say "You pay's your monies or you take your chances"

 

There are so many noises coming from the engine, it's hard to detect the sound of a failing pre-cat. If you are lucky, and have very good hearing that can detect a ticking sound different from other ticking sounds in a normally running 360 engine, that's great. And you have to know what a normal baseline sounds like, too. Most of us can't tell, especially because we have exhausts that run loud enough to drown out most other noises.

After a brief, non-scientific survey of friends with 360s, it seems that excessive heat is the main cause of pre-cat failure. This can be caused, as RifleDriver said, by lack of response to a maintenance issue, or by the high heat caused by prolonged, hard running on a track.

The pre-cats appear to be pressed into place, held by friction. When the headers get really hot, they expand, and repeated, high heat cycles seem to work the pre-cats loose with the other vibrations and pressures associated with exhaust flow. When they start rattling around, they start to come apart.

This is what pre-cats look like when removed after failing. These show evidence of flaking of the honeycomb material.
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When the fine tolerances of standard engine operation are negatively impacted by poor diagnostics and poor servicing (it happens, not everyone can go to a Rifledriver to get their car serviced), the management software should be able to raise a fault code [CEL] and inform of the problem to prevent it going further (unnoticed) and eventually causing catastrophic engine failure.

You shouldn't really have to be trained to listen for tell tale signs of cat breakup. Sensors should be doing this job for you in a well designed system. Ofcourse, IMHO the Cat headers, being a US option that was retro fitted later, just simply never got any intelligent sensor tech added. Obviously this consideration was never designed in from day one.

Even Ferrari expect people to retrofit aftermarket exhaust at some point ( indeed a large proportion of customer base do this ), in the case of the press fit of the header cats, extra vibration/heat was always going to be an outcome. Nobody ever fits an exhaust or cat to quieten down their car more than stock. This can only exacerbate the issues however many manufacturers would consider an aftermarket exhaust system as 'voiding' the warranty so perhaps this suggests that if you do fit a non Ferrari exhaust perhaps you should address the header cats too (just in case). Also as the cars get older (and these pre-header cat's age) its only a matter of time before they eventually let 'go'. No matter how pristine the servicing is, cats still can crack, vibration and heat can still cause issues and metal does indeed fatigue.

If it where my car, the fact you gain significant torque, power and throttle response from removing them, and all of these cars are waaay out of the factory warranty period now, I'd have no hesitation (especially if I'd gone down the aftermarket system route) to also do the headers too.

 

+1. Apart from the fact it is illegal to remove them in California. Of course, California is not going to pay for the engine damage when (not if?) they let go.

 

Well I don't condone doing anything illegal (heaven forbid!) so I'd just alter my suggestion to in any states where its legal to do so!!! In CA, buy a '99 model or make damn well sure you live near Rifledriver

Joking.

Obviously your going to need to keep your fueling system in absolute pristine condition to help prevent the cats overheating.

1. Are your fuel injectors clean and spraying perfectly? (if not get them cleaned and replaced)
2. What about the resistance from the ignition coil packs (if not again swap 'em out)
3. When did you replace the spark plugs?
4. Are your header gaskets leaking?

A lot of this stuff can be monitored (along with temps from the cat themistors - which measure how hot it is getting - triggering a SLOW DOWN on the dash). I imagine long term inefficiency on any of the fueling side of the engine normally just causes poor mpg (on most cars) but in this case the cats getting blasted with super hot temps just don't stand a chance in the longer term...

 

Did he mention a specific code

Sent from my XT1019 using Tapatalk

 

Also add to this list probably worth replacing the o2 sensors too if you want really good fuel efficiency.

 

It is illegal throughout all the US. Fine can be $100K, so do what you want.......

 

Well that settles that then!

Wow, so just how can companies offer catless headers (not just offer but actually FIT them) to US customers for road car applications (not offroad challenge cars) knowing that fitting them is illegal? US law can be as strange as fiction!

 

They can't legally fit them to road cars. The aftermarket headers without cats are for "off road use only". IF the buyer chooses to use it on the road that isn't an error of the manufacturer/seller. In fact, in CA you can't install any high flow cats on a road car because they aren't certified by the air resources board.

Now, many states don't test smog or inspect cars so it is pretty wide open. Not really a loophole but lack of enforcement in some locations.

 

After reading this thread, I'm ready to change my CS headers to Fabspeed or Euro CS headers. In doing so, will I have any CEL problems to contend with ? Any insight is appreciated.

Also, assuming you do a thorough major on the car every three to five years, plugs, plug wires, etc., what exactly are we talking about service wise that leads to these running condition issues? The annual services are just fluid changes........
What exactly are people neglecting to do that causes this?

 

Yes, you'll probably get a cel. On my 03 Modena I managed to resolve things with big daddies mini cats, and left the O2 sensors active instead of eliminating them with a tune. Just look at where the O2 sensors are mounted -if it's the same as a Modena you'll see how it's more likely to get a cel with headers than with cats.

 

There has been a recent case where the Feds ran down a supplier, shut them down, followed up by contacting it's customer base and checking cars. They can and will, confiscate the car as well as fine................. Depends if anyone shakes the applecart and they feel the need to justify their existence............