Can some body help here?

"EGT and AFR mean nothing. That damage was caused by cats being overheated, not exhaust gas. AFR does not overheat cats, hydrocarbons do. AFR can be perfect and the hydrocarbons still off the scale.

Like I said, bad diagnostics.

AFR results presuppose a motor in otherwise good condition and correct tune. Any variation from that and an AFR reading is meaningless. It was never meant or properly used for diagnostics and is just a crutch for those with no understanding of the combustion process. The combustion process creates several gasses of interest but AFR? Who cares about that until the motor runs properly?"

OR

"AFR is a mass measure of hydrocarbons as a fraction of air supplied. Fuel is nearly 100% hydrocarbons. If the AFR is ok then there can be no excess of hydrocarbons. The car would be running rich to have excess hydrocarbons which is not conducive to hot exhaust gasses and hence over heated cats.

If the cats were over heated the EGT sensors would have set off a CEL I believe. That is what they are there for as burnt cats don't control emissions well.

One does get AFRs in shape to get the motor running properly. That is what you do when you fiddle with a carb."

 

Thanks Steve, 2 opinions on what AFRs are all about in relation to possible over heated cats. The car's EGTs were working fine so should have set off a CEL if the cats had overheated? AFRs were never richer than 11-12:1 under load nor leaner than stoichiometric at cruise as recorded by a wideband sniffer located down stream of the cats.

More importantly which statement reflects the facts about the relationships of these parameters best. ie: "AFR can be perfect and the hydrocarbons still off the scale." just doesn't make sense to me. The car ran perfectly by the way with regard to ignition timing. If we can just make sense (or not) out of the statements first I will post the complete story with images. I think you have gathered the second statement was mine.

 

Now we are talking. I just followed the instructions given with an Innovate single sensor wide band device. I went through all of this before on the 3inch exhaust thread where nothing was said about the installation or the instrument (except by me). It does make sense that a better AFR reading might be read before a cat. The O2 sensor is the exact same sensor as found x 8 on my 575.

The EGT is an exhaust gas temperature sensor which Ferrari has installed each side to alert the ECUs about abnormal after cat temps. I have never had such a CEL, in fact the car has had very few in my ownership, none that Taz' reset procedure hasn't fixed. My mechanic's Leonardo has not found any such cat issues in reading the relevant ECU. Surely if my cats had fried I would have been alerted? Surely if I had ignition problems giving an incomplete burn, the same?

As I proposed in my original thread in the 456/550/575 section called 'cracked manifolds; what if at some stage before my ownership the cats had been abused and cracks were initiated in the sheet metal manifolds and then the HC problem was fixed. I get the car and immediately start red lining it many times while doing my 60-100mph all in 3rd gear V box times. The cracks started by heat propagate by vibration? Is this a possibility?

I say all this because a 575 which is supposedly as sick as you say it is will not be quicker than stock no matter how big my exhaust. Since the last mail order tune from DMS who were armed with my AFR vs RPM data at full load, my car improved even further to 4.1 sec vs 5.4 sec (stock 60-100). The car has been running extremely well other than the blown fuse which immobilised it and spurred me to get the belt change done while being fixed. It was then that the mechanic heard exhaust leaks with his stethoscope and advised that he pull them and have a look.

So I have already had the cam timing set for SA specs with an improvement noted even with cracked manifolds and only after that I have on the bench, the manifolds which FBB and Paul have agreed are junk. I then think, well I might as well build headers for the car as what came off are ridiculous in their flow potential and it will be far cheaper than buying new garbage. I received criticism for changing the car before fixing the problem, as in the timing and the exhaust manifolds before diagnosing the problem. I am supposed to re-time the cams back to stock and find a good set of manifolds and only then source the cat culprit? Ie: don’t shine the turd. Too late for that.

Now for the hard part, please advise how in a 575 I am to accurately make sure my new cats are not overheating? I will be getting O2 bungs installed on a header each side, right after the ports. I have variable FRP adjustment so will use that to alter the AFR to 12.8-12.9:1 under full load. I will correspond this with the V-box times and hopefully find the best result is at the target AFRs. This will all assume that my ignition is still in its existing perfect working order. The intake manifold has been off and new gaskets installed.

What does a burnt cat look like? Do the cells close up or disintegrate? I hope to get a metallurgy test as from the pics I can’t see heat caused discolouration.

I do know I am a smart arse and that may be the reason for the initially less than helpful responses. I ask that you ignore the me and look at a guy who is having a go at making his F car motor perform as Enzo would have wanted in a less than ideal part of the world for finding expertise around the corner. If the me is ignored perhaps some professional interest by the gurus in this 575 project with a great result in the end, will help others to not make the same mistakes I apparently have. I do truly appreciate the helpful advise I have had so far in this project. Cribbj et al, cheers.

 

My mechanic has seen no metal discolouration anywhere on the cats or the sheet metal manifolds, nor is there any evidence of cat cell material damage when looking in each end of the cats. The cat matrix was intact. Thanks for the interest and assistance, I think the new cats will be ok. I have sure learned a lot more about AFRs in any event.

I am apparently at my limit regards attachments. When I fix I will post some cat pics.

 

I still have not received the pics of the opened cats however here are the manifolds I have had made. They contain cats right after the 3 into 1 collectors. There are extra O2 bungs for proper AFR testing.
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Rustybits, you fail to see the 2 extra O2 bungs before the cats on two of the collectors to temporarily install O2 sensors for my wideband AFR reader. The others are fore and aft of the cats just like the stock positions.

 

Thanks Finnerty, these are being installed on my 575M to mate up to my 3inch exhaust.

 

John, the stainless pipe size is 45mm, same size as the long side of the not square port. I would replace any stock heat shields over the new cats but no taping. I have never had a car with headers which needed shielding or tape.

 

Earnie those measurements are not taken on full load. At full throttle and load the ECUs revert to a fixed MAP. That is the AFRs determined by that MAP which I try and tune. The ECUs seem to do just fine at all part throttle situations.

 

John, I will have to get back to you with the SS grade and wall thickness. The pipe is thicker walled and not as shiny as I used on the exhaust. I haven't seen my car yet, just got back to Oz.

 

John, the headers are made of 304 SS with a 1.6mm wall thickness

 

Quote:
Originally Posted by Rifledriver View Post
A proper diagnosis should have been done but instead, and as usual, it was modified instead.

It is the standard MO of those that do not know how to diagnose.

If you can't make what you already have run correctly it typically means you won't really be able to get what you are building to run correctly either.

FB is correct. Those manifolds are scrap.

And because no overheat warning came on does not mean it was not running too high for long periods as those manifolds suggest. There is an old story in the medical community. The short version is the patients chart shows a healthy man yet he is laying in his hospital bed dead.
Which do you believe? The chart?
See it each and every day.

Oh, and unlike many here, I am unable to fix cars on the internet. Just have not developed that talent."


So Rifledriver, "It is the standard MO of those that do not know how to diagnose". I respectfully suggest Rifledriver that you are often premature in your comments (diagnoses) and always quick to criticise. You and Fat Billy Bob looked at images of my cracked manifolds then you both made the diagnosis that I had fried my pre-cats. You totally ignored the fact that my car is a rocket compared to most 575s which could not happen if it was a turd. You both were then were derisory of mine and my mechanics efforts. The only turds that needed shining were your comments. The images of the cut open pre-cat of the worst cracked manifold speak for themselves. The inlet (top) and outlet faces of the cat matrices are perfect. They have never over heated. The stock manifolds are the turds and believe it or not many many Maranello manifolds are probably cracked as well. My mechanic who is ex-Ferrari dealership says that half of all 360s which came in for service had cracked manifolds also. These were replaced with 430 manifolds. He was not surprised at all at the condition of mine. Having said all that, despite having to squeeze you for information, I did learn a few things. Cheers.

I have also posted this on the technical forum in my thread 'Can some body help here?'

 

The pics referred to below. The rest of the posts are in the 575 section in my post "Cracked manifolds"
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