V12 Misfire & Cat ingestion

[Dewi 2]

My guess is that the reguations became stricter in about 2010, because that was when the V8 Vantage first had a pair of cats fitted in the manifolds.

[Caslad]

Simpo Two said:

Thanks. I can understand that 12 cylinders have 3x the chance of a misfire than 4, but why would they be more difficult to detect? A Foxwell with the right software can find them. (Unless you mean feel during driving of course).

Presumably the cats were put there for some other reason because they didn't realise the risks... not great design IMHO.

Is it unfeasible to retro-relocate them further away?

I believe that the manufacturers have to make a car which will conform to a certain emissions level on start up, hence the primary cats, secondary air pumps and the like. However as down the line the MOT only tests emissions on a warm engine and not the emissions on start up such devices do not benefit the customer directly* and often serve only as another thing to go wrong.
So to answer the question, ‘Is it unfeasible to retro-locate them further away?’ then as an individual owner there’s no point, just do away with them & the secondary cats will easily suffice for the MOT.

• except of course to reduce air pollution for us all.

[Simpo Two]

LTP said:

stuff

Caslad said:

I believe that the manufacturers have to make a car which will conform to a certain emissions level on start up, hence the primary cats, secondary air pumps and the like. However as down the line the MOT only tests emissions on a warm engine and not the emissions on start up such devices do not benefit the customer directly* and often serve only as another thing to go wrong.
So to answer the question, ‘Is it unfeasible to retro-locate them further away?’ then as an individual owner there’s no point, just do away with them & the secondary cats will easily suffice for the MOT.

Interesting. I have no great desire to remove the primary cats, but as and when the primary cats get fried due to misfires, just hoik them out and carry on...?

[Caslad]

Simpo Two said:

Interesting. I have no great desire to remove the primary cats, but as and when the primary cats get fried due to misfires, just hoik them out and carry on...?

Indeed. This is exactly what BR offer with their primary decat- retain the manifolds but simply cut a hole in the ‘canisters’ which contain the ceramic catalyst matrix, remove said matrix & weld the hole back up.
The aftermarket manifolds available have no primary catalyst to begin with & all options rely on high flow secondary cats to meet the emissions requirements.
After I had Quicksilver manifolds & ‘race cats’ fitted the emissions at MOT were lower than the OEM set up!

[nickv12]

“The solution” is not always an option.

I have a V12 AMR, so never came with secondary cats. Therefore if I’m to avoid this according to the originator, I’d probably have to install aftermarket primary cats. I’m sure emissions regs means I can’t remove the primaries and only have secondaries.

But I’m still under Timeless warranty. So if I have these third party primary cats installed and something then went wrong, trashing the engine along the way, AM would be in the right to void the warranty claim.

Sorry to read an earlier responder that they’ve experienced it twice!

[LTP]

db11far said:

Hi

DB11 V12 owner here. Purchased Q3 22. Misfire + debris ingestion. Happened twice.
First time in AMB dealership, around £25k spent on repairs under warranty incl. new cat, fuel pump, plugs et al.
Second time again for another misfire, same sort of thing, in AMR dealership now under warranty.
Pity as the only two times it happened (in c2500 miles), was when the lady was in the car with me... she has only been in it about 3/4 times so far.

I doubt that your car has the same problem as the DB11 V12 has turbochargers, and the catalysts are downstream of the turbos. Turbocharged engines are unlikely to be able use valve overlap to pull exhaust gasses back into the engine as they want the exhaust gases to drive the turbos.

I suspect (but don't know, obviously) that whatever ails your car it isn't ingestion from a catalytic converter, or ingestion of anything from the exhaust.

[Minglar]

LTP said:

db11far said:

Hi

DB11 V12 owner here. Purchased Q3 22. Misfire + debris ingestion. Happened twice.
First time in AMB dealership, around £25k spent on repairs under warranty incl. new cat, fuel pump, plugs et al.
Second time again for another misfire, same sort of thing, in AMR dealership now under warranty.
Pity as the only two times it happened (in c2500 miles), was when the lady was in the car with me... she has only been in it about 3/4 times so far.

I doubt that your car has the same problem as the DB11 V12 has turbochargers, and the catalysts are downstream of the turbos. Turbocharged engines are unlikely to be able use valve overlap to pull exhaust gasses back into the engine as they want the exhaust gases to drive the turbos.

I suspect (but don't know, obviously) that whatever ails your car it isn't ingestion from a catalytic converter, or ingestion of anything from the exhaust.

Must admit LTP I’ve never heard of this problem with the 5.2TT V12. I was always under the impression that any primary cat ingestion, as rare as it may be, was only an issue with the previous gen Gaydon V12 engines, ie DB9, Virage, DBS, Vanquish, V12V etc. Mine is going in for a service in a few weeks time and I’ll ask them to check for any out of range misfiring, as that seems to be the initial cause of the problem. Thanks for the heads up on the engine warning light. Seems strange to me that it only shows up when potentially the damage has already been done. But as said elsewhere, it’s easy to ignore these warnings, and I guess one does so at ones peril. Better to be safe than sorry. Fingers crossed nothing shows up.

Best Regards

Minglar

[db11far]

LTP said:

I suspect (but don't know, obviously) that whatever ails your car it isn't ingestion from a catalytic converter, or ingestion of anything from the exhaust.

Interesting. Thanks for confirming re turbochargers. The previous dealership definitely stated that they replaced the cat due to debris being present inside it however, where it came from... I would not know and they were not particularly transparent either. They started off with a fuel pump.

From my side, the one commonality is the sound of "debris" when idling and a misfire. I also tend to stop driving immediately following the engine warning popping up.

[Calinours]

LTP said:

db11far said:

Hi

DB11 V12 owner here. Purchased Q3 22. Misfire + debris ingestion. Happened twice.
First time in AMB dealership, around £25k spent on repairs under warranty incl. new cat, fuel pump, plugs et al.
Second time again for another misfire, same sort of thing, in AMR dealership now under warranty.
Pity as the only two times it happened (in c2500 miles), was when the lady was in the car with me... she has only been in it about 3/4 times so far.

I doubt that your car has the same problem as the DB11 V12 has turbochargers, and the catalysts are downstream of the turbos. Turbocharged engines are unlikely to be able use valve overlap to pull exhaust gasses back into the engine as they want the exhaust gases to drive the turbos.

I suspect (but don't know, obviously) that whatever ails your car it isn't ingestion from a catalytic converter, or ingestion of anything from the exhaust.

^^ This. (as regards the V12 turbo)

I can’t say for certain when they got introduced in the 5.9 V12, however Pre-cats or exhaust manifold cats were introduced to the V8 with the 2011 Vantage S. The same solution was deployed in standard V8 from around 2012. It is a bit of a shame that the introduction of the S overlapped exactly with the requirement for the pre-cats, as the S, had it not had to have them, with its new ignition strategy, active airbox and otherwise full revised exhaust would have been 440hp, as the later GT8 cars that dropped the secondary cats were. Even sadder was that the bean counters forced the abandonment of the planned twin throttle intake as they felt it would have made the already costly V8S too expensive. Even with the pre-cats the S would have been 450bhp.

The reason for the new cats was that the S, being homologated post a certain date, had to be compliant with the newer emissions regs, which at that time was Euro V.

Euro V introduced stricter criteria for the ‘warm up’ time of the car, ie how long the engine could run from cold before the CO from the exhaust met the limit. It meant one thing, the cats had to get much nearer the exhaust port, so they could ‘light off’ much faster. Of course, being so much closer to the engine meant not only did they ‘light off’ much faster, but they were also exposed to more heat in general, peak operating temperatures went up, closer to the limits of some of the catalyst matrix substrate materials.

Only after this solution had been readily deployed by many manufacturers (all needing to comply with the stricter criteria with new models) did reports begin to surface of some engines where high valve overlap was deployed for either high rpm scavenging or EGR purposes, where post failure tear downs identified catalyst ingestion as a root cause, with one of the identified onset mechanisms being malfunctioning ignition or fuelling systems.

The way to ameliorate any risk, real or otherwise, is to remove the primary catalysts. While they are needed for the homologation testing, they are not needed for an MOT, which actually requires the engine to be warm before the gas is analysed. Any ‘normal’ or even race (200cell) secondary catalyst (or ‘normal’ catalyst) is enough, though you do have to make sure the race ones are really hot before submitting for MOT, as I found.

If this isn’t palatable, or you have a car with primaries only, and don’t want to swap them for a new manifold and a new secondary cat (effectively the older freer breathing but MOT passing spec) then the way to minimise the risk is to keep to the maintenance regime very strictly, replacing ignition and fuel system components according to whatever develops as best practise, which may be more or less often than that specified in the OEM manual, which it must be remembered, would have been originally written with less in service knowledge than now exists.

Edited by Calinours on Saturday 15th April 13:20

[Simpo Two]

Caslad said:

Simpo Two said:

Interesting. I have no great desire to remove the primary cats, but as and when the primary cats get fried due to misfires, just hoik them out and carry on...?

Indeed. This is exactly what BR offer with their primary decat- retain the manifolds but simply cut a hole in the ‘canisters’ which contain the ceramic catalyst matrix, remove said matrix & weld the hole back up.

Thanks very much; I feel I no longer need to worry too much about misfires. And if that is the simple BR solution you wonder why they seem to make a career of worrying people about misfires and cat destruction.

[Dewi 2]

Simpo Two said:

Thanks very much; I feel I no longer need to worry too much about misfires. And if that is the simple BR solution you wonder why they seem to make a career of worrying people about misfires and cat destruction.

Imagine that you are an independent Aston Martin garage and (say) only two of your customers had V12 engine destruction, caused by ceramic cat particles.

If you also liked making YouTube videos, would you keep silent about the experience of your two customers ?
( It might have happened twice, but no need to say anything to other V12 owners. Must not worry them. )

We don't know how many BR have encountered. Presumably it is not zero.
If I remember, I might ask when there next time.

[Wafu7]

Calinours said:

^^ This. (as regards the V12 turbo)

I can’t say for certain when they got introduced in the 5.9 V12, however Pre-cats or exhaust manifold cats were introduced to the V8 with the 2011 Vantage S. The same solution was deployed in standard V8 from around 2012. It is a bit of a shame that the introduction of the S overlapped exactly with the requirement for the pre-cats, as the S, had it not had to have them, with its new ignition strategy, active airbox and otherwise full revised exhaust would have been 440hp, as the later GT8 cars that dropped the secondary cats were. Even sadder was that the bean counters forced the abandonment of the planned twin throttle intake as they felt it would have made the already costly V8S too expensive. Even with the pre-cats the S would have been 450bhp.

The reason for the new cats was that the S, being homologated post a certain date, had to be compliant with the newer emissions regs, which at that time was Euro V.

Euro V introduced stricter criteria for the ‘warm up’ time of the car, ie how long the engine could run from cold before the CO from the exhaust met the limit. It meant one thing, the cats had to get much nearer the exhaust port, so they could ‘light off’ much faster. Of course, being so much closer to the engine meant not only did they ‘light off’ much faster, but they were also exposed to more heat in general, peak operating temperatures went up, closer to the limits of some of the catalyst matrix substrate materials.

Only after this solution had been readily deployed by many manufacturers (all needing to comply with the stricter criteria with new models) did reports begin to surface of some engines where high valve overlap was deployed for either high rpm scavenging or EGR purposes, where post failure tear downs identified catalyst ingestion as a root cause, with one of the identified onset mechanisms being malfunctioning ignition or fuelling systems.

The way to ameliorate any risk, real or otherwise, is to remove the primary catalysts. While they are needed for the homologation testing, they are not needed for an MOT, which actually requires the engine to be warm before the gas is analysed. Any ‘normal’ or even race (200cell) secondary catalyst (or ‘normal’ catalyst) is enough, though you do have to make sure the race ones are really hot before submitting for MOT, as I found.

If this isn’t palatable, or you have a car with primaries only, and don’t want to swap them for a new manifold and a new secondary cat (effectively the older freer breathing but MOT passing spec) then the way to minimise the risk is to keep to the maintenance regime very strictly, replacing ignition and fuel system components according to whatever develops as best practise, which may be more or less often than that specified in the OEM manual, which it must be remembered, would have been originally written with less in service knowledge than now exists.

So does this mean the post-2012 V8V (and post-2011 V8VS) has the very same vulnerability as the NA V12s? My pre-purchase research threw up the potential issues with V12s, which rolled into my eventual decision to go the V8 route, and I thought I'd read something somewhere about no V8s having that vulnerability, regardless of production date (damned if I can find it now). Do I need to add some additional pennies to my twin plate clutch kitty?

[Calinours]

In a word, no. I’ve never heard of it on the V8. Remember they are completely different motors, employing different valve timing, different pre cats, and different ignition strategies, and perhaps also a longer minimum distance to the pre-cat. whatever, as others have stated, it seems there is not a huge amount of evidence that the issue is even already affecting the V12, however as the V12s age and perhaps the odd bit of ignition maintenance is neglected, I would not entirely bet against it affecting some V12s sometime in the future.

In a nutshell, from all the I have ever seen and read, it would appear you are pretty safe with any V8V.

Edited by Calinours on Saturday 15th April 17:03

[Simpo Two]

Dewi 2 said:

Simpo Two said:

Thanks very much; I feel I no longer need to worry too much about misfires. And if that is the simple BR solution you wonder why they seem to make a career of worrying people about misfires and cat destruction.

Imagine that you are an independent Aston Martin garage and (say) only two of your customers had V12 engine destruction, caused by ceramic cat particles.

If you also liked making YouTube videos, would you keep silent about the experience of your two customers ?
( It might have happened twice, but no need to say anything to other V12 owners. Must not worry them. )

We don't know how many BR have encountered. Presumably it is not zero.
If I remember, I might ask when there next time.

Why not; a sense of proportion is a wonderful thing and help people get a true picture.

You make a good point regarding Apocalypse 3 - Engine Destruction, though again how many of x,xxx V12s produced have been destroyed in that way?

Maybe it's all a cunning plan by makers of coilpacks and sparkplugs and gets lots of clicks on YouTube...

[Felonious]

Caslad said:

On the other hand if the car was to be a keeper (as is the case with mine) significant engine damage would be a disaster not just because of cost but due to the unavailability of a replacement engine & therefore a primary decat makes more sense. Going with aftermarket manifolds such as BR, Quicksilver, VAP may also add some performance improvements.

As always you pays your money & takes your choice.

Mine's a keeper and I went for the BR manifolds and sports secondaries. I didn't do it because of any fear of cat ingest (although it's nice to know that will not happen) but because the V12 is a wonderful engine heavily constrained by the standard manifolds. It was a pleasure to drive before, and now it's even better. So much more grunt, and in case you ever want to go really quickly it's somehow even more willing. Also, it sounds (according to a friend) better than any road car he's ever heard. Like a Pagani, apparently. I'm personally very happy with the work done and the outcome (although my motives were unrelated to the thread topic).

[Wafu7]

Calinours said:

In a word, no. I’ve never heard of it on the V8. Remember they are completely different motors, employing different valve timing, different pre cats, and different ignition strategies, and perhaps also a longer minimum distance to the pre-cat. whatever, as others have stated, it seems there is not a huge amount of evidence that the issue is even already affecting the V12, however as the V12s age and perhaps the odd bit of ignition maintenance is neglected, I would not entirely bet against it affecting some V12s sometime in the future.

In a nutshell, from all the I have ever seen and read, it would appear you are pretty safe with any V8V.

[Jon39]

Calinours said:

In a word, no. I’ve never heard of it on the V8.

The BR videos suggest that any potential V12 ingestion, only involves a few specific cylinders, where there is a very short distance between exhaust port and primary cat.

When primary cats were introduced on the V8 cars, the primary cats in the manifolds are further away from all the exhaust ports, so different circumstances. Anyway, I don't think it uses the cam overlap technique.

Edited by Jon39 on Saturday 15th April 19:17

[LTP]

Calinours said:

In a word, no. I’ve never heard of it on the V8. Remember they are completely different motors, employing different valve timing, different pre cats, and different ignition strategies, and perhaps also a longer minimum distance to the pre-cat. whatever, as others have stated, it seems there is not a huge amount of evidence that the issue is even already affecting the V12, however as the V12s age and perhaps the odd bit of ignition maintenance is neglected, I would not entirely bet against it affecting some V12s sometime in the future.

In a nutshell, from all the I have ever seen and read, it would appear you are pretty safe with any V8V.

Adding to your list of differences V8 to V12, the V12 uses an internal EGR (Exhaust Gas Recirculation) system using valve overlap to pull exhaust gasses back into the cylinders at the start of the induction stroke, the V8 has an external EGR system where exhaust gasses are piped from the exhaust system into the engine.

As an aside, this external EGR on the V8 is the system where some people will try to convince you that you need (and sell you) a (pointless) oil catch tank

Clarification added

Edited by LTP on Sunday 16th April 00:14

[Simpo Two]

LTP said:

...to pull exhaust gasses back into the cylinders at the start of the induction stroke... exhaust gasses are piped from the exhaust system into the engine...

It gives a whole new meaning to 'running on fumes'... To me the idea of getting an engine to eat its own st makes no sense, so presume it's for emission reduction?

There's some good solid info coming up on this thread; good reading and learning.

[LTP]

Simpo Two said:

It gives a whole new meaning to 'running on fumes'... To me the idea of getting an engine to eat its own st makes no sense, so presume it's for emission reduction?

Yes, apparently. It reduces peak combustion temperature, which reduces NOx and also protects the catalytic converters from the exhaust gasses being too hot.