V12 CAT question

[melhuishjames]

Hi,

I speculatively put my V12V up for sale yesterday evening. I think I’ve already changed my mind !


But I had a question today and didn’t understand what was being asked or why:

“have the cats been removed from next to the manifold?”

Just curious what this was about, I’m not conscious of an issue re the cats or need to move them so just wondering have I missed something?

Thanks James

[Simpo Two]

Decatting TVRs to make them louder was a well-known thing, so he's probably thinking of that.

[vpr]

You can delete primary or secondary cats.

Most do secondary’s. Sounds lovely

[melhuishjames]

Thanks for feedback. Pleased if that’s all it is. Thought maybe I’d missed a common issue.

As is after 3 enquiries I’ve lost interest in selling. Moment of weakness I think..

[GT3ZZZ]

IIRC, the AMR exhaust that came with the factory powerkit had the secondary cats deleted.

For even more noise, the primaries can be deleted so just secondaries are run.

I have a set of Velocity AP Manifolds (primaries deleted) and secondary cat pipes on the shelf if anyone's interested.

[Finding Neutral]

melhuishjames said:

Hi,

I speculatively put my V12V up for sale yesterday evening. I think I’ve already changed my mind !


But I had a question today and didn’t understand what was being asked or why:

“have the cats been removed from next to the manifold?”

Just curious what this was about, I’m not conscious of an issue re the cats or need to move them so just wondering have I missed something?

Thanks James

It’s actually a pretty valid question and I’m really surprised nobody has mentioned it yet.

The v12 Astons are known for cat ingestion, where the engine recirculates cat debris back in to the motor and pops the motor.

It’s a fairly common mod to remove the cats from the manifold to avoid this happening. A replacement engine is not cheap as you can imagine. It’s really not worth the aggro leaving the cats in as the scope for damage if it does happen is massive.

Edited by Finding Neutral on Monday 6th February 19:29

[andy_ran]

melhuishjames said:

Hi,

I speculatively put my V12V up for sale yesterday evening. I think I’ve already changed my mind !


But I had a question today and didn’t understand what was being asked or why:

“have the cats been removed from next to the manifold?”

Just curious what this was about, I’m not conscious of an issue re the cats or need to move them so just wondering have I missed something?

Thanks James

It was a much more common issue on DB9s. But if the car develops a misfire, it has a high chance to break the primary cats down, which are in the manifolds, when they break down they get sucked back through the engine totalling the block

Its common to fit aftermarket manifolds and keep the secondary CATs in place as they are too far down the exhaust path too 1, get broken up by a misfire and 2 too far away to get sucked back in

V12Vs don't seem to suffer the same common fate as the DB9s from what I understood - But I know when I had a coil start to miss, Aston Insisted I didn't drive the car any more and got it towed in as there was a worry over CAT breakup

[Jon39]

andy_ran said:

It was a much more common issue on DB9s. But if the car develops a misfire, it has a high chance to break the primary cats down, which are in the manifolds, when they break down they get sucked back through the engine totalling the block. ...


... V12Vs don't seem to suffer the same common fate as the DB9s from what I understood - But I know when I had a coil start to miss, Aston Insisted I didn't drive the car any more and got it towed in as there was a worry over CAT breakup

In one of the BR videos, I thought there was mention of the V12 manifolds being the same for several V12 models.
Think one particular pair of cylinders were described as being closest to the cats, so they begin the chain of events if there is trouble.

Also there was a reason given for the sucking back. Designed in to achieve something with dirty gasses. Anyway along those lines. Need to watch the video again, but mine is a V8, so manifold design not the same.

[Longy00000]

This is a question about the 4 primary cats on the header pipes. There is a 'risk' of ingestion of any debris from the inards of a broken down cat sometimes caused by a misfire where unburnt petrol gets passed out ghe cylinder into the cat which is hot enough to ignite it which burns and hence ultimately breaks down the cat. Some of that debris then gets passed back into the air intake side via the exhaust gas recirculation system ( emissions driven) where it can damage the cylinder internals.
It's quite a remote chance though BR go on and on and on about it yet to the point you woukd think every V12 had imploded because of this. I'm sure it's happened to someone and may be it was more common on the DB9s(?) But I've still not met anyone who has suffered from it or even knows someone who has suffered from.it.
It's not something I concern myself with, at least not yet. It's perhaps more relevant on older models where the cats are obviously older and at more risk of breaking up internally and perhaps where rhe maintenance isn't quite as full as it could have been (more chance of a prolonged misfire not being attended to)
ThevBove is my understanding of the issue so its a valid question but not necessarily a huge issue and in my belief an overblown issue at that. I'm sure others will beg to differ

Edited by Longy00000 on Monday 6th February 21:58

[lime1]

Primary cat ingestion on the V12V engine may be a rare event but if I recall correctly it has happened to someone on PH previously. The science behind it seems plausible (see BR video). My V12V had already had secondary decat. I decided it was worth the relatively modest price (compared to full engine rebuild) to do a primary decat and put in some 200 cell secondaries, for my peace of mind.

[phumy]

BR seem to mentioning primary cat ingestion almost every other video now that he has an engine build facility, talk about scaremongering tactics. He's been banging on about it for a couple of years now, yet I've never heard of one being mentioned on this forum. Mike does like to bang his drum but also loves to scare people, and I'm sure that plenty of owners fall for it too and splash out thousands for no reason except to make a lot of noise and an extra 20HP that you'd never notice over and above the 565HP it already has.

[nickv12]

That cat ingestion topic

If you have a V12 which develops a misfire, it would be advisable to stop driving ASAP and get it recovered and fixed.

The V12 AMR (for the UK market, at least) weren’t fitted with secondary cats, so the only was to remove the front ones is to add secondary ones. And many wise people have already removed the secondary cats for full effect anyway.

[phumy]

If it was so prevalent then we would be hearing about it very regularly on here, but we don't.

Its all scaremongering and too many people believe it, running straight to BR and aying out a fair wedge to get the cats removed.

[AdamV12V]

GT3ZZZ said:

IIRC, the AMR exhaust that came with the factory powerkit had the secondary cats deleted.

The factory powerkit and AMR were V12VS specific and did not apply to a V12V

[Felonious]

lime1 said:

Primary cat ingestion on the V12V engine may be a rare event but if I recall correctly it has happened to someone on PH previously. The science behind it seems plausible (see BR video). My V12V had already had secondary decat. I decided it was worth the relatively modest price (compared to full engine rebuild) to do a primary decat and put in some 200 cell secondaries, for my peace of mind.

How are you getting on with it, Lime1? Noise, any discernible increase in grunt (not that it needed it!)

[ds666]

phumy said:

BR seem to mentioning primary cat ingestion almost every other video now that he has an engine build facility, talk about scaremongering tactics. He's been banging on about it for a couple of years now, yet I've never heard of one being mentioned on this forum. Mike does like to bang his drum but also loves to scare people, and I'm sure that plenty of owners fall for it too and splash out thousands for no reason except to make a lot of noise and an extra 20HP that you'd never notice over and above the 565HP it already has.

BR have a lot to answer for. They seems to be set on creating real fear about everything they offer a solution to ...

I haven't heard other specialist harp on about anything - mind they aren't as " in your face " as BR .

[M1AGM]

Valid question by the potential buyer, refers to the primary cats.

My understanding is that all the Gaydon V12s have the same ceramic primary cats in the manifolds. I’d be interested to know where the previous poster got the DB9 specific information from?

From what I have read, ceramics were used as a cheaper option, as is the system managing the gasses. Ceramic cats will eventually start to break down due to repeated heat cycles, so I would expect this issue to become less rare in time.

Is this really ph? A car owner spending their hard earned to make their car louder, faster, and mitigating the cause of a potential engine failure - ‘no reason’.

[ds666]

To add some balance


From McGurks' website

"There is a lot of talk about the threat of your catalytic Converter failing and causing untold damage to your engine. This is possible however it is not something that has ever caused us a problem. John McGurk has been buying and selling Aston Martins for almost 25 years during which time we estimate conservatively he has bought something in the region of 3500-4000 Aston Martins. He has never had an engine issue due to a Catalytic converter failing and writing off the engine."

[Jon39]

ds666 said:

To add some balance ...

Did I read about a 'hotel' stay, following something about not telling the truth ?

[Felonious]

Can we conclude that:

a) valid reasons for removing the primary cats are to improve performance reduce weight and make the car louder;
b) invalid reasons are in case the engine inhales the cats and promptly dies.

?