No probs...

Yes, the V12 would ingest a failing cat.

The V12 is basically 4, 3 cylinder engines. Yes, each bank shares a common inlet manifold but the exhaust headers group cylinders 123 - 456 - 789 - 10,11,12.

I had never seen this before working at Aston, and is a phenomenon.
Due to the firing pulses created by a group of three cylinders sharing a header (each header has its own starter catalyst), if the catalyst matrix fails the debris is sucked back up into the engine, into the inlet manifold and distributed amongst the adjacent cylinders - happened a number of times to me and others in development. As the catalysts are bomb-proof on V12 I dont expect this to be a problem for anyone to worry about. Just a development tale....

The V8 would not do this as the resonance / breathing in the headers is not the same from a group of 4

 

I'm not an expert on this, but my understanding is that normal EGTs for naturally-aspirated engines are much lower than that, by a few hundred degrees F. If this engine really runs EGTs that high (850 C is around 1560 F) then I think something is wrong. If that's tied in with the spark angle as you say, then there's a design flaw with the cylinder head. And the restrictive cats would definitely be an issue, as that heat would be trapped and the air compressed, leading to more heat. And if a small change in AFR is enough to raise the temp enough to melt the exhaust valves, then how is it that in thousands of miles of driving among the different supercharged cars (with 200-250 hp over stock) we haven't seen any blown valves?

Again it goes back to this...since this is not a high hp/liter, high-revving, maxed out engine, then the parts should not be under that much stress or develop those temperatures. If the engine is that fragile that such a small change could melt the exhaust valves, then there's a problem. And if the engine is that fragile how could it stand up to the endurance tests you mentioned?

 

[QUOTE=AM Dragon Maker;3204743]No probs...

Yes, the V12 would ingest a failing cat.

The V12 is basically 4, 3 cylinder engines. Yes, each bank shares a common inlet manifold but the exhaust headers group cylinders 123 - 456 - 789 - 10,11,12.

I had never seen this before working at Aston, and is a phenomenon.
Due to the firing pulses created by a group of three cylinders sharing a header (each header has its own starter catalyst), if the catalyst matrix fails the debris is sucked back up into the engine, into the inlet manifold and distributed amongst the adjacent cylinders - happened a number of times to me and others in development. As the catalysts are bomb-proof on V12 I dont expect this to be a problem for anyone to worry about. Just a development tale....

Well that's a frigen relief.

 

Based on similar EGTs from other newer Ford 4-valve V8s, typical NA EGTs are in the 1000-1200F range, and this applies only in higher gears where both load and duration of acceleration are higher. In lower gears during quicker bursts its even less than 1000F. Turbocharged/Supercharged cars can get into the 1300-1500 range, but its very hard to do an on NA motor, especially one as well designed as ours.

I too noticed that contradiction ... how can these motors be so fragile, and yet endure 150+ hours at redline continuously in order to pass the test. If they can handle those levels of stress & heat for such a period, pushing the car for bursts of 15-30 second on a street application will never pose any problems at all. Yet, the risk of these engines blowing up is all of a sudden extremely high b/c of a perfectly healthy tune with zero detonation and healthy EGTs ... it doesn't make any sense.

Mike, if you are saying they detuned the car in order to save the cats/emissions, I can agree with that to some extent ... however, you specifically said the stock cats are good to 1000C which is higher than the 850C valve threshhold. Yet cats fail all the time on stock tunes with running super rich. Another contradiction is that EGTs have nothing to do with whats going on outside the cylinders, yet you bring cats into the arguement which imply they do matter (which of course is the correct position). Cats do matter, a substantial amount in fact. The more the restriction, the higher the pressure & heat, which will in turn increase backpressure, which will also affect the combustion cycle as the valves open and close.


Not trying to nit pick or be difficult at all, but there are contradictions left and right in every arguement put forth. Sticking with one position will help this discussion so that we can all be better informed as to what your exact position is. Perhaps its just not being articulated clearly which is why some of us are confused.


Obviously, there is no major risk/danger at the current state. Under extreme conditions (AFR higher than 15:1, or high boost, or etc) yes all kinds of bad things can happen. But to assume that its happening simply b/c a car has a conservative healthy ECU tune seems a bit overkill. You stated your position that you are against all ECU tunes, but yet nobody with any ECU tunes has had any issues. Quite the opposite, most people with tunes (myself included) have improved their health of their tune but not running so absurdly rich, which in turn also improves fuel effiicency and etc. This extreme rich condition is what was causing the extremely short life-cycle of the cats on our application in the first place.

If there is a major design flaw in the engine I would like to know, but having scoured many ford V8s forums endlessly I have not seen a single case describing such a condition (especially on the newer 4-valve modular fords that tend to be pretty bulletproof).

All in good spirit of the discussion ...
________
Harmed by nexium

 

But what about aftermarket cats on the V12 Vantage?

 

Hi.

Aftermarket cats on V12 should present no problem....

It would be a replacement secondary cat, not primary cat. So if the secondary cat failed it could not be ingested as it could not go past the primary cat in the manifold. But, there is no reason to question why an aftermarket cat should fail if it were designed and manufactured correctly.

The ratio of BHP gain for exhaust back pressure reduction is high on V12, so an aftermarket cat and silencer on V12 represents a good modification - significant power increase and a glorious exhaust note to match...

 

Good questions, I think some confusion and crossed-lines is / are creeping in here.. Let's set the record straight.... hopefully...

Firstly, the V8 and V12 Aston engines are absolutely bullet proof in terms of durability and longevity. Ford insisted that all Ford group companies passed EXTREMELY stringent durability sign-off tests before being allowed to be introduced into production. This is the reason why modifications such as the pressure charger kit 'lives' on a standard engine. Modifications such as these eat into safety margins engineered in, sometimes without problem, sometimes with failures.

850 Deg C exhaust gas outlet temperature and 950 degrees C catalyst temperatures, as control points, are perfectly normal and industry wide standards. The materials of the components within the engine are of high enough grade to withstand these conditions. Any engine in production nowadays that does not use these materials and sets these industry standard control points is running at a disadvantage. In fact, materials technology today can push EGT's to 870ish and catalyst to 1050ish.

In the case of the AMV8, 850 EGT's will only be experienced during prolonged high engine speed running. There is no need to panic, there is no fragility, these conditions are industry standard. If you rev the engine up to 7300 rpm on a power test on rolling road the EGT's might top 780 - if the engine was held for 30 further seconds at maximum power speed the temperatures would slowly creep towards 850. To pass the stringent durability tests the fuelling is set so that under the heat soak condition the engine is safe. So here is a common theme - aftermarket 'tuners' eat into safety margins they have little experience of and do not understand all the parameters that come into play that could present an error state. If they did they wouldn't be working in the land of aftermarket - if they truly understood the variables they would no doubt be highly experienced and qualified calibration engineers and take their pick of jobs at the best OEM's.....

I would really like to see how many hours the pressure charged kit survives on the Ford 150 hour high speed sign-off test... This test basically cycles peak torque / peak power speed at wide open throttle for 150 hours. To sit down and watch the cycle on a dyno is an experience in itself - ITS HARSH, and these Aston engines survive it - without exception. I can only guess, but my experience would tell me that the pressure charged engine would last 10 hours maximum. Ok, more real world situation then - the Nurburgring. Would the car even last one lap around the formidable race track in the hands of a racing driver? IMHO, I doubt it, this kits lives because it comes off the back of a bullet proof engine and is not being held at high speed / high load conditions long enough by customers to heat soak high temperatures and pressures which lead to failure. But hey, this is no problem. I can see the desire for pressure charger and I have modified my own cars and bikes in a way that I know would never survive the long term - this is OK for me in the privacy of my own garage, as I can rebuild and rebuild myself after failure and I take that hit in trade for the benefit I get.

Finally then, and back to the start - any small change in AFR or spark would affect the engine under extremes of operation which are taken into account in the safety factor of the standard calibration - eroding this in the search for a few extra BHP allows error states to creep in and is a mistake IMHO

So, this is not a discussion about stock engine fragility - it is a discussion about not altering from the precise setpoints engineered and controlled by OEM in stock calibration which might cause a problem at a later date

 

 

I presume you're talking about the manifold-integral primaries rather than secondaries?

 

WOW! A-M Dragon Maker. I have never learned so much about the fine tuning of an engine by the ECU. Thanks for all your expertise and clear discussions. I for one am very pleased to know that my stock A-M engine is so bullet-proof and will stay that way for the life of the car. (I wish fewer people, like myself, were not having the irritating problem of the thermostat gasket coming apart--but that's another issue). I live at an elevation of 6,500 feet, so I lose about 20% of my sea-level HP. However, I bought my A-M primarily for its Beautiful Body, and FUN taking it on vacations--so squeezing the last bit of HP out is not a big thing for me. If I need extra power, say for passing--I just go to a lower gear. One point I would make is, since HP is still climbing at Red-line, it would be nice if Red-line could be set 300-600 RPM higher.

 

Here is a driving history for a supercharged AM. You can see that car spent one minute at redline and WOT out of 6D1H25M = 8725 minutes. This was over a year and 4K miles At this rate 150hrs at redline will never be achieved. This is why the Ford testing essentially means the engine is indestructible!

 

Mike, I have several questions for you related to the V12V:

First, on the topic of catalyst breakdown, are there any measures that can be taken to prevent catalyst from being sucked up into the engine? You said the stock cats are bulletproof, but what if one of them is defective or has a manufacturing flaw? Also, if there is such a flaw, is the cat likely to break down early in its life (i.e., during the warranty period) or later?

Second, you mentioned there are significant gains to be had with aftermarket cats/exhaust. Do you have any idea of how much power can be liberated?

Lastly, I've read several times that pulling fuse 22 (fuse 15 on newer cars) reduces low end torque. Do you have any idea of how much torque is lost? I just pulled my fuse yesterday, but only notice the sound difference.

Many thanks!

 

Sorry Mike, just caught this, disregard my prior post!

 

Mike, I think there are a lot of very qualified, passionate and knowledgeable people working in the aftermarket industry. Not everyone wants to follow the same career path, and you'll probably find as you spend more time in this industry that lots of people arrive here from well respected paths.

For example, I know of a super-knowledgeable and highly qualified guy who left a job at one of the best OEM's to start his own aftermarket business catering to Aston Martin owners....

 

This is a great point, and I think also applies to a lot of the NA tuning as well.