Codes P0420 & P0430. V8 catalytic converter issues

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armybrat
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Something else to consider, and previously mentioned...oil consumption. The specs call for "up to" 1 qt/1200 miles. That's a lot of oil being burned, and that has to make an impact on the cats. Have a look at your exhaust tips, they will tell the tale. Even with catch cans installed, I wipe my tips down everyday, and still gather a fair amount of soot. (yeah I am picky about dirty looking tips) Doesn't matter if your car is stock or tuned. If it's coming out of your pipes, you know it's going through your cats. With this particular motor, I'm afraid that it's going to be an ongoing issue with the stock manifold configuration. Only way I see to (maybe) improve it is to take a used set of manifolds to a custom shop like Kooks and have headers made. Install bolt on aftermarket hi flow cats where the secondary cats resided, and retune the car. It would be a significant investment though, around 3k for the fabrication alone, not counting labor and cost of installing them plus labor and cost of the cat installation.


Oh yeah this time of the year is worse, due to the colder air temps. Warmer weather yields a lot less soot, at least my car does. My rag is barely covered in soot when it's warm, compared to this time of the year.


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armybrat wrote:
Mon Jan 21, 2019 8:48 am
Oh yeah this time of the year is worse, due to the colder air temps. Warmer weather yields a lot less soot, at least my car does. My rag is barely covered in soot when it's warm, compared to this time of the year.
Yep, my CEL went off in the summer and came back once temps got near freezing.

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Ilya wrote:
Mon Jan 21, 2019 1:45 pm
...
Yep, my CEL went off in the summer and came back once temps got near freezing.
Ilya (or anyone else really), do you still have access to your family car lift?
Do you think you'd be able to inspect the manifold area, preferably during the cold season when the CEL comes on?

Please remind me, are you getting both P0420 and P0430 or only 420, bank 1?
This whole fiasco could be over a crack in the manifold, or some defect that rears its head when the outside temps affect the material in such a way.

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armybrat wrote:
Mon Jan 21, 2019 5:42 am

Good catch! I meant to say that the second cats are downstream of the O2 sensors. IMHO removing those wouldn't affect anything emissions wise...however, the flange with the baffle is before the sensor like you pointed out - you might be on to something there. I've never pulled any O2 codes; just the P0420. The firing order is 1-8-7-3-6-5-4-2. The exhaust pulses are not in order on the left bank, per se. The right bank fires 8-6-4-2 while the left bank fires 1-7-3-5. From your drawing it looks like the manifold tubing routing has something to do with this, and that's why they are different. Maybe the baffle helps to balance the exhaust pulses somehow. Could also have something to do with VVEL on the left bank. I found some good engine specs here:

https://www.engine-specs.net/nissan/vk56vd.html

Might be able to glean something from there.
It might not affect emissions testing (in most jurisdictions), but it is guaranteed to affect the vehicle's emissions if you did a tailpipe test. Without the factory installed secondary catalytic converters, the vehicle is certainly releasing more pollutants than it was certified for.

So, back onto the engine layout, all of the Nissan V8s I referenced earlier used the same firing order. All of them used an exhaust manifold that was mainly log style. The M56 at least tried with the Tri-Y manifolds.
When you look at them in firing order, it makes sense to me as to why the collectors are laid out the way they are. From my limited knowledge of designing manifolds, my understanding is that these 4-2-1 manifolds are designed for a cylinder to be paired with another cylinder as far as possible in the firing order... for exhaust scavenging purposes. In this case they are either going to be 270* or 450* away. (see attached sketch)

Image

Image

Image

I tried to imagine why they didn't make the left and right manifold the same, and I think that was locked by crankshaft and camshaft design, hence firing order. If the left manifold was made to look exactly like the right one, then cylinder 3 and 7 would be sharing a collector and would only be 90 degrees apart, according to the firing order.
You would run into similar problems if you tried to make the right one work exactly like the left one - cylinder 2 & 4 are next to each other in firing order. Sigh,... this is why engine development costs millions.

The more we dig in, the more that baffle on the left bank is bugging me.
Maybe after all, the design is perfect for flowing exhaust gases but then the unforeseen loading on this Tri-Y is causing structural issues? As I mentioned earlier, it wouldn't be the first time a Nissan V8 suffered cracked manifolds which could show up as catalyst inefficiency issues.

Man, why don't any of you guys live closer to St. Louis? We'd have all kinds of fun troubleshooting these issues.

Image
This last picture is either a bonus or a distraction. To make sense of the firing order, I re-numbered the cylinders according to firing order, and at what degree (multiple of 90*) each cylinder would fire. Look at the blue numbers and assume they are bolts you are going to tighten.
To use a reasonable example of it as a valve cover, to tighten your bolts in sequence without warping it, start from 8-1-2-3-4-5-6-7-8 again... which corresponds to actual cylinder numbers 2-1-8-7-3-6-5-4-2 again.
That is pretty much how firing order maintains balance in the crankshaft.

Regarding oil consumption: Remember those VK45DEs, I keep referring to? Yes. Those could be some serious oil burners, but apart from the cracking in the earlier versions of the engine, exhaust manifold issues were unheard of.
Also, oil that makes it into the intake should be equally distributed to each bank, so if all of you are getting only bank 1 issues, I can't explain why bank 2 isn't causing similar issues.


I think I'll wait for more troubleshooting or diagnosis on the left side manifold. As of now, I don't see anything inherently wrong with the way it was designed. The more I look at it (on paper), the more amazed I am by the engineering that went into it.

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EdBwoy wrote:
Mon Jan 21, 2019 10:16 pm
Ilya wrote:
Mon Jan 21, 2019 1:45 pm
...
Yep, my CEL went off in the summer and came back once temps got near freezing.
Ilya (or anyone else really), do you still have access to your family car lift?
Do you think you'd be able to inspect the manifold area, preferably during the cold season when the CEL comes on?

Please remind me, are you getting both P0420 and P0430 or only 420, bank 1?
This whole fiasco could be over a crack in the manifold, or some defect that rears its head when the outside temps affect the material in such a way.
I do have access to my dads lift still...I haven't been disowned...yet :rotflmao.

I will be needing an oil change in another 1kmi or so, should still be cold so I'll take a look. Which side is bank 1 when looking from under the car? sorry lol.

Also, I'm only having the P0420 last I checked.

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Ilya wrote:
Tue Jan 22, 2019 7:16 am
...

I do have access to my dads lift still...I haven't been disowned...yet :rotflmao.

I will be needing an oil change in another 1kmi or so, should still be cold so I'll take a look. Which side is bank 1 when looking from under the car? sorry lol.

Also, I'm only having the P0420 last I checked.
Awesome! So far, so good. Keep up whatever you're doing to distract the family for at least the next 1,000 miles.

Bank 1 is the left side of the engine. That is the driver side for the US models. From under the car, it's going to be the one closest to the steering shaft. I'd send you a picture, but... jackstand crew here. Lol
You might as well check both manifolds though.


Edit: from a picture you posted elsewhere in the forum, I have highlighted bank 1 for the V8. It is the opposite for the V6
Image

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EdBwoy wrote:
Mon Jan 21, 2019 11:51 pm
It might not affect emissions testing (in most jurisdictions), but it is guaranteed to affect the vehicle's emissions if you did a tailpipe test. Without the factory installed secondary catalytic converters, the vehicle is certainly releasing more pollutants than it was certified for.
Here in NC, I don't know if they do a tailpipe test. They hook up their scanner device to the OBD2 port and perform their test of the emissions system. They run the car for a length of time and make sure it doesn't pull any codes. In addition, they do a visual inspection. The print out of the results just say pass or fail. In my case, the visible amount of soot seems to be the same with the custom exhaust vs the original exhaust. I've been wiping my exhaust tips since day 1, so if there's a difference in output it's negligible to the eye.

EdBwoy wrote:
Mon Jan 21, 2019 11:51 pm
So, back onto the engine layout, all of the Nissan V8s I referenced earlier used the same firing order. All of them used an exhaust manifold that was mainly log style. The M56 at least tried with the Tri-Y manifolds.
When you look at them in firing order, it makes sense...
Very good write up, something to think about.

EdBwoy wrote:
Mon Jan 21, 2019 11:51 pm
I think I'll wait for more troubleshooting or diagnosis on the left side manifold. As of now, I don't see anything inherently wrong with the way it was designed. The more I look at it (on paper), the more amazed I am by the engineering that went into it.
I agree about the engineering with respect to the engine. However, I disagree about exhaust manifold design with this particular motor. The exhaust system for the VK56VD sucks, period. Manufacturing the exhaust manifold and catalytic converter as one unit and having to lift the motor to change it out is a poor design even if (hypothetically) the unit is supposed to last the "lifetime", aka 100,000 miles, of the vehicle. There is no need to have a secondary set of cats; the primary cats could've been installed in that space under the car, bolted to the same manifold flange and flanged on the exit end to the Y-pipe just like the 3.7 engine. Instead, the engine is having to force the exhaust through 2 pairs of cats and a pair or resonators that choke down to 1-3/4" diameter. No wonder the cars run rich and clog the cats, especially in the colder months, evidenced by excess soot at the tail pipes. Sorry excuse for an exhaust system IMHO.

On a side note, the Cataclean seems to be working. Like I reported earlier, the CEL light came on briefly but went out on its own, for the second time. This time, it stayed out but I ran another bottle through it anyway. Got about 400 miles since, so far so good.

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EdBwoy wrote:
Tue Jan 22, 2019 8:56 am
Bank 1 is the left side of the engine. That is the driver side for the US models. From under the car, it's going to be the one closest to the steering shaft. I'd send you a picture, but... jackstand crew here. Lol
You might as well check both manifolds though.

Edit: from a picture you posted elsewhere in the forum, I have highlighted bank 1 for the V8. It is the opposite for the V6
Image
Great pic, looks like the AWD - noticing that the passenger side secondary cat may be the offset one, maybe to clear the transfer case? I know I mentioned in my previous post that the driver's side cat was the one that was offset...hard to tell though.

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armybrat wrote:
Sat Jan 26, 2019 9:03 am
EdBwoy wrote:
Mon Jan 21, 2019 11:51 pm
It might not affect emissions testing (in most jurisdictions),
Here in NC, I don't know if they do a tailpipe test. They hook up their scanner device to the OBD2 port and perform their test of the emissions system. They run the car for a length of time and make sure it doesn't pull any codes. In addition, they do a visual inspection. The print out of the results just say pass or fail. In my case, the visible amount of soot seems to be the same with the custom exhaust vs the original exhaust. I've been wiping my exhaust tips since day 1, so if there's a difference in output it's negligible to the eye.
Might be negligible to the human eye, but not to the atmosphere.
Most places do not do tailpipe tests, that's why I said a modified car would still pass emissions in most places. My point was that the manufacturer determined that the vehicle needed 2 sets of "air cleaners" and that removing one set was undoubtedly going to result in less air cleaning when parked side by side to a stock car, whether we can see/smell the difference or not.
I don't fully understand the difference/allowance in the secondary cats that are unmonitored, but I know of someone who did more or less what you proposed. Gutted the primary cats and put the downstream o2 sensor after the secondary cats, thus using the secondary cats as primaries. There are no codes but the car stinks. Which to me means that for CEL purposes, the secondary and primary cats clean just as efficient as the other. I also infer that having 2 sets is important for thorough cleanup beyond being marginally legal.


armybrat wrote:
Sat Jan 26, 2019 9:03 am
EdBwoy wrote:
Mon Jan 21, 2019 11:51 pm
I think I'll wait for more troubleshooting or diagnosis on the left side manifold. As of now, I don't see anything inherently wrong with the way it was designed. The more I look at it (on paper), the more amazed I am by the engineering that went into it.
I agree about the engineering with respect to the engine. However, I disagree about exhaust manifold design with this particular motor. The exhaust system for the VK56VD sucks, period. Manufacturing the exhaust manifold and catalytic converter as one unit and having to lift the motor to change it out is a poor design even if (hypothetically) the unit is supposed to last the "lifetime", aka 100,000 miles, of the vehicle. There is no need to have a secondary set of cats; the primary cats could've been installed in that space under the car, bolted to the same manifold flange and flanged on the exit end to the Y-pipe just like the 3.7 engine. Instead, the engine is having to force the exhaust through 2 pairs of cats and a pair or resonators that choke down to 1-3/4" diameter. No wonder the cars run rich and clog the cats, especially in the colder months, evidenced by excess soot at the tail pipes. Sorry excuse for an exhaust system IMHO.
As a DIYer, I 100% agree with you that the design sucks for at home repairs. But we have to agree to disagree on the other aspects.

For one, nobody ever complains about the design/engineering of components unless we need to do a repair and can't quickly access it.
Secondly, I can't authoritatively say a manufacturer did not need to have secondary cats. Catalytic converters are expensive and the manufacturer isn't throwing you a single penny they don't have to.
When an engine is designed, they go for the main 3 principles of a production engine - (emission, output/power, and fuel economy). If an engine fails and cannot be reasonably improved, then out it goes and it never sees the light of day. Then other components are designed around the engine. The manufacturer tells an exhaust company what they expect the car to do and the exhaust company will design the exhaust system (sometimes from engine to tailpipe, sometimes just a section).
So, the exhaust is designed by a company that does exhaust systems all day and presumably understands what emissions regulations to follow. For Nissan, we are talking about Calsonic Kansei and Sango (Sango for the V8, is my guess). These guys then work around size, weight, packaging, sound levels, performance etc... and COST.
I believe that if the 5.6 direct injection injection engine could share infrastructure with the 3.7 port injected engine, then they would. In fact, that would make it cheaper for Nissan to produce similar templates, and just flange the catalysts. It's just they can't do that and stay legal and/or within budget. No official word from Nissan, this is my opinion as a design engineer.

Remember, it's not that manufacturers intentionally go out to frustrate owners. If we are able to repair something at home, then well and good. But it's a perk, not exactly a design goal. They design for functionality. We are typically seen as drivers, and the manuals are written for certified technicians.
This is my assumption of a conversation leading to product launch:
  • Let's make a new engine. Cool. About time we did
  • Does it fit in the engine bay with the V6? Yes, good
  • Does the exhaust fit in the car packaging without modification? - Yes, good
  • Does it achieve our goals of power, weight, noise levels etc...? Yes, good
  • Does it meet our budget? - Yes, good
  • Is it repairable? Yes, but complicated
  • Well, is it a frequent failure? No
  • Why do you think it's complicated anyway? The technicians will have to lift the engine to do it
  • But it's still possible right? Yes, they are equipped and trained for it
  • And the customer still pays for the time, right? Yes
  • You should be fine. You won't have to do the job for 300,000 miles if the car is running in tip top shape. Maybe in 100,000 miles if the manifold develops a crack. We've had concerns with those in the past.
Trust me, it might seem like I am going to bat for Nissan on this issue, but not just for the sake of it. A lot of manufacturers of high output V8s and V10s utilize the same design. A car as a whole can overlook a lot of different things, but a lot of work & money goes into an engine and emissions. Then that powerplant is tested in various climates & conditions to ensure functionality. My M56 does soot up a little more than the M45, but not as much if left to get to temperature. My 4.5s with deleted cats do soot up more than the stock ones. The supercharged VK45DE soots up like a wood stove, so I think output has an effect (but it also has the primary cats gutted, stock would have been a good comparison)
You and I are free to install 3" true dual exhausts and delete the cats once we get the car, but in reality we are affecting an aspect of that engine triangle. Whether we give a crap about power, fuel economy or emissions then is a matter of personal opinion, but it is a scientific fact that most of the "mods" we do before the muffler with good intention end up tipping the scale unfavourably for intended design.
I typically do not engage when I see posts of people opening up the power by enlarging the "restrictive small diameter" OEM exhaust/intake. I understand there is more to it.

Here are some sample screenshots from one such exhaust designer:
Image

Image

Image

Image


Again, we can choose to agree to disagree on the engineering and design. I agree that they are a pain for you and I to replace at home, and expensive to pay someone to do.
Hopefully soon, with enough digging, we can find what the problem is.

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EdBwoy wrote:
Sat Jan 26, 2019 1:43 pm
I typically do not engage when I see posts of people opening up the power by enlarging the "restrictive small diameter" OEM exhaust/intake. I understand there is more to it.
I was pleased to see this posted on an enthusiast forum, as a bonafide geezer it gives me hope for the future of DYI "hot-rodding":

Backpressure is one of the most misunderstood/misrepresented issues within the aftermarket DIY modification world, even many aftermarket exhaust manufacturers and vendors don't get it or they lie about it to sell their absurdly oversized systems--Backpressure Myths I and Backpressure Myths II.

Here's a good document about headers from S&S Headers, sadly no longer with us.

And one more re: "HIgh-Flow" cats, from Bear River Converters...

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EdBwoy wrote:
Sat Jan 26, 2019 1:43 pm
Might be negligible to the human eye, but not to the atmosphere.
Most places do not do tailpipe tests, that's why I said a modified car would still pass emissions in most places. My point was that the manufacturer determined that the vehicle needed 2 sets of "air cleaners" and that removing one set was undoubtedly going to result in less air cleaning when parked side by side to a stock car, whether we can see/smell the difference or not.
Point taken. Soot is a visible signature only...however, the EPA sets the standard for the Clean Air Act, the states voluntarily enforce those standards in exchange for funding, the EPA is left to enforce it in those states that choose not to participate. Also within the states who do enforce the standards, there are counties who choose to let certain provisions slide for older vehicles. For example, here in NC, vehicles 25 years and older are exempt from emissions inspections. As long as my car doesn't throw any codes and passes the state emissions test then I am still in compliance regardless of less cleaning from removing the secondary cats.
EdBwoy wrote:
Sat Jan 26, 2019 1:43 pm
I don't fully understand the difference/allowance in the secondary cats that are unmonitored, but I know of someone who did more or less what you proposed. Gutted the primary cats and put the downstream o2 sensor after the secondary cats, thus using the secondary cats as primaries. There are no codes but the car stinks. Which to me means that for CEL purposes, the secondary and primary cats clean just as efficient as the other. I also infer that having 2 sets is important for thorough cleanup beyond being marginally legal.
Maybe a little more clarification - I was not talking about gutting the primary cats. The secondary cats are not designed to function as primary cats, plus they are too far away from the manifold to function properly anyway. I was talking about redesigning the exhaust manifold altogether, making it longer similar to headers, and bolting the primary cat directly to it, similar to the 3.7 motor. The AF and O2 sensors would have to be relocated to maximize proper function, and retuned of course to comply with emissions testing.
EdBwoy wrote:
Sat Jan 26, 2019 1:43 pm
As a DIYer, I 100% agree with you that the design sucks for at home repairs. But we have to agree to disagree on the other aspects.

For one, nobody ever complains about the design/engineering of components unless we need to do a repair and can't quickly access it.
Secondly, I can't authoritatively say a manufacturer did not need to have secondary cats. Catalytic converters are expensive and the manufacturer isn't throwing you a single penny they don't have to.
When an engine is designed, they go for the main 3 principles of a production engine - (emission, output/power, and fuel economy). If an engine fails and cannot be reasonably improved, then out it goes and it never sees the light of day. Then other components are designed around the engine. The manufacturer tells an exhaust company what they expect the car to do and the exhaust company will design the exhaust system (sometimes from engine to tailpipe, sometimes just a section).
So, the exhaust is designed by a company that does exhaust systems all day and presumably understands what emissions regulations to follow. For Nissan, we are talking about Calsonic Kansei and Sango (Sango for the V8, is my guess). These guys then work around size, weight, packaging, sound levels, performance etc... and COST.
I believe that if the 5.6 direct injection injection engine could share infrastructure with the 3.7 port injected engine, then they would. In fact, that would make it cheaper for Nissan to produce similar templates, and just flange the catalysts. It's just they can't do that and stay legal and/or within budget. No official word from Nissan, this is my opinion as a design engineer.
True...however, the VK56VD has only been around since 2010, so there was no reason to complain. Now a lot of these motors are reaching, or have reached, the so called "lifetime" threshold, and we are beginning to see (IMHO) a design flaw in the exhaust manifold system, and heck yeah, folks are complaining, and not just the DIY'ers. Most folks didn't know that the exhaust manifold was an integrated assembly, and also were not aware of the complexity and cost of having it replaced. It's not just here and there; it seems to be a universal issue among the 5.6 owners, stock or modified.
EdBwoy wrote:
Sat Jan 26, 2019 1:43 pm
...A lot of manufacturers of high output V8s and V10s utilize the same design...You and I are free to install 3" true dual exhausts and delete the cats once we get the car, but in reality we are affecting an aspect of that engine triangle. Whether we give a crap about power, fuel economy or emissions then is a matter of personal opinion, but it is a scientific fact that most of the "mods" we do before the muffler with good intention end up tipping the scale unfavourably for intended design.
I typically do not engage when I see posts of people opening up the power by enlarging the "restrictive small diameter" OEM exhaust/intake. I understand there is more to it.

Here are some sample screenshots from one such exhaust designer:
Image

Image

Image

Image


Again, we can choose to agree to disagree on the engineering and design. I agree that they are a pain for you and I to replace at home, and expensive to pay someone to do.
Hopefully soon, with enough digging, we can find what the problem is.
Just out of curiosity I looked up a few integrated exhaust manifolds. There are several as you mentioned in the 4 and 6 cylinder configuration. Not really that many in the V8 and V10; only examples I was able to find are the Lexus LS460, the Cadillac 4.6L, the BMW X5 and M5 E60 and S85 motors. I really didn't look much; I'm sure there may be a few others, but from what I found, there are a lot more that use bolt on cats, especially performance models...no reason why our cars can't do the same thing.

I agree that the engine performance is a function of power, fuel economy and emissions as you stated. The car is tuned from the factory to run optimally within all three parameters. If you mess with any aspect of the engine or exhaust it does alter performance, at the expense of either fuel economy or emissions, or both.

I agree that there is a considerable amount of R&D and engineering that go into engine design, including the exhaust, optimized as stated above.

I still maintain that the manifolds and cats can and should be redesigned as separate items...at the very least, Nissan/Infiniti should address the problem and come up with a solution. Something was mentioned about cracked manifolds; I am not aware of any issues with cracking; only the threshold efficiency issue. Thanks again for your input and for hearing me out.

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Maybe a little more clarification - I was not talking about gutting the primary cats. The secondary cats are not designed to function as primary cats, plus they are too far away from the manifold to function properly anyway. I was talking about redesigning the exhaust manifold altogether...
Gotcha now. Pardon my misunderstanding.
It is good that more of us understand that fitment does not equal design. Just because pipes can be plumbed to fit does not make it properly functioning.

So on that emissions and passing stuff, last time I checked, cars around my area were exempt from 95 or so. I wanted to use a 1990 Infiniti Q45 as an example of a cat-less but legal car, but from the catalogs, it seems they had both primary and secondary cats too.
The modern cars is where the line gets blurry I suppose. I choose to see things differently than others. While others focus on "does it pass" by tuning the monitors out or using foulers, I choose to retain OEM function. The governing bodies in conjunction with the car manufacturer have agreed on what readings the o2 sensor will need to see to be called a pass on the OBD2 system... yet a secondary and unmonitored cat was deemed to be necessary for various cars.
With an admitted bias on my scientific background, I respect the EPA and what regulations they impose on us. I hated emissions tests when I was a broke college kid who couldn't pass inspection because of a check engine light, but I still understood the purpose.
It is personal principle and like most other things, I am fine agreeing to disagree on that.

...folks are complaining, and not just the DIY'ers. Most folks didn't know that the exhaust manifold was an integrated assembly, and also were not aware of the complexity and cost of having it replaced. It's not just here and there; it seems to be a universal issue among the 5.6 owners, stock or modified.
I don't know how to appropriately respond to the highlighted area. Nissan has been doing it in the States since the 90s. I understand that not everyone pops the hood of a car and looks underneath before they buy it... in fact people close to me have told me it's very strange that I do that, but I usually look up and down to anticipate what kind of repair and maintenance is possible with the engine in place.
I acknowledge though, most people would not know until today, if the catalytic issues were not coming up.
But do folks NEED to know that the manifold is of the integrated design, or that they don't have a transmission dipstick? - I do know that info. But again, I like to read the owners manual and the service manual too.
My opinion is that it would sure be nice if we were all knowledgeable about our autos and how they function, but objectively speaking there really is no need for everyone to know what their car is made of, if they focus on being drivers; which was sort of my point. This is how I draw parallels:
If I rarely change my own transmission fluid, why should I complain when the 7 speed trans comes without a dipstick? Yeah, it costs $300 to get it done, but that is an infrequent cost on a rather cheap to maintain luxury-sport sedan... But I can still do it at home if I was motivated enough.
Or when my refrigerator breaks, I either replace it or call a professional to repair it. I don't dig in and pick apart why one, two or three components are not standard design to make it tougher for DIY repairs. I mean, it worked and did refrigerator things despite anything I now consider a design quirk. I bought it as a system and trusted the manufacturer to do more than put new skin over their old system if I am paying more for the newer model... But I can still repair it in my kit-chen if I was motivated enough.

... There are several as you mentioned in the 4 and 6 cylinder configuration. Not really that many in the V8 and V10; only examples I was able to find are the Lexus LS460, the Cadillac 4.6L, the BMW X5 and M5 E60 and S85 motors. I really didn't look much; I'm sure there may be a few others, but from what I found, there are a lot more that use bolt on cats, especially performance models...no reason why our cars can't do the same thing.
I honestly don't know what fraction of V8 and V10 manufacturers use the integrated manifold versus a flanged cat, but I do know that more than our vehicles do, which means it's not just a Nissan quirk. I didn't look too deep either, but I was going off memory of the cars I'd owned and viewed with intent to purchase. I also researched lightly a few years ago when replacing manifolds on an M45. (I'll explain more at the bottom). I had seen the Lexus LS430 and it had a flanged cat, didn't know they went integrated on the LS460.
My guess as to why our cars can't follow the other design option?
Business relationships - Manufacturers seem to keep long relationships with their suppliers of major components. So if Sango or Calsonic Kansei specializes in this kind of manifold and that's all they offer, Nissan will keep buying if they achieve all other goals. Most businesses focus on their niche and buy turnkey parts from the specialists (for example Enkei as a wheel supplier, Akebono for brakes).
Maybe Toyota got a different supplier for the LS460 versus the LS430, or maybe the same supplier just redesigned. Remember the supplier is also trying to provide the parts with the lowest production cost.
Packaging - on the sedan side specifically, the engine bay is tight. If the engine bay was like a Dodge/Chrysler sedan, I am sure we could get creative with exhaust design... but I prefer the handling and chassis dynamics of my Infiniti sedans.
Cost - it is the most cost efficient design, and it works well beyond the warranty period.
It seems most of them hold it together beyond the warranty period. If people stopped buying Nissan V8s because of manifold issues, then they would be forced to respond either by redesign or killing the line.
So yeah, they can, and maybe could be designed another way but it probably comes at a cost that the bean counters might not want to entertain.

Something was mentioned about cracked manifolds; I am not aware of any issues with cracking; only the threshold efficiency issue
Yep, that's me who keeps mentioning it. That 03 M45 I bought had a P0420 catalyst code. Efficiency below threshold, etc. It had been misdiagnosed as a clogged cat which was then gutted. When through a series of unfortunate events, I got to an engine replacement, I realized the manifold was cracked. Looking online, I started seeing more complaints from Nissan V8 owners with that type of manifold.
I know I looked at a number of VK56DE issues with the code and cracked manifolds.
Consider that the 06+ M45 with the same integrated manifold had similar oil consumption habits, but zero of the p0420 and cracked manifold issues of the prior years. It employed a flex pipe though.

I am not saying that that is certainly the issue with our cars, but I propose we look there as well. I like to attack issues with an open mind to all possibilities. Otherwise, we could be stuck on trying to find faults with other aspects of the design yet it is a structural issue.
If the cracking is the cause of the P0420 code, then we can try the patching option to see if any improvement is made. If not, we can go on our way redesigning instead of buying another Nissan unit... or maybe we'll just replace with another OEM unit because they have been proven to last 100K. :gotme
Consider that one of the benefits/goals of this close-coupled manifold design is lightweighting. Adding a flange will probably go against that intent and could cause cracking even earlier... if the crack is the problem here.
If there is no crack in the first place, then we can start looking at internal issues - internal to the engine or the manifold.

Personally, I don't have the code but I know 3 of us V8 owners in here have reported P0420. As I mentioned in a different thread, I am here discussing these issues and want to buy an (ideally high mileage) M56 to look into and get ahead of the issues.
If it proves too difficult to obtain one and I can't get any collaboration on troubleshooting the current issues, then it's just as well to shelve the project and we'll revisit in 2022 when more people are feeling the pinch.

***
I appreciate you engaging with me as well. I hope we'll get somewhere before you are forced to start buying Cataclean by the gallon.

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For no reason than plain admiration, I will share an engine whose introduction I have been following for a while. Simply because I can't think of many all-motor engines shattering the 1000 horsepower ceiling from the factory. Aston Martin is doing it with a V12 in conjunction with Cosworth.

Image

Image

Image

Image


Well, yeah. Admittedly I also linked it here because of the exhaust manifold design. In the video below, they'll mention that they actually have 4 cats because each catalyst was designed for 3 cylinders etc. And again, we encounter the triangle of death (emissions, performance; fuel economy apparently doesn't matter for a supercar). I have no idea whether it will need secondary cats though, but if I had $4 Million lying around, I'd definitely ask them to jack the car up for me on the showroom floor to take a looksie.

Source of the pictures: Article link
Youtube video: Video link

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Thanks Ed - I was reading about this engine last night and how Aston Martin had contracted with Cosworth to build a 950hp V12 and how they were all surprised when it delivered over 1000hp - all without turbo or superchargers! Having driven many turbocharged engines recently, I always love getting back in my naturally aspirated car. So many of the 4 cylinder turbos sound like they're pushing beyond their limits to get you up to freeway speeds. It will be interesting to see the life of those engines.

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That's pleasing to look at.

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Woah!! Cosworth is very well known back home. Their work on Fords, Mercedes, and others is absolutely brilliant! When you have that kind of a beast, I reckon you report gas mileage as FPG (feet per gallon), LOL

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cliffyk wrote:
Sun Jan 27, 2019 7:45 am
...
I was pleased to see this posted on an enthusiast forum, as a bonafide geezer it gives me hope for the future of DYI "hot-rodding":

...
Sorry I had missed your post Sir; and thank you. I suppose I'm an old soul as well. I am not anti-modifying things.
In fact, I wouldn't mind modding my own car for the sake of a more pleasant sound for example. I just don't like spending resources on things that I find either useless or harmful.
Plus I take a very pragmatic approach (your money, your choices) to most matters. However I like to dig deep and demystify confusing topics for the benefit of the general public.
Summarized as: I won't stop you from spending your money as you please, but I darn sure will give you objective information to prevent you from wasting it or hurting someone.


***
Thanks for the links. Good bedtime reading for tonight

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Larz wrote:
Fri Feb 01, 2019 5:56 pm
Woah!! Cosworth is very well known back home. Their work on Fords, Mercedes, and others is absolutely brilliant! When you have that kind of a beast, I reckon you report gas mileage as FPG (feet per gallon), LOL
Or SPM, smiles per mile lol. :rotflmao :rotflmao

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Ilya wrote:
Fri Feb 01, 2019 9:15 pm
Larz wrote:
Fri Feb 01, 2019 5:56 pm
Woah!! Cosworth is very well known back home. Their work on Fords, Mercedes, and others is absolutely brilliant! When you have that kind of a beast, I reckon you report gas mileage as FPG (feet per gallon), LOL
Or SPM, smiles per mile lol. :rotflmao :rotflmao

I've also used SPG. Smiles per gallon
And driving the Ms, I'm always like this from one gas station to the next :biggrin: :biggrin: :biggrin: :biggrin: :biggrin:
I can only imagine what 1,000 hp can do to my face.

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EdBwoy wrote:
Sun Jan 27, 2019 1:48 pm

...folks are complaining, and not just the DIY'ers. Most folks didn't know that the exhaust manifold was an integrated assembly, and also were not aware of the complexity and cost of having it replaced. It's not just here and there; it seems to be a universal issue among the 5.6 owners, stock or modified.
I don't know how to appropriately respond to the highlighted area. Nissan has been doing it in the States since the 90s. I understand that not everyone pops the hood of a car and looks underneath before they buy it...
Oh yeah you'd be surprised at how many folks don't really know the intricacies of their vehicles. Some don't even know their engine size LOL. A lot of M56 owners didn't know about the oil consumption, and I am willing to bet that the engine failures that folks have been experiencing can probably be attributed to not checking the dipstick and adding oil in between scheduled maintenance.

Something was mentioned about cracked manifolds; I am not aware of any issues with cracking; only the threshold efficiency issue
EdBwoy wrote:
Sun Jan 27, 2019 1:48 pm
Yep, that's me who keeps mentioning it. That 03 M45 I bought had a P0420 catalyst code. Efficiency below threshold, etc. It had been misdiagnosed as a clogged cat which was then gutted. When through a series of unfortunate events, I got to an engine replacement, I realized the manifold was cracked. Looking online, I started seeing more complaints from Nissan V8 owners with that type of manifold.
I know I looked at a number of VK56DE issues with the code and cracked manifolds.
Consider that the 06+ M45 with the same integrated manifold had similar oil consumption habits, but zero of the p0420 and cracked manifold issues of the prior years. It employed a flex pipe though.
The newer M's also employ flex piping. I believe those are instrumental in minimizing vibration which can cause manifold cracking plus help with cabin noise. When I installed my custom exhaust, I added flex connectors to mimic factory specs. I will keep a lookout though.


***
EdBwoy wrote:
Sun Jan 27, 2019 1:48 pm
I appreciate you engaging with me as well. I hope we'll get somewhere before you are forced to start buying Cataclean by the gallon.
Yes sir - so far, no CEL!

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kmiles wrote:
Fri Feb 01, 2019 8:35 am
...So many of the 4 cylinder turbos sound like they're pushing beyond their limits to get you up to freeway speeds. It will be interesting to see the life of those engines.
Agreed! Aston Martin provides some very good numbers. They guarantee it for around 60,000 miles. As a reference, the most popular supercars offer 3 year/unlimited mile warranties as standard. Hehehe, what a catch to be in!

I'll quote the popular mechanics article:
And then there's maintenance. Race car motors are, with few exceptions, built to last for the duration of a race. Even millionaires wouldn't buy a car that needs an engine rebuild every 500 miles. Which means the components that go into spinning the Valkyrie V-12 had to be exotic enough to withstand four-figure power at five-figure revs, but not so new and exotic that engineers couldn't be sure they'd last for decades. Cosworth stuck to known materials, and aside from some carbon-fiber structural components, it was made with relatively conventional steel and aluminum alloys.


And then I read a road & track article that offered this:
Wood claims that Cosworth shied away from using the latest sci-fi materials whose reliability wasn’t wholly known, preferring to use the best of established stuff. So there’s aerospace quality alloy heads, and titanium rods and valves, but it’s all proven tech. And while the engine lifespan isn’t going to worry a small-block Chevy, Aston’s V12 will last at least double the 31,000 miles AMG says it’s motor will need between rebuilds. Maybe more, according to CEO Andy Palmer:
Image
"Our expectation is that by 100,000km (62,000 miles) it won’t have blown up, but some of the components will be worn out," says Wood, before adding: "not that many owners will ever get anywhere near that figure."

But Cosworth subjected the engine to over 200 hours of dyno testing (‘much of it at full throttle’) to make sure they would last the course without needing a tear-down after every third Sunday drive. The service requirements are relatively modest give the spec, comprising an oil change every 3-4000 miles.
Well, that's pretty impressive on paper, and if I could afford buying and fuelling one, the unlimited mileage warranties of supercars make them excellent daily drivers. I don't know if they account that a sizeable chunk of a supercar's life these days is spent doing cold starts and promptly revving its heart out for YouTube exhaust videos... So the real world longevity is yet to be determined.

***
I'd like to pivot that into a general discussion of reliability. For most commuter cars, you can safely bet that the car and most components will last beyond the manufacturer-stipulated mileage/time duration for the warranty.
They test their systems and of course do their best to ensure they don't lose too much money correcting issues under warranty or voluntary recall.

They do high endurance tests like the one above and everything holds up at high RPM on a warmed up engine with every other system functioning. But no matter how good their tests and modeling software is, nothing beats the real deal. Age and harsh environments with their sometimes cyclic characteristics cause failures in interesting ways. Modifications, abuse and neglect from owners will also drastically shorten the predicted lifespans of components.
Sometimes you just have to learn in action though. For example, just launch the darned engine on schedule, and if complaints of timing chain issues start rolling in in within 5 years, investigate and redesign, then issue a recall... and life goes on!

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EdBwoy wrote:
Sun Jan 27, 2019 1:48 pm
***
I appreciate you engaging with me as well. I hope we'll get somewhere before you are forced to start buying Cataclean by the gallon.
I just wanted to update my ongoing P0420 issue...the CEL came on again at 99,000k, and it went out on its own after about 150 miles or so, for the third time. For the second time, it stayed out. The first time it stayed out, I went ahead and added a bottle of Cataclean anyway. This time, I decided to not add any. I reset the DTC, and I'm at 100,100k and still going strong.

I want to mention that I was using 93 ethanol free gas for a while, before getting my first P0420 DTC. I was getting better mileage but I believe that using this gas may not be the best thing for the three way cats. My thought was that it burns hotter so it should be better for the cats, but it doesn't burn as clean. It may be ok for the older two way cats or for cars without any cats but from what I've read the ethanol gas actually works better with the newer three way catalyst. I have since switched back to BP 93 ethanol gas. I believe doing this, plus using the Cataclean is helping remove the buildup (possibly caused?) from using the ethanol free gas. It's just a theory, so I guess we'll see what happens...still doesn't explain why it's just the left bank though. I believe it goes back to the crossplane firing order of the left bank vs the right, like you mentioned earlier.

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Hmm...I did start using ethanol free gas about a year ago (although I still regularly use ethanol gas too if I have a discount for gas from my grocer). Maybe I should use one or the other instead of mixing and matching?

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Ilya wrote:
Sun Mar 10, 2019 10:15 am
Hmm...I did start using ethanol free gas about a year ago (although I still regularly use ethanol gas too if I have a discount for gas from my grocer). Maybe I should use one or the other instead of mixing and matching?
I would go back to the premium ethanol gas. I believe the ethanol free gas is not good for the three way catalytic converters that are in our cars. Save that gas for lawn equipment or for older cars with two way cats or no cats at all. Using motor oils with higher levels of ZDDP, like high mileage motor oils can also hurt your cats as well.

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I'll do so as it seems to make sense...but I wonder if my damage is already done...

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There is no problem running 100% gasoline in a gasoline engine. There were however, incompatibility issues that arose when using ethanol in older engines. The M56 manual implies that you can use fuel with an ethanol content from 0-10% [Note, the V6 allows for 15%]
If I were to make a blanket statement, it would be this :
  • Do not use ethanol gas in your lawn mower,
  • or Do your best to use ONLY 100% fuel in the lawn mower,
  • or ONLY ethanol-free gas is good for the lawn mower
Not this other one which I see as a misinterpretation:
  • ethanol-free gas is ONLY good for the lawn mower.
***
Ilya wrote:
Sun Mar 10, 2019 10:15 am
Hmm...I did start using ethanol free gas about a year ago (although I still regularly use ethanol gas too if I have a discount for gas from my grocer). Maybe I should use one or the other instead of mixing and matching?
I wouldn't worry about it. As long as the octane rating is above 91 on the pump, it's fine. LINK
However, since you can easily get the ethanol-free stuff, if you would like to help out and do an experiment and give us another data point like we did with UpRev earlier in the thread, I'd encourage you to keep using the non-ethanol fuel while armybrat goes with ethanol-added fuel. After a while you and he can compare notes.
I do not think any damage has been done by the fuel, but I recall you mentioning that the code came when it got cold outside. If this issue is triggered mainly by outside temperatures, then these next months might be tricky to collect good data since it's warming up. Maybe temperature is the reason armybrat's code has stayed off so far? (Not sure what the ambient temperatures are where you are Sir)

***
armybrat wrote:
Sun Mar 10, 2019 7:40 am
... I believe it goes back to the crossplane firing order of the left bank vs the right, like you mentioned earlier.
I apologize if I misguided you on that matter. I do not think there is anything wrong with the firing order that Nissan has used since at least 1989. I think the issue is structural - probably a crack in the manifold, or even a faulty catalyst element; none of which we can confirm without a visual observation. However, the ethanol vs. non-ethanol experiment might help shed some light.

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I could do that...I could run 100% ethanol free gas for a few months and see if anything changes. But yes, I've seen my light go off on its own in warmer months (that's what happened last year, it came on in like late September and then I saw it go off on a warm October week and ran to get my car inspected lol).

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Edbwoy, you had mentioned in a previous post that an exhaust manifold leak might be the cause of the catalytic converter codes. I am in Canada and we recently have had a very prolonged cold spell (avg temp in -20C/-4F range). During this cold weather, I noticed a very noticeable knocking sound that varies with engine RPM during cold starts in these conditions. The noise eventually goes away after 2-3 minutes after the vehicle have been driven for a while (coolant temp starts moving off from bottom) and the vehicle drives normally. My M56 currently have around 100km/60miles and no CEL so far.

To diagnose this knocking sounds, I purchased a mechanic stethoscope and have pin pointed the noise to be coming from around the cylinders on the drivers bank towards to windshield area. One hypothesis I have is that it might be due to a leaking exhaust manifold as you had described or it could be worn cylinders having piston slap upon cold start up, I will take a video to share if the temps drop again but the noise is very similar to piston slap videos on youtube.

Does anyone else with the P0420/30 code notice any excessive knocking sound from the engine during first 5 minutes of cold start? Once i knew what to listen for the noise can be clearly heard from inside the cabin. The presence of knocking noise in cold could indicate leaks in exhaust manifold eventually triggering the catalyst inefficiency code.

As ambient temperatures are warming up currently ~(0C 32F) the noise is no longer audible.

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tlaspec wrote:
Wed Mar 13, 2019 1:38 pm
...I will take a video to share if the temps drop again but the noise is very similar to piston slap videos on youtube.

Does anyone else with the P0420/30 code notice any excessive knocking sound from the engine during first 5 minutes of cold start? Once i knew what to listen for the noise can be clearly heard from inside the cabin...
I harbor no ill will against my Northern friends, but I sure hope that the temperatures drop back down for you guys for the sake of our experiments :chuckle: :gapteeth: . We are already into the 50-60*F range over here. St. Louis Metro area.

I am glad you could pick out a sound, and I hope other members who actually have the issue are willing to give us some feedback.
In the past, I have experienced an exhaust leak that made a "putt-putt-putt" sound, or it could be described as a sharp "thup-thup-thup" or ticking sound. In most cases, the offending sound went away when the engine warmed up.
For one such example of an exhaust leak with this sound, look up videos of "Hemi exhaust tick" that Dodge/RAM owners experience.

The way I saw it, when ambient temperatures make metal move like so, there was a small enough gap to leak exhaust gas through. When the manifold warms up, whatever gap there was gets sealed due to metal growth with temperature.
Scenario 1
If the gap is somewhere between the mating surface of the head and exhaust manifold, then tightening the exhaust studs could be a possible solution. It wouldn't be the first time a part needed to be torqued down after leaving the manufacturer and being in use.
That is, unless the studs are broken or the gasket has a breach (unlikely - Nissan typically uses a multi-layer steel gasket there).
Scenario 2
If the gap is somewhere on the sweeping tubes of the manifold itself due to a weld crack or plain fatigue loading, then the first thing I would do to plug it up is careful application of furnace weld, or any other type of fix-a-leak/patch-a-leak product from JB weld, etc to see if anything changes. People have tried to reweld cracked headers, and sometimes it works while other times the manifold finds another place to crack soon enough.
Visual inspection with mirrors, borescopes and the like can be tricky with the tight spaces in the engine bay, but once a manifold has been removed we can confirm the presence or lack of cracks and faults. Which is why I have been trying to get everyone's

******************

Remember, P0420 and P0430 codes could be due to:
  • a catalyst issue
  • an exhaust leak
  • an intake leak
  • a fuel injector issue
  • an ignition issue
but with diagnoses such as tlaspec's, it makes sense to focus on the exhaust issue. Plus, the few who have reported manifold replacements, have had no problems with the codes since.

******************

So here's the kicker - if we all have cracked or leaking manifolds, why do only a few of us have the P0420 or P0430 code? Are we all bound to have it at some point?

I think yes, it's very likely. I'll share something I've been intentionally withholding for a while. I have experienced both a cracked manifold as well as a catalyst material issue in other cars. They both had this oddity so I'll refer to both symptoms as one.
I honestly did not track it seasonally, but seemingly randomly, the CEL light would come on accompanied by the P04## codes. I would clear them and could drive for thousands of miles before the code came up again. Aggressive driving and especially high speed runs would trigger the codes almost immediately though.
  • I have seen a manifold with gutted cats immediately pop codes
  • I have also seen others run cat-less for a long distance before any codes show up
  • Likewise, erasing those codes can keep them away for a short time or a long time
  • And sometimes the codes would go away by themselves
  • Depending on the timing, the vehicles would pass emissions testing flawlessly
There are obviously other factors at play here, including the general health of the engine.

This discussion also implies that cataclean might be useless in this application, depending on the accompanying code manipulation. If you immediately erase the codes right after an application of cataclean, that is not a good gauge of its effectiveness. Ideally, when I make changes, I leave the code untouched and if I really fixed the issue, the code will go away on its own.
... But yet, I just gave examples of the codes sometimes randomly going away on their own, right? What I am saying is that using any other fuel-compatible substance in place of cataclean will probably give you the same results.

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I don't hear anything weird other than usual engine sounds when I start my car when its cold (and I live in Upstate NY just south of the Adirondacks).


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