Exhaust System Information
DISCLAIMER
The information provided here is for general guidance purposes only. It is a combination of manufacturer guidance, first- and second-hand experience, and personal opinion. It may me inaccurate, incomplete, or outdated.
There are three basic types of exhaust systems used by Gaydon-era Aston Martins: Early V8 Vantage, late V8 Vantage, and V12 cars. All of these exhaust systems use the same four-section layout, but the actual components used in the sections of each are different. I discuss each of the sections in order of front-to-rear on this Information Page.
The information here is presented as it specifically relates to these cars.
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General Exhaust Information
Legality
Exhaust systems are one of the first things that gets changed when a person modifies their car. Doing this allows us to change how our cars sound, can free up some power, and often will reduce weight. However, it can be illegal. Car manufacturers design exhaust systems to comply with regulations for both emissions and noise limitations. Modifying any part of the exhaust system may run afoul of those, so make sure you’re obeying any applicable laws or regulations. This is particularly true when removing or replacing any catalytic converters.
Warning: It is your responsibility to check and abide by any relevant laws, regulations, or statutes. Failure to do so may result in fines or other penalties.
Emissions Monitoring and o2 Sensors
Catalytic converters (commonly called “cats”) are used to reduce certain emissions gasses that come out of the engine and a pair of o2 sensors is used to monitor that reduction. The “upstream” o2 sensor takes a reading based on the exhaust gasses going into a cat, and the “downstream” o2 sensor takes a reading of the gasses coming out of the cat. The engine control system of the car then compares the two readings to see whether or not each of the readings are within their own parameters and how the two readings compare to each other. The comparison of the upstream and downstream o2 sensor readings is used to determine if the cat is doing its job of reducing emissions. If any of the readings or comparisons are out of their specified parameters, a check engine light (CEL) and emissions warning will be displayed on the gauge cluster.
This is all super-basic stuff, but it’s worth reiterating because knowing which cats are monitored and which aren’t can affect how you modify your exhaust system.
Check Engine Light and Emissions Warning
I often joke that getting a CEL and emissions warning in an Aston Martin just means the engine is on. If only it was funny. Emissions warnings are an annoying part of Aston Martin ownership that many of us have just come to accept will happen from time to time. Any time the emissions warning is displayed, there will be a CEL displayed as well. Getting both at once may be scary, but don’t panic. It’s surprisingly common and can be caused any anything from a bad o2 sensor to a loose gas cap. That’s not to say the CEL and emissions warning should be ignored. They’re there for a reason and as with any warning, you’ll want to chase it down and fit it. but a yellow CEL triangle doesn’t mean you should avoid driving the car. If the yellow CEL triangle turns red… then you can panic.
The “bad o2 sensor” scenario is not unusual as the V8 Vantage tends to demand new upstream o2 sensors more than any other car I’ve ever owned. It adds insult to injury that the o2 sensors for these cars are fairly expensive. I don’t think potential buyers should worry about these being a deal-breaker that would prevent them from buying an Aston Martin, but it’s enough of a concern that I added the o2 sensors to my list of items to watch out for in my Maintenance Guide.
Because emissions warnings are so common with these cars, a lot of owners will simply dismiss them, and even tell people to just ignore the message and clear it with a scan tool. Yes, most OBDII tools can read and clear an emissions warning from an Aston Martin. However, it’s still important to figure out what is causing that warning in the first place. Clearing the warning is fine, but you should take note of the P-code so the problem can be sorted.
Components
Gaydon-era Aston Martins have the same general exhaust system layout. From the engine to the rear of the car:
Exhaust manifolds (also called “headers”)
Catalytic converters (also called “cats”)
Mid-pipes
Muffler (also called “backbox”)
Note: I’ll use the above sections to detail each piece of the exhaust system, but keep in mind that the exhaust manifold section may or may not have catalytic converters in addition to the catalytic converters located immediately behind the exhaust manifolds.
Each side of the engine has its own exhaust piping that run from engine all the way to the tail pipes. Meaning, the left and right side of the engine each have their own exhaust manifold. The left and right exhaust manifold each go into their catalytic converter. Each catalytic converter goes into its own mid-pipe. The left and right mid-pipe each has its own entry into the muffler. And the muffler has an exhaust tip for each of those pipes.
Section 1: Exhaust Manifolds
Exhaust manifolds (also called “headers”) are a component of the exhaust that uses runners to take exhaust gasses from the individual cylinders of the engine and then combine them into a single exhaust pipe. The V8 Vantage had cat-less headers until halfway through 2010 (MY10.5). From that point on, headers in a V8 Vantage contained a pair of cats. All factory V12 headers all have a pair of cats on each side. If a car has cats in the headers, then those cats are the primaries and they are monitored.
The factory headers on the early V8 Vantage were cat-less units that featured a 4-2 design. Yes, technically the headers end without joining the two larger runners into one, and that 2-1 merge is done upon entry into the cat behind it. The headers were double-walled for sound and heat insulation and were actually quite good for factory equipment. However, their unequal length runners mean there’s room for improvement. Replacing the factory headers with equal-length ones, like the VelocityAP headers I put on my 2007 V8 Vantage, will improve the efficiency of the exhaust system.
There’s plenty of information on the internet about the benefits of equal-length headers so I’ll just summarize it briefly here.
Having equal-length runners prevents the exhaust pulses from colliding with each other. When exhaust pulses collide, it causes turbulence in that spot and makes it more difficult for subsequent exhaust pulses to flow through the exhaust pipe, which reduces performance. If this happens close enough to the engine, it can cause certain runners to flow less efficiently than others, which may lead to the cylinders for those runners to have different temperatures than other cylinders and potentially have pre-detonation. If serious enough. Equal-length headers prevent all of that from happening, and generally flow better than unequal-length headers so they allow the engine to produce more power. Reducing or eliminating exhaust pulse turbulence smooths out the exhaust flow which also smooths out the sound of the exhaust, which results in a more exotic-sounding exhaust note.
Exhaust manifolds are a bit difficult to replace so most people address the cats behind them first, or just skip doing the headers entirely. But they’re still worthwhile if you want to get all the performance you can out of a pre-MY10.5 V8 Vantage. Since there aren’t any cats in these headers, they can be replaced without worrying about a CEL or emissions warning, and engine tuning is not required for them.
About halfway through the 2010 model year (MY10.5), Aston Martin changed the layout of the V8 Vantage’s exhaust system. These headers are in a 4-1 design with all four runners dumping directly into the cat. While the previous cars had one set of cats (the primaries by default) positioned after the cat-less headers, the cars going forward would have the primary cats integrated into the headers and a set of secondary cats positioned where the primaries had previously been.
Note: The exhaust manifolds from a 4.3L V8 and 4.7L V8 are not interchangeable unless the corresponding catalytic converters are also used.
Aston Martin moved the primary cats into the exhaust manifolds to comply with stricter emissions standards in some of its markets, especially those related to cold-start emissions. By having the primary cats closer to the engine, the cats would heat up more quickly and improve cold-start emissions from the car.
The benefits of using equal-length headers also apply to the post-MY10.5 cars, but with the added benefit of eliminating the cats and freeing up the exhaust flow even more. Because the primary cats are monitored, removing them will cause a CEL and emissions warning so an engine tune is required.
All Gaydon-era V12 cars have had their primary cats in the exhaust manifolds. These headers were each in a 6-2-1 design with three runners dumping into two cats and then merged into one before the end of the manifold. Since the primaries are monitored, replacing these will result in a CEL and emissions warning so an engine tune is required.
A lot of power can be gained from the V12 by swapping out the factory headers with equal-length headers for the same reasons as replacing them on the MY10.5+ V8 Vantage - the catalysts are being removed and the piping length is being equalized, both improving exhaust system performance and efficiency.
There is an additional reason to replace the headers on a V12 Aston Martin, which is due to the possibility of the catalyst material breaking apart inside the cats, getting into the engine, and causing damage. While I wouldn’t say this is a common issue, it can and does happen. Being preemptive about this is a tricky thing, though. The headers contain the primary cats, so replacing them with non-catted headers could be an issue for legal restrictions, and they’re very expensive to replace with OEM units to swapping out older factory headers with newer ones may be a costly exercise in paranoia.
Personally, the catalyst concern for the V12 wouldn’t stop me from buying one as this issue is pretty rare. But it’s still worth knowing so you don’t get surprised if you’ve got one of these cars and come across a story about a V12 eating a cat - which sounds a bit wild without context.
Section 2: Catalytic Converters
Behind the exhaust manifolds are catalytic converters, with each of the headers emptying into a cat.
For the pre-MY10.5 V8 Vantage, these are the only cats in the exhaust system, so they are the primaries and are monitored. What’s interesting about the OEM cats is that they actually only monitor part of the catalyst in the unit. You can see this in the picture below - the OEM cat on bottom has the downstream o2 bung (left-most of the bungs) positioned near the middle of the catalyst unit. Anything downstream of that second bung (to the left of it) isn’t monitored by the o2 sensors. In a sense, that means that the pre-MY10.5 cars do have both primary and secondary cats, but they’re bundled together inside the same unit.
Replacing these monitored catalytic converters with high-flow cats may result in a CEL and emissions warning, and replacing them with cat-delete pipes definitely will. If you want to replace the cats on a pre-MY10.5 V8 Vantage, I’d highly recommend getting an engine tune in conjunction with it to prevent any warning lights or tuning issues.
For the post-MY10.5 V8 Vantage and all V12-engine cars, these are secondary cats and are not monitored. They can be replaced with high-flow cats or cat-delete pipes without triggering a CEL and emissions warning, and they can be replaced without needing a tune. Aston Martin even offer a cat-delete pipe of their own for the V12 cars.
Note: The catalytic converters from a pre-MY10.5 and post-MY10.5 V8 Vantage are not interchangeable unless the corresponding exhaust manifolds are also used.
Although not primarily designed to do it, catalytic converters do act as a muffler for an exhaust. Switching to high-flow cats or cat-delete pipes will result in a louder exhaust, even if the rest of the exhaust is kept the same.
Here’s a video showing how to replace the primary cats on an pre-MY10.5 V8 Vantage, along with a sound comparison at the end.
The process in that video is the same for the secondary cats on a post-MY10.5 V8 Vantage or V12 car, which has the secondaries in the same location as the primaries you see in my video. The main difference is that secondary cats don’t have o2 sensors since they aren’t monitored, so you won’t have to deal with those like you see me doing on my 2007 V8 Vantage in the video above.
In addition to high-flow cats, you can also use cat-delete pipes here. On the pre-MY10.5 V8 Vantage, a tune will absolutely be needed as having no cats at all will definitely trigger a CEL and emissions warning. On the post-MY10.5 V8 Vantage and the V12 cars, the secondaries aren’t monitored so they can be replaced with high-flow cats or removed entirely without any issues. You can use a set of cat-delete pipes, or you can replace them with an X-pipe.
Cat-delete pipes completely remove any catalyst from this portion of the exhaust so be ready for an even louder exhaust than you’d get with high-flow cats. There’s also the possibility you’ll smell the exhaust more if you go fully cat-less, so expect that as well.
An X-pipe can be used in place of cat-delete pipes on the post-MY10.5 V8 Vantage or V12 car. An X-pipe is basically pair of cat-delete pipes that cross over or merge before splitting apart again. The crossover allows exhaust pulses to better flow through the exhaust system, improving performance and efficiency. Replacing the secondary cats with an X-pipe gives more power, less weight, and a more exotic exhaust note, and it doesn’t require a tune. Personally, I consider it a better option than just using cat-delete pipes.
Replacing this portion of the exhaust is probably the most common first step in modifying an Aston Martin. It, along with an engine tune, will give the best “bang for your buck” for performance when looking for more power.
Section 3: Mid-Pipes
The mid-pipes consist of a pair of exhaust pipes running somewhat parallel to each other. Their job is to carry exhaust gasses from the cats to the muffler.
There’s not a whole lot to say about the mid-pipes when it comes to performance or options. They’re a simple thing with a simple job. Some people do cut a section of the mid-pipes out to add in an X-pipe crossover on the pre-MY10.5 V8 Vantage, and that supposedly can free up a little power. VelocityAP make mufflers with an integrated X-pipe design, so if you’re planning to get one of those then there’s even less reason to worry about the mid-pipes.
The mid-pipes use hangers to support their weight in addition to being held in place at each end. The hangers slot into bushings that are attached to the underside of the chassis, which you can see in the cut-out portion of the heat shield in the picture below.
In that picture you can also see the mid-pipe hangers are part of a bracket, and this design is unique to the Vantage. The DB9, for example, has these hangers welded directly to the mid-pipes.
These bushings were really worn out on my car when I pulled my mid-pipes during a major overhaul I did with my 2007 V8 Vantage in January 2022 when it had around 95,000 miles on it. They were so worn out that it took absolutely no effort whatsoever to pull the mid-pipe hanger out - the bushings were that busted. Granted, I’ve put my car through more than most people ever will so I’d imagine mine are more worn than what would be typical, even if we ignored the high mileage of my car. The bushings are easy to replace with the mid-pipes out of the way and are common to most Gaydon-era Aston Martins.
One thing about the mid-pipes that does concern me on the Vantage specifically is the hanger that’s used to support them. The first issue is that the bolts are some of the most exposed fasteners on the entire car which can cause them to rust out very easily. Not only that, but they’re Torx bolts, which means they can be very difficult to remove if they strip. You can see in the picture below that these bolts pass through a bracket, which is actually welded onto the underside of the mid-pipes.
These hangers on the topside can be a serious annoyance for us Vantage owners. The issue is down to their design, which involves the “nut” that the bolts thread into from below. If these break loose, the bolt will just spin when attempting to remove it. A set of vice grips remedies this, but an actual repair would require welding the nut back onto the hanger bracket or replacing the bracket entirely.
The picture above shows the issue on my own car, but you can also see how much clearance is there for a set of vice grips to hold the nut in place when removing the bolt. I’d definitely recommend replacing the bolts any time removed from this particular spot, though.
Section 4: Mufflers
The role of a muffler is to control how loud the exhaust is. In fact, that’s why it’s called a “muffler” - it muffles the sound of the exhaust. The factory mufflers from Aston Martin are valved, meaning there is a valve system that redirects the exhaust flow to make it louder or quieter. This gives the exhaust the “best of both worlds” when it comes to controlling sound level. In low RPMs and low throttle, the valves are closed and the exhaust gases are forced through the muffler baffling, keeping it quieter. At high RPMs and high throttle load, the valves are open and the exhaust gases can flow in a more linear path, making it louder.
A few things have changed over the years so this may be different on later years and models, but the early DB9 and V8 Vantage muffler valving behaves the same way:
Between idle and 1500 RPMs, the valves are open.
From 1500 to 3000 RPMs, the valves are closed.
Above 3000 RPMs, the valves will open and close based on throttle load.
The valving will behave differently for cars that have Sport Mode as the parameters for that change from one mode to the next. Generally speaking, the more aggressive the mode, the earlier in the RPM range the valves will open.
It’s possible to keep the valves open at all times by removing the fuse responsible for them. The fuse box in the trunk holds this fuse - not the fuse box in the engine bay or the fuses of the CEM in the cabin. The fuse for the exhaust bypass valves was originally Fuse 22 but was later moved to Fuse 15, possibly around the MY10.5 point when the engine was changed from 4.3L to 4.7L. If you’re not sure which one it is for your car, you can check the Fuses section of your owners manual but it might wrong - the fuse location in the owners manuals weren’t updated until at least a couple years after it was moved.
As far as the engine is concerned, there isn’t any real risk involved with removing the fuse to keep the exhaust valves open full-time. There is, however, the risk of the valves seizing and becoming inoperable. Removing the fuse will keep the valves open at all times, which means they aren’t opening and closing on a regular basis. Over time, that can lead to them seizing up and not being able to function properly even after the fuse is put back in place. Many people may not care about it, but it’s something to keep in mind if you ever want to revert to using the valving function of the OEM muffler. it’s also worth noting that the muffler valves can seize if even the fuses are never removed due to age, lack of use, environmental conditions, or all the above.
In addition to controlling sound levels, the opened valves also increase performance at high RPMs. I don’t know how much of a difference it actually makes, but Aston Martin’s literature states that it does reduce back pressure to enhance top end performance. Regardless of what the actual measured difference is, the factory mufflers do flow really well. From what I’ve seen, aftermarket mufflers typically only gain a few horsepower over the stock ones.
Since little performance is to be gained from a muffler, it makes the primary reasons to replace the OEM muffler with an aftermarket one is the ability to choose how the exhaust sounds, and for the weight loss benefits. The weight loss is simple: the factory muffler is incredibly heavy. VelocityAP claim a 32.2-lb (14.6 kg) weight reduction with their non-valved mufflers, and a 25-lb (11 kg) weight reduction with for valved mufflers.
There are three typical sound levels used to describe the mufflers for a Gaydon-era Aston Martin:
Touring (the quietest)
Sport (the middle level)
SuperSport (the loudest)
There’s nothing defining these sound levels - they’re just used by exhaust manufacturers as loose descriptions to help differentiate their own products. For example, the Touring muffler from one company may sound different from the Touring muffler from another company.
Choosing the sound level of a muffler can be a bit complex because other parts of the exhaust can affect it. Specifically, changing out the headers or cats of a vehicle can make it louder, even if the original muffler is kept in place. It’s something to keep in mind when modifying an exhaust system and choosing your muffler, because the changes in sound do add up when any part of the exhaust is modified. It’s all down to personal taste so there isn’t much of a right or wrong way to do it.
It’s a good idea to plan ahead when changing out parts on a car in case old fasteners, gaskets, or other hardware need to be replaced. This is true for the muffler as well.
There’s a pair of donut gaskets between the muffler and mid-pipe, exhaust clamps between the mid-pipes and muffler as well as between the muffler and exhaust tips, and there are spring-loaded bolts between the mid-pipes and muffler. Gaskets should be replaced whenever removed from the car, but the donut gaskets are really robust so don’t be too surprised if they look good when they come out.
The same can’t be said about the spring bolts:
Two of the bolts broke when being removed. Luckily they broke in a way that released them so we didn’t have to drill out the remnants.
It was also the case for the pair of exhaust clamps that secure the muffler to the tail pipe tips on my car:
The clamps on both sides looked the same and neither was salvageable. In my case, we ended up using a cutting wheel to cut the middle of each bolt and replacing the clamps with new ones.