It’s become a startlingly common trend, and it's one that frustrates ‘car people’ everywhere. Fake exhaust outlets are seemingly everywhere, with faux-chrome circles applied to rear bumpers that often have no correlation to where the engine’s exhaust gases actually come out.
And it's not just cars at the cheaper end of the spectrum that are sporting these fraudulent apertures, either. From the Toyota Corolla to the Bugatti Chiron, fake exhausts are found in all corners of the automotive landscape.
Why, then, do they exist? Over the course of my career I’ve spoken to plenty of car designers and engineers about precisely this subject, and as it turns out there are a quite a few reasons why one of my most hated car design trends has become ‘a thing’.
Reason #1 - Aesthetics
This is the big one. It turns out that when designers don’t have to consult the engineers from the powertrain division about the aesthetic qualities of the exhaust tip, it suddenly becomes much easier for them to craft a cool-looking rear bumper because the ‘exhaust’ bit can be more seamlessly integrated with the rest of the car’s bodywork.
The obvious side-effect of excluding those engineers is that they then go and do their own thing, which usually means the exhaust tip gets turned down to face the road and thus expels gases below the bumper, rather than through it.
In these circumstances, what might look like the ‘exhaust’ is actually just a sealed-off bit of black plastic surrounded by a ring of plasti-chrome, while the real exhaust's position doesn't even correlate.
The other scenario is that the designers do the engineers the favour of styling an exhaust tip that's integrated with the bumper, but actually allows gas to pass through it rather than being a mere blanking plate.
In these circumstances, the exhaust pipe itself won’t touch the faux tip that’s visible to bystanders, and that has a lot to do with the next couple of points:
Reason #2 - Cost
The smallest things can result in big costs when it comes to production line efficiency, and the less time a worker spends aligning an exhaust pipe with a bumper cutout, the more cost-effective that worker becomes.
Faux exhaust tips that do actually lead through to the exhaust muffler (but don't physically touch it) permit quite a bit of misalignment to take place without anyone being the wiser.
Beyond that, eliminating a chrome tip makes it simpler and cheaper to fabricate an exhaust, especially if the same visual effect can be achieved by finishing the exhaust area with a metalized plastic trim piece instead of real metal.
The cost savings per car may only amount to a few dollars apiece, but when a carmaker is pumping out vehicles by the hundreds of thousands every year, that adds up to a significant amount of money.
Reason #3 - Safety
Exhaust gases are hot. REALLY hot if the engine is working hard, and most plastics used in vehicle bumpers tend to melt into a polymer goop when exposed to high heat.
Ergo, having an actual exhaust pipe come in close proximity to a rear bumper is a no-no, especially at the sort of clearances that modern car designers typically favour.
Don’t forget that heat makes metal expand quite significantly, so the position of an exhaust tip when a car being driven with a hot engine versus when it’s parked and cold can differ markedly.
If there’s not enough space around the exhaust to account for that dimensional growth, then there’s the risk of hot metal making contact with plastic and causing damage. It’s often just easier to make the exhaust hardware physically separate from the hole in the bumper.
Reason #4 - Cleanliness
This one applies to diesels most of all. Accumulation of exhaust soot on a car’s back bumper can make even a brand-new whip look like a haggard old hack, but there’s an easy solution: point the exhaust tip down at the road instead of straight back.
That directs most of the dirty exhaust out of the swirling airflow behind a car, lengthening the amount of time that the back bumper stays soot-free. It’s a minor reason, but one that makes a difference to the long-term ownership experience.
And there you have it - there is both rhyme and reason behind the proliferation of the pretend exhaust tip. And now that you know they exist, you'll be looking for them everywhere...