By on April 5, 2016

 

exhaust tips. shutterstock user KULLAPONG PARCHERAT

Jeff writes:

Sajeev:

I have a question that I don’t believe you have answered before in your talking about design features, and that is the weird obsession car makers have with exhaust outlets.

I really like driving big iron that can get out of its own way “with haste.” One of my favorite and much missed cars (except for the repair bills) was my BMW E38 750iL. This car was a great sleeper; big and fast, it didn’t need to shout for attention. One of the ways that it did this was by having a rear valence that completely wrapped around the back side of the car. No shouty exhausts on this Bavarian beast!

Fast forward to today: my daily driver is a ’00 Jaguar Vanden Plas Super V8 (Nice ride! — SM). It has dual exhausts with bigger outlets than the standard XJ8, though I bet the actual exhaust tubing isn’t any bigger compared to the regular V8s. Every big car that I have looked at recently has big protruding tips at the end of the exhaust. Mercedes-Benz S600/S65 AMG/S55 AMG, Audi S8, and even the Jaguar XJ Supercharged cannot provide simple turndowns.

Is there a technical reason for this, or does everyone feel that they just need to have big tubes out back?

Sajeev answers:

From a (Piston Slap) engineering standpoint?  Turn down exhaust tips shall flow the CFMs worthy of today’s turbo luxo-sedans. And perhaps the real estate freed up allows for a deeper rear valance with better aerodynamics. Or not, but I digress

The aforementioned turbo-barges do generate extra heat, adding extra sensitivity to restrictive muffler designs, exhaust bends and diameters, but all vehicles cool exhaust gases significantly between the front manifold and the rear bumper. With cooler exhaust temperatures comes a smaller, denser product, therefore something as minor as a turn down on a constant diameter pipe changes nothing.

I reckon smaller diameter rear pipes are within the realm of possibility until a certain horsepower threshold. And here’s my proof: this modified GT-R uses the flashy stock pipes as a design feature, but there’s a legit exhaust turn down to get the job done:

How many cars on the market today make power like this bad-boy? Riddle me that, Son. 

From a Vellum Venom design standpoint? Every industrial designer, be it product or transportation, was exposed to these dilemmas as a youth. Product guys (and gals) likely sing the praises of stuff like the iconic Coke Bottle over aluminum cans, and transportation design peeps remember the design intricacies of whips from their childhoods. My love of 1987-93 Fox Body Mustangs is no different.

 

The LX 5.0 — the more appealing/valuable design today (especially the lighter 2-door Sedan) — had looooong chrome tailpipes, one of the few differentiators from the similarly clean look of the LX 2.3. The pipes added purpose without altering the LX’s nerdy Ford Fairmont DNA relative to macho Supras, F-bodies, DSMs, and others flaunting their bespoke sports coupe platforms.

 

But the Mustang GT? Peep the drop-jaw front bumper (awesome), side skirts emblazoned with the “Mustang GT” logo (meh) and fake scoops aplenty (yuck). But the cake’s icing was that deep-skirted rear valance with that GT logo and hidden, turned-down exhaust tips. It looked modern and upscale(-ish) for the changing, diversifying late-’80s performance car scene. The invisible tailpipes were part of the curb appeal.

The invisible LX 5.0 and the boisterous GT were equally appealing in my Fox Body-centric childhood. And today, it doesn’t matter if a new car is more LX 5.0 than GT in the rear: both designs are right.

[Images: Shutterstock user KULLAPONG PARCHERAT]

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41 Comments on “Vellum Venom Vignette: Turn Down (Exhaust Tips) For What?...”


  • avatar
    Vulpine

    There is one point against the turn-down inside the rear valence instead of extending beyond it and that is that some exhaust gasses can get trapped underneath the car and potentially leak up into the cabin, creating the potential of carbon monoxide poisoning. A previous VV article pointed out the exhaust vents in the trunk area of vehicles which, while designed to let air out could work the opposite way if the driver has the vent system shut down for whatever reason. With the pipes clearly outside the body, there is lower risk and creates a sportier look.

  • avatar
    NoGoYo

    I always liked those mufflers with the twin diagonal-up exhaust tips. First saw that in the first Fast and the Furious.

  • avatar
    heavy handle

    What bugs me, design-wise, are fake exhaust tips built into the rear valance, through which you can see the actual unfinished exhaust pipe.

  • avatar

    There’s also an aerodynamic impact to the turned down pipes. I know that side pipes have a huge impact, especially at speed when you need smooth airflow. I would think the down pointed pipes would mess up underbody airflow as well. Perhaps even contributing to lift at speed. Engines pump a LOT of air.

  • avatar
    dwford

    The exhaust tips are getting a little crazy. From the odd shaped ones that have tiny actual tailpipes sticking out of them to the total fake rear bumper trim shaped like exhaust tips like the Lexus IS-F (and others), the dual exhaust tips look is the VPL (visible penis line) of car design.

  • avatar
    Land Ark

    The GT tail lights kinda look like the American flag – complete with 13 stripes (counting the painted part first).

  • avatar
    Chets Jalopy

    I still love the LX 5.0 exhaust pipes. They are infinitely manlier than the little straw dangling from the 2.3’s rear valance.

  • avatar
    relton

    For both of the cars I designed, I used turned down exhaust pipes. I used fake exhaust pipe ends for styling reasons. No need to get the fake pipes dirty with real exhaust, or try to isolate real exhaust pipes from the body, or worry about alignment, and so on.

    I can’t believe that exhaust pipes at the rear end of the underbody have any measurable effect on the aerodynamics of the car at any speed. The airflow at the back of the car is so turbulent, especially with cars with no underbody shielding (which is most of them) that there is little aero gained or lost at that point.

    The pipes on that 1st pictured Mustang look like they are already misaligned to the holes in the fascia. I year’s worth of soot and dirt will undoubtedly mess up the look of the pipes, and a few months on Michigan’s roads will have the pipes banging against the fascia knocking off some paint.

    Bob

  • avatar
    2drsedanman

    I bought a then brand new 1989 Mustang LX 5.0 with 5 speed in the fall of 1989. Really fun car. I remember the back tires being completely bald by 12,000 miles. The front of my Mom and Dad’s house looked like a drag strip with all that rubber on the road. Good times.

    To find one of these cars today in good shape with low miles is not easy. When you do, it is usually in the $10-15k range. I gave $13.6K for it new. Holding their value pretty well I think.

    • 0 avatar
      RHD

      In my town, the worst drivers are young males with new Mustangs. By “worst”, I mean aggressive, red-light-runners, burnouts, speeding, and general obnoxious idiocy. Nothing personal, 2drsedanman, of course.
      After about a year or so of getting tickets, the Mustang tends to disappear.

      While on the subject, the worst drivers in my town in terms of not looking before backing up, not using turn signals, driving too slowly, poor car control and general confusion, are the numerous fine folks from a very large Asian country that is not China.

  • avatar
    Driver8

    It’s easier to dragon straight pipes.

  • avatar
    WheelMcCoy

    Aside from being (nice) jewelry, exhaust tips also can become a signature for the car. It can also help identify the trim; on a MINI, twin pipes in the middle indicate the turbo model.

    On an EV, no pipes makes sense. I’ll also accept turned down tips on a hybrid because hybrids aspire to not need them. On an ICE, it feels a little dishonest to hide exhaust pipes… not dishonest in the VW diesel sense, but dishonest in the BMW fake-engine-noise-piped-into-the-cabin sense.

    Sajeev’s fine example of the Mustang is not dishonest because in those days, the ICE was the only game in town. Hiding or showing pipes were legitimate design experiments. Today, with EVs and hybrids in the mix, exhaust pipes, or lack thereof, are loaded with additional meaning.

  • avatar
    DenverMike

    The difference is just cosmetics. They’re not “turned down” as in straight down. The exhaust leaves the back of the car at about a 45 degrees or less, just enough to clear the body. At least with the Mustang GT and other performance cars with “turned down” exhaust.

    The exhaust tips of the LX 5.0 are Foxtastic and pure sex. The limp weenie LX 2.3 exhaust did point straight down, but back then, cheesy ‘base cars’ embarrassed you into stepping up to the performance versions. Now its hard to tell at a distance, the base Mustang from a GT.

    Just a reminder though, both the GT and LX 5.0s have true ‘dual exhaust’, 2.5 inch stainless steel, crossover pipe and true headers.

  • avatar
    Fred

    Turned down exhausts are also quieter.

  • avatar
    nels0300

    Holy CRAP!!!!

    I had that EXACT same green LX 5.0L coupe. Man. I miss that car.

  • avatar
    PrincipalDan

    I honestly feel that all cars with V-style engines should have dual outlets poking out somewhere. Just my two-cents. I never was one for “invisible” exhaust especially on upper trim levels or if you bought the biggest displacement engine available.

    My base V6 Highlander doesn’t even have factory V6 badges on it, let alone dual exhaust. That is a bit of a letdown in my book.

  • avatar
    SCE to AUX

    Buy an EV – problem solved.

  • avatar
    Boff

    For an Exhaust Pipe Fetishist like myself, turned down pipes will never do. Nor will the recent, execrable, trend towards little bitty tailpipes emptying into openings that are part of the rear valance. Even the new GT350 does this. BOO.

    Side note: when I see turn downs, I am always reminded that many Euro diesels had turn down pipes whereas the corresponding petrol models would not.

  • avatar
    spamvw

    Don’t forget the classic pinched Ford Taurus Exhaust Pipes

    (My TDI has twin outlet turned down pipes, fancy.)

  • avatar
    Kyree S. Williams

    I think the exposed exhaust tips are just to show off. Acura bucked the trend and did away with them on its latest wares, although they were just re-added to the MDX for MY2017.

  • avatar
    CoreyDL

    I like the quad center exhausts on the Corvette currently.

    And also the special 6-outlet dual exhausts only available on the first STS.

  • avatar
    Uncle Mellow

    I always thought the fashion for hidden exhausts came from Germany, as a response to the Greens. Clearly visible exhausts pollute the environment. Hidden exhausts are kind to animals and small children and especially the planet – and might even indicate an electric car ! Of course, diesel cars had to have down-turned exhausts to ensure the soot particles stuck to the road and not to the back of the expensive car. Diesel vans with straight exhausts always had black back doors that you could write your name on, if you didn’t mind getting a sooty finger. Straight exhausts on diesel cars only happened when diesel particulate filters became the norm.

  • avatar
    MRF 95 T-Bird

    The Fox body Mustang LX looks great with the chrome pipes but the GT looks nice and clean with the rear skirt and hidden pipes. The chopped out holes with tips as shown above just look cheap. An afternoon at Pep Boys with a hole saw.

  • avatar
    JimInRadfordVA

    I miss side-pipes.

    http://www.spiralturbobaffles.com/images/corvette/istockphoto_278208-corvette-side-pipes.jpg

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