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Thread: Side running exhausts

  1. #1
    Why do teams have exhausts that run along the sides of their car? It seems like it would just add weight, a little bit of complexity, and heat the cockpit. The only advantage I can see (and it seems like a stretch to me) is that it could heat the tires and give better grip. This has confused me for a while.

  2. #2
    If you mean like Illinois does I'd assume its for packaging.

  3. #3
    Senior Member
    Join Date
    Oct 2009
    San Antonio, TX
    Because megaphone

    With a single cylinder engine, it allows us to package a reasonable exhaust tuned length without crazy muffler packaging or excessive headpipe bends in the back of the car. There are rules regarding the maximum height and rearward placement of the tailpipe orifice if it exits the rear of the car. Running the muffler forward allows for more muffler length.

    The only added weight and complexity would be the requisite heat shielding, but check out Formula North 2013 for some examples with negligible weight. If you're already running a sidepod for aesthetics, I see no added weight or complexity. Cockpit heating from a muffler in close proximity is negligible in comparison to the bundle of glowing snakes an inch from your back on a 4-cylinder car. The acoustic batting in most mufflers insulates to the point that aluminum and carbon fiber muffler shells last thousands of miles on production bikes. Mounted an inch from a closeout panel and with airflow around it, the muffler does little to heat the cockpit.
    Matt Birt
    Engine Calibration and Performance Engineer, Enovation Controls
    Former Powertrain Lead, Kettering University CSC/FSAE team
    1st place Fuel Efficiency 2013 FSAE, FSAE West, Formula North
    1st place overall 2014 Clean Snowmobile Challenge

  4. #4
    I would also like to add that running the exhaust/muffler on the side of the car as opposed to out the rear lowers and centralizes the mass (in most cases). Not really sure where you see the added weight and complexity.
    Owen Thomas
    University of Calgary FSAE, Schulich Racing

  5. #5
    Originally posted by Racer-X:
    If you mean like Illinois does I'd assume its for packaging.
    I was one of the engine guys on the Illinois team the first year we did this (2011).

    That year, we started with a more traditional exhaust layout. We ended up having a nightmare passing sound at Michigan. Furthermore, we had some concerns about cooling as our exhaust wrapped around the engine. So between Michigan and California, we made a quick modification to bring the exhaust to the side runner you see now (funny enough, I completely forgot to ask the guys why they retained it).

    Ends up sound was still a bit of an issue, but it was attenuated enough to get by a little easier.

    Ask me now though and I'll say that our sound problems went a bit beyond the placement of the exhaust.

    Prashant Jayaraman

    Bosch Motorsport - Sensor and Component Devleopment
    Illini Motorsports
    Engine, 2009-2011
    Minion, 2008

  6. #6
    Packaging issues make sense. In terms of weight and complexity I was thinking about the engine being in backwards. For some reason I was thinking of the headers as facing back, making it harder to get the pipes to the sides without going through/melting everything in the way.

  7. #7
    We're running ours to the side because the muffler would stick out too far from the rear if we went the other direction. Also, you can balance the weight by sticking an oil cooler in the other sidepod.

    There are other good reasons to do it, too.

  8. #8
    There is one pretty major risk though: if your brackets or supports for your muffler fail, things like this happen:

    Illinois car on fire

    Prashant Jayaraman

    Bosch Motorsport - Sensor and Component Devleopment
    Illini Motorsports
    Engine, 2009-2011
    Minion, 2008

  9. #9
    Like Owen Thomas sais: It's to get the weight to the middle of the car. This reduces your moment of inertia.

    And I'd say you don't want to heat up your tires with your exhaust. Then your left tire and your right tire would have different temperatures and therefore different grip.
    There are other ways to get your tires up to temperature if you have problems. But I have never experienced problems with low temperature at the rear tires. You will have an influence on your tire temperature but I would say you shouldn't let your tail pipe point on the tire.

    Addition: In my eyes your tail pipe should always point a bit into the sky. Think about the measuring method at the noise test...
    In Italy 2011 an Indian Team came to us to ask for mineral wool because they were not able to pass the noise test. Our exhaust guys went to them and saw, that their tail pipe pointed in the direction of the microphone. They suggested to change this by turning the end cap at the damper. Afterwards it pointed 45 into the sky in a vertical plane (not horizontal as before). They easily passed the test with this configuration (without more mineral wool).

  10. #10
    I've noticed a few teams running side exhausts with the muffler exit pointed directly into the oncoming air flow (i.e. in the direction the car is travelling).

    It is my understanding that you want as little resistance as possible for your exhaust flow, so wouldn't this hinder it? Or is there some kind of underlying witchcraft going on that makes this preferable?

    Dalhousie University

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