4 ms·
Sounds amazing, would love for something like this for racing sims (CPUs these days have more cores than good uses for those cores...) For the gotchas - I'd gu
by Scene_Cast2 4y ago
Sounds amazing, would love for something like this for racing sims (CPUs these days have more cores than good uses for those cores...)
For the gotchas - I'd guess that the exhaust manifolds would make a huge difference in terms of sound, and they seem hard to simulate. For example, engineers tune the individual per-cylinder exhaust distance - this way, the exhaust fumes from each individual cylinder align nicely once the exhaust from each cylinder merge into the final exhaust pipe. Otherwise, if, for example, the firing pattern is 1-5-..., then the air from cylinder 1 might arrive to the exhaust pipe at the same time as air from cylinder 5, given high RPMs and limited speed of sound.
And the fluid dynamics of the cylinders are something that is extremely critical to modern cars, too. And I'd guess that this is where things like misfires can be simulated.
Disclaimer - this is all based on my highly unsophisticated mental model,
- Neil44 4y agoI understand they time the exhaust primary lengths so that the next cylinder to open does so into low pressure, to get the most stale gas out of the cylinder possible enabling the most fresh gas possible to come back in later. However since the speed of the pressure waves is somewhat fixed and the speed of the engine cycles vary greatly the lengths chosen only work over a narrow rpm band. Where you decide to put this band during the design phase depends on what you’re optimising the engine for.
- collimator 4y agoThat's like what I heard.
- sakopov 4y agoI think it's the length of the headers that contributes to the sound (I'm sure in combination with other components). I know the boxer engine in Subaru WRX/Impreza STI models has unequal length headers which allowed exhaust fumes to exit in a staggered pattern producing the iconic Subaru rumble.
- Tempest1981 4y agoIs this "curly exhaust" idea a new thing? "Why are the 2023 Acura Integra's Exhausts Are Shaped Like Curly Fries?" https://www.integratalk.com/threads/why-are-the-2023-acura-integras-exhausts-are-shaped-like-curly-fries.306/ https://www.integratalk.com/threads/why-are-the-2023-acura-i... Excerpt: By snaking the exhaust piping into that circular route, Honda is lengthening the exhaust pathway, lowering the resonance frequency without using a traditional muffler . Honda engineers tell us that the design as first installed in the Si also emphasizes the 300Hz to 600Hz frequencies "to deliver a more aggressive sound." Skipping the muffler, Honda also was able to achieve that sound with a 27-percent increase in exhaust flow.
- olivermarks 4y agoIt's very common for aftermarket exhaust headers to be a spaghetti of equal length curved tubes into a collector for better flow. Lots of videos on this discussing specific engine types and goals. I'm assuming Acura are taking this approach further down the exhaust system as well?
- ericbarrett 4y agoI imagine fluid modelling with all the variables needed to meet manufacturing requirements (material, space constraints, across RPM ranges, etc.) and the speed to allow an engineer to iterate the design—keeping up with integration requirements—hasn't been practical until recently. I bet this saves the money, too; a muffler is an extra component you need to source and/or build. Bending some extra pipe seems a lot cheaper.
- tekknik 4y ago> I bet this saves the money, too; a muffler is an extra component you need to source and/or build. Bending some extra pipe seems a lot cheaper. Now hold on, extra length on the exhaust manifold / headers are not going to reduce sound so much you don’t need a muffler. And the muffler is far from the most expensive part in the exhaust system, which would be the catalytic converter.