Unequal headers

Seeing as some modern cars (Subaru WRX STI, Shelby GT350R (actually not sure, is this right?)) use unequal headers, would it be feasible to add them into the game, at least for boxers, to give cars a bit more personality?

I am not sure what purpose this feature would serve in terms of gameplay because using uneven length headers is mostly for packaging constraints and sometimes for tuning the sound of the engine. Actually, in most cases uneven length exhaust runners incur a performance hit since it disrupts resonance in the stream and thus exhaust gas scavenging.

In short its so specific to mundane, nit picky, real world constraints that its effect on gameplay would range from moot to agitating / confusing.


The purpose they would serve would be pretty much entirely sound-based, but the performance/size difference should also be put into account. Also, unequal length headers are literally the identity of the Subaru brand, so people who want to make cars that have their iconic “burble” would be happy.

Then again there isn’t much point. The game doesn’t consider the exhaust note beyond loudness and probably shouldn’t because it takes a very attentive ear to notice the differences. Even I don’t most of the time and will be goddamned if the 8.4L Viper V10 is one of the most unique, best sounding engines ever.

The performance difference may be detectable but its minuscule. There other things that affect performance and packaging - and thus gameplay - significantly more that we should be talking about then. Things like Front-Forward versus Front-Mid engine layout (which is key to Subaru’s AWD layout which is a LOT more iconic), separate transfer case versus fully unitized transaxle, variable intake / turbo geometry, or freely adjustable V angle. And of these, only variable turbo geometry is going to be implemented, the others either having been previously shot down or too hard to implement.


Well, at least engine sounds should be more varied. At the moment the only differences I can notice between engines is mufflers and VVL. Other than that, they all sound exactly the same.

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Agreed, it’s actually quite a letdown that pipe diameter doesn’t affect pitch, nor does header design affect the base acoustic profile.

Considering how much of a long and complicated proccess it is to get even the current sets of sounds generated (intake & exhaust sounds for both open and muffled configurations of every cylinder configuration), that’d just make everything even more ridiculously complex sound wise.

Plus, to be honest, I think a lot of the time you can’t specifically identify the sound difference of different header designs (beyond ones with weird pairing or unequal length).

I reckon about 95% of the sound difference in engines is how muffled the exhaust and intake are, what the cylinder configuration is, if it’s turboed, and what the cam profile is like. (and those are the things we consider)


I can agree about difficulty, and my previous comment wasn’t meant to imply I’m unhappy with the game, or even expecting that to change.

However, header design and (In real life) crossovers have a HUGE part in acoustics. You can’t tell me that this sounds like a normal LS7, for example. Or how putting on equal length tubulars on an S8 sounds anything like factory headers. Heck, on Engine Masters they tested no crossover vs H-Pipe vs X-Pipe and even with them there was a fairly pronounced difference in sound.

Like I said, I get that it would drive cost/development time up ridiculously, so I’m certainly not asking for it, nor even wondering why it’s not in - I totally get that. Just a little sad that it isn’t is all.

Actually fair enough, that Audi is a good example of something that does change quite a bit (I assume because the factory configuration is unequal length).

There definitely are a few things that would make quite a difference (like crossover GT40 style headers on a crossplane V8) that we don’t simulate.

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Maybe it would be better to just let player use sliders to adjust an engine’s sound. For example, an “aggression” and/or “smoothness” (maybe have engine smoothness affect this instead?) slider in the exhaust tab that makes engines sound different instead of louder/quieter like mufflers do now.
This would affect loudness, which in turn affects other stuff, but not performance.

Is that even possible? I thought engine sound was purely down to the size, oversquardeness/undersquaredness if thee engine, components etc. Seems a bit gimmicky anyway to have an ‘engine sound silder’ as it were.

That was suggested a while ago, and it’s not really doable.


Yep yep. Still, as I said above, I wouldn’t stress about things. It’d be a huge amount of effort, and to be honest, the game already covers a ridiculous amount of bases. I don’t think you’ll find a soul on these forums who isn’t beyond impressed with what you’ve all accomplished.

Wow, I didn’t know engine sounds were that complex. The method you use is practically the exact same as granular engine sounds (what GTA V uses), but I bet your method sounds better anyway especially since they’re already done and tweaked.

when watching the engine tests and power/torque graphs in the engine masters vid, did anyone else expect the engine to start bouncing off the redline like in the game?


Eh, I’ve done some experiments with impulse responses, modeling (to some extend) different types of resonators and different models of mufflers, basically an algorithm based EQ that removes or boost certains frequencies depending on materials and how sound waves bounce or are absorbed… not suitable for being in game tho, but they do add some nice flavour to engine sounds (especially works nice with V8s and L4s) I’ll post results and files some day, when I have the time…


Hah yeah, no worries, not taking it as an insult :wink:

Actually, I tell a lie. I’m not sure if it works at the moment, but the crossover headers did at least at one point sound different (like a flatplane!) :smiley:

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Nah, we’re not using the granular stuff, that is interesting tech, but didn’t really work the way we needed.

Ours is just a bunch of samples for different loads and RPMs, and exhaust/intake openness, all crossfaded to each other sort of thing… plus a bunch of EQ weirdness, and tremelos to do rev limiters and cammy idles.

All the samples can be blended because they’re proceedurally generated, so they match very well and don’t sound like a chorus of seperate engines.