Exhaust sound tuning

[ydeardorff]

I was curious if anyone knows much about exhaust systems.

Given the WRX and the Air cooled VW have literally the same firing order, and same type of engine, why do they sound so different with custom exhausts?

The WRX in the other post I made had an outstanding tuned sound, without snapping or popping. I haven't found a single Air cooled VW exhaust that sounds as good. Ever....

Is their something more going on between the two cars that makes them different, in a way that they cannot sound different?

I was just curious on what could be done to get that nice throaty sports car sound that's not obnoxious, nor typical bug sounding.

Theirs one video on this site of a blue eureka i think that has a very nice sound, but the audio is so distorted its really hard to tell what it actually sounds like....

 

[letterman7]

I'm sure much of it has to do with cylinder and valve size and timing, Yaughn, along with the associated exhaust plumbing. The only similarities between a bug engine and the Scooby is they are both flat fours. Trying to interpret any other similarities between the two is pointless since you're comparing a fuel injected watercooled engine to a carburated air cooled. The Scooby is coming down through a set of tuned pipes for the motor, through a resonator, catalytic converter and finally through the muffler. A VW has no such restrictions - just right out through the muffler, which in itself is tuned to try to maximize horsepower out of the engine (four-into-one headers do the best here). There's just no comparison, unfortunately. I'll have to get my camera out in my buggy this weekend if it doesn't rain and see if I can't capture it's sound - through two mufflers and a resonator pipe. Sounds nothing like a VW at speed, and only a little at idle.

 

[ydeardorff]

I look forward to seeing that!

Thanks

 

[letterman7]

Ok, here's a video of the buggy on the road. Crude, but at least you'll get to hear the motor sing!

[ame="http://www.youtube.com/watch?v=kVsSWGwD-KI"]YouTube - Manx SR ride NEW[/ame]

 

[ydeardorff]

Nice, I think I hear a straight cut cam gear in there too!

One of the wierdest sounds Ive ever heard coming out of an air cooled Vdub motor was a 2275 turbo.
The thing sound like a giant jiffy pop machine. LOL

I do like the nice deep throaty sound you have there!

Im hoping to take a couple of videos, maybe some mp3's to a really good muffler shop and have them tune the exhaust to the sound Im looking for.

Id hate to end up with a fart box!*kiss my butt*

 

[letterman7]

Good ear, Yaughn! Yep, it has straight cuts as well. Not so obvious at highway speeds, but I love it at 'around town' levels... Unfortunately, the car is now up on eBay - gotta make room for working on the Sterling!

 

[ydeardorff]

I found this system this morning. I really like the cobination of sounds coming from it. deep and rumbly at idle, but gets more raspy as the throttle increases. Reminds me of the gallardo exhaust sounds.

[ame=http://www.youtube.com/watch?v=gT7-K0_kRPA&feature=related]YouTube - apexi dual n-1 sound[/ame]

 

[ydeardorff]

Resurrecting and old thread here abit,

Ive done some more research on the exhaust, and have come up with a hypothesis based upon some other input ppl have given that know both V-dubs and subaru's in regard to the reasons why bugs sound a certain way and Subarus sound different even though they are very similar in design.

The untested hypothesis is in regard to the exhaust difference between bugs and Subies. Subarus have two types of exhaust headers (excluding the turbo models) An equal length header, and an unequal length header. Where the V-dub counter part has only unequal length headers (J pipes, etc to the collector point).

I dont have any video or audio demos to show the difference between bugs and subarus. But as I read, they were saying the WRX's deep baritone rumble is due to the unequal length of its headers, and the standard legacy, outback, and impreza's with only a muffler mod will have a higher more raspier sound due to the equal header lengths (side to side).

So in theory, a bug could be made to sound very similar (in theory) if there was an option for equal headers. yes?

Id like to hear some thoughts on this.

It makes sense (to me) in the aspect of the noise frequency emitted by the exhaust. The unequal length would have the ability (in theory) to make more of a pronounced pulse (lower frequency) emission. Where the equal length header would be a more unified higher pitch sound. yes? no?

This would then explain why the subaru sound is so unique, and also why a V12 would have such a high pitch in there exhaust.

Heres a couple of videos of subarus with the different headers installed

Subaru WRX with equal length headers
[ame]http://www.youtube.com/watch?v=mh6IsUD-7E0&feature=related[/ame]

Subaru with unequal length headers
[ame]http://www.youtube.com/watch?v=xqveIeGpHs4[/ame]

 

[letterman7]

I think you're getting too far into this, Yaughn. As I've said before, header pipe length enters into the equation, but you're forgetting about cylinder displacement, cam overlap, timing, etc, etc. A Bug sounds like a Bug because of it's relatively small displacement - header lengths don't make much difference here. Find someone with a 2332 engine with a merged system then tell me what you think - you'd swear there was a small V6 hiding under there.
Much can be done to change tones with resonators and muffler systems. You'll have to experiment... bottom line - what to you want the car to sound like? Some WRX's running around here sound like lawn mowers... freer flowing exhaust isn't necessarily a good thing!

 

[ydeardorff]

true, I suppose. you know me I just like to flip all stones to check everything out.

I was just surprised by the sound difference between the equal and unequal length headers on a Subaru engines.