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More exhaust sound questions...

FM Former Member
Ok, thanks to the forum, I know that a relatively livable exhaust sound can be had in terms of loudness and drone ( Intermechanica dual muffler good, QB muffler good etc)

Now I need to know the science behind what makes these VW engines sound more Porsche like. I heard a JPS 1776 with dual small webers and although I didn't drive it for the drone question, I still noticed that it definitely did not sound very VW like. It did not have that awfull high pitched whistle which drives me crazy and neither did it have that metalic exhaust note of "tat tat tat uhh tat uhh tat tat ...). These are the terrible sounds of near stock VW engines that sound cheap and tinny. His sound was more "haaareeeeemmmmm bamp bamp haaaaarrrrrremm bamp ...." which is a much better low rpm sound ( 1500 to 25000 rpm).

I know all this sounds rediculous, but we all know the sound of an old stock bug and it really does sound weak and somewhat pedestrian and not sporty at all.

The question is what is making these metallic whistles and exhaust taps (not lifter taps) and why are they peculiar to only some air cooled VW engines and not others.?
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FM Former Member
Ok, thanks to the forum, I know that a relatively livable exhaust sound can be had in terms of loudness and drone ( Intermechanica dual muffler good, QB muffler good etc)

Now I need to know the science behind what makes these VW engines sound more Porsche like. I heard a JPS 1776 with dual small webers and although I didn't drive it for the drone question, I still noticed that it definitely did not sound very VW like. It did not have that awfull high pitched whistle which drives me crazy and neither did it have that metalic exhaust note of "tat tat tat uhh tat uhh tat tat ...). These are the terrible sounds of near stock VW engines that sound cheap and tinny. His sound was more "haaareeeeemmmmm bamp bamp haaaaarrrrrremm bamp ...." which is a much better low rpm sound ( 1500 to 25000 rpm).

I know all this sounds rediculous, but we all know the sound of an old stock bug and it really does sound weak and somewhat pedestrian and not sporty at all.

The question is what is making these metallic whistles and exhaust taps (not lifter taps) and why are they peculiar to only some air cooled VW engines and not others.?
Ron ORon O1984/2010 IM, B.C. Canada
I don't know the answer to your question, but I can tell you that there is a world of difference between the sound of my 2110 (in my IM) and the sound of the 911 flat six motor in my 1970 single cab. Both are air cooled, but you'd never confuse to two. The sound of a flat six Porsche, as it hits 6500 is something else.
Ron
FM Former Member
It IS unique. The following MP3 is a 911 through some low restrictive exhausts. It's loud because the mike is clipped to the rear apron.

Think of the difference between a V twin Harley, and a Honda 4, both built. Then think of a 4 and a 6! Have you ever heard a Jag 12?

Anyway click or paste this and listen. It will aut0load as it is inbedded. If you don't have Fat Tube it might take a couple of minutes to load.

www.dubudee.com/new_page_151.htm

Jim
Ron ORon O1984/2010 IM, B.C. Canada
Jim, that sounds GREAT. Mine sounds about as loud, but raspier. I've got a sport muffler on it, with a nice big crack in the body (it's 16 years old), so it's loud. Friends tell me that when I wind it out they can hear me a block away. It's too loud, and when I can afford it I'm going to replace it with a big Magnaflow. It's not that loud in the cabin, because the motor is so far away.
Ron
FM Former Member
Ron,

I was just looking over your pics of the Vert D. That is one sweet looking engine bay.

I think you will like the Magnaflow. I used one on a CB Merged 1.5 sysytem with boxes and loved the sound. It hung out some and so I went to the CSP system with the dual (unknown brand.. german) 5" x 16.5" mufflers running abeam the heads. The system should be less restrictive but I have found a small performance drop off with it. I thought it was maybe my imagination, but after my local VW ace drove it he said the same thing. It also doesn't sound as sweet as that Magnaflow. It does sound good, but just not quite the low gut thunder that I like. I think the restriction is definitely in those twin unknowns.

I may look at some substitutes to fit in the system that are approx 16x5..... any ideas?
Ron ORon O1984/2010 IM, B.C. Canada
Jim, I know that Henry, at IM, has tried a number of muffler combinations. I've seen both his dual Dynomaxes and dual Magnaflows. From what I can gather the Dynomaxes are a bit quieter (over the Magnaflows) and both are VERY free flowing. I've heard that the Dynos gain a hp or two over the Magnas, but I haven't seen any data to back this up. Anyways, could you feel 1 or 2 hp? The Mangaflow on my 2110 is a stainless 2 1/4" straight through. How much loss can there be when you can look down the 'in' pipe of the muffler and see out the other side?
I think that Eddie uses a system like yours, with dual Dynomaxes.
Ron
FM Former Member
Paul, it was once explained to me by a recording engineer that sound deadening is not very effective unless it is very thick. The reasoning being that unless the sound deadening material can contain the entire sound wave, it will not deaden the sound. Sound waves have a frequency at which they oscillate, and a 'length' to that oscillation. The higher the pitch, the shorter the length. The lower the pitch, the longer the length. So, sound deadening material that is an inch thick will only deaden the high frequency, or high pitch, sounds. That is why when a car drives by with the stereo on loud, all you can hear is the bass. That applies to all stereos, not just the kids and their boom box cars. Try it with your home stereo. Turn it on loud and go outside. The bass always carries the furthest because it takes very thick walls to stop the long length of bass sounds. Another test, put your car in the garage and leave it running. Go inside the house and close the door. All you will hear is the low rumble. My point is not that you shouldn't use sound deadening, but that you shouldn't expect too much from it.
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