TheSamba.com :: View topic - Getting that signature whistling muffler sound back?

Wed Aug 05, 2015 2:10 pm

Luft kühl wrote: Adjust tail pipe length (from tip to muffler) to:

8 9/32 in. (210 mm) on 1961-1973 models

8 7/8 in. (226 mm) on 1974 models

Tail pipe length affects exhaust flow and engine back pressure.
Great information - but where from - if you don't mind?

I took a horrible aftermarket 4 tip Ansa(?) system off ours, and replaced with all fresh silencer, Tips and clamps. I backed off the tips by about 20mm (1"), and it sounds so much better, quieter, and more civilised. And it has the makings of the fweem? Sound.

Wed Aug 05, 2015 2:12 pm

Aussiebug wrote: Some years ago I wrote an article on the reason for the Bug's distinctive sound.

The beat part comes about through the flat 4 arrangement coupled with the muffler design. The rear two cylinders mount direct to the muffler (which is essentially just an open box) and the front two cylinders connect via the headers/heater boxes. But inside the muffler, the two rear cylinder connections each have an internal pipe across the muffler, so the headers for all 4 cylinders are the same length (two cylinders internal and two external). This results in the pulses coming out the tail pipes as left/left/right/right, rather than left/right/left/right, and our stereo hearing hears that as a distinctive beat. But because the muffler is in fact open inside and some of each pulse can leak across to the other tail pipe, it's really LEFTrightLEFTrightRIGHTleftRIGHTleft which you hear.

The whistle sound does indeed come from the peashooter tips. It's the inner perforated tube with fibreglass packing behind the perforated pipes which does it, and incidentally THESE are the true mufflers - put plain pipes in there and hear the difference! The narrow internal diameter of the perforated pipe, resulting in a high gas speed, plus the perforations, creates the whistle sound - a bit like blowing through a snake-light perforated tube.
Quality post.

Thu Aug 06, 2015 1:14 am

ROCKOROD71 wrote:
So...Reader's Digest version is: Jam pipe in all the way, back it out 6mm? Or are my reading skills that bad?

That's about it. When the tail pipes are pushed all the way in, they come up against the crossed over header pipes inside the muffler, so if left there, they get a restricted airflow into the tail pipes.

Pulling them back out a little clears them for a normal gas flow.

Thu Aug 06, 2015 5:45 am

Aussiebug wrote: ROCKOROD71 wrote:
So...Reader's Digest version is: Jam pipe in all the way, back it out 6mm? Or are my reading skills that bad?

That's about it. When the tail pipes are pushed all the way in, they come up against the crossed over header pipes inside the muffler, so if left there, they get a restricted airflow into the tail pipes.

Pulling them back out a little clears them for a normal gas flow.

Thank you sir, as always your imput is appreciated! :D

Thu Aug 06, 2015 5:14 pm

http://www.ratwell.com/mirror/Muir/Muir.html

speaking of beetle sounds...check this out. The sound quality isn't great by today's standards - but it's a very interesting site nevertheless.

Mon Aug 21, 2017 7:36 pm

Zylinderkopf wrote: http://www.ratwell.com/mirror/Muir/Muir.html

speaking of beetle sounds...check this out. The sound quality isn't great by today's standards - but it's a very interesting site nevertheless.

A little late to the game :roll: , but I thought this was a great post, very cool site! I wasn't even driving before Muir died, kind of cool to hear him describe these various things.

Sun Sep 23, 2018 9:38 am

pb_foots wrote: Luft kühl wrote: Adjust tail pipe length (from tip to muffler) to:

8 9/32 in. (210 mm) on 1961-1973 models

8 7/8 in. (226 mm) on 1974 models

Tail pipe length affects exhaust flow and engine back pressure.

Only issue with this is the various lengths sold by the aftermarket. The tip to muffler measurement is only good if the entire tailpipe is stock length.

My blue Bentley says this:

On 66-67 cars the tail pipes should not enter muffler more than 1.8 inches. On 68-69 models 3.4 inches is the limit. Obtain these fittings by first measuring total length of pipe and then subtracting the length protruding after insertion.

Orange Bentley says:

Measure the tailpipes. 3 lengths are used. depending on model, these lengths are 276 MM, 249 MM and 226MM. The last length is on 73 and 74 cars only. (However, 74 pipes have an inside diameter of 23MM, not 20MM as in 73).

On 74 cars only, install the tailpipes so that they project 155 MM from the muffler

On 70-73 cars, insert the left tailpipe. Then insert a steel tape measure through the center of the pipe until it contacts the pre heating pipe inside the muffler.

Move the pipe in and out until its outer end aligns with the correct graduation on the pipe.

The correct graduations are 270MM for 276MM pipes, 243MM for 249MM pipes, and 220MM for 226 MM pipes.

Not sure it's worth the hassle for a whistle!

Do these numbers look odd? Can the pipe stick out less than the length of the pipe?

Sun Sep 23, 2018 10:13 am

Those aren't the measurements of what's sticking out, it's the length Vs: the tip of the preheat pipe inside the muffler.

Quote: On 70-73 cars, insert the left tailpipe. Then insert a steel tape measure through the center of the pipe until it contacts the pre heating pipe inside the muffler.

Move the pipe in and out until its outer end aligns with the correct graduation on the pipe.

Sun Sep 23, 2018 9:03 pm

busdaddy wrote: Those aren't the measurements of what's sticking out, it's the length Vs: the tip of the preheat pipe inside the muffler.

Quote: On 70-73 cars, insert the left tailpipe. Then insert a steel tape measure through the center of the pipe until it contacts the pre heating pipe inside the muffler.

Move the pipe in and out until its outer end aligns with the correct graduation on the pipe.

Sorry, wrong preposition. I meant to say "in". The numbers I see in the Bentley show the pipe sticking out LESS than the length of the pipe, which suggests the pipe sticks in and somehow part of the length mysteriously disappears.

"Move the pipe in and out until its outer end aligns with the correct graduation on the pipe.

The correct graduations are 270MM for 276MM pipes, 243MM for 249MM pipes, and 220MM for 226 MM pipes."

So, if the pipe is already 276mm, it can't be pushed in any more. The outer end is already at 276mm, so pulling it out will register more than 276mm, not less. It would need to be pushed in to get to 270mm, but it is already pushed all the way in.

These numbers don't look right to me.

Sun Sep 23, 2018 9:42 pm

sdebaker wrote: busdaddy wrote: Those aren't the measurements of what's sticking out, it's the length Vs: the tip of the preheat pipe inside the muffler.

Quote: On 70-73 cars, insert the left tailpipe. Then insert a steel tape measure through the center of the pipe until it contacts the pre heating pipe inside the muffler.

Move the pipe in and out until its outer end aligns with the correct graduation on the pipe.

Sorry, wrong preposition. I meant to say "in". The numbers I see in the Bentley show the pipe sticking out LESS than the length of the pipe, which suggests the pipe sticks in and somehow part of the length mysteriously disappears.

"Move the pipe in and out until its outer end aligns with the correct graduation on the pipe.

The correct graduations are 270MM for 276MM pipes, 243MM for 249MM pipes, and 220MM for 226 MM pipes."

So, if the pipe is already 276mm, it can't be pushed in any more. The outer end is already at 276mm, so pulling it out will register more than 276mm, not less. It would need to be pushed in to get to 270mm, but it is already pushed all the way in.

These numbers don't look right to me.
How much it sticks out of the muffler does not matter, as long as it's stuck in 6mm further than the end of the preheat pipe it's all good. That spec is the length of the pipe vs: the end of the preheat pipe only.

Mon Sep 24, 2018 4:55 am

busdaddy wrote: How much it sticks out of the muffler does not matter, as long as it's stuck in 6mm further than the end of the preheat pipe it's all good. That spec is the length of the pipe vs: the end of the preheat pipe only.
^^ This.

With the tail pipes out of a stock muffler, if you take a flashlight and look in the holes you’ll see the end of the pre-heat pipe (part of system used to heat the intake manifold) in the center of one of them — usually the left / driver’s-side hole on most models (pre-1974 or so, I think). The outer dia. of that pre-heat pipe is significantly smaller than the inner dia. of the tail pipe, so they can overlap / slide over each other without any problem.

So as mentioned above, you want to adjust the one tailpipe so that it overlaps the pre-heat pipe by about 1/4” (6 mm). This will give the correct low pressure at end of pre-heat pipe, so that exhaust gases will flow through that system correctly. Finally, adjust the length of other tailpipe (one on side w/out pre-heat tube) to match the first tailpipe’s insert length.

Mon Sep 24, 2018 6:30 am

Take a look at this

http://www.vw-resource.com/muffler_discussion.html#fweem

Rick

Mon Sep 24, 2018 6:34 am

Take a look at this

http://www.vw-resource.com/muffler_discussion.html#fweem

Rick

Sun Oct 07, 2018 8:23 am

I installed a new set of tail pipes recently (bought from WW -- 249mm/~10in and 23mm ID). The inner perforations were a bit loose and these pipes whistled form the get go.

The previous set I have (I don't know where I bought it - and I installed it on a Dansk muffler) did not whistle and I had tried various things with no luck at getting this sound.

But, now that I do have it, I hated it. Went back to my old mufflers (but now installed on a NOS Ernest muffler).

The old pipes were also 249mm, but were 20mm ID with the perforations starting about 1/2" from the inside end. The WW ones are 23mm ID with the perforations starting about 1.5" from the inside end. Not sure what year that it is for since Bentley says the 23mm ID pipes should be 226mm long and are for 74s.

Sat Apr 03, 2021 12:34 pm

I am even later to the game, but let me post my experience....

The sound mostly comes from the tail pipes / pea shooters. But not from all of them :?

I tried many different lengths, stainless steel, or normal steel, I could not get the typical "fweem" sound from new pipes.

Once a friend (that I knew that his car had the "fweem") had an engine problem and I helped him, I "persuaded" him to give me his old pipes, in exchange for new stainless steel ones....

I put his old pipes on my car, and I got instant "fweem". Only at idle, unfortunately, but better than nothing.

After that chapter, I also tried some cheap new ones. They were quiet at first, but slowly started fweeming too, but in other RPM ranges.....

So from my experience, if you're after that sound, the best bet would be to hunt for some pipes that are known to fweem.....Or try your luck with new cheap ones, and wait for them to fweem.

I could not discover any relation to the length of the pipes. I think you should not stick them too far inside the muffler, the rest may not be so important...? Not sure on this thought.

Best regards,
Vlad

Sat Apr 03, 2021 6:43 pm

I had posted about 5 years ago that my tailpipes did not fweem. Then in 2016 or 17 I bought another set from WW as I was refreshing my engine. These tailpipes were fweeming right from the start. I could see where the inner baffle was vibrating near the exit top. If I held it down the fweeming would stop.

Turned out I hated the fweem sound. So I pulled off the new ones and reinstalled the old ones which were still very good. The newer ones are on my KG now. I drive it much less so it bothers me less.

Btw, the fweem had little to do with the tailpipe positioning IME. It seems more like it stems from a design weakness in the tail pipe.

Sat Apr 03, 2021 6:58 pm

Fweeming who knew? Not me I’d never heard of this till I landed on Samba😀

Sat Apr 03, 2021 9:12 pm

I've had my Sun Bug for a year and it has not fweemed once! It just isn't a Type 1 without the fweem. I am grateful that others have delved into all aspects of owning our VWs and so now I have the information I need to make it fweem. Thank you all.

While we're here, has anybody installed a venturi ring? I've never heard one and am curious of the sound they make.

Sat Apr 03, 2021 11:13 pm

Interesting! I compared both sets (with and without fweem), and coult not really tell any difference, but didn't think to poke around while the engine is running.

creative native wrote:
While we're here, has anybody installed a venturi ring? I've never heard one and am curious of the sound they make.

If you're talking about the one for the cooling fan, yes, I have one in my Ghia. Some report a "vacuum cleaner" like fan sound, but I see no difference compared to my Bug which had no Venturi ring....
But what I did notice, is that the engine temp. is very low (for an aircooled car....) so maybe that ring is working too well :roll:

Vlad

Sun Apr 04, 2021 8:03 pm

Vladiiiii wrote:
If you're talking about the one for the cooling fan, yes, I have one in my Ghia. Some report a "vacuum cleaner" like fan sound, but I see no difference compared to my Bug which had no Venturi ring....
But what I did notice, is that the engine temp. is very low (for an aircooled car....) so maybe that ring is working too well :roll:

Vlad

Vielen danke Ihnen für Ihre Hilfe, Vlad. I have considered buying a venturi ring and eventually installing it. Can anybody help with information on who sells them?