Intro from Montana: '73 2.0L rustoration thread Options

[wonkipop]

i have a bit of stuff on file re factory vw mufflers i found when i was modifying mine to fit properly. back then i was trying to figure out if there was any real difference between 1.8 mufflers and kombi mufflers. i ended up figuring there was none apart from exhaust inlet mounting plates orientation.

there are some german test figures for the standard kombi muffler that jp group make.

test = 91db at 3,450 revs stationary. 79db on the move. i think measured at 1.5m from the exhaust outlet for the stationary one. the bursch is probably not far off that.

i did not want a loud 914 either. i think part of its original design ethos was to be relaxed at high speed on the autobahn.

thinking about it, the shape of the snorkel is a sound suppression resonator of sorts anyway - tapering down tube.

attached a picture of the fairly extreme snorkel/silencer on the wankel in a citroen birotor. NSUs had all the same components but arrayed a differently in the engine bay.

[mb911]

Brent I would like to look at that muffler this winter. I am half wondering if I sent you the wrong muffler. Pretty sure I didn't but want to make sure and I can make it quieter for you even if it is the right muffler. But again it is so odd that Phil gets about 85 dbs with gt3 tail pipes.

Hi Ben. Would love to get your assessment. I've wondered the same thing about whether I got the quiet muffler. I can tell you it does not look like the quiet mufflers on your website. Mine is a single straight cylinder rather than the 3-section curved ones on our site. 2-1/2 diameter tailpipe too if that helps. Seems big but I don't know your design.

Anyway, it is off the car now so I can send it at any time. The Bursch is on getting ready to take it for a test drive. I'll probably run this muffler for the rest of the summer anyway because it will soon have a wide band bung so I can test AFR. I'm getting 91 db 5 ft behind the car.

The ones pictured on the website are my 1st 10.. I later changed to a single straight muffler for ease of build. All the tail pipes are 2.5 inch.

[bbrock]

The ones pictured on the website are my 1st 10.. I later changed to a single straight muffler for ease of build. All the tail pipes are 2.5 inch.

Thanks for the clarification. Was hoping that might be an easy solve to the mystery. Just let me know when is the most convenient time for me to send it to you for inspection.

[mb911]

The ones pictured on the website are my 1st 10.. I later changed to a single straight muffler for ease of build. All the tail pipes are 2.5 inch.

Thanks for the clarification. Was hoping that might be an easy solve to the mystery. Just let me know when is the most convenient time for me to send it to you for inspection.

Pm me. I am going to make a new one and just trade you out the one you have and then sell it to cover costs.

Sound good?

[Cairo94507]

Yet another example of Ben's character. I have dealt with Ben on a few things and always found him to be a 100% stand-up guy. We are very fortunate to have his skill/experience set making parts for our cars. (IMG:style_emoticons/default/beerchug.gif)

[bbrock]

The ones pictured on the website are my 1st 10.. I later changed to a single straight muffler for ease of build. All the tail pipes are 2.5 inch.

Thanks for the clarification. Was hoping that might be an easy solve to the mystery. Just let me know when is the most convenient time for me to send it to you for inspection.

Pm me. I am going to make a new one and just trade you out the one you have and then sell it to cover costs.

Sound good?

Sounds fantastic Ben and way above what I expected. I hope you know I did not intend this to turn into a referendum on your muffler. The quality, of course, is impeccable and I bought it knowing that you can't know how any muffler is going to sound on a particular vehicle until you try it.

I got a chance to test the Bursch at highway speeds last night and it is a mixed bag. It is noticeably and measureably quieter from outside the car but is still a loud muffler. I'd say it is at the limit of what is acceptable, but is a step in the right direction. Inside the cabin, it does sound quieter but the numbers don't support that. db levels at all rpms and speeds are barely lower than before. However, the frequency distribution is much different from before. Unfortunately the free app doesn't let me save the traces but there is less energy in the very low frequency range which feels easier on the ears.

I'm not confident of the numbers the phone app is providing other than relative sounds levels between conditions/treatments. I noticed it seems more sensitive to certain frequencies which isn't much of a surprise for a phone microphone. So I ordered a modestly priced sound level meter that got good reviews from people who appear to know what they are talking about to provide a reference.

The most noticeable difference is that at highway speeds, I now hear the wind whistling through a couple small gaps i the window weather stripping I've needed to address but have been surprised they didn't make more noise. Turns out they did, I just could hear it. Also, the engine noise is more noticeable than it was before. It sounds mostly like mechanical racket but I will be experimenting with the intake snorkel and possibly additional/other sound deadening. I think I'm on the right track to try to get the exhaust as quiet as possible first and then work through other components one step at a time.

[mb911]

The ones pictured on the website are my 1st 10.. I later changed to a single straight muffler for ease of build. All the tail pipes are 2.5 inch.

Thanks for the clarification. Was hoping that might be an easy solve to the mystery. Just let me know when is the most convenient time for me to send it to you for inspection.

Pm me. I am going to make a new one and just trade you out the one you have and then sell it to cover costs.

Sound good?

Sounds fantastic Ben and way above what I expected. I hope you know I did not intend this to turn into a referendum on your muffler. The quality, of course, is impeccable and I bought it knowing that you can't know how any muffler is going to sound on a particular vehicle until you try it.

I got a chance to test the Bursch at highway speeds last night and it is a mixed bag. It is noticeably and measureably quieter from outside the car but is still a loud muffler. I'd say it is at the limit of what is acceptable, but is a step in the right direction. Inside the cabin, it does sound quieter but the numbers don't support that. db levels at all rpms and speeds are barely lower than before. However, the frequency distribution is much different from before. Unfortunately the free app doesn't let me save the traces but there is less energy in the very low frequency range which feels easier on the ears.

I'm not confident of the numbers the phone app is providing other than relative sounds levels between conditions/treatments. I noticed it seems more sensitive to certain frequencies which isn't much of a surprise for a phone microphone. So I ordered a modestly priced sound level meter that got good reviews from people who appear to know what they are talking about to provide a reference.

The most noticeable difference is that at highway speeds, I now hear the wind whistling through a couple small gaps i the window weather stripping I've needed to address but have been surprised they didn't make more noise. Turns out they did, I just could hear it. Also, the engine noise is more noticeable than it was before. It sounds mostly like mechanical racket but I will be experimenting with the intake snorkel and possibly additional/other sound deadening. I think I'm on the right track to try to get the exhaust as quiet as possible first and then work through other components one step at a time.

No worries either way let's get this figured out for you. My 914-6 is incredibly quiet except for the intake and -6 engine whine

[bbrock]

The ones pictured on the website are my 1st 10.. I later changed to a single straight muffler for ease of build. All the tail pipes are 2.5 inch.

Thanks for the clarification. Was hoping that might be an easy solve to the mystery. Just let me know when is the most convenient time for me to send it to you for inspection.

Pm me. I am going to make a new one and just trade you out the one you have and then sell it to cover costs.

Sound good?

Sounds fantastic Ben and way above what I expected. I hope you know I did not intend this to turn into a referendum on your muffler. The quality, of course, is impeccable and I bought it knowing that you can't know how any muffler is going to sound on a particular vehicle until you try it.

I got a chance to test the Bursch at highway speeds last night and it is a mixed bag. It is noticeably and measureably quieter from outside the car but is still a loud muffler. I'd say it is at the limit of what is acceptable, but is a step in the right direction. Inside the cabin, it does sound quieter but the numbers don't support that. db levels at all rpms and speeds are barely lower than before. However, the frequency distribution is much different from before. Unfortunately the free app doesn't let me save the traces but there is less energy in the very low frequency range which feels easier on the ears.

I'm not confident of the numbers the phone app is providing other than relative sounds levels between conditions/treatments. I noticed it seems more sensitive to certain frequencies which isn't much of a surprise for a phone microphone. So I ordered a modestly priced sound level meter that got good reviews from people who appear to know what they are talking about to provide a reference.

The most noticeable difference is that at highway speeds, I now hear the wind whistling through a couple small gaps i the window weather stripping I've needed to address but have been surprised they didn't make more noise. Turns out they did, I just could hear it. Also, the engine noise is more noticeable than it was before. It sounds mostly like mechanical racket but I will be experimenting with the intake snorkel and possibly additional/other sound deadening. I think I'm on the right track to try to get the exhaust as quiet as possible first and then work through other components one step at a time.

No worries either way let's get this figured out for you. My 914-6 is incredibly quiet except for the intake and -6 engine whine

@mb911 Thanks Ben! What kind of sound deadener are you using on the firewall? I think I'm getting pretty good attenuation there, but wondering if there are additional gains to be made.

[raynekat]

This is the one I went with.
High tech and very, very lightweight.

https://www.aasesales.com/products/c6a-r142...eeb51&_ss=r

I used contact cement to apply it to the firewall.
Very happy with it.

[raynekat]

Ending up shaving or trimming the upper edge such that the engine lid "swang" freely if you know what I mean???? (IMG:style_emoticons/default/wink.gif)

[bbrock]

This is the one I went with.
High tech and very, very lightweight.

https://www.aasesales.com/products/c6a-r142...eeb51&_ss=r

I used contact cement to apply it to the firewall.
Very happy with it.

That's the one I have in mine now too (bought it from RIX 914 Parts but looks like the same material/part). I measured a 1 db reduction in interior noise compared with the cheaper closed foam/foil face underhood liner I installed first. I did not cement mine in as that type of mat shouldn't depend on tight bonding to the panel that constrained layer masses like Noico do. I also have Noico stuck on the firewall behind the sound pad. Seems like a quality product, but mad scientist would love to know how it compares with the heavy oem slab. Unfortunately mine has lost most of the probably asbestos fiber so wouldn't be a good test.

[mb911]

The ones pictured on the website are my 1st 10.. I later changed to a single straight muffler for ease of build. All the tail pipes are 2.5 inch.

Thanks for the clarification. Was hoping that might be an easy solve to the mystery. Just let me know when is the most convenient time for me to send it to you for inspection.

Pm me. I am going to make a new one and just trade you out the one you have and then sell it to cover costs.

Sound good?

Sounds fantastic Ben and way above what I expected. I hope you know I did not intend this to turn into a referendum on your muffler. The quality, of course, is impeccable and I bought it knowing that you can't know how any muffler is going to sound on a particular vehicle until you try it.

I got a chance to test the Bursch at highway speeds last night and it is a mixed bag. It is noticeably and measureably quieter from outside the car but is still a loud muffler. I'd say it is at the limit of what is acceptable, but is a step in the right direction. Inside the cabin, it does sound quieter but the numbers don't support that. db levels at all rpms and speeds are barely lower than before. However, the frequency distribution is much different from before. Unfortunately the free app doesn't let me save the traces but there is less energy in the very low frequency range which feels easier on the ears.

I'm not confident of the numbers the phone app is providing other than relative sounds levels between conditions/treatments. I noticed it seems more sensitive to certain frequencies which isn't much of a surprise for a phone microphone. So I ordered a modestly priced sound level meter that got good reviews from people who appear to know what they are talking about to provide a reference.

The most noticeable difference is that at highway speeds, I now hear the wind whistling through a couple small gaps i the window weather stripping I've needed to address but have been surprised they didn't make more noise. Turns out they did, I just could hear it. Also, the engine noise is more noticeable than it was before. It sounds mostly like mechanical racket but I will be experimenting with the intake snorkel and possibly additional/other sound deadening. I think I'm on the right track to try to get the exhaust as quiet as possible first and then work through other components one step at a time.

No worries either way let's get this figured out for you. My 914-6 is incredibly quiet except for the intake and -6 engine whine

@mb911 Thanks Ben! What kind of sound deadener are you using on the firewall? I think I'm getting pretty good attenuation there, but wondering if there are additional gains to be made.

Just noico and 1/2" aviation insulation with perlon over it.

[Superhawk996]

mad scientist would love to know how it compares with the heavy oem slab. Unfortunately mine has lost most of the probably asbestos fiber so wouldn't be a good test.

As a generalized statement about NVH, sound transmission loss effectiveness increases with increasing mass. That is why OEM mats (internal & external) are so heavy.

If you don’t mind the weight there were advantages to the heavy OEM barriers.

Generally speaking the light weight, fibrous, or foam barriers are only going to serve to absorb mid to high frequency. For low frequency and structural boominess, you want mass and constrained layer solutions.

FYI - Dynamat (and Noico) are a mixed mass & constrained layer solution. You can add double or triple layers of Dynamat to build mass. Check the specs on Dynamat vs Noico. My recollection is that Noico had less mass per square foot but don’t flame me if I’m wrong. Don’t have numbers in front of me. (IMG:style_emoticons/default/happy11.gif)

[bbrock]

mad scientist would love to know how it compares with the heavy oem slab. Unfortunately mine has lost most of the probably asbestos fiber so wouldn't be a good test.

As a generalized statement about NVH, sound transmission loss effectiveness increases with increasing mass. That is why OEM mats (internal & external) are so heavy.

If you don’t mind the weight there were advantages to the heavy OEM barriers.

Generally speaking the light weight, fibrous, or foam barriers are only going to serve to absorb mid to high frequency. For low frequency and structural boominess, you want mass and constrained layer solutions.

FYI - Dynamat (and Noico) are a mixed mass & constrained layer solution. You can add double or triple layers of Dynamat to build mass. Check the specs on Dynamat vs Noico. My recollection is that Noico had less mass per square foot but don’t flame me if I’m wrong. Don’t have numbers in front of me. (IMG:style_emoticons/default/happy11.gif)

Nope, you are correct about Dynamat vs. Noico. I also don't have the numbers but remember that Dynamat is slight thicker/more mass. There was also a sound attenuation test I ran across that showed Dynamat outperforming the competitors, but the difference was small compared to the triple price of Dynamat.

What's interesting about the OE mat is that not only does it have the heavy tar-like coating, but the fiber portion is also dense and heavy. I would have reused mine except for the fact that it is shot. I contemplated spraying this new mat with several coats of rubberized undercoating to create a bit of a mass layer on the engine side. I did that with the uxel foil faced foam. Does the relative location of the mass vs fiber matter? Effectively, I now have the reverse of the factory mat with thick fiber on the engine side and then Noico butyl mass stuck to the firewall. The total weight savings over the OE mat is still substantial. I'm too lazy to look up the numbers I posted before to update with the new mat number.

I'm also wondering about something like this to either replace or add to the rubber sheet on the interior side of the firewall. https://www.amazon.com/Self-Adhesive-Automo...;language=en_US
(IMG:http://www.914world.com/bbs2/uploads_offsite/m.media-amazon.com-20845-1626461395.1.jpg)

[worn]

Traveling to Rt66 I took the plunge and tried Hey Siri with my phone for directions. With highway noise Siri couldn’t understand me and I sure as heck couldn’t hear her. I didn’t add much sound deadening, which is fine. But not in line with the rest of the world.

[bbrock]

Traveling to Rt66 I took the plunge and tried Hey Siri with my phone for directions. With highway noise Siri couldn’t understand me and I sure as heck couldn’t hear her. I didn’t add much sound deadening, which is fine. But not in line with the rest of the world.

That's no test. Siri, Google, Cortana (remember her?) Alexa... none of them can understand me in a dead silent room. Oh wait, Google did understand me once when I got so mad I spewed out just the right series of profanity to get this response, "Okay, one of us needs to take a breath, and I don't have lungs." I have never been able to replicate it, but oh how I have tried... (IMG:style_emoticons/default/av-943.gif)

[bkrantz]

Traveling to Rt66 I took the plunge and tried Hey Siri with my phone for directions. With highway noise Siri couldn’t understand me and I sure as heck couldn’t hear her. I didn’t add much sound deadening, which is fine. But not in line with the rest of the world.

That's no test. Siri, Google, Cortana (remember her?) Alexa... none of them can understand me in a dead silent room. Oh wait, Google did understand me once when I got so mad I spewed out just the right series of profanity to get this response, "Okay, one of us needs to take a breath, and I don't have lungs." I have never been able to replicate it, but oh how I have tried... (IMG:style_emoticons/default/av-943.gif)

You're lucky your phone did not report you to the authorities.

[Superhawk996]

l

I'm also wondering about something like this to either replace or add to the rubber sheet on the interior side of the firewall. https://www.amazon.com/Self-Adhesive-Automo...;language=en_US
(IMG:http://www.914world.com/bbs2/uploads_offsite/m.media-amazon.com-20845-1626461395.1.jpg)

Yup something like that on interior over the top of the Noico.

Seems pretty similar to DynaPad 4 layer urethane pad coming in around 1lb/sf. That is still probably less mass/sf than OEM interior pad but is a good mass add in addition to the Noico.

https://www.dynamat.com/wp-content/uploads/...l-Sheet_Web.pdf

[bbrock]

l

I'm also wondering about something like this to either replace or add to the rubber sheet on the interior side of the firewall.

Yup something like that on interior over the top of the Noico.

Seems pretty similar to DynaPad 4 layer urethane pad coming in around 1lb/sf. That is still probably less mass/sf than OEM interior pad but is a good mass add in addition to the Noico.

https://www.dynamat.com/wp-content/uploads/...l-Sheet_Web.pdf

Looks like the Dynapad is thicker @ 3/8" vs 1/4" I have Noico on the engine side of the firewall, not on the interior. Right now on the inside, I just have the factory rubber pad that goes behind the backpad. I have enough Noico to do the inside too but trying not to get too crazy with weight unless I have to.

I still need to work on reducing the sound being produced first. I'm thinking reduce exhaust as much as possible first as that is still the main culprit and makes the car obnoxious outside as much as inside. Then dial in the intake although I really don't think that is a major source. I don't think I can do much about the mechanical noise. Then work on sound dampener. Once I have the better sound meter in hand, I might throw the ratty original firewall mat in and see how it compares just for grins.

[bbrock]

Snorkel, test drive, and running like (IMG:style_emoticons/default/stromberg.gif)

Had some errands to run in town today so decided to finally get the snorkel installed on the lowered air cleaner properly. Two adjustments needed to be made. One was to lower the support bracket to match the new, lower height of the plenum box. The other was to shorten the snorkel itself because I did not account for the backward "lean" of the firewall in front of the engine, or the thickness of the sound pad. The snorkel barely fit.



I lopped off more than an inch off the tip. Ooh, that doesn't sound good (IMG:style_emoticons/default/pinch.gif) (IMG:style_emoticons/default/blink.gif) Well, I did it anyway.





After a bit of reshaping the bugle flare on the end, here is "Shortie" snapped onto the lowered bracket.



Then I hit the open road to further check out sound levels. With the top off and windows up, I hit the Interstate at 75-80mph. The first thing I noticed was that the engine noise has completely disappeared and it is all wind noise at that speed. That is a switch because before, the exhaust note was very noticeable at any speed as you could hear in the previous driving video. Today I couldn't hear the engine at all at highway speed and I really tried. The next indicator was being able to order lunch at a drive-thru window while the car was idling. Before I had to shut the engine off to be able to hear. Then I found a shady spot to park to eat my lunch and got pretty good evidence the sound levels I'm getting on my phone are not reliable. With the engine off on a very quiet back road and the radio playing at a relatively low volume, the Decibel X app read an average of 100 db! I'm confident I was not anywhere near ear damaging sound levels. It will be interesting to see how the sound meter I ordered compares. I do think the app is decent at reading relative loudness even if the actual numbers are off.

It runs like shit
I noticed my ignition misfiring on my last test drive a few nights ago and suspect the old ratty coil I put in to pair with the points was going bad so I ordered a new Bosch blue coil which should be here this week. I rechecked the dwell just to make sure the points hadn't gotten out of adjust and it was still spot on. As I ran errands today, the misfires and jerky engine got worst and it started backfiring slightly at low engine speeds. Every time it misses, the tachometer jumps which makes me think coil. I guess the other possibility is fouled plugs from carbs running too rich. I'll pull the plugs to inspect when the engine is cooled down and still need to get the lambda installed to measure AFR.