Making a 914-6 Conversion your own, The Quest for Quiet Options

[Root_Werks]

The Six Conversion:

2.7 CIS with 993 cams, 46/40 valves, 911S 8.5:1 CIS Pistons with Nikasil cylinders. Guessing it produces slightly more than stock 2.7S HP and has a much lower, broader TQ curve.

Current exhaust is stock 914-6 HE's and one of Ben's SS Quiet mufflers. Been very happy with the exhaust note the past few years, but always wondered if stock would be quieter.

Ben's Quiet Muffler ( I did have to reclock the tip as it was more for 1974-up 911):

[Root_Werks]

Took the 914 out and ran some baseline numbers using a DB meter:

Ben's Quiet Muffler:

Idle outside - 80
Idle inside - 70
30mph - 78 4th gear
60mph - 86 5th gear
70mph - 88 5th gear

All runs were engine warmed up, windows up and maintaining speed. No acceleration or deceleration.

Pulled the SS muffler and prepped to install the new Dansk muffler I've been sitting on for 10 months:

[Root_Werks]

Ran the same tests as close as I could, same stretches of road and highway, windows up, same gears etc.

Dansk muffler results:

Idle outside - 80
Idle inside - 67
30mph - 77 4th gear
60mph - 85 5th gear
70mph - 87 5th gear

As the DB goes, not much of a difference by the numbers. Although I could tell on the freeway the note was toned down a bit.

Was it worth it? Eh, probably not. Not really much of a difference in overall cabin noise and I gained back that 5-6lbs right on the tail of the 914 (Dansk is heavier than SS).

Not sure if I'll swap back to the SS or not. I do like how the Dansk is hidden a little better.

Next steps to queit the cabin down:

Pull the rear window and swap out for safety glass version. I did this once many years ago on a 914-4 and was shocked how much engine noise was deadened.

Also noticed I need to adjust my rear trunk stop on the Left side.

[mb911]

Man 86 dbs is pretty quiet for these cars

[worn]

When I first got the 3.2 engine in the car I decided to cut up the 911 muffler that came with the motor using an article in Upfixing Der Porsche as a guide. Fit it to MSDS headers. Over time I had a loss in faith about my own handiwork and swapped out the homemade muffler for a very pretty Dansk sausage. Net result was, eh. I couldn’t hear or feel much of a difference. The only positive was that I no longer worry about doing it wrong.

[Steve]

With my 3.2 most of the noise came from the fan and chains. The 3.6 is way more quieter. I only hear my obnoxious M&K two in two out muffler. I wouldn’t have it any other way!

[mepstein]

With my 3.2 most of the noise came from the fan and chains. The 3.6 is way more quieter. I only hear my obnoxious M&K two in two out muffler. I wouldn’t have it any other way!

One of the reasons I like the smaller engines. But it’s hard to argue that the 3.6 based engines are more powerful and refined.

[Montreal914]

@Root_Werks , when you say Bursh, do you mean Dansk? Also, is this a stock Dansk or the sport one?

I have been thinking about what muffler to use with my 3.2 that will be equipped with Ben's beautiful SS heat exchangers/headers. (IMG:style_emoticons/default/drooley.gif)

I am looking for a single output and quiet.

Seems like the stock /6 muffler might be restrictive for the 3.2. Maybe not the best example but this /6 conversion in the classifieds has quite a step from the headers collector tubes to the inlet of the stock /6 banana mufler. I would assume this creating some restriction... (IMG:style_emoticons/default/confused24.gif)



I do have the SS 1-in 1-out from the 3.2 original exhaust system and have been wondering if it could be converted to a 2 in 1 out somehow. I would appreciate if you could post a link of that modification.

Happy Thanksgiving! (IMG:style_emoticons/default/beerchug.gif)

[mb911]

https://achtungkraft.com/pages/gtk-muffler-line


This is what I run now. I like it for the most part. I do miss the super quiet system as this is a little louder only with the top on really

[Root_Werks]

Stock Dansk, sorry about that.

[mb911]

Stock Dansk, sorry about that.

Nothing to be sorry about.

[mlindner]

I have Ben's sport muffler and headers. Great sound, little dronning at 3,000 rpm but I don't spend much time there. Mark

[horizontally-opposed]

Very interesting thread, and agree the readings are surprisingly quiet for these cars—and suggest a lot of the noise may be chains/valvetrain/lack of water jackets/etc. In other words, engine noise.

I remember having an old factory Leistritz on my 2.2 six conversion initially, which was quiet until a giant hole blew out of it. But it was a little too quiet for me (and this as someone who doesn't love loud cars on the street anymore), and more importantly with too "normal" a note for an occasional use toy. I replaced it with a two-pipe sport muffler from Patrick Motorsports as a placeholder while I reviewed the two-pipe SS options out there, several of which looked appealing but seemed like high risk if you didn't like them. Turns out, the PM muffler is just about perfect for my needs. I do need to get around to having it professionally coated, however...

I sure do like the single-pipe look on your car. Understated, and cool—as if that's how a 914-6 would have looked in 1975-1976 had they still been making them.

[Steve]

914toy on the forum is also on this quest. He has Ben’s quiet muffler and made special air cleaners for his webers to quiet them. I think they are motorcycle air cleaners. He also has a 2.7. When I replaced the 2.7 with a 3.2 I noticed allot more engine noise. 914toy (Keith) is now looking into a modified fan based on the 993 to quiet it down. He says that’s where most of the current noise is coming from.

[914Toy]

I use the 914-6 air cleaner.
I am investigating a modified engine fan from the later Porsche engines, that have fan blades curved in more than one direction (as per the stock fan), which I suspect is to reduce the "siren" whine at above 3000 rpm engine speeds.

[mb911]

I really do miss the quiet system when the roof is on and windows up. My current system is great with top off

[mepstein]

I use the 914-6 air cleaner.
I am investigating a modified engine fan from the later Porsche engines, that have fan blades curved in more than one direction (as per the stock fan), which I suspect is to reduce the "siren" whine at above 3000 rpm engine speeds.

Yes. The later fan is quieter. We actually went the other direction on a custom 3.8 build. The customer wanted carbs and the earlier fan to reproduce much of that Porsche raspy engine sound.

[914Toy]

I use the 914-6 air cleaner.
I am investigating a modified engine fan from the later Porsche engines, that have fan blades curved in more than one direction (as per the stock fan), which I suspect is to reduce the "siren" whine at above 3000 rpm engine speeds.

Yes. The later fan is quieter. We actually went the other direction on a custom 3.8 build. The customer wanted carbs and the earlier fan to reproduce much of that Porsche raspy engine sound.

Thanks for your feedback, which reinforces my quest. (IMG:style_emoticons/default/beerchug.gif)