1984 3.2 header/exhaust

[Cherry Bomb]

I chose Fabspeed RSR package with heat. No regrets, definitely altered my experience and car's character. Noise is in pleasing to me.

[famoroso]

Originally Posted by Peter M

Frank,
Did you ever do dyno runs to confirm the improvement of each upgrade?

Each one? Every permutation? No. I'd need someone to start a very successful Go Fund Me page for all the dyno runs that would have taken.

No, I could only afford two...

1988 3.2 with open air box lid, Web 20/21 cams, stock HEs, Dansk pre-muffler and a Dansk 1 in / 1 out 84mm sport muffler...



1987 3.4 with open air box, 964 cams, 10:1 CR, M&K longtube headers and M&K 2 in / 1 out muffler...




I tried to use the same dyno for both cars, but the first dyno was no longer available.

[Mr. Merk]

What were the results, Frank?

[famoroso]

Originally Posted by Mr. Merk

What were the results, Frank?

The results were... Good.

[famoroso]

Originally Posted by famoroso

The results were... Good.

I kid, I kid. Here you be, including links to the photo galleries for Easter eggs and some vids of the pulls...


https://amoroso.smugmug.com/1988-Porsche-911-M491-M470-Poi/1988-911-Dyno-tune-at-Game

*BTW, I wouldn’t put any stock into this “before” pull as the car had a 24 pin ECU with a chip of unknown provenance in it. Steve swapped it out for a 28 pin ECU with custom programming based on nine additional dyno pulls.





https://amoroso.smugmug.com/1987-Porsche-911-M491-M470-Gemini-/Steve-Wong--Ed-Pink-dyno-tuning-21623




Shame the tests couldn't have been done on the same dyno.

[famoroso]

Spoke with Eric Williams at Air|Water on Saturday about his / Bursch's newest offering for those that don't want to incur the expense of a GT3 rear muffler system...

Looks intriguing. Then again, I'm intrigued by a lot of different mufflers.

[Bill Verburg]

Originally Posted by famoroso

Spoke with Eric Williams at Air|Water on Saturday about his / Bursch's newest offering for those that don't want to incur the expense of a GT3 rear muffler system...

Looks intriguing. Then again, I'm intrigued by a lot of different mufflers.

It's an awful design


the turbulence created where the star is destroys flow

here is what the flow looks like for an SC or Carrera 3.2 w/ separated sides

[famoroso]

Originally Posted by Bill Verburg

It's an awful design


the turbulence created where the star is destroys flow

here is what the flow looks like for an SC or Carrera 3.2 w/ separated sides

Interesting. What's the effect of the valved outlet when closed then?

[Mr. Merk]

The X pipe is the problem here, which Bill has covered many times over. I believe the vacuum operated valve is just for drone control as it keeps the passenger side outlet closed until WOT

[Shaun @ Tru6]

Originally Posted by Bill Verburg

It's an awful design


the turbulence created where the star is destroys flow

I know nothing about mufflers but that caught my eye, directonal air being pushed into opposite directional air.

Why would a known exhaust manufacturer do this? Are there any benefits at all?

[Mr. Merk]

It might help the sound a bit, but probably hurts performance. These setups became popular with odd-firing V8s, and I think a lot of people just assume the same logic applies to any dual-exhaust engine. But like Bill pointed out, even-fire engines don’t really benefit from it. If you look at Porsche’s naturally aspirated race cars — at least the ones I’ve seen — they never merge the exhaust, which says a lot.

[Bill Verburg]

Originally Posted by famoroso

Interesting. What's the effect of the valved outlet when closed then?

on a GT3 muffler?


the upper, red, is the quiet pipe it exits into the large central chamber where the gases expand and are routed to the exit, blue.

The lower inlet is the loud pipe, black flow,

here there is a properly designed x over between the 2 exits, The sole purpose of the xover is sound tailoring and attenuation.

[Bill Verburg]

Originally Posted by Mr. Merk

It might help the sound a bit, but probably hurts performance. These setups became popular with odd-firing V8s, and I think a lot of people just assume the same logic applies to any dual-exhaust engine. But like Bill pointed out, even-fire engines don’t really benefit from it. If you look at Porsche’s naturally aspirated race cars — at least the ones I’ve seen — they never merge the exhaust, which says a lot.

correct, that was my theory too. odd fires do need the crossover, but even there care needs to be taken to merge the 2 flows, unless a bundle of snakes exhaust is used where 1 left and 1 right cross to the other side collector





no even fire engine need ta cross over and if used it's solely to expand the acoustic volume for nise purposes

if a x-over is used on an even fire engine then care is still taken to smoothly merge the 2 sides as on this Cox design




If a x-ober like the Bursch is used it's best to just have a glancing blow where the 2 sided connect and there have only a relatively small opening

sort of like this

[famoroso]

"Glancing blow" Nice.

Thanks for the explanation.

May explain why Car Bone opted to not crossover their muffler flow...




https://www.carbone.pl/en/products/carbone-active-bypass-muffler-gtu_07-5051


There are SO MANY muffler options nowadays, including valved / active configurations. It's an embarrassment of riches. Oh how I'd love to dyno them all back to back to back to...

[Bill Verburg]

Originally Posted by famoroso

"Glancing blow" Nice.

Thanks for the explanation.

May explain why Car Bone opted to not crossover their muffler flow...




https://www.carbone.pl/en/products/carbone-active-bypass-muffler-gtu_07-5051


There are SO MANY muffler options nowadays, including valved / active configurations. It's an embarrassment of riches. Oh how I'd love to dyno them all back to back to back to...

For street use where sound quality & quantity is likely to be far more important than the last few hp the best muffler I've ever had is the Fabspeed RSR, no highs, quite enough to hear the cooling fan, nice basso burble everywhere, no resonance.

I haven't dynoed mine yet but the car is far livelier, not really an apple to apple comparison as I also resealed the engine.

[Bill Verburg]

Here's a utube in my garage
993 engine in "76 Carrera 3.0 chassis w/ Fabspeed RSR exhaust

[famoroso]

Originally Posted by Bill Verburg

For street use where sound quality & quantity is likely to be far more important than the last few hp the best muffler I've ever had is the Fabspeed RSR, no highs, quite enough to hear the cooling fan, nice basso burble everywhere, no resonance.

I haven't dynoed mine yet but the car is far livelier, not really an apple to apple comparison as I also resealed the engine.

Love the sound of the sound of that! Especially for my more wife-friendly cars. Agree on sound quantity and quality being more important on street cars.

For hot rod, I still like the GT3 muffler. No subtlety there. There's no hiding throttle position & load there. Everyone knows what the drivers right foot is doing. My experience is with that on a 3.5 liter, dual plug, MoTec motor. It has sound quantity and quality and it may well have every last horsepower too. ;-)


Interesting that Fabspeed seems to offer an X-piped muffler option too...

[Bill Verburg]

Originally Posted by famoroso

Love the sound of the sound of that! Especially for my more wife-friendly cars. Agree on sound quantity and quality being more important on street cars.

For hot rod, I still like the GT3 muffler. No subtlety there. There's no hiding throttle position & load there. Everyone knows what the drivers right foot is doing. My experience is with that on a 3.5 liter, dual plug, MoTec motor. It has sound quantity and quality and it may well have every last horsepower too. ;-)


Interesting that Fabspeed seems to offer an X-piped muffler option too...

Yes the Fabspeed w/t he x has cats, which introduce their own own issues, the x is an ok design if you have to have one

I had a Ti GT3 for a summer it was ok, but much louder than the RSR and performance elt the same open or closed.

I think that the gt3 is much more efficient w/ a 3.8 or 4.0, when I drive a buddies 4.0 Rothsport w/ Motec triggered GT3 at WGi it's eye opening, compared to my 993 3.8 RS

but around town, not so much, and the GT3 is louder, they have issues at LRP noise, stock

[famoroso]

Originally Posted by Bill Verburg

I had a Ti GT3 for a summer it was ok, but much louder than the RSR and performance elt the same open or closed.

Was the GT3 louder than the RSR on the "quiet" setting too? What was the "quality" (low tone, high tone, raspy, etc) of the GT3 in your experience? I know it will differ on different motors.

My 3.4 is generally raspier than I would like, regardless of the eight (or was it nine?) mufflers that I've tried (if you can count the Bisimoto Pulse Chamber as a "muffler") so far.

[Bill Verburg]

Originally Posted by famoroso

Was the GT3 louder than the RSR on the "quiet" setting too? What was the "quality" (low tone, high tone, raspy, etc) of the GT3 in your experience? I know it will differ on different motors.

My 3.4 is generally raspier than I would like, regardless of the eight (or was it nine?) mufflers that I've tried (if you can count the Bisimoto Pulse Chamber as a "muffler") so far.

yes, similar quality just louder w/ GT3, I hesitate to bring in the Rothsport motor as it has far more cam than either my 3.8 RS or 3.6 hotrod