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Any custom exhausts available for 931?
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Thu Oct 25, 2018 1:34 am    Post subject: Reply with quote

Oooh. I'd be concerned about using lightweight/thin wall on a turbo exhaust, especially right at the turbo. I assume you're not going with inconel?

I'd probably want to use the heaviest gauge available, for durability... at least for the front half...
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Mike9311  



Joined: 14 Dec 2004
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PostPosted: Thu Oct 25, 2018 2:36 am    Post subject: Reply with quote

924RACR wrote:
Oooh. I'd be concerned about using lightweight/thin wall on a turbo exhaust, especially right at the turbo. I assume you're not going with inconel?

I'd probably want to use the heaviest gauge available, for durability... at least for the front half...


Yeah this is my dilemma... If I go with 0.035 right off the turbo it would be 321. I was thinking I might coat that too

I do agree that it probably should be 0.065 which would make it considerably cheaper and I could do it in 304

At the very least make it so the 3" down tube is its own separate piece just in case
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1979 924 NA M471/M481 ohne M650 Herausnehmbares Dach
1982 931 Red Resurrection - NEW!
1982 931 parts car or resurrection?
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1843
Location: MI

PostPosted: Fri Oct 26, 2018 6:36 am    Post subject: Reply with quote

My pipe is a stock gutted cat and a straight pipe replacing the muffler.. It's not all that loud..
That muffler was heavy.. It might get a pretty chrome tip some day..


I think the stock pipe is pretty damn good.. Quite a nice piece..

Maybe their are gains to be had by increasing the down pipe size? You think?

When? @ stock? 200hp? 250hp? 300hp?

I don't imagine increasing the downpipe size would help much until you are making enough power for it to start becoming a restriction..

What did the GTS have for a downpipe? I'm pretty sure it had the same manni-turbo-J-WG setup but did it have a bigger downpipe?
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Mike9311  



Joined: 14 Dec 2004
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PostPosted: Sun Oct 28, 2018 4:37 am    Post subject: Reply with quote

Fasteddie313 wrote:

I think the stock pipe is pretty damn good.. Quite a nice piece..

Maybe their are gains to be had by increasing the down pipe size? You think?

When? @ stock? 200hp? 250hp? 300hp?

I don't imagine increasing the downpipe size would help much until you are making enough power for it to start becoming a restriction..


Its popular to put in a larger down tube to get the turbo to spool sooner but its also based on space restrictions to not carry that larger section all the way out

Stock is actually good and for most of us just fine. Supposedly 2.5" is good up to 250HP and 3" too small for 400+. I wouldn't even mind taking out the flattened sections and putting in a lighter muffler

I am just trying to put something lighter into the '82 since I have to do something anyway (due to all the damage and poorly repaired sections).
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1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 ohne M650 Herausnehmbares Dach
1982 931 Red Resurrection - NEW!
1982 931 parts car or resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1885
Location: Somerset, UK

PostPosted: Sun Oct 28, 2018 8:31 pm    Post subject: Reply with quote

Fasteddie313 wrote:
My pipe is a stock gutted cat and a straight pipe replacing the muffler.. It's not all that loud..
That muffler was heavy.. It might get a pretty chrome tip some day..


I think the stock pipe is pretty damn good.. Quite a nice piece..

Maybe their are gains to be had by increasing the down pipe size? You think?

When? @ stock? 200hp? 250hp? 300hp?

I don't imagine increasing the downpipe size would help much until you are making enough power for it to start becoming a restriction..

What did the GTS have for a downpipe? I'm pretty sure it had the same manni-turbo-J-WG setup but did it have a bigger downpipe?


The GTS is almost the same set up as stock RoW except the centre silencer/muffler was deleted
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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K-Roll931  



Joined: 08 Jul 2017
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Location: Southfield, MI

PostPosted: Tue Feb 05, 2019 5:11 pm    Post subject: Reply with quote


My 931 came with what I'm pretty sure is 951 rear section. But with one of support bracket welds cracked and/or broken at the muffler and base and one finger-length crack along the pipe, I'm willing to do a budget-friendly test if this can't be salvaged.
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morghen  



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PostPosted: Tue Feb 05, 2019 6:42 pm    Post subject: Reply with quote

Looks like the correct 931 part to me.
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Tue Feb 05, 2019 11:37 pm    Post subject: Reply with quote

We'll get it figured out, one way or the other, Karl!

I'd be down with trying out some alternatives; may just be a matter of identifying a suitable alternate rear chamber...

Then again, the simplest might even be just starting with trying a straight pipe in there. Just needs a sleeve joint, plus a little fabrication to match up with one of the stock hangar points at the back...

To just swap in a straight tube for the rear muffler, doesn't take too much more than getting a straight section from these guys:
https://catalog.woolfaircraft.com/viewitems/product-catalog/staight-tubes

They're just down in Romulus (though I ship, anyway, takes too long to get there).
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K-Roll931  



Joined: 08 Jul 2017
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Location: Southfield, MI

PostPosted: Thu Feb 07, 2019 9:52 am    Post subject: Reply with quote

924RACR wrote:
We'll get it figured out, one way or the other, Karl!

I'd be down with trying out some alternatives; may just be a matter of identifying a suitable alternate rear chamber...

Then again, the simplest might even be just starting with trying a straight pipe in there. Just needs a sleeve joint, plus a little fabrication to match up with one of the stock hangar points at the back...

To just swap in a straight tube for the rear muffler, doesn't take too much more than getting a straight section from these guys:
https://catalog.woolfaircraft.com/viewitems/product-catalog/staight-tubes

They're just down in Romulus (though I ship, anyway, takes too long to get there).


That's what I'm thinking! I'm apprehensive of a straight pipe on the first go, however. I've heard that on the YouTube and it's way too loud for me, so some form of muffler is gonna have to stay back there. But whoever and however this was done, I like this one!
https://www.youtube.com/watch?v=_OHH-AMlxVo
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1843
Location: MI

PostPosted: Thu Feb 07, 2019 2:03 pm    Post subject: Reply with quote

K-Roll931 wrote:
924RACR wrote:
We'll get it figured out, one way or the other, Karl!

I'd be down with trying out some alternatives; may just be a matter of identifying a suitable alternate rear chamber...

Then again, the simplest might even be just starting with trying a straight pipe in there. Just needs a sleeve joint, plus a little fabrication to match up with one of the stock hangar points at the back...

To just swap in a straight tube for the rear muffler, doesn't take too much more than getting a straight section from these guys:
https://catalog.woolfaircraft.com/viewitems/product-catalog/staight-tubes

They're just down in Romulus (though I ship, anyway, takes too long to get there).


That's what I'm thinking! I'm apprehensive of a straight pipe on the first go, however. I've heard that on the YouTube and it's way too loud for me, so some form of muffler is gonna have to stay back there. But whoever and however this was done, I like this one!
https://www.youtube.com/watch?v=_OHH-AMlxVo


The one on youtube in my signature?
It is honestly pretty quiet in the car and much quieter in general than a non-turbo straight piped car.
I had a 318is that was wayy louder with a glasspack.
I had to put inline a 2nd glasspack after the 5th or so time I got pulled over they finally gave me a ticket for it, and the cops still almost wouldn't pass it with 2 glass packs but it barely passed their meter with me being very ginger on the throttle


Here is the same straight pipe as my sig video flat out @ 15psi of boost from in the car on a very early run of mine.. https://www.youtube.com/watch?v=REaoapuzrzY

Well, I have drove some pretty darn loud stuff so "quiet" to me is subjective.
I find it quite quiet in the car due to the exhaust being past the rear bumper, and the turbo quiets the engine a lot, about equal to a cat I'd say.
Definitely quiet compared to a car with a broken exhaust anywhere under the floorboard, lol..

The one you linked a video to sounds like a motorcycle to me and you can't hear the turbo whistle at all..

I love the turbo whistle "SHHWEEETT SHHHHWWWEEETT" sound in my exhaust while the turbo is still spinning slow enough to be within audible range, and the "agricultural" musclecar-esque-ness of it seems period correct to me, fitting.


I think you get more turbo sound with a bigger turbo too because it stays within audible range before it spools up more..

I got my "custom" exhaust here https://www.youtube.com/watch?v=x_L9dm8uH94&t=99s
That is a slightly craked OEM exhaust, right before the muffler, and is way louder in the car than the straightpiped 931..

My M3 is probably only slightly quieter with its cats straightpiped and OEM catback muffler..
Here is a video of it trying to diagnose a slight idle miss I fixed..
https://youtu.be/0eS4VDeU81g?t=65
Revs at 1:05
That car sounds sick (as in great) in it's own way that is not really comparable to the 931.

A straight pipe is basically free DIY. I'd say you should atleast try it. Experimenting is fun.
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Last edited by Fasteddie313 on Thu Feb 07, 2019 2:26 pm; edited 1 time in total
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K-Roll931  



Joined: 08 Jul 2017
Posts: 53
Location: Southfield, MI

PostPosted: Thu Feb 07, 2019 2:13 pm    Post subject: Reply with quote

Fasteddie313 wrote:
K-Roll931 wrote:
924RACR wrote:
We'll get it figured out, one way or the other, Karl!

I'd be down with trying out some alternatives; may just be a matter of identifying a suitable alternate rear chamber...

Then again, the simplest might even be just starting with trying a straight pipe in there. Just needs a sleeve joint, plus a little fabrication to match up with one of the stock hangar points at the back...

To just swap in a straight tube for the rear muffler, doesn't take too much more than getting a straight section from these guys:
https://catalog.woolfaircraft.com/viewitems/product-catalog/staight-tubes

They're just down in Romulus (though I ship, anyway, takes too long to get there).


That's what I'm thinking! I'm apprehensive of a straight pipe on the first go, however. I've heard that on the YouTube and it's way too loud for me, so some form of muffler is gonna have to stay back there. But whoever and however this was done, I like this one!
https://www.youtube.com/watch?v=_OHH-AMlxVo


The one on youtube in my signature?
It is honestly pretty quiet in the car and much quieter in general than a non-turbo straight piped car.
I had a 318is that was wayy louder with a glasspack.
I had to put inline a 2nd glasspack and the cops still almost wouldn't pass it but it barely passed their meter

Here is the same straight pipe as my sig video flat out @ 15psi of boost from in the car on a very early run of mine.. https://www.youtube.com/watch?v=REaoapuzrzY

Well, I have drove some pretty darn loud stuff so "quiet" to me is subjective.
I find it quite quiet in the car due to the turbo and the exhaust being past the rear bumper.
Definitely quiet compared to a car with a broken exhaust anywhere under the floorboard, lol..

The one you linked a video to sounds like a motorcycle to me and you can't hear the turbo whistle at all..

I love the turbo whistle "SHHWEEETT SHHHHWWWEEETT" sound in my exhaust while it is still spinning slow enough to be within audible range and the "agricultural" musclecar-esque-ness of it.

I think you get more turbo sound with a bigger turbo too because it stays within audible range before it spools up more..

I got my "custom" exhaust here https://www.youtube.com/watch?v=x_L9dm8uH94&t=99s
That is a slightly craked OEM exhaust, right before the muffler, and is way louder in the car than the straightpiped 931..



A straight pipe is basically free DIY. I'd say you should atleast try it. Experimenting is fun.


Yours was actually my reference for muffler delete haha. I love the sound, I was just worried about how loud. I reckon it wouldnít hurt to try since it is free. I did try it on my Ecoboost Mustang and didnít think that was overly loud. Maybe thatíll be the same here.

The absolute loudest I think I can handle for this car is Carrera GTS loud.
https://youtu.be/LeEGCQ8tM3o
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Fasteddie313  



Joined: 29 Sep 2013
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Location: MI

PostPosted: Thu Feb 07, 2019 3:35 pm    Post subject: Reply with quote

If you make the straightpipe long enough to just barely stick past the rear bumper I think that is the key to it being quiet in the car.
Get the noise past the underside of the car and it is plenty quiet cruising around.

The GTS seems quite loud and you can hear the turbo in the exhaust like I was saying (while it is smoking) but it appears to have a can of some sort in the muffler position.

My 931 in all the videos is straightpipe catback with a gutted cat.
I think it isn't loud enough for the cops to be bothered.


I don't feel as if my stock downpipe and exhaust will hinder my performance goals so it is not something I plan to upgrade but maybe tidy it up a bit.
I think it will do to 20psi and that will be plenty..

I think exhaust could get you another 10-20 HP @ high boost sure, but if you don't already have a gutted cat, an intercooler, and running 13psi or better I don't think it will get you much of anything.

Maybe it will spool faster but it doesn't bother me that it doesn't get full boost until 2.9-3k rpm. It is the character of the car like a 2-stroke powerband and I love it. It's wild..

Best bang for your buck upgrade? Intercooler.. No question..

I understand wanting a $1,000+ exhaust for your beautiful car but that's just not me..
I prefer the "Yeah, I made that" kind of cool..

BassGT's exhaust however is another level of cool, 2nd kind of cool (as nutnfancy says), that is epic history cool..
I have ledfoot's boostgauge
I would love even a switch from BassGT's car.
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Carrera RSR  



Joined: 08 Jan 2010
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PostPosted: Thu Feb 07, 2019 11:24 pm    Post subject: Reply with quote

Fasteddie313 wrote:

I think exhaust could get you another 10-20 HP @ high boost sure, but if you don't already have a gutted cat, an intercooler, and running 13psi or better I don't think it will get you much of anything.

Maybe it will spool faster but it doesn't bother me that it doesn't get full boost until 2.9-3k rpm. It is the character of the car like a 2-stroke powerband and I love it. It's wild..


My recommendation is no muffler until the back end of the pipe. You want quicker gas flow off the turbo only suppressing the noise at the end of the pipe. It will give you quicker spool and the potential additional power will be from spooling earlier. Its also far easier to cut off/weld on differing sizes of muffler to tune the noise to your taste. No muffler at all sounds awful. I did it. Far too much noise which was not a nice noise.


Fasteddie313 wrote:
Best bang for your buck upgrade? Intercooler.. No question..


Absolutely. #1 priority if you want a little to a lot more power


Fasteddie313 wrote:
BassGT's exhaust however is another level of cool,
I would love even a switch from BassGT's car.


That exhaust is on my car......

2nd bit of cool is I now have Morghens K27/26 hybrid turbo to install soon from his GTS wannabe. Will be awesome with all other mods on my car to support its bigger compressor
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Thu Feb 07, 2019 11:46 pm    Post subject: Reply with quote

I'm pondering throwing one of these on the back:
https://www.jegs.com/i/Dynomax/289/24215/10002/-1

We use them on the 924 NA racecar to good effect, and I know they've held up very well on that car through countless seasons of racing. Of course, a turbo has a hotter exhaust... but OTOH if it's only at the very back...

They're also definitely higher quality and longer-lasting than your typical glasspack. Just have to find a nice-looking tip.

I like gutted cat, easy and cheap... though it's also not so hard to just splice in a straight section, admittedly. Biggest pain would be just joining back in the wastegate exhaust, if you don't re-use any of that plumbing...

Looking forward to putting something like this behind my soon-to-be-rebuilt turbo unit... sometime this spring...

Karl also pointed out a Magnaflow muffler that looks like it might be better than the above Dynomax, a little quieter/more streetable, yet still a straight-through - just more volume to absorb...
https://www.amazon.com/MagnaFlow-Exhaust-Products-10425-Muffler/dp/B000XQO0UW
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K-Roll931  



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PostPosted: Thu Feb 14, 2019 5:28 pm    Post subject: Reply with quote

My new plan is to gut the cat and run the exhaust as such to start. If I need to go louder, I'll go from there. Just need to finish getting my car back together first!
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