991.2 GT3 with Dundon Street Headers on the Dyno! - Rennlist - Porsche Discussion Forums

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991.2 GT3 with Dundon Street Headers on the Dyno!

Old 10-23-2018, 12:27 AM
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Default 991.2 GT3 with Dundon Street Headers on the Dyno!

Has been lots of interest in the Dundon 321 SS Long Tube Catted Headers for the 991.2 GT3/RS. We're just about back in stock with them so wanted to update the latest Dyno results for them.

Dyno's were done on our Dynapack Hub Dyno, ambient air temps in the 70's, car put in "rolling road mode" with our PIWIS (factory tester) and we ran with the stock muffler
  • No Drone
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Dundon 321SS Long Tube Street (catted) Headers and Valved Side Deletes on 2018 991.2 GT3 Manual.


46lbft gains at 4400rpm
20whp gains at 8400rpm

We did notice the stock ecu intervening at 475whp or so, so definitely into the torque limiters. As the cars get a bit older, out of warranty or for those more adventurous types an Ecu tune may unlock a bit more up top.

This is a great combo for the stock muffler, or in combo with one of our Lifetime Loud Mufflers!

https://www.dundonmotorsports.com/po...aders?carid=40
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Old 10-23-2018, 12:55 AM
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Nice results and on a proper dyno. Well done!
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Old 10-23-2018, 02:26 AM
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Any updates on the race header setup on the .2’s?
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Old 10-23-2018, 05:23 AM
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So there isn't the drop in toruque like on the .1 without tune? Whats the reason for this? I guess the .1 works with overlapping valve-times to realise an exhaust gas recirculation which doesn't work with the free flowing headers. Is this dfifferent on the .2?
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Old 10-23-2018, 11:57 AM
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Originally Posted by Cay_PI View Post
So there isn't the drop in toruque like on the .1 without tune? Whats the reason for this? I guess the .1 works with overlapping valve-times to realise an exhaust gas recirculation which doesn't work with the free flowing headers. Is this dfifferent on the .2?
I was wondering the same thing... looks like this is stronger throughout all rev ranges when compared to stock. Any downsides from current, previous, or perspective owners?
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Old 10-23-2018, 12:11 PM
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Originally Posted by Apex Ace View Post
Nice results and on a proper dyno. Well done!
🙏🙏
Originally Posted by drdonger View Post
Any updates on the race header setup on the .2’s?
Will have updates in a few weeks after our testing. We seriously just got our car back the end of last week!

Originally Posted by Cay_PI View Post
So there isn't the drop in toruque like on the .1 without tune? Whats the reason for this? I guess the .1 works with overlapping valve-times to realise an exhaust gas recirculation which doesn't work with the free flowing headers. Is this dfifferent on the .2?
the 991.2 has different and larger cam profiles than the 991.1. You’re correct that there isn’t the same cam timing effecting the mid range.

Originally Posted by Jarhead32 View Post
I was wondering the same thing... looks like this is stronger throughout all rev ranges when compared to stock. Any downsides from current, previous, or perspective owners?
Have quite a few installed on 991.2 GT3’. Many in conjunction with our Lifetime Loud Muffler. We offer a 30day try it and love it guarantee where your only risk is shipping and installation costs.
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Old 10-23-2018, 12:12 PM
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Originally Posted by Apex Ace View Post
Nice results and on a proper dyno. Well done!
+1
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Old 10-24-2018, 12:13 AM
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Originally Posted by [email protected] View Post
and we ran with the stock muffler
What are the expected results if you did this same test with the ORANGE rear muffler or the BLACK rear muffler?
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Old 10-24-2018, 03:09 AM
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Originally Posted by marchitect View Post
What are the expected results if you did this same test with the ORANGE rear muffler or the BLACK rear muffler?
Orange is about the same as it’s the same cross section as stock but will less dB. Black will be a bit more (2-3whp) but not so easy to consistently measure as the ecu is trying to limit the torque.

We’re not claiming any additional HP with the Orange or Black mufflers. We are just offering different levels of sound and of course a lifetime of trouble free use.
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Old 10-24-2018, 09:59 AM
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Anxiously awaiting the race header results as well. Is there any plan to run street vs race back to back (meaning same car, same day, same conditions)?
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Old 10-24-2018, 10:13 PM
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Jamie, does this street version run 2.5” inlet into the stock muffler you mentioned using on your initial post ? Would have expected 3” especially with your torque and hp increases. Thanks
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Old 10-24-2018, 10:33 PM
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Originally Posted by horns View Post
Anxiously awaiting the race header results as well. Is there any plan to run street vs race back to back (meaning same car, same day, same conditions)?
we have it, waiting on a chance to swap headers to our 991.2 GT3 to get the CEL handled. Should have a chance next week to do that. Then I’ll post that.

Originally Posted by Campy View Post
Jamie, does this street version run 2.5” inlet into the stock muffler you mentioned using on your initial post ? Would have expected 3” especially with your torque and hp increases. Thanks
The street version we tested was on the stock muffler. Wanted it to be a realistic “worse” case. If you buy a catted header and lifetime muffler we can do the side deletes as 3” to take full advantage of the 3” internals in the muffler.

Last edited by [email protected]; 10-27-2018 at 04:06 PM.
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Old 10-26-2018, 10:10 PM
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I apologize if this has specifically been addressed already.

1) How does the sound compare between the street header with black rear muffler to the race system with OE rear muffler? I imagine the cats of the street system are more restrictive and noise attenuating than the OE rear muffler?
2) Are the rear mufflers failing only under prolonged track use, or are they failing from street use only?
3) Is the rear muffler pretty much guaranteed to fail with the race header system regardless of driving conditions?
4) Any difference in rear muffler failure/durability between the GT3 rear and the Ti rear on the RS?
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Old 10-27-2018, 12:23 AM
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Originally Posted by horns View Post
I apologize if this has specifically been addressed already.

1) How does the sound compare between the street header with black rear muffler to the race system with OE rear muffler? I imagine the cats of the street system are more restrictive and noise attenuating than the OE rear muffler?
2) Are the rear mufflers failing only under prolonged track use, or are they failing from street use only?
3) Is the rear muffler pretty much guaranteed to fail with the race header system regardless of driving conditions?
4) Any difference in rear muffler failure/durability between the GT3 rear and the Ti rear on the RS?
i’ll go one by one:

1. Street with Black is a about the same as Race with OEM. The quality of the sound is a little different. With Race, the pops from a pdk shifting are a bit clearer, but only in a subtle way.

2. Mainly on the track, but if you push hard and often the OEM muffler will fail, especially a Ti muffler (OEM or other maker). Street headers are less likely as the cat helps “chop” the pressure waves up into smaller waves.

3. Race header/Ti muffler is likely to have trouble.
Race Header/Steel muffler less likely
Street Header/Ti muffler less likely
Street header/Steel muffler less likely.

4. What we tell folks is if you’re going to change the exhaust on your RS and you’re going to track it, get a Lifetime Muffler. Same with a GT3. Otherwise see above!
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Old 10-27-2018, 07:27 AM
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My wife and I have bought homes without as much difficulty as buying an exhaust for my car. lol I have spent more time and energy trying to figure out what i want it to "sound like" And be able to enjoy a 700 mile weekend without a migraine. How much power gain would you see between the race header and the street header (both long tube) both with the loud center muffler?
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