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  #1  
Old 17th December 2018, 05:58 PM
sean sherry sean sherry is offline
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Smile freeing up exhaust

I used to be a fan of this but I fear today's cars don't respond to any interference with the back pressure.
Inlet, firing, and exhaust are now a designed continuous loop, computer controlled. Disturb one element and performance drops.
I'm very fond of a comment made to a young Gun Ho teen who wanted to modify the engine in his V Tech Honda.....what makes you think that you know more than 40,000 Honda engineers ???
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Old 17th December 2018, 08:01 PM
irvine irvine is offline
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Default Re: freeing up exhaust

Fair comment, but....

Exhausts then AND now are designed both restrictive and with efficiency in mind.

Take for example the “mines” one piece titanium turbo back exhaust for the Nissan r34 grr has been shown to produce up to 100bhp over the standard exhaust system, and that’s before you go crazy on tuning.
It’s been proven even the material of the exhaust can gain bhp.

I know I’ve a lowly 280 d-jet but I’m planning a full stainless exhaust, no cat and centre box with a free flow back box. Should see a “few” bhp.

Neil.
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Old 17th December 2018, 10:37 PM
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Default Re: freeing up exhaust

Quote:
Originally Posted by irvine View Post
Fair comment, but....

Exhausts then AND now are designed both restrictive and with efficiency in mind.

Take for example the “mines” one piece titanium turbo back exhaust for the Nissan r34 grr has been shown to produce up to 100bhp over the standard exhaust system, and that’s before you go crazy on tuning.
It’s been proven even the material of the exhaust can gain bhp.

I know I’ve a lowly 280 d-jet but I’m planning a full stainless exhaust, no cat and centre box with a free flow back box. Should see a “few” bhp.

Neil.
In addition, Mercedes designed their exhaust systems to be very quiet. You obviously don't want it to drone, but the M110 sounds great above 4000 rpm. Reducing restriction should hopefully allow some more engine note at high RPM while maintaining quiet cruise.
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Old 18th December 2018, 07:00 AM
sean sherry sean sherry is offline
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Smile Re: freeing up exhaust

I would hate to see the $$$$ signs for modifications to modern Cars.,noise restrictions are part of the Law. But don't tell that to Harley Owners.
Why are they not Policed ????
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Old 18th December 2018, 07:19 AM
sean sherry sean sherry is offline
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Smile Re: freeing up exhaust

P.S. Ten years ago I fitted a flow free exhaust system from a leading specialist manufacturer to an SS Ute V8'. I did not notice a blind bit of difference except for on increase in noise. I can't remember if I also fitted Headers. I sold the car to a dealer and all he was interested in was that it did not have an accessory metal cover instead of the factory canvas. I learned a lesson, in that if you can't see it you can't sell it.
I also understand that Men are visually stimulated in more ways than one !!
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Old 19th December 2018, 01:39 PM
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Default Re: freeing up exhaust

I dont know about other cars but I can confirm with dyno sheets extractors and decent exhaust makes over 20jp at the rear wheels difference with a 6.9
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Old 19th December 2018, 06:30 PM
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Default Re: freeing up exhaust

Quote:
Originally Posted by sean sherry View Post
I would hate to see the $$$$ signs for modifications to modern Cars.,noise restrictions are part of the Law. But don't tell that to Harley Owners.
Why are they not Policed ????
Sean, a most valid observation. I get Harleys driving past my home on a fairly busy, although weight restricted major thoroughfare, and some of those Harleys are absolutely abominable - yes, they should just seize them and fix up the exhaust. How horrible ! Regards Styria
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Old 19th December 2018, 06:42 PM
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Originally Posted by c107 View Post
In addition, Mercedes designed their exhaust systems to be very quiet. You obviously don't want it to drone, but the M110 sounds great above 4000 rpm. Reducing restriction should hopefully allow some more engine note at high RPM while maintaining quiet cruise.
HI Bryce, you have driven my Gleaming Beauty, and you can probably vouch for the fact that she emits a fairly raucous sound - and I also think some very useful extra ponies. I would certainly be happy to take on any 6.9 and also 6.3 for that matter. I achieved this "extra horsepower" (!!) by fitting a 1973 - 350SL standard Mercedes first muffler plus a straight through
huge stainless steel second muffler. The sound is toxic, especially as you are climbing up the revs, and I reckon on at least an extra 5% to 10% of extra power. Regards Styria
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Old 19th December 2018, 06:46 PM
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Default Re: freeing up exhaust

Quote:
Originally Posted by Styria View Post
HI Bryce, you have driven my Gleaming Beauty, and you can probably vouch for the fact that she emits a fairly raucous sound - and I also think some very useful extra ponies. I would certainly be happy to take on any 6.9 and also 6.3 for that matter. I achieved this "extra horsepower" (!!) by fitting a 1973 - 350SL standard Mercedes first muffler plus a straight through
huge stainless steel second muffler. The sound is toxic, especially as you are climbing up the revs, and I reckon on at least an extra 5% to 10% of extra power. Regards Styria
I like what you have done with the exhaust on your 6.9. Its not annoying at low RPM, but if you plant your foot you get a great V8 rumble.

I did something similar with my Jag, its fairly quiet normally but if revved you get the snarl of the DOHC 6.
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Old 19th December 2018, 07:50 PM
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Default Re: freeing up exhaust

6.9 with extractors and duel 2.5 inch exhaust https://youtu.be/luR2a-s5Gu8
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  #11  
Old 20th December 2018, 12:52 PM
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Default Re: freeing up exhaust

Standard exhausts are a huge compromise between functionality, noise, budget, economy and performance. As a ‘tuner’ you can decide which way to weigh that equation...
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79 6.9#5541 (Red Bull)
78 6.9#4248 (Skye)
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Old 29th December 2018, 08:30 AM
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Default Re: freeing up exhaust

For best results you should undertake intake mods too...
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01 Ford AU 5L (Deep Blue)
88 420L Euro#-P
88 420L#-P
88 420L#2477-P
87 560L#2020 (Dora 2)
87 560L #9987
87 420L#4309-P
87 420L#-P
86 560L#5896-P
79 6.9#5541 (Red Bull)
78 6.9#4248 (Skye)
79 6.9#3686 (Moby Dick)
78 6.9#1776 (Dora 1)
77 450L#7010-P
75 450L#8414 (Gold Nugget)-P
57 Buick 73A (Titanic)
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