Member Since: 11 Mar 2009
Location: Somerset
Posts: 3551
Exhaust back pressure
Hi all I'm making an exhaust and wanted to keep an eye on the back pressure,I'm keeping the bore size as standard just removing and adding different silencers to achieve a nice note, oh and the cat as been lost to
So if anybody knows what psi pos/neg I'm supposed to be looking for at what rpm would be a great help.
I take it i need to take the readings/tap into the exhaust around the area where the cat would of been
I've never had to do a back pressure test before so if i'm talking fill free to rip me a new one
Thanks
Woody.Wanted D4s non runners pm for competitive price.
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19th Dec 2011 11:42 pm
lad
Member Since: 17 May 2008
Location: Blackburn
Posts: 634
In regard to the lost cat , the MOT test from next year states that if a car originally had a cat on it should still be in place.
Im sure I read it like that, if not I'm sure someone will correct me.
20th Dec 2011 12:44 am
woody32 Site Sponsor
Member Since: 11 Mar 2009
Location: Somerset
Posts: 3551
Hi lad it states that On vehicles that qualify for a full cat emissions test, check the presence of the catalytic converter.
So the only vehicles that qualify for a full cat emissions test is a petrol engine vehicle and the equipment used to test it is looking for hydrocarbons (HC) Carbon monoxide (CO) and a lambda reading, and on a diesel engine it is only a smoke test not a full cat emissions test and uses a different machine so During this test, a calibrated smoke meter is used to assess the density of the smoke from compression ignition(diesel) engined vehicles. Wanted D4s non runners pm for competitive price.
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21st Dec 2011 1:02 am
lad
Member Since: 17 May 2008
Location: Blackburn
Posts: 634
sounds good to me!!! cheers
21st Dec 2011 1:06 am
woody32 Site Sponsor
Member Since: 11 Mar 2009
Location: Somerset
Posts: 3551
Wanted D4s non runners pm for competitive price.
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21st Dec 2011 1:41 am
robmikkers
Member Since: 17 Nov 2011
Location: Oss
Posts: 22
I think you need no backpressure at all, a turbo is depends on the pressure-drop, (AFAIK) when the gasses pass the turbo, there should be as little pressure as possible in the exhaustpipe.
21st Dec 2011 7:06 am
amazing
Member Since: 05 Mar 2011
Location: chengdu
Posts: 1542
under pressure
back pressure is not required post turbo but be aware of harmonic shock waves disrupting things up.It is better to have and not need it then need and not have it.
21st Dec 2011 10:01 am
robmikkers
Member Since: 17 Nov 2011
Location: Oss
Posts: 22
Harmonic distortion occurs mostly in exhaust-manifold, where all gasses come together, further down the pipe there will be far less distortion. As long as the downpipe has enough flow for the gasses to cool down, get compacter, and slow down, you will be fine...
21st Dec 2011 10:15 am
THFC
Member Since: 01 Sep 2010
Location: Biggin Hill
Posts: 743
Woody, why don't you just put the cat back on and just do away with the rear boxes, that will give it a good sound PRIDE OF NORTH LONDON
AUDERE-EST-FACERE
22nd Dec 2011 5:22 pm
woody32 Site Sponsor
Member Since: 11 Mar 2009
Location: Somerset
Posts: 3551
Cheers guys didn't give Harmonic distortion a thought
THFC i removed the cat didnt make much difference then i removed the rear silencers and sounds quite nice but i'm going to put the cat back on and replace what i think is a resonator box in the middle with a silencer as i think this is the sound sponge in the system will let you all know how it goes Wanted D4s non runners pm for competitive price.
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