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1.5" restrictor before main cat????


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Cheers andy.

is it likely this will have been removed? im fitting a boost controler soon and have a few other mods... but with all that back pressure surely ill be losing a shit load of power!

 

 

Probably not. You ought to be able to knock it out with a hammer and a cold chisel.

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after reading "Back-pressure - what's that all about then?" and folowing the links there is a bit on there compairing jap-us-uk spec cars.... and on the jap one it says there is a 1.5" restrictor before main cat.... surely this is going to reduce power?!

 

Before the main cat ?

Will that be in the main cat pipe ? (not even had a look at the exhaust yet)

How easy/hard is it to take off, have a look and remove if required ?

 

CheerZ

Paul

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I've recently replaced my zorst with a Mongoose item (and its fanny-tastic). when the old system fell apart (well the back-boxes literally fell apart). I noticed that the flange from the cat back looked like it had restrictors in each pipe, and about 1.5" in diameter.

 

This is after the cat - this was quite noticable since the Mongoose has a much large diameter (so much that I didn't think it would fit at the time).

 

If anyone is interested I could take a picture - the old exhaust is still in my garage awaiting a trip to the tip.

 

CheerZ

 

StuartR

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I'll get the camera on it tonight - and see about posting something tomorrow.

 

attachment.php?attachmentid=16030&stc=1

 

Here is the picture I took of my old exhaust (replaced with the Mongoose :hyper: ). These are the flanges that bolt onto the cat exit - you can seem some restrictions (about 1.5") in each pipe that could probably be tortured out!

 

Looks like these restrictions are post cat.

 

Getting the system off and on again is quite easy if you approach removal systematically starting from the front to the rear. I just replaced mine up on wheel ramps.

 

HTH

 

StuartR

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attachment.php?attachmentid=16030&stc=1

 

Here is the picture I took of my old exhaust (replaced with the Mongoose :hyper: ). These are the flanges that bolt onto the cat exit - you can seem some restrictions (about 1.5") in each pipe that could probably be tortured out!

 

Looks like these restrictions are post cat.

 

Getting the system off and on again is quite easy if you approach removal systematically starting from the front to the rear. I just replaced mine up on wheel ramps.

 

HTH

 

StuartR

 

Stuart, what part of the exhaust are they in, sorry not had much of a look under the car yet, can you get a pic of all of that part of the zorst up at all ?

 

 

StuartR

 

 

StuartR

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I only took pictures of the flange close up - so you could see the restrictors in place.

 

This is the part of the exhaust which is effectively under the front seats, and is unbolted from the cat. I've highlighted the part a diagram from the online manual (with appropriate kudos to whomever holds all the legal stuff to this.....)

 

attachment.php?attachmentid=16031&stc=1

 

StuartR

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attachment.php?attachmentid=16036&stc=1

 

If you remove the exhaust, do the hangers as step 1, 2, 3 in the diagram. Put back on in reverse order. Otherwise it can be a real PITA to get the back-box hangers back in place.

 

I don't know how much difference removing the restrictors would make - I changed my system cat back.

 

CheerZ

 

StuartR

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Interesting but as the question of " how much difference on performance will it make be" answerd yet? I suppose the inserts would cause a little more back pressure but i dont think that alot of difference will be made as you still have the restriction of the cats. So in reality you are just moving the restriction along the system. Might be wrong though. I would like to hear the results.

[sIGPIC][/sIGPIC]

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after reading "Back-pressure - what's that all about then?" and folowing the links there is a bit on there compairing jap-us-uk spec cars.... and on the jap one it says there is a 1.5" restrictor before main cat.... surely this is going to reduce power?!

 

Back pressure is caused by when the exhaust valve is opening to get rid of burnt gases and enters the manifold. If the manifolds are shared then the normal cycle of combustion will cause a certain amount of pressure(back pressure). If there is to much it will hinder the performance by reducing the flow, hence the restrictor before the cat. I imagine nissan put it there to slow down the gases and to give better running on restricted engine. This is why people opt for headers instead of manifolds as all cylinders get an individual pipe at equal lenght making gas flow better. Thats the reason why people on the site ditch the cats and get divorced headers. As i said earlier in the thread, i think you will just be moving the restriction ;) but remember you need some back pressure for better running on tick over etc...

[sIGPIC][/sIGPIC]

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