Anthony I need your help....

[Neil82]

Anthony, if I tell them I want the system to be fairly quite will this stop me making as much HP as possible. Or does it not work like that?

Do you want my old GT exhaust trim? 10 pounds to you, it cost me 50!

Have a look at this
http://www.btinternet.com/%7Emarkhorton/Power.htm

and this

http://www.fastcar.org.uk/MAZDA.html

[Anthony]

Ummmm.... noise and performance don't always go hand in hand.

If you stick a crappy backbox on the car, it'll be loud but you won't gain any performance. If you put on a quality item, then chances are it'll be louder than stock but much quieter than the el-cheapo backbox.

As a general rule:

• Removing the cat increases noise levels
• Larger diameter piping increases noise levels
• Straight through mufflers increase noise levels

How loud is your system Kevin whilst moving at speed? It sounded nice when you were in the parking area on Sunday, but obviously I arrived too late to see your runs on the strip.

Oh, and yes I'll have that GT exhaust trim Neil, as the standard SRi tip looks pants...

[Anthony]

Although I've gotta admit Neil - you've wet my appitite for a decent exhaust, and that place you linked to in St Albans is only about an hour and a halfs drive from me....

Tempting.... very tempting :sun:

[P11GT]

About the noise level, Doggy (my cousin) said that it wasnt really that loud, as he was standing at the side of the strip watching me run, so i guess that means its acceptable to most people. However, even though the Primera is well insulated from road noises, i can hear the roar of the exhaust, its pretty loud inside the car, but still acceptable, but remember, mine has a 5" straight thru Apexi box, whereas a powerflow back box would normally be slightly quieter i would have thought.

[ragt20]

how do U get around the Mot if the Cat is removed, wot is exactly meant by Cat back system anyway????

[Anthony]

You'll fail an MOT if your cat is missing on all post 1991 cars. If you fit a cat-replacement pipe, you'll have to refit the cat to get the car though an MOT.

"Cat back" systems are basically the backbox, and piping from the backbox to the cat. The piping bolts onto the cat rather than replacing it.

Hope that helps

[ragt20]

thanx that clears a few things up.......
ps wot about from the engine to the cat....any possible mods there.??

[P11GT]

yep, from engine, get something like a Hotshot Header, that will apparently free up some horses.

[Anthony]

Right, lets clear this up...

First of all after leaving the engine, the exhaust gases go through the exhaust manifold (called a exhaust header in the US). Since you have a Primera GT, you already have a partly uprated manifold as standard. You would see performance increases from fitting an uprated header from Hotshot or AEBS.

After the manifold, the gases pass through the downpipe. This pipe normally comes with the exhaust manifold and an uprated item is not available seperately.

The downpipe then connects to the cat. This can be removed or swapped for a more free flowing aftermarket item. The performance gain from the free flowing cat is fairly small though, so it is probably only worth considering if you have knackered your existing cat and need to buy a new one.

After leaving the cat, the exhaust gases go through the b-pipe. Replacing this with a 2.5" mandrel bent pipe will give you more top end power as there will be less restriction. This pipe is included when you buy a cat-back exhaust system.

The finally thing the exhaust gases go through before escaping into the air to destroy another bit of ozone is the backbox (called a muffler in the US). You can buy aftermarket backboxes on their own, or as part of a cat-back exhaust system.

Hopefully that will clear things up...

[ragt20]

cheer Ant!!!!:jump: :jump:

[Anthony]

No problem