Exhaust advice!

[rob_bower]

Right guys leaving work last week my exhaust finally gave up the ghost!! so im in the market for a full stainless and seen as there are no good ones off the shelf it looks like ill be going custom!! but im after some advice about what will be best ie what size pipe etc etc any advice that might come in handy, or suggestions im after something purely for performance and not overly noisy!!

Cheers guys

Rob

[Jozinobi]

Im gonna make this short rob

Your existing oem pipe diameter is 1 3/4".

The available and most suitable upgrade sizes for the EP N/A are 2" and 2.25".

I use 2" but a lot of people will recommend 2.25".

I use the smaller because of the slight understatement in power the car has.

A larger increase in pipe size will give you slight losses in torque the larger you go if you dont have the power or torque to maximise it.

i.e on my 4efe the 2" system lost me lots of torque, I added the 5efe and everything was evened out. Right now its sexual.

The factory exhaust design is maximised for good early low down torque and economy.

Make sure to never EVER get a pipe bent system. i.e powerflow or similar. I have one and its crap.

This is due to them pipe bending the angles in the exhaust thus making the bends smaller diameter at the bends restricting flow.

You want a mandrel bent system where they use mandrels put inside the exhaust pipe when bending which are the exact same size as the exhaust pipe diameter thus you will get even sizes at the bends to optimise even air flow. This would be a more professional approach (mandrel bent exhaust system) and may cost a tad more but will give you peace of mind.

A removable decat is optional. Apply cat back on for mot times if needed. Mine passes with full decat from manifold back. i.e nothing...

Also there are off the shelf solutions such as the Blitz Realize systems or a jdm n/a system from yahoo auctions but they will be £500+ easily.

As for noise Rob, a 4" jap can is always going to be noisy and thats the sort of thing I like, something 3.5" would quiet things down, i.e I have a quiet remus for example.

Sparky should be able to give you some insight too as he recently had a system made, maybe he can tell us what he had done.

My 2p

Joz

[rob_bower]

cheers joz i knew you would have some input the to main companys near me are a powerflow center and exhausts uk both of which ive heard bad things about but i hopefully will be going to have a look round a new small company next week.

thanks for your input thoguh joz

[nic1.3]

i just want to ask sumthing here. as yere talking exhausts

ive seen an apexi back box on the yahoo auctions and have looked into it apexi sell an insert that u place into the exhaust tail pipe which is suppose to reduce noise....do there sound reducers really work or are they crap???

[4EFTE Sol]

Also how much is it roughly guna cost for a half decent kit?

[Jozinobi]

Fenny

First you need to find the gt turbo there and get into the parts.

Check exhausts and the n/a systems will be lower down.

There is a v.high probability that the n/a systems there are the same as oem pipe size wise.

2" is not an easily obtainable aftermarket system size for the EPs.

Hence custom.

Joz

[burneyk]

Rob ime having my new shiny exhaust fitted at Top Gear Doncaster this Saturday so i will let you know how i get on. somone recommended this place to me so hope it is ok. Ile let you know.

[RobSR]

back pressure is all bull, its a myth and no one belives it is...its not the diameter of the exhaust that loses you the power its if the "harmonics" of the exhaust are wrong....

I could explain in more detail, but thats simple.

[nic1.3]

back pressure is all bull, its a myth and no one belives it is...its not the diameter of the exhaust that loses you the power its if the "harmonics" of the exhaust are wrong....

I could explain in more detail, but thats simple.

what do u mean by "harmonics"???

[Jozinobi]

what do u mean by "harmonics"???

I agree with what you said about 2" piping nic having experienced the difference myself.

Have a straight thru 2" exhaust on the 4efe and you lose some bottom end, add a silencer/centrebox and you get some back.

Joz

[RobSR]

right explanation it is then....had a big discussion with a top tuner in the UK, and this was the outcome:-

The best possible exhaust for a four stroke engine is a large bore straight piece of pipe which is cut to the correct length. The reason it needs to be the correct length is because pressure waves (caused by the exhaust valve operating) in a pipe always cause and are greatly effected by acoustic harmonics (like a pipe in a church organ)â?¦ If anybody ever complains "I put a big exhaust on and I lost power/torque" this is because the exhaust designer didn't do the harmonics calc's properly, not because the engine lost back pressure.

[alan0387]

right explanation it is then....had a big discussion with a top tuner in the UK, and this was the outcome:-

The best possible exhaust for a four stroke engine is a large bore straight piece of pipe which is cut to the correct length. The reason it needs to be the correct length is because pressure waves (caused by the exhaust valve operating) in a pipe always cause and are greatly effected by acoustic harmonics (like a pipe in a church organ)â?¦ If anybody ever complains "I put a big exhaust on and I lost power/torque" this is because the exhaust designer didn't do the harmonics calc's properly, not because the engine lost back pressure.

So would a de cat pipe and backbox be best for the n/A then? leaving the rest of the system standard? im thinking of cutting out the centre box and cat and replacing with a straight pipe, but weld flanges on so i can pt the cat back for the NCT

(irish MOT, every 2 years tho!)? i am reading very diff opinions here, slightly confusing! i dont want to lose torque/power by putting a 2" full system on, maybe just help the system along?