Exhaust for EP91 N/A

[ste91]

I've been doing a bit of searching but can't seem to find a definate answer on N/A exhausts.

I'm trying to find what will be best for performance on an N/A without it being loud. I was going to just get the standard system de-catted and get a nice backbox but have decided to wait and go for a full system with a manifold aswell.

I know of the OBX and Pacesetter manifolds but these are for the 5E, although they still fit the 4E, correct?

What other manifolds are out there - and more importantly which one is best for making power, preferably at the top end, but without losing too much bottom end. As Rich or someone said a few days ago a 4-2-1 should be fine aslong as the pipes are fairly long (or something like that, I've forgot now).

As for the exhaust itself, I should stick as close as possible to the standard diameter, correct?

But, I don't want it loud, so what silencers should be there? I was looking on the blitz website yesterday and they make those active silencer things which go in the end of the exhaust - do they help to make it quieter or do they just lose power?

And finally the backbox, are there any manufacturers out there that make subtle 2-2.5 inch backboxes as they all seem to be 3-4 inches.

Basically I want more power without it sounding like a fart in a tunnel, I know there will be some increase in noise but I just want to keep it nice and quiet if possible.

Bit of an essay but should help with non turbo owners who want to know more

[Jozinobi]

He said the 421 was fine but has he tried it?

The OBX will fit 100% on your 4EFE Ste.

Its the OBX you want. People will rant about the Pacesetter but trust me on this one.

I had mine on 4E and 5E. There are small clearances issues, but nothing that an angle grinder wont cure.

The decat pipe it comes with also doesnt line up (can be made to), but dont forget its meant for a Paseo.

Also the OBX will greatly change your power band/rev range, get ready to rev to 4k RPM for maximum effect and you will lose some bottom end.

The OBX diameters are 2" all round so will require either a custom exhaust or aftermarket solution. The OEM system definitely wont do.

Don't be fooled into thinking a brand spanking full exhaust is going to give you much 'more' power as it wont.

However a combination of things will make your engine breath much better.

Ive got an NA Fujitsubo Legalis R on its way, if you check their jap website you can see what gains it gives as an example.

There so much more for me to say but back to work for me...

There is some existing info in this section on na exhausts I suggest you check it out.

Catch me on msn some evening jozman18@hotmail.com

Joz

[ste91]

I have read through almost every bit of the exhaust section

About a new full system vs modifying the old one - what do you do when you want to fit a new manifold on there though? Or is it just a case of taking it to an exhaust place and they will sort it?

[Jozinobi]

There are two things you can do to fit a new manifold (you should have aftermarket or custom exhaust) you can either weld it straight onto the exhaust or you can create a flange so each end can connect to make the manifold removable (recommended). The OBX will have its own flange. You will also need matching exhaust gaskets.

A competent and flexible exhaust place can do this for you. Note I said 'competent and flexible', be specific in what you want done or you will get a monkey.

Joz

[Rich]

Yeah basically what I've read up is that a 4-2-1 header with long primaries and a large tapered collector at the end that attatches to the rest of the system (similar to Joz's 4-1) will get you the best of both worlds (broader range of power and good top end). However the Internal diameter of the rest of the exhaust is always going to make or break the system.

Too small a diameter and the engine won't breath as well, too big and it won't have that all important velocity. 2" exhaust is the biggest a N/A 1.3 will ever need as its good for 150+ bhp on an N/A motor. 1 3/4" is good for a virtually standard engine i.e. air filter, inlet manifold etc. 2" will be good with uprated cams, throttle bodies etc.

Having a small amount of backpressure is a myth and a no no. What you need is a header designed to draw in the inlet air and fuel mixture so that you are increasing the amount that the engine can inhale as it were.

Also think along the lines that an exhaust doesn't give the engine power it lets the power out

[Jozinobi]

The OBX is a 4-2-1 My hotshot is a 4-1.

Sorry the OBX is provisionally sold.

Joz

[Rich]

4-1 will work best with your setup Joz, as Im sure you are aware. High RPMS FTW

Might just attack my standard one with a dremel for now...