Hello everyone, recent owner of a Mini JCW 11/2011

A friend heavily suggested I pull the trigger on a used Mini 'Challenge' edition rear silencer and I did without doing much research.

The silencer is basically the backbox plus the piping that I believei should reach the mid-pipe. Picture below for reference.


Now, I have received the silencer but immediately noticed that the piping diameter is significantly larger than stock JCW tubing. I believe I'm running a factory set-up STEP2 exhaust configuration.

Stock diameter should be 2.25 inches, the challenge silencer is 2.75 instead.

Because of this, it's clearly not a simple cut and weld, and I will need an adapter tubing.

This said, I have two questions:

1. If the final portion of the exhaust, is larger than the previous portion (2.25>2.75), will there be any back pressure issues and potential loss of power? (ECU thinking there's an exhaust leak, etc.)

2. Is it a hackjob/crappy thing, to go with the adapter and weld this silencer to the stock 2.25 setup?

In hindsight I would have just gone for a 200cell downpipe, but here I am now, and am wondering if it's worth to-do or makes more sense to try and re-sell.

Thanking everyone in advance for input!

 

So..If you are not tuned(ECU) and all the rest are also stock i would say that the Scorpion "challenge" cat-back system is not for you and yes the car might be "slower" how. Its NOT back pressure its velocity!
Actually there is no reason to have different diameter exhaust system (downpipe-catback).
If i were you i would put the downpipe of scorpion as well(70mm) and i would tune a bit the car..70mm exhaust is way too big for 210ps as the 63.5mm is the super upper limit for a 280+ps.
Hope it helps!

PS:Get prepared for a LOUD system exhaust.

 

Yeah, I agree that the challenge ehaust may be a bit excessive for a non tuned car. I might go for a Stage 1 tune in the upcoming months but first I need to properly assess the conditions of the internals. (valve cover gasket slightly leaky, easy fix, but need to check the rest).

As far as the exhaust goes, I don't know, how bad can it be to weld the silencer (backbox + single tube) to the step 2 exhaust? Step 2 exhaust should have a mid-pipe resonator, so even if the silencer is non-res, it shouldn't be that loud?

Could you define, how much slower the car will feel if I install the silencer? Basically with the tubing going from 2.25 to 2.75 on the last but? Velocity of exhaust fumes will be slower because of larger diameter of piping but at the same time, correct me if I'm wron, stock step 2 exhaust is resonated and thus has some resistance in it, while the challenge doesnt.

 

Exhaust velocity is less critical on a turbocharged engine. Having a higher pressure drop across the turbine will help with power. A larger diameter exhaust will help with pressure drop, thus helping with power.

I would get a 2.5-2.75 exhaust adapter coupling and just bolt the rear box in place, rather than welding it up. Will make re-installing the OEM exhaust much easier if you don't like the challenge muffler.

http://www.everyexhaustpart.com/cart...-expander.html

 

Large diameter exhaust is partial though, as in, from downpipe to mid-pipe its 2.25 (57mm) and then with an adaptor it will go to 2.75 (70mm), so there will unequal size diameter piping. Does this matter? Will there be any benefits/drawbacks?

I ordered a 2.25 to 2.75 adapter coupling, similair to the one you've mentioned.

It's a very strange combination of exhaust parts (STEP2 Base + Mini Challenge backbox + connecting pipes to mid-pipe. I'm still on the fence.

 

Having the step in diameter won't matter much. The challenge exhaust is loud and deep, however.