Dont fancy a twin system all the way back to the rear bumber then ? (one either side).

my 3.0 responded very well to have a remus backbox and the 2 middle boxes removed. gained just over 25bhp i think.
cat removal actually loses power from other reports and as mentioned the manifolds are crap!

so....i would recommend you make some new manifold that provide power increases

miniator wrote on 24. Apr 2009 at 17:27:


Seem to remember I heard some guy on Autostormers was doing Manifold re design?, how did that work out?.

bappy wrote on 24. Apr 2009 at 17:31:

Are you sure that it's the manifold that you are looking at and not the heat shields that cover the manifolds?

I'm sort-of going down the idea 1 road, but i am going to have a backbox on both corners.
A friend of mine has offered to make me a system, hopefully in time for the pvs, but that's the way i'm going.
2 backboxes, center sections removed.

The stainless you refer to by the engine manifold is undoubtedly the heat shield, not the manifold itself which is cast into a plenum chamber rather than a 3 pipes into one set up that you might imagine. This has been a topic of some debate on oof as to how it affects performance and how an alternative design might tune the power curve.

With this in mind and the fact that the cats have oxygen sensors and wiring which will need terminating in a way that the ecu will understand to avoid error codes and a permanently lit dash light, i would consider sticking to a cat back system?

Boring and unadventurous as it may sound, its a safer bet imho. You can always go back when further solutions become clear, esp re manifolds, and join the system in the usual place.

As Kevin says i would be reluctant to alter the original design too much re boxs and routing without knowledge of shock wave scavenging,flow rates, and how annoyingly loud it will be on the motorway at constant revs. Although its nice to have v6 grumble when you boot it, that same roar is a right pain at cruising speeds. Some manufacturers use an exhaust valve to controle this noise to give the best of both worlds but this will require ecu input that the omega does not have.(i wonder if multi ram inputs could used for this?... The front one perhaps... No probably not )

You may also want to consider the rear end  esp. the irmscher style twin pipe design which exits either side of the number plate, seen some pics of that box on here somewhere. Or simply a twin pipe exit on a single box as the elites.

bappy wrote on 27. Apr 2009 at 13:47:


Balance pipes have their advantages, mainly on square-plane V8 engines, to maintain scavenging from the exhaust ports with the odd firing order but only when their position is precisely calculated with respect to the speed of the pressure pulses travelling down the system and, even then, it's probably only effective on engines that are in a fairly high state of tune.

I would say that without modelling what's going on in terms of pressure pulses in the system you are more likely to do harm than good. A pipe without junctions will be less restrictive anyway so my inkling would be to go with something like idea 1 and keep it simple.

Kevin