Custom Exhaust for V6 GTV

I want to sort out an optimal exhaust system for my 2001 CF3 3.0 V6 GTV and would like some opinions on what do to.

For background the OEM setup has the exhaust manifold from the front and rear banks go in to 2 flexis, which meet at a cat section with 2 seperate cats and lambda probes. The cat section joins to a common centre pipe with 1 silencer, then this leads to an end section with 2 silencers and a single exit. So in summary it is 6-2-1.

The previous owner of my car had an DTM rear section fitted (Autodelta) but of course the 2 branches come from a common section. However, this section is corroding at 7 years old, so I want to consider what to use as a replacement.

I am wondering if I could get a real dual-pipe system made - ie 6-2-2. What I have in mind is to take the output from the front bank manifold and the rear bank manifold entirely separately to exit on either side of the car, with appropriate silencers and cat sections. Here's a picture of what I have in mind in principle, although not in terms of styling.

I am wondering 1) if it is possible in terms of space and mounts, 2) is there any advantage in doing so (I am assuming freer flow but I haven't the knowledge to back that up), 3) any disadvantages (eg would gasses quicker and reduce flow), 4) where could I get such a system made?

I'd be grateful for your considered knowledge and opinions on all this.

Cheers, Richard.

OJZ engineering. They are on the www. Recommended

Pic of my Gta/stratos exhaust, made by OJZ. Matching lengths, quick release and ALL stainless. Thats something to check when looking at a system.

hayward and scott are recommended by my Alfa Specialist. Most of his tuned cars go there for custom systems.

powerflow - had dual exhaust system made for mine by them

I agree Powerflow will do the trick as the choice of sound and style is up to you.

Cheers for the links guys. Both look good, but OJZ a little nearer to me. Will contact them first.
However, any thoughts as to whether a completely dual exhaust system is or isn't a good idea?
Trickii - at what point does your exhaust become dual - is it common from the cat section to the centre pipe? Or dual all along from the exhaust manifolds back?

I've wondered that if you have separate pipes all the way front the manifold that it could sound strange due to some unwanted phasing as inevitably the volume of each exit system would probably be different.
But this is only an "out there" theory of mine, possibly complete rubbish

you would need to ensure the pipe diameters and section lengths were spot on to ensure optimal flow... a tuning specialist should be able to calculate / design this for you. i doubt powerflow would know enough to get this right... they seem to favour just using big bore pipe and getting it fitted. not always the best for performance but then, most saxo drivers dont know this either

might be worth a phonecall to autodelta to run it past them also? get some advice at least

http://www.alfaowner.com/Forum/attac...2&d=1193768640

Fantom Alfa - the last box was replaced by powerflow and the pipes then split from there

[quote=marko;1899016]you would need to ensure the pipe diameters and section lengths were spot on to ensure optimal flow... a tuning specialist should be able to calculate / design this for you. i doubt powerflow would know enough to get this right... they seem to favour just using big bore pipe and getting it fitted. not always the best for performance but then, most saxo drivers dont know this either

Marko - i defo dont agree with wot you say about powerflow - that will depend on who the dealer is. The guy who did mine was very knowledgeable. The thing you say about just wanting to put a big bore pipe on and thats it couldnt be further from the truth. They will do that if that is what you want but they advise not to. They offer you the design and the sound to suit how and when you drive your car. I think they do a fantastic job and i couldnt reccommend them more.

perhaps it also depends on what branch you visit... last time i was at newcastle one they didnt really have a clue other than how to bend the pipe to fit. no mention of diameter recommendations or flow paths, primary lengths etc

Originally Posted by strat24v

OJZ engineering. They are on the www. Recommended

Pic of my Gta/stratos exhaust, made by OJZ. Matching lengths, quick release and ALL stainless. Thats something to check when looking at a system.

That looks very nice work. I suspect it was expensive. Would you mind telling me how much (by email if you prefer). Cheers.


As for Powerflow, I do agree it depends on the branch - I think they are a franchise. The one local to me doesn't seem much good, though I haven't spoken to them for a couple of years so they could have better knowledge now.

I had my quad system done by a branch of Longlife and they seemed really good, the specialist that's serviced my GTV said it was a excellent system. though I'd heard bad things about other Longlife branches, so I guess all the franshised chains are a bit random

Well, I have just spoken to Lance at OJZ (cheers for the recommendation John). He's very helpful and very straight-talking. I told him what I was after and he said he could do it, but wouldn't recommend it. Although to me as a layman it sounds like a completely dual exhaust set up would be a good idea he says that in reality it does not work that way in any car application that he has ever known (though he couldn't rule out it being the right thing for specific cars). In fact he was saying that all the Jags from a certain era were made that way and traditionally people still fit dual exhausts to them, but in reality it robs them of power compared to a single exit exhaust. I would have liked to have quizzed him on the theory but it would have only exposed my ignorance more and wasted his time.
So, with that idea ruled out I need to work out the best way forward. I have the Autodelta J10 upper and rear apron so that limits my choices to either replacing the Autodelta J10 quad exhaust but adding more wadding, or getting a custom dual oval rear section by Powerflow or Longlife, something similar to Trickii's.

I've spoken to Alfaholics and ordered their stainless steel front pipes and flexis. Unfortunately this will probably make things louder but a new rear section should see to that.