tbtstt

Hi all, just wonder if someone out there can satisfy my curiousty and answer me a quick question; does anyone know what exhaust is used on the Group N Impreza rally car? I assume they run a full decat system, but I just wondered what the brand of choice is (or if specific brands are stipulated).

I can't see anything in the "obvious" (i.e. online) regulations, so I wondered if someone out there has any knowledge of the Group N machine?

Thanks in advance for any information!

Oh, and apologies if this should be under "technical", but I thought I had more chance of a reply posting in the general section!

V4JDMSTi

iTrader: (2)

IIRC the bore is limited, 2.5" i think and they don't use an open neck downpipe. They are decatted. TSL make a nice grp n system.

Stevesbluewrx

iTrader: (4)

To be honest the Group N and WRC cars do have cats as they have to comply with public roads etc.

In terms of the bore. pass. Grp N and WRC have to resemble the production line model which I have never understood the Citreon and Ford's as the do not run 4x4 public models etc in other words the lines and appearence stays the same.

But what this means is you should be able to bolt on turbos,exhausts etc. You tell me what car maker gives you ALS as standard?

Hope that helps

Steve

Splitpin

That's an impossible question to answer as there isn't one single system available. There are now 15 variations of the "Group N Impreza rallycar", for starters.

No, or at least they shouldn't. Catalysts are mandatory in MSA and FIA sanctioned competitions. You might see some cars "getting away" without them in clubman events but the MSA has tightened the regulations in the last year.

If everyone followed that reasoning, where'd we be? Besides, the people most likely to know the answers to technical questions are likely to be browsing the technical forum.

tbtstt

Thanks for the informative replies!

Stevesbluewrx - if I'd known you had the answer(s), I'd have posted the question on a more local Subaru forum...

Oops. I knew that... as much as I love rallying I have to admit my knowledge of some of the rules is lacking. I've found some of the Group N cars more interesting than the WRC recently, and I was just curious as to what changes have to be made (plus it never hurts to know the difference between my car and the rally car! ). Didn't realise there were sub-divisions within Group N though.

Thats interesting. I assumed that the Group N cars were fully decatted as they run ALS. I guess that cooked cats are an expense you have to live with if you choose to run ALS then?

I know that the WRC cars have a bit more flexibility, but its true that as Group N is suppose to be "as the car left the factory", you wonder how they are allowed to change suspension, ECU, exhaust etc. within those regulations.

Splitpin

Loads. Just look at the price tag of a fresh built international Group N Impreza!

That "15" comment referred to the number of distinct different homologations of the Impreza. 1-6 were the classic shape, 7-12b were the newage saloon, and 14/15 the current shape hatchback. Next year's is 16. There effectively are informal subdivisions though; there's a big price and performance difference between a "basic" clubman car and a full house international one built to the full extent the regs allow. Then, as Butty's exhaust has illustrated, different local requirements around the world.

That's part of the reason why the cat is moved further down the system. Even then, aggressive ALS is unfriendly to most of the bits on the exhaust side of the engine.

TBH the ethos of Group N being a "showroom" class has changed fundamentally over the last decade. You can change huge amounts of stuff now because the rules have gradually been relaxed.

You can change the ECU, for example, because the the regulations only stipulate that the physical case of the thing looks stock. So, you just open it up, throw away the standard PCB and fit your Pectel, Motec, or whatever implant you want. Simple.

It isn't that the rules allow you to change stuff, they just don't prevent you from doing it. Long gone are the days when the car's interior carpet needed to be retained (usually rolled up and stuffed under one of the seats). It's closer to Group A now - a modern full house Gp N Impreza is probably quicker than a late Gp A or early WRC car, even with the smaller restrictor.

Butty

iTrader: (2)

Piccy of parts to a 2002? Group N system I never fitted :



Like Splitpin says, there are so many combinations of exhaust sections that Prodrive offer rather than a single unit.
The one above had a rear silencer marked as being for the US. Cat is in the rear of the centre section.
It was a very very light but don't know what material it was.
It was all slip jointed so would need some sealant at joints to make it quiet until warmed up.
All sections were the full 2.5" to comply with being sized as per production models - although std rear box pipework is more like 2 1/4".

The bellmouth was a cast item but with the standard mouth, although I understand that full open mouths can be bought?

nick

Splitpin

Noise regs over there must be a lot less restrictive - backbox like that would never get through an MSA test.

Almost certainly titanium.

tbtstt

Thanks for replying again Splitpin - very interesting reading!

Sorry, I misunderstood your reply a bit there; But I guess my initial question was a bit vague in that "Group N Impreza" could cover many different iterations of the car. I was looking with my own car in mind (2005 STi - which would be N9?), but it was only as I started to notice that a lot of the more recent Group N cars have a lot of non-standard bits on them I wondered if one particular brand of exhaust was stipulated as a replacement. By the looks of it though a number of manufacturers offer "Group N" components.

As you say, gone are the days when Group N cars were models direct from from the production line.

I was actually looking at the TSL website after I made my last post and see they offer downpipes with ALS friendly cats. It looks like all the "Group N" systems offered all retain the 2.5" bore of the original factory system though, so that bit seems consistent.

stevie1982

iTrader: (16)

have a look on here

you might find what you are looking for

Home - Subaru WRC Spares Ltd

steve

tbtstt

Thanks - but I already spend far too much much time looking at that, the Prodrive and the Litchfield sites!