The downpipe on my 360 needs to come out, as the gasket between manifold and the downpipe is blowing. The garage reckons it's a big job, as they need to raise the engine a bit to get it out. Since the old downpipe has been in there for nearly 10 years, it might be an idea to replace it while they're at it.
They're NLA from Volvo, and pretty expensive from Walker / Bosal, so I've been looking around the usual sources.
I could get this one:
but unfortunately it has a dent in one of the pipes (see closeup):
Is that a problem (flow restriction?) or doesn't it really matter? Being a catalysed 360 there's a fair bit of restriction in the exhaust system anyway, what with the cat, the two silencers, and the spaghetti-shaped back box ...
OK, thanks for that There is a difference in downpipe design between RHD and LHD versions due to the steering column being in the way in RHD cars - but I'd have thought that'd make the work harder rather than easier ... 30 pounds sounds pretty good!
this dent can make the engine a fair bit less powerfull..
exhaust on a atmospheric engine relies on the length/flow of the header and downpipe, the exhaust flow of 1 cyl will help the other cyl by creating a little vacuum, sucking the exhaust flow of the other cyl out. since this dent is in 1 of the 2 not yet connected pipes this effect can't be optimally achieved for all 4 cylinders.
the extra resistance of the catalyser, the two silencers, and the spaghetti-shaped back box aren't the section of exhaust where the function for every engine cylinder is achieved.
i'm not talking major powerloss, let's say 5hp and 10nm
I have a feeling that dent is meant to be there to get it to clear something. It won't make a jot of difference. The flow is already up the spout with the cat, middle and back boxes so a slight dent in the downpipe won't do anything IMO. Yes it might make a few vortices and swirl patterns, but really materially it won't affect the power.
That's a good point, Andy. I just went to the car to have a look. In fact, the downpipe barely clears the front crossmember, I can't get my fingers between one of the pipes and the piece of metal underneath.
Unfortunately, it's a bit difficult to tell from the picture where the "dent" actually is on the pipe, the area with the least clearance is right at the tightest bend on the pipe, whereas on the pic is seems slightly away from that. Remember: LHD car, so no problems with clearance of the steering column.
If the power reduction is negligible then I may go for it (it will be nothing in comparison to the drop due to the A/C I'm sure).
Regarding labour times for the swap - I checked my old bills. I had to have it changed on the GLT when I was away from home - 2.8 hours. A Volvo garage ... and they had to use a Bosal part. Back in early 2007 ...
OK, my new ("dented") downpipe has arrived and ...
... the old downpipe (also a Volvo part) has the "dent" in exactly the same place - even though there's nothing to clear in that area as far as I can see ... Funnily enough, the Bosal part fitted to the GLT doesn't have the dent.
So ... it's a Volvo feature and there for a reason Why ... I have no idea.
There is a difference in downpipe design between RHD and LHD versions due to the steering column being in the way in RHD cars - but I'd have thought that'd make the work harder rather than easier ... 30 pounds sounds pretty good!
All the catalyser stuff is already reducing the power by around 5 - 6 bhp ...
A Volvo garage ... and they had to use a Bosal part. Back in early 2007 ...
