Under and Over SEAC Exhaust system
Under and Over SEAC Exhaust system
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rev-erend

Original Poster:

21,623 posts

314 months

Monday 26th April 2010
quotequote all
For Adam and others who may be considering the SEAC style under axle Exhaust system as opposed to the 400SE style over drive shaft system.

The SEAC has a 3 inch outlet pipe from the centre box - which the divides into 2 X 2 inch pipe, takes a 90 degree left, and a 90 degree right and goes up to join into another 3 inch final outlet pipe.

Here are a few pictures:

As you can see pipe is central and has 2 hangers - one in the centre of the car and another near the tail pipe area (not actually on there at the moment)


Slightly more detailed picture - pipes on the floor (offset just for the photo)- you can probably see I have cheated and had my centre box made very shallow (3.5 inches smile ):


Overhead view:


Side view:


Detailed view of bashing to help get ground clearance in axle frame area:


Upsweep of pipes to tail piece


So, as you can see if is fairly elaborate but would be much simpler if made from a single 2.5 inch pipe .. as that is what is used on the 400/450SE centre box outlet and is all the pipe size that is required.

2 x 90 degree bends and a few feet of 2.5 inch pipe are all that's required. Cost of the parts is about £30 in stainless..

Edited by rev-erend on Monday 26th April 21:34

adam quantrill

11,679 posts

272 months

Monday 26th April 2010
quotequote all
Rev - what diameter is the centre-box big pipe, and the two smaller side-by-side pipes?

Does it go directly under the diff?

It does look simple to recreate in 2.5" pipe, however the section under the diff has been made flatter than a circular cross section so it can be as high as possible to avoid clearance issues further back.

On the SE (and SX) the centre box exit goes off to the side, so the pipe would end up under the driveshaft, so it could be slightly higher and have less chance of catching on anything.

rev-erend

Original Poster:

21,623 posts

314 months

Monday 26th April 2010
quotequote all
adam quantrill said:
Rev - what diameter is the centre-box big pipe, and the two smaller side-by-side pipes?

SEAC is 3 inch and 2 X 2inch.

Does it go directly under the diff?
yes

It does look simple to recreate in 2.5" pipe, however the section under the diff has been made flatter than a circular cross section so it can be as high as possible to avoid clearance issues further back.
yes but bear in mind the SEAC system uses 3 inch pipe - so a 2 1/2 inch pipe will be a little slimmer anyway but it stick down as you say but I suspect it will not be an issue as the centre box is always lowest.

On the SE (and SX) the centre box exit goes off to the side, so the pipe would end up under the driveshaft, so it could be slightly higher and have less chance of catching on anything.

Campbell

2,500 posts

313 months

Tuesday 27th April 2010
quotequote all
Hi Rev

Are you going to replace your rear section, its looking a little rough wink

You should get some thing to match your manifolds...

rev-erend

Original Poster:

21,623 posts

314 months

Tuesday 27th April 2010
quotequote all
No - I have no plans to.

gsx600

2,740 posts

278 months

Tuesday 27th April 2010
quotequote all
adam quantrill said:
Rev - what diameter is the centre-box big pipe, and the two smaller side-by-side pipes?

Does it go directly under the diff?

It does look simple to recreate in 2.5" pipe, however the section under the diff has been made flatter than a circular cross section so it can be as high as possible to avoid clearance issues further back.

On the SE (and SX) the centre box exit goes off to the side, so the pipe would end up under the driveshaft, so it could be slightly higher and have less chance of catching on anything.
I have donethis on mine in steel, comes out of the silencer in the middle straight drainpipe 2 3/4 in I think then a right angle that sweeps up and collects the original 400 style
Works ok and still the silencer is the lowest part and no fowling on suspension or diff etc

AM400

1,196 posts

293 months

Wednesday 28th April 2010
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Is there a rubber mounting on the rear pipe behind that nut? guessing it might be the same as the silencer bobbins?

Got me thinking about changing the over axel pipe on my 400, it looks much easier to put on and take off on the SEAC.

Andy

rev-erend

Original Poster:

21,623 posts

314 months

Friday 30th April 2010
quotequote all
Yes and removal of the rear is very easy apart from the sleved join and thats best slip once off the car.

grahamw48

9,944 posts

268 months

Friday 30th April 2010
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If anyone has a used, but still gas-tight system to fit a 390SE ('standard' type) I'd be interested. Been let down by supplier again. rolleyes

Waynester

6,532 posts

280 months

Saturday 1st May 2010
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It may be easier to fit/remove but ground clearance is reduced a little, especially if your springs are soggy!

adam quantrill

11,679 posts

272 months

Wednesday 5th May 2010
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So I spent a half hour lying on my carpet under the wedge. It looks like the under-the diff option is less appealing.

a) on mine the centre box has a right-angle to the passenger side lading to a flange. This would have to ba hacked off and a new straight bit welded on.

b) under the diff the clearance would be less with a 2 1/2" pipe. So I'd have to have 2 2" pipes side by side like Rev's and even then it's about even. Yhis means having a splitter and collector.

c) It means heating up the diff

d) further back there's a problem getting it up with more bends going towards the rear valance.

So I've thought about it and I'm probably going to get an over-axle pipe made up in bits. This means one more bend than I was planning for but it's only a 125 degree bend over the axle. Total pipe length is about 2m.

Hopefully all the bits will be about a tun and then I get to weld it all together - this time not upside down and I'll have plenty of gas to stave off the rice krispie syndrome!

Incidentally has anyone looked at how these things went on in the first place? It looks like all one piece so the rear suspension wasn't there when it was fitted - or am I missing something? Perhaps it comes out through the wheelarch? Anyhoo if it doesn't come off easily then it's angle grinder time ;^)

JVaughan

6,025 posts

313 months

Wednesday 5th May 2010
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Just catching up ...

I have one centre 2 1/2 inch pipe running front to rear following the same route as the SEAC exhaust.
The bit that passes below the diff hanger has over time been made oval, but it then finishes in a 3" tail pipe, pointing slightly down.