craig1410
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| posted on 28/7/04 at 08:56 AM |
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Mild steel exhaust bends needed.
Hi,
Where, other than custom chrome and demon tweeks can I buy mild steel pre-bent tubing? Specifically I need 1 5/8" (41.28mm) 16swg tubing which
has been pre-bent into the tightest possible radius without seriously affecting flow rate. This is the size of pipe used on the output of the Rover
V8 SD1 manifold which I am using. I can find places which supply stainless pipe of this size but can't find anyone who does boring old mild
steel...
Cheers,
Craig.
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James
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| posted on 28/7/04 at 09:36 AM |
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You tried Lolocost? I seem to remeber they do pieces.
HTH,
James
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craig1410
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| posted on 28/7/04 at 09:55 AM |
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Thanks guys, two good suggestions there. Yes there is a Partco in my home town so I'll try them. I'll also check Lolocost's website
tonight.
Cheers,
Craig.
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ChrisJLW
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| posted on 28/7/04 at 10:09 AM |
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http://jetex.co.uk/jetexwebsite/index.html
Should link to both Laser (if you want some bling bling s/s) and Jetex exhaust parts.
Ooops, just realised you're after 1 5/8", oh well might be good for future feference
[Edited on 28/7/04 by ChrisJLW]
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craig1410
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| posted on 28/7/04 at 08:06 PM |
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Syd,
I tried Partco but they only do the flexy stuff now. You know, the convoluted hose type stuff. I'm not sure how far this sort of stuff can be
bent but I think I read a spec on one brand of it and it could only achieve about 45 degrees in a length about 10 or 12 inches long. I need tighter
turns than that but I'll nip in to Partco on Saturday and take a look at it anyway.
Another thought I have had which I'd appreciate your opinions on is whether it is feasible/sensible to consider using a sort of exhaust
"plenum chamber" with a three bolt flange connecting to the manifold and then just take the exit pipe in whatever size I want and at
whatever angle is most convenient for me. The Rover V8 isn't the easiest car to tune the exhaust on anyway so I won't lose too much there
but I wondered if a plenum chamber would flow better or worse than having a number of quite tight 1 5/8" bends followed by a 2 into 1 collector
(1 5/8" in and 2" out). I was thinking of using a piece of 4" or 5" 16swg pipe with the ends closed off as a plenum and just
cutting holes in it to suit the input and output pipes.
Have any of you seen such an exhaust system and is it worth considering?
Cheers,
Craig.
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Jon Ison
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| posted on 28/7/04 at 08:51 PM |
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get behind your local exhaust center with an hack saw, the two times ive asked iv'e not been turned away.................
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craig1410
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| posted on 29/7/04 at 09:19 AM |
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Syd,
Yes maybe it is a local thing or maybe the person I spoke to just didn't know what I was talking about... I'll try the Glasgow branch of
Partco at lunchtime today. I'm also going to try Viking International in Glasgow who are a big wholesale exhaust supplier.
As suggested above, I may also try a local tyre and exhaust centre and see if they'll give me access to their scrap bin.
Cheers guys,
Craig.
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Bob C
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| posted on 29/7/04 at 09:33 AM |
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Hi craig,
I got some "mild steel weldable elbows" from a local steel supplier in 3mm wall 44mm ID, I can find out who if you want but it
wasn't hard to find.
4-2-1 exhaust won't help on the V8 due to weirdo firing order - I did my own bizarre thing on my old V8 with 4 tubes going to the back pairing
2&4 6&8 1&5 3&7 - all these pairs are on 3/5 beat. I'm not convinced this is much cop but it seemed the best I could do within
the space constraints on the mx5
cheers
Bob
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mackie
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| posted on 29/7/04 at 12:12 PM |
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quote:
Originally posted by Bob C
Hi craig,
I got some "mild steel weldable elbows" from a local steel supplier in 3mm wall 44mm ID, I can find out who if you want but it
wasn't hard to find.
4-2-1 exhaust won't help on the V8 due to weirdo firing order - I did my own bizarre thing on my old V8 with 4 tubes going to the back pairing
2&4 6&8 1&5 3&7 - all these pairs are on 3/5 beat. I'm not convinced this is much cop but it seemed the best I could do within
the space constraints on the mx5
cheers
Bob
I think it ends up being 4-2-1 because that's what the standard manifolds give you which is I believe what craig is using...
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Bob C
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| posted on 29/7/04 at 12:44 PM |
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Hah - I thought the standard manifold was "everything into one big pipe" - more like the plenum idea above - but it's a long time
since I looked at a standard SDI manifold......
cheers
Bob
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craig1410
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| posted on 29/7/04 at 04:28 PM |
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Yes it's 4-2-1 but each side of the "V" has a different method of combining the 4 into 2. The nearside combines 1-5 and 3-7 which I
believe is optimum but the offside combines 2-4 and 6-8 which is not. However, the SD1 manifolds are considered much better than the previous P6
manifolds which is why I am sticking with them. Someday I might build a pair of tubular manifolds...
Cheers,
Craig.
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Bob C
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| posted on 29/7/04 at 10:39 PM |
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Interesting - same cylinder combinations I went for! rover are as daft as me then..... seriously though if you lookat the firing order it's the
best of a bad job..
Bob C
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craig1410
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| posted on 30/7/04 at 12:05 AM |
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Bob,
Yes I see now what you mean. I had assumed (incorrectly) that Rover had just compromised the performance of the offside manifold to accommodate an
exhaust heated airbox but you are correct, it is a better system due to the exhaust pulse pattern.
For those who can't see what we are meaning, here is a brief explanation:
The firing order is 18436572 with 1 being front left (viewed from drivers seat) and 2 front right. A "text book" engine would fire each
primary header pipe once every 8 sparks (10000000) and each secondary header every 4 sparks (10001000). In the case of a side-pipe silencer system
each silencer would get an exhaust pulse every 2 sparks (10101010)
However, on the Rover V8 the firing order is a bit wierd due to the fact that it doesn't use a flat-plane crankshaft and so this optimum layout
is not possible. The best compromise yields a system where each primary is still fired every 8 sparks (obviously) but each secondary is fired on spark
1 and 6 (10000100)which gives a 5 spark spacing on one half of the cycle and a 3 spark spacing on the other half. The 3 spark spacing doesn't
give the exhaust system quite as much time to dissipate the gases although this is made up for to some extent by the 5 spark spacing on the other half
of the cycle.
The effect on the silencer is similarly compromised as you get a pulse pattern of 10010110 for every 8 sparks on each side. A balance pipe can be used
to link the two sides to help balance out the assymetry and improve performance but I expect this is a tricky system to design effectively and pipe
lengths will be critical to success.
By the way I have decided on how to approach my exhaust design after some head scratching tonight. Rather than combine my two secondary pipes (1
5/8" inside the engine bay, I am going to bring the secondary pipes through the bodywork and turn towards the back of the car before I combine
them into a 2" pipe using a collector before feeding the silencer.
This is primarily because I can get a tighter bend using 1 5/8" pipe and not having the collector in there, but it should also benefit
performance by having longer secondaries. I've found a company in Glasgow (Silencer Distributors Limited) who stock Bosal exhaust components
including bends. Hopefully they can help me out.
Cheers,
Craig.
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craig1410
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| posted on 30/7/04 at 06:49 PM |
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Hi,
Just to let you all know, I think I've found the thing I was after. I visited SDL today and got a Bosal "Welding Bend" (Part number
263-638) which is basically a 90 degree bend with a bend radius of about 4" (centreline radius) and a pipe outer diameter of around 42mm. They
only had one in stock but have ordered another 7 for me which should be here on Monday. They are only £3.70 or so each so are much cheaper then the
likes of Demon Tweeks although these are not mandrel bends and do have some degree of narrowing evident (not much though).
Remarkably, when I arrived, the sales guy just told me to look around the warehouse and see if anything they had was suitable. I wish I'd known
about them earlier because they have all shapes and sizes of silencer just hanging there and it would be very easy to find a silencer which was ideal
for a Locost using any type of engine. Excellent resource for any other Locost'ers in the Glasgow area.
Cheers,
Craig.
 
Bosal Welding Bend
[Edited on 30/7/2004 by craig1410]
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