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.

You tried Lolocost? I seem to remeber they do pieces.

HTH,

James

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.

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]

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.

get behind your local exhaust center with an hack saw, the two times ive asked iv'e not been turned away.................

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.

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

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

---

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

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.

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

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.

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]