rusty_wingnut Posted January 17, 2011 Share Posted January 17, 2011 For my lightly hotted up 2ltr S1 engine, I wish to build a new exhaust manifold to improve the performance a bit. The engine already has a few little tweeks which have helped but the exhaust ports and manifold are very restrictive and none of the branches an equal length. I know folk will say fit a V8/tdi etc but I wish to retain the original engine but give it some almost "period mods" to make it go a bit better, mainly I am aiming to have enough grunt to pull 7.50s and OD. I have no problem designing the manifold and have read about calculating the length of the primaries based on exhaust opening and engine rpm. I am going to go for a simple 4-1 manifold and link into a modified down pipe. I am struggling to source small bore tubing to make it out of though! Realistically due to waterways the exhaust ports can only be opened up to 30mm. Can anyone suggest a source for pipework in that bore size that I can bend on a decent quality pipe bender? Cheers Quote Link to comment Share on other sites More sharing options...
ian_s Posted January 17, 2011 Share Posted January 17, 2011 how about something like this: Merlin Motorsport 1.2 mm wall thickness, i think 1 3/8" OD should be fairly close to what you want. 1 1/4" would be closer, but they dont seem to list it. Ian Quote Link to comment Share on other sites More sharing options...
Vit rich Posted January 17, 2011 Share Posted January 17, 2011 I get all mine from a local exhaust fab company, ive got about 4 meters of 35mm stainless sitting on the rack at the moment, shame your not closer otherwise i would have sold you some of that. Try ebay, theres plenty of exhuast components on there aswell. Rich Quote Link to comment Share on other sites More sharing options...
zoltan Posted January 17, 2011 Share Posted January 17, 2011 Can anyone suggest a source for pipework in that bore size that I can bend on a decent quality pipe bender? Cheers Pipe benders for thin wall tube tend to be very very expensive mandrel benders. You could try sand bending if the diameters are smallish if you have access to oxy acetylene but there is masses of skill involved in this Try Elmdon Metals for tube http://www.elmdonmetals.co.uk/ Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted January 17, 2011 Share Posted January 17, 2011 Rather than sand fill it with molten lead to prevent collapsing, following the relevant safety procedures of course and when its cooled you can bend it as if it was a solid bar, then with a blow lamp run the lead back out. Quote Link to comment Share on other sites More sharing options...
landmannnn Posted January 17, 2011 Share Posted January 17, 2011 I doubt if you will ever get enough from it to pull 750's on overdrive though. Quote Link to comment Share on other sites More sharing options...
zoltan Posted January 17, 2011 Share Posted January 17, 2011 I am going to go for a simple 4-1 manifold and link into a modified down pipe. Why 4 into 1? Normally this will produce more top end power than low to midrange, is this the characteristic you want? Plus making the collector can be more problematic Quote Link to comment Share on other sites More sharing options...
longlandy Posted January 17, 2011 Share Posted January 17, 2011 Rather than sand fill it with molten lead to prevent collapsing, following the relevant safety procedures of course and when its cooled you can bend it as if it was a solid bar, then with a blow lamp run the lead back out. You dont use lead the metal used for this melts at the same tempature as the boiling point of water and has very little in the way of adhesion .I cant spell it but is seracast serabend Quote Link to comment Share on other sites More sharing options...
dirtydiesel Posted January 17, 2011 Share Posted January 17, 2011 You'd be better making your manifold out of weld elbows as the manifold will be less prone to cracking, stronger and easier to weld up. As regards design a 4-2-1 with equal length relativley short primary's, into long secondary's would probably give the best results. Quote Link to comment Share on other sites More sharing options...
Ratty43 Posted January 17, 2011 Share Posted January 17, 2011 Cerrobend, I'm not being smart but I was interested enough in what you were talking about to go looking for it. Sounds a damn sight simpler than sand. Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted January 17, 2011 Author Share Posted January 17, 2011 I doubt if you will ever get enough from it to pull 750's on overdrive though. you'd be suprised, with comp pistons and a new cam it will pull 7.50s happily enough, even pull away it second, just needs a few extra bhp to make OD work comfortably. thanks for the advice, chaps, I am making final adjustments to the CAD model to try and equal out the primaries as much as possible. Cheers Quote Link to comment Share on other sites More sharing options...
longlandy Posted January 18, 2011 Share Posted January 18, 2011 Cerrobend, I'm not being smart but I was interested enough in what you were talking about to go looking for it. Sounds a damn sight simpler than sand. I use it for making low volume press tools as you can use a master/original panel to cast off, just made a batch of parts for a porsche 356 using this method Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted May 27, 2011 Author Share Posted May 27, 2011 well I took DirtyDiesel's advice and bought a selection of elbows and pipe, fabricated some 6mm flanges and went for the 4-2-1 design. I spent a whole weekend cutting and welding pipe and elbows and the result is a manifold with 2 seperate flat mating faces that haven't twisted, with both 1&2 and 3&4 linking into each other and then into a big collector to link into a 2a downpipe.And it worked! The engine runs cooler on the back cylinders now and holds its power for longer. It also noticeably quicker on pickup. Quote Link to comment Share on other sites More sharing options...
MECCANO Posted May 27, 2011 Share Posted May 27, 2011 We need pictures Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted May 30, 2011 Author Share Posted May 30, 2011 oh go on then The packaging of the engine is tricky as underneath the exhaust manifold is the exhaust rockers, and you need to be able to get the cover off still, ideally witohut removing the manifold. I have just about managed it but you have to be really careful with the cork gasket. I know the welding isn't perfect but it is suprisingly hard wleding round things Quote Link to comment Share on other sites More sharing options...
mickeyw Posted May 30, 2011 Share Posted May 30, 2011 Nice bit of fab there Dave Quote Link to comment Share on other sites More sharing options...
MECCANO Posted May 31, 2011 Share Posted May 31, 2011 Thats awesome, very retro-esk! What did you paint it with? Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted May 31, 2011 Author Share Posted May 31, 2011 It was painted with Frosts manifold paint (only one type listed in their catalogue. It has peeled off some of the galv where I haven't 'keyed' it particularly well but I'm not fussed. Thanks for the comments chaps, I didn't hold much hope of it working tbh, just making the flanges took long enough - holesawing through 6mm steel isn't easy, but I'm lucky the old man has one of those really old quality pillar drills. I'm just pleased it works and we managed to keep it all straight throughout the welding process. The only thing I forgot was a bung for the lambda sensor for the Meqasquirting Quote Link to comment Share on other sites More sharing options...
cackshifter Posted June 2, 2011 Share Posted June 2, 2011 Just need a nice period supercharger now driven with double vee belts, like a Shorrocks....I'll get my coat. Nigel Quote Link to comment Share on other sites More sharing options...
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