stainless exhaust - tubular manifold?

[jon]

Some time next week I'm getting a stainless exhaust made for my Acclaim, sick of patching up the cracked downpipe on the old one.
I'm planning on a slightly larger diameter pipe and easing off some of the bends under the car, should help the gasflow as the original exhaust design looks quite restrictive. I'm not after boy racer loudness or anything like that, more the fit and forget solution, but as its being custom made I might as well specify something that might improve performance a little.
Was wondering if its worth getting a stainless tubular manifold made at the same time? it does seem that most of the restriction to the gasflow is where the 4 outlets go into 1 within a few inches, and as I'm spending a fair bit of cash on the pipes I might as well spend a bit more and go the whole hog, its going to need some new mounting points/hangers if I do go down this route, and it will be 4 pipes with a bend vulnerable to cracking rather than 1 (4 flexi sections perhaps), could be more trouble than its worth or could make a real difference to the performance, I just don't know yet.
so has anyone got some experience of something similar on an Acclaim that they could share? stop me making an expensive mistake perhaps, or suggest a design tweak that might be an improvement?

Will have a nearly new rear silencer with the early 3 point flange fitting going spare when its all done if anyones interested.

Jon

[Jacorosso]

Hi Jon

It's Jamie the guy who had the seat belt plug off you.

My car has a stainless exhaust so your more then welcome to have a nose and see how they did mine

[Barry Acclaim Guru]

Hi
the manifold on the acclaim is not a bad casting with a long center branch in the casting . The cracking you are suffering from may be caused by the engine void bushes on the torque rods, and the support bracket on the down pipe. I had a simple system made for herculese a few years ago, with an immediate improvement in performance, but quite a lot louder.
hope this helps
B

[Tim_343]

considered the whole manifold thing hen i had mine done but the guy explained to me that to just make that bit with all the manufacturing of it )because you have to get each pipe exactly the same length or one becomes more dominant than another and so on losing back pressure in the cylinders its quite complex for what it looks like on the surface ) it would cost as much as the rest of the system if not more so what they did with mine was just cut off the top of the mild steel one where it bolts onto the manifold and welded it to the stainless one and hey presto lol also its the silencers that restrict the gas leave the diameter standard get a power flow stainless system as it allows increased gas flow and not to much louder mines got one and it goes like shite off a shovel lol hope that helps.

[logicaluk]

heres my thinking on the acclaim mainifold





as you can see its a good size & looks like it should breath quite well if matched to the head, so they added a restriction.



im going to open this up to match the pipe when i build my exhaust. imgoing to see what boxes & pipes the exhaust stockist has that might be made to fit. i would recomend using two boxes as the one box system on rupert is rarther annoying on long trips.

Dan

[ferny]

You may find that's there to increase the speed of the gases, so don't be too surprised if you gain a small amount of top end but lose a chunk of torque.

[logicaluk]

i was thinking somthing like that this morning. ive got plenty of exhaust manifolds to play with so im not worried about wasting one. if acclaimaxhausts had been in better supply i would have probabley just incrased the size of the down pipe a little maybe changed the first box then gone back with the standard system.

[logicaluk]

the mk1 bosal exhaust ive got matches the manifold at about 40mm, now we need some clever person to work out if thats going to be big enough. i think its a little small 48 mm would be the next size up, 51mm after that.

[jon]

Thanks for all your comments on this, the car is now booked for friday week.
I'm now planning on sticking with the original manifold and pipe diameter, but easing off the bends under the car and getting a more free flowing silencer. Based on a combination of the advice on here and what the exhaust manufacturer told me.
I have checked the bushes and they appear to be in A1 condition, as is the bracket, I suspect the cracking is purely down to the age of the exhaust, which could well be the original as the car was laid up for a couple of decades in a heated garage before I got it (still had the original tyres then too, they have since been changed for some that don't feel like they're made of oak) its the mk 1 exhaust which I understand was prone to cracking just there anyway.
Just got to choose a tailpipe design (so much choice!), think I'll go with something that looks fairly standard rather than the 'steal me' drainpipe type.