I understand you weren't meaning the wheel, the change in cross section is seen in the collector before the turbo at all. Another method is stepped runners but thats just getting mind flexingly complex. A common mistake is a collector with a huge change in cross section when compared to the runner, this would dampen the strength.
The thing to understand about runner length is the ball park rpm that you'd like to benefit, there's always pulses that can be doing less good but the question is why tune the runner length to an rpm which isn't where you'd like to gain those high power numbers, would we tune to 3500 rpm and forget about 7000 rpm, I think not.
The worst thing about manifolds such as are available is the cheated joints seen is most all of them, these make for power loss when compared to non cheated runners. It's hard to do and why I believe the turbo in the standard area is something to forget about. Usually they are massively cheated off the flange, barely out of the cylinder and the gases are being asked to do something they don't like.
It's hard to do you are right, a lot of conflicting advice and theory as you say even from pro exhaust/manifold manufacturers. It's most likely an impossible thing to pin point but for me the effort has to be there is all areas, runner dia, material choice, collector dimensions, smoothest flowing bends possible, runner length (ball park will do, there is no option) wastegate provision or not, thoughts towards the downpipe off the turbo, correct welding methods, flange transitions etc etc, the list goes on.

That would require a lot of work sir. Ceramic coating would be much easier then.

Absolutely right, i will have some shiny shxx also, and strangely enough it will probably sell better then an well thought/made one.

Have some time left now, so will just make an oem.located manifold, just for fun and see where it ends up. Damping/reflections/sonic behavoir/floefd etc. wont be taking in account with the first layout tho.

Maybe will even make it shiny .

Main problem with the manifold being even if you make everything as theory would say is correct, the only way you'll know is to back to back compare.
Paul

"turbo not in the standard area"

Exactly what I was thinking Nik, GC explained some things to me in person when I first went to him long before he posted on that other thread on here some weeks ago, so I got a bit of a head start.
Iv'e seen stepped headers, it looks to be a promising theory but hard to make no doubt and even harder to get your head round.

Anti-reversion makes perfect sense but I would'nt go out of my way to put something right in the flow path, you must have seen expanded pipe ? old fashioned plumbers technique you could use to the advantage at the headers entrance then the head would be the reversion dam, keeping the csa constant in the manifold and a smoth transition into.

Talking of collectors what do you think of Burns stuff ? The X- design looks good to me.

Paul, I'll supply the 321, the tig and the sandwihges. You get the engine dyno and the engine and we'll have some fun !

Rich

Remco, what was your manifold ID again ?

If I remember correctly, the bends were quite nicely formed.

Talking of shiney, an old saying in my trade it goes : Trying to polish a turd.

:)Yeah,I'm familiar with an expanded tube, a transition in my mind. Still even with a good transition the joint onto the flange is often cheated, look at No4 on the ever popular manifold, that has a transition but is way off the flow direction, loadsa degrees. A reversion step has nowt to do with it. A tube with 1 3/4" dia can't be formed onto a flange to suit our head without a transition.

Burns do the best collectors, its what I have, you could buy two cheap manifolds for the cost of one collector. The X-design will get you in the ball park, Vince will look after you no problems.

Ah, I thought I might of tempted you to post your comparison between oe manifold and yours, you do have that data don't you? Maybe just a simple flow test or possibly a same day dyno comparison?

http://4.bp.blogspot.com/_yWtU9FLaI...600/integrale+16v+Ex+manifold+test+1.JPG

here is a test

Trying to polish a turd, lol.

But for the sample you saw, the bends were ok, but surely far from perfect. The inner dimension was 38 mm, 2,1mm wallthickness so that makes an 42.2mm o/d.

Have some nicer larger radius bends now, so can play some more. Also i very much like the stepped idea, have been thinking about that also, but this is a bit of an grey area.

For the oem i turned the collector(not burns, so not perfect) 45 degrees, that way the famous 4th cilinder actually has some room now. Still it has an slight angle, but not the sharp turn it normally has on the "classic" manifold.

But still an relocation would be best as we know.

Regards remco

You already know the results of the simple flowtests from the oem/paul/tigart i assume?

A test performed by about the biggest idiot I know, I would disregard that.

No, afraid not, I was hoping to be schooled.

Remco, forgive me I'm not sure I've seen your handy work, is there a picture somewhere I might see?

Hi remco, 38 ID is probably the minimum I would like to use, if not too much losses through the bends.

Any pics of your latest one ?

Were getting overlapped here !

That comparison is about as much use as the guy who made it.

sorry for asking, but what is wrong with that test ?
doesnt he know how to use flow bench, or what ?

that is the only test I could find.

The flow benchs calibration is a mile off and the pillock using it couldn't test bath water. What he is good at though is telling you what you want/need to hear, wheel him in here and lets have a go at him :-)

Nik, forget No 4. The 'typical' manifold I bought was disgustingly bad on all four entrys. They had completely missed the flange with the pipe and filled up the gap with weld, almost no attempt to crush the pipe to shape and one exhaust valve from every port was seeing a brick wall. I'll try to find some pictures.

Good thread btw -

Suby dooby thread

It's subaru orientated, (if your familiar with that strange setup! ) It's long with a lot of arguments but bear with it, a good read.

"couldn't test bath water "- Use your elbow don't you ?

ok, thanks for answer.

Been saving this one for a thread just like this . .

No I don't have any datacomparing mine to others. However I do agree that a flow test tells nothing of how it works in real life. Maybe one day someone will do a comparison. Sendo did report 9bhp gains accross the rev range with my manifold though.
Paul

That's a pity, maybe something to set up Paul?

Ok found a picture, this was one of the better ones No. 3 I think, the weld has been ground down a bit but the sharp edge it makes, whooo boy.

Indeed the 38 is the minimum, chose this size because i wanted it to fit with some length underneath the bonnet of the coupe. And people are still not willing to stick their neck out and change alot like for example Guy,you,me would like it to be.

Will make some pictures for you to see soon, not quite satisfied with it now, but should keep the exhaust valves intact for a change.

And i really love the picture of the homemade manifold, hope i will reach that level of craftsmanship asap, lol.

Imagine the inside is as smooth also, hmm.

regards remco

Ahh, ok, i thought you had some interesting results to show. But i only have some results from your dear friend also.

An picture of my ehh playing around was just posted by tricky, dont tell me you just dont love it.

Take a good look at the precision welding, would that not be an nice suprise underneath the cristmastree this year?

Thanks for that - I read it over a couple of hours and now the head hurts.

Looking at the OE manifold - and forgive the state it has been "in storage" the gases coming out of number 4 basically come out into a walled top open chamber with flow coming in from above



the other 3 cylinders are dealt with in a different manner



surely number 4 cylinder is a pretty bad way to join the mix even by OEM log manifold standards? This is why I had a custom manifold made in OE position but have no back to back testing. Am I right in thinking though these manifolds were used to over 400bhp in WRC type integrales?

Remco,

Whilst I'm harsh (I can see how that might be the way I'm taken) there is one thing I'll not diss and thats DIY effort, if you've made anything I'll not disrespect the effort, it's very much the way I am, I like to make stuff too. Post some pics please.

Nik

I will post some pics dont worry. Dont mind if you would be harsh though. Most that i made is not on my wish list.

so soon, very soon when i can get to the pictures i will show you(laptop charger died).

Regards

remco