Custom One off z4m specific turbo kit?

[GuidoK]

so what words am I putting in your mouth exactly?
You say
"this is how a turbo intake should look like:"
"I wanted to illustrated what a well made intake looks like,"
"Most high HP BMW turbo builds in Sweden run an intake like that."

I say that a well made intake can look vastly different. I also say that a well made intake may look displeasing to the eye. It can still be well made and not nicely made. So its ugly.

And I point out that on both examples you post there are definately sharp edges, to be exact on the side where the intake runners connect to the plenum. exactly the same as with the ebay manifold.
And that is where flow is the most important. Flow restriction there results in less cylinder filling.
And as for the big flat surfaces, the ebay intake has what it looks like 2 pins inside and you have no idea how strong it really is as you dont know the thickness of the material. All you can see is that it's a used intake and that it has no apparent cracks. So as of yet its still strong enough.
What significant proof do you have that it isnt strong enough? Because I think that is what youre saying. Or am I putting words in your mouth again?
The ad also says its tested up to 30psi. How much boost you're planning to run on an ebay kit?

Originally Posted by Westersund

I never said anything about performance or size, even though the one I posted first is big enough to run 750 hp despite looking smallish.

Maybe the discussion should go about performance or size? I mean that should be key in a remark about 'a well made intake'. The sharp edges of the boxy shape if the manifold are imho of hardly any importance. It's a pressure vessel. The influence of the boxy corners imho dont influence how the air flows from the plenum to the intake runners. How the intake runners are welded to the box do however and that is the same as the ones in your examples. that side also has a flat sheet of aluminium where the round pipes are welded into without any gradual transition. You can calculate a pressure drop on a sharp transition and a gradual transition.
If you look at the cast manifold for example on beedubs car (the ess cast manifold) there they tried to put some gradual transition on where the intake runner enters the plenum. Thats where you want to have good flow as the movement of air from the plenum to the cylinder is a pulsated rush of air (valve opens). But the corners of the plenum opposite to the intake runners are imho of far less importance in the scope of that. It's not a transition in the flow path.
A round corner makes for a structually stronger corner, but as I said, the ad states that the manifold is pressure tested up to 30psi, which is more than I'd ever dare to run with a bolt on kit without compression ratio reduction.

[Westersund]

You can twist and turn how much you want, it won't change the fact that the Ebay plenum looks like a hack job.

[GuidoK]

Originally Posted by Westersund

You can twist and turn how much you want, it won't change the fact that the Ebay plenum looks like a hack job.

I dont twist and turn. In what way do I twist and turn?
Did I contradict that the ebay manifold is ugly? No I didnt. It's obviously a one off made by a hobbyist person in his shed and not by a professional company. It absolutely not finished to a professional seriesproduction standard.
And he's obvously asking too much money for it (like I wrote before)
But I'm not the one that evades a discussion about performance and function.
And I dont make claims I cant proove or back up.
Still I'm pretty sure that no one here can make a tig aluminium intake that looks better though. So you can disapprove by its looks but only because you can buy a nicer looking one, not because you can do a better job.
Otherwise you'd post pictures of that.

In my opinion this kit is too expensive (way to expensive, maybe worth $1,5k) and also for the wrong car.
Not that the z4m isnt suitable for turbo's but the z4m is still a pretty expensive ($15k-30k) and rare car. If you have one, you're not going to fuss about with home made turbo kit that may or may not work (the z4m ecu and electronics are also difficult).
But if you have an old e36 328i worth about 2k and not rare, and this kit would fit that car (and would be less expensive than the current price), a younger guy might have a go. Easy electronics (no drive by wire) and just megasquirt it.

[Westersund]

You don't have to be a singer to tell if someone can't sing.

I haven't really made any crazy claims. Large flat surfaces aren't ideal for a plenum meant for high boost. Agree or disagree? A smoother shape is more desirable than sharp edges. Agree or disagree? I haven't talked anything about ratios or other stuff, that's all your doing.

[GuidoK]

Originally Posted by Westersund

You don't have to be a singer to tell if someone can't sing.

I haven't really made any crazy claims. Large flat surfaces aren't ideal for a plenum meant for high boost. Agree or disagree?

Depends. If its strong enough its strong enough. The manifold is tested to 30psi. So on a kit that makes 8,5psi I'd say its strong enough. I think a home made 30psi turbo setup is pretty radical and maybe a bit too complicated for a diy project.
And not possible on a non build engine...

A smoother shape is more desirable than sharp edges. Agree or disagree?

Depends.
If you have a square box and smoothen the edges the volume gets lower. I'd have to run a CFD model to see if those square edges really restrict flow to the intake runners. And thats way to complicated to do on a fridaynight.
I know enough about thermodynamics that thats way to complicated to predict on rules of thumbs. We're talking about corners and edges that are not in the direct flow path from/at the intake runners as the edges where the intake runners go into the plenum on that ebay intake box are just as square as the edges on the intake manifolds you posted as examples.
Look at beedubs intake manifold. that is also basically a pipe with hard square edges at both ends but the edges at the intake runners are smoothened out. If you're casting a manifold it doesnt take any extra efford or cost to smoothen out those edges at the end. Yet ESS still didnt do that. Why not? Maximize volume? I'm sure the guys at ESS can think of the laymans rule that 'a smoother shape is more desirable than sharp edges' yet they chose not to do that in that spot.

I haven't talked anything about ratios or other stuff, that's all your doing.

I know, and I think on a car forum in a topic on a self made turbo system where there's doubt on the functioning of the parts I think the discussion should concentrate on that. That the box looks like a hobbybob project everyone can see for themselves.

[Westersund]

Which one would you pick for your own car if you had to choose, the Ebay plenum or one of the plenums I posted?

[GuidoK]

Originally Posted by Westersund

Which one would you pick for your own car if you had to choose, the Ebay plenum or one of the plenums I posted?

If they're the same price I'd pick yours. I dont deny that looks arent important. For the first one I'd have to think about the size.

But if it was sized like this:


I'd probably pick the ebay one no matter how polished this one is. Although on the ebay one I dont like the cramped feed point as I wrote.
Plenum ratio should be a minimum of 1.5 on low boost and ideally 2 or so on high boost. So on a 3.2L engine on high boost you need 6,5L or plenum volume.
Some plenums might make 750hp, but who's to say that a similar setup with larger plenum wont make more?
If one or more cylinders get less cylinder fill it can also reduce engine life. And the cylinder fill is really hard to measure unless you have an egt probe on every exhaust valve. A real racecar has that but on a hobbycar that's pretty radical.