Turbo Manifold Construction

[vex]

So I'm checking around on the internet for different ideas on how I want to build my turbo manifold and so far this is one article I really think does a good job on getting a good deal of information down your throats.

It's in two parts:
http://autospeed.com/cms/A_2604/article.html
http://autospeed.com/cms/A_2605/article.html

Now originally I was planning on using a tight mandrel bent 2" U bend or two for construction of the manifold, but they offered quit a good case for using steam pipe butt weld pieces. I don't believe I'll need tons of pieces to make it work, but i also would like to have a very nice manifold made (I'd like to make it myself) that is quite tight fitting and for the price of the 2" U bend, I'm not sure it would be worth it to use butt weld pipe like that. I'll check around to see what I come up with.

All in all I'd like to see some pointers on turbomanifold construction, maybe even an RCC article about it.


I've checked out alot of the manifolds sold online, and well... they seem to be more manifold than is really needed for anything really.

So any pointers before I start ordering these parts on monday?

[vex]

Simple question: I'm thinking of having the wastegate actually on the bottom of the manifold (i've only seen the wastegate allocated to the top portion of the manifold for ones being sold online) which would allow for easier adjustment of turbo pressure as well as provide a cleaner install. Is there any reason I should not construct a manifold like that?

[classicauto]

You can use those "butt weld" fittings - most places normally sell them as "els" (at least up here in Canada) - they'll be alot more heavy duty then tubing. Although tubing will work fine also.

Really depends on you space restriction, the els will be easier to make tight bends (and save alot of cutting vs. tube) but will require more welding etc........its a matter of preference or what the space dictates in most cases.

I don't see a problem with mounting the wastegate at the bottom, except for the fact there isn't much physical space there to put it between the manifold, subframe, and right frame rail. Most tap their runners into the top, then merge them at the gate to the rear of the manifold, making the gate easily accessible from under the car....

But more of a concern then being able to muck with the wastegate afterwards (because in reality, you shouldn't have to) should be where and how the runners are tapped into the primaries. Keep them near the turbo inlet for the best boost control. But alot of locations can work really.......

[vex]

Originally Posted by classicauto

You can use those "butt weld" fittings - most places normally sell them as "els" (at least up here in Canada) - they'll be alot more heavy duty then tubing. Although tubing will work fine also.

Really depends on you space restriction, the els will be easier to make tight bends (and save alot of cutting vs. tube) but will require more welding etc........its a matter of preference or what the space dictates in most cases.

I don't see a problem with mounting the wastegate at the bottom, except for the fact there isn't much physical space there to put it between the manifold, subframe, and right frame rail. Most tap their runners into the top, then merge them at the gate to the rear of the manifold, making the gate easily accessible from under the car....

But more of a concern then being able to muck with the wastegate afterwards (because in reality, you shouldn't have to) should be where and how the runners are tapped into the primaries. Keep them near the turbo inlet for the best boost control. But alot of locations can work really.......

Thanks for the info!

I was thinking about having the primary runners be split right after they come out of the exhaust port... maybe within the first 3 in (of course, this is all dependent on what actually does happen and how much room I have). I was then contemplating that the flow would be equal and instant as soon as the wastegate opened. This would keep the pressure from spiking and provide a very responsive wastegate location. Is my view skewed with this?

[classicauto]

I'm sorry but I don't understand what you're describing

Split the primaries? They are seperated ("split") with regards to front and back rotors until they merge at the wastegate runners (unless you have two gates)....did you mean merge them 3" from the exhaust port?

[vex]

Originally Posted by classicauto

I'm sorry but I don't understand what you're describing

Split the primaries? They are seperated ("split") with regards to front and back rotors until they merge at the wastegate runners (unless you have two gates)....did you mean merge them 3" from the exhaust port?

(yes)
hmmmm....
think of a mirrored image on how the turbo connects. Instead of joining the runners perpendicular (for a wastegate) run another lower pair of runners angled down to join the wastegate. So you'd have an upper pair that looks roughly like > and a lower pair that looks like > but they're angled up and down respectively to give the best flow possible. I'm just thinking out loud on how I'd want to join the pieces and how far apart to make the join.

I imagine a smooth transition between the two would yeild the best results, however I wonder if that would cause un-needed turbulence in the exhaust flow. I suppose it doesn't really matter as it's the temperature and pressure difference which drive the turbine, and turbulent flow: flows faster than lamnir, but I just can't seem to figure out how the exhaust will work in the manifold.

[classicauto]

I think I understand what you're saying, and if I understand correctly, its not a great idea. Given that they'll diverge (from primaries into the wastegate runners) at a shallow angle, you'll *probably* have OK boost control - but placing them (the wastegate runners) that close to the start of the primaries is completely backwards with regards to boost control.

Tapping the runners in as close as possible to the turbine will get the best results. Ideally, on the outside of a bend.

Also personally, I wouldn't want that many merged/welded pipes directly at the entry of the manifold at that spot will get ALOT of heat. Not to mention if I'm envisioning this correctly, you're basically doing a >- right out of the engine on either port, yes? If so, the inside corner where those two pipes merge is going to get so hot from the exhaust pulses that it may not survive long - especially if its welded.

As an example of the above, on my dual exhaust system, the Y pipe shows massive colouration at the spot where the exhaust splits. And thats after its been out the engine, through the turbo, through a cat, and spat back towards the mufflers. Having a Y directly out the engine like that would amplify that heating wildly.

[vex]

Originally Posted by classicauto

I think I understand what you're saying, and if I understand correctly, its not a great idea. Given that they'll diverge (from primaries into the wastegate runners) at a shallow angle, you'll *probably* have OK boost control - but placing them (the wastegate runners) that close to the start of the primaries is completely backwards with regards to boost control.

Tapping the runners in as close as possible to the turbine will get the best results. Ideally, on the outside of a bend.

Also personally, I wouldn't want that many merged/welded pipes directly at the entry of the manifold at that spot will get ALOT of heat. Not to mention if I'm envisioning this correctly, you're basically doing a >- right out of the engine on either port, yes? If so, the inside corner where those two pipes merge is going to get so hot from the exhaust pulses that it may not survive long - especially if its welded.

As an example of the above, on my dual exhaust system, the Y pipe shows massive colouration at the spot where the exhaust splits. And thats after its been out the engine, through the turbo, through a cat, and spat back towards the mufflers. Having a Y directly out the engine like that would amplify that heating wildly.

I see your point. I'll have to think about that. So if I move it closer to the turbine inlet should I have a steep angle or a shallow angle? I imagine that the turbo is going to indeed get quite hot with higher boost levels (I'm currently aiming for 5psi) which would adversely affect the the life span of components.

I think no matter what angle I go at the welds are going to see some large temperatures. suggestions on minimizing the temperatures to the welds?

[classicauto]

Don't really need to worry about the welds, its just that the position of the merge you were suggesting would make much more likely that they'd break down - they'd be getting pulsed by (effectively) a blow torch while under pressure. A typical joint or butt weld wouldn't have that much heat at the weld itself just due to positioning. Thats the only reason I said that - the position of the weld.

As for merging the wastegate runners, a shallow angle would be best, fairly basic really. Imagine that when the wastegate opens, you want the flow to be as easy as possible from the engine to the valve seat. That said, my a-spec manifol merges its wastegate runners on the inside of the turbine entry, at roughly 80 degrees to the primaries. It works fine, and they've only utilized a couple of the "rules" for good response/boost control.

But space will be the largest restricition and will likely dictate alot of the design.

[vex]

Originally Posted by classicauto

Don't really need to worry about the welds, its just that the position of the merge you were suggesting would make much more likely that they'd break down - they'd be getting pulsed by (effectively) a blow torch while under pressure. A typical joint or butt weld wouldn't have that much heat at the weld itself just due to positioning. Thats the only reason I said that - the position of the weld.

As for merging the wastegate runners, a shallow angle would be best, fairly basic really. Imagine that when the wastegate opens, you want the flow to be as easy as possible from the engine to the valve seat. That said, my a-spec manifol merges its wastegate runners on the inside of the turbine entry, at roughly 80 degrees to the primaries. It works fine, and they've only utilized a couple of the "rules" for good response/boost control.

But space will be the largest restricition and will likely dictate alot of the design.

Thanks for the pointers. It's helpful.

I'll see what transpires as I build it up. I'll see if I can't get more pictures for it and what not. I'll even attempt to do flow testing on it (but I doubt that will be possible with current state of affairs).

[vex]

Alright, I'm looking at mcmasster-carr for some schedule 40 but their prices are expensive. I'm getting roughly 13 bucks for the 3 in bend (90*) and 50 bucks for the 2 in bend (90*). This is for 304. Is there anyway I can reduce the price? Could I go with schedule 10? Is there another store or shop that sells this pipe for cheaper? I don't mind buying the 3 in bend, but I'd like to keep it down to maybe 5 bucks a bend, maybe a little more?