DIY Turbo Mainfold Question
 

While planning my turbo build, I looked for cost efficient turbo manifolds. Since I could not afford a FM or BEGI one so i figured the next best thing would be to make one. I'm a novice welder at best but there is no better way to learn then just to drive right in! Its fairly straight forward of a job since I'm just making a log style one but I cannot find much info online about making manifolds. So I have the manifold welded but I could not find the best way to situate the turbo flange. I'm going to be running a T25 turbo so space is less of a concern than flow. I know logs are not the most efficient but its what i have to work with and i want to make it as best as it can be. From what I found online a lot of people recess in the flange into the manifold. This seems like the best option but just straight out? Angle it down? Make a small runner from the manifold to the to the flange? Also after the manifold is finished i have seen some people put it in/ near a fire. The only explanation i could come up for this was to release internal stresses but I really do not know. Is that even neccessary? I will have the exhaust manifold flange decked once its finished but need to finish the turbo flange first. Any insight would be greatly appreciated!

a piece of rectangular pipe that's notched to the round pipe works pretty well and makes it easier.

Or sell that flat flange and pick up one of these. Simply figure out where you want it on the log, mark the inside of the log around the flange. Cut the hole open with an angle grinder. Then weld on the flange.

Definitely recommend this.

Eliminates you having to either notch the flange you have or essentially 'box in' the flange with flat steel.

@shuiend Do you happen to know the outside dimensions of the T2 flange? I can measure my T3 for the differences. Not listed in the link.

​​​​​​​Like the physical dimensions of it? I could take some measurements tonight if need be.

Yes, really just looking for how different <length and width> it is vs the T3 version you use in case I was thinking of cutting off the T3 to put the T2 flange on one of the 2 manifolds I have (that came from you).

YGPM. I will also take some measurements of both tonight for you.

Answered PM... Don't need the measurements!

Wow I wish I would have known about those before lol. That would be so much less of a hassle. Probably gonna stick with the flat flange just because i have it on hand but will definitely remember these. Thanks

Sorry new to the forums, forgot to quote you. But also your saying it does not matter where on the log you put the manifold?

Thanks! Either going to do this or notch into the manifold. Do you think either has an advantage over the other?

I mean it probably does matter some, but won't ever matter enough for what the power a stock motor would handle. I would base it more on where you can fit the turbo, make the downpipe easy, and route IC pipes around AC/PS.

it depends on if you have the space for the turbo to be spaced out or not. (chances are you do have the space)
I wouldn't notch it in too far. you want to leave a nice amount of flange sticking out to be able to surface it (even for down the road when you might need to surface if you lost a bolt and warped it with heat)

I haven't done a notched manifold, is the exhaust stud expected to seal the hole in the flange?
I would expect to notch the pipe deep enough to get a full weld on the flange your flange is going to be sticking quite a bit into the pipe.

Although I don't do log manifold anymore, if I needed to I would source a piece of rectangle tube and go that route. Im sure you could even send a basic drawing to a water cutter and have them cut you a piece of tube with a proper notch in it.

To me, one virtue of DIY log is to end up with the outlet around Cylinder 2, rather in the middle. This gives a lot more room for your downpipe. It's not a balanced flow, but IT"S A LOG. Look at Shuiend's MK Turbo design.

Here is a T2 log manifold that I worked on this weekend. It is AC/PS compatible and does not require cutting up your shelf any to fit the turbo.


​​​​​​​Attachment 230454

The log I made put the turbo in the same location as above. I still got a TD04-20t to spool at 2900 rpm at 11 psi. It was AC/PS compatible and made making the downpipe pretty simple without cutting the shelf at all.

All the exhaust gases are hitting each other in a log manifold anyway (rather than flowing to the turbine), so you're relying solely on pressure differential to get the exhaust gas from the manifold through the turbine wheel. Putting the flange over runner 2 likely wouldn't be any less ideal than centered, and could possibly provide some benefit of having the 2 runner directed at the turbine. All in all, put it where it fits.