Divided turbo manifold, shared port exhaust. Ideas ?
 

I'm pondering building a divided turbo manifold to take full advantage of the Divided turbo I've ordered through Bryan. I'm stumped though as the best way to divide the exhaust ports since the renesis has the shared center exhaust port.
The possible configurations I'm considering are:

-Combine the front and back exhaust ports for one tube and give the shared port its own. This would give both sides of the turbine a pulse for each firing. Since the shared port is smaller, I would run that one to the outside half of the turbine. The combined main ports to the inner half. This seems to somewhat defeat the purpose of dividing them at all, but is an option.

-Combine the shared port with the front or back port. Again favoring the inside turbine inlet for the higher flow combination. This would give the inside a pulse for every firing, but would divide the main(front and back) pulses between the inside and outside of the turbine housing.

-Save myself the work and just make a singe tube manifold. Knife blade the center of the flange.

Any opinions, input or advice? :)

Come on, where are all our turbo geeks? How dare you guys have better things to do on a sunday! :lol:

Do you have a twin scroll snail?

I think a twin scroll on the Renesis is rather difficult and useless.....the center shared exhaust ports is smaller (like you said) and flows less air.

Making the center port it's own runner would be useless given it's lower airflow, or it's benefits wouldn't be worth the extra work.

If you insist on doing it, I would divide the center port into two runners at the flange and then collect each split side into it's respective front or rear rotor runner......

Also remember if you do build a twin scroll manifold you need twin external wastegates (one for each divided section, since it's essentially two manifolds). This also makes packaging the manifold REALLY difficult, I think you are overestimated the amount of working space you have to fit a manifold and downpipe in the space for a front mount turbo, let alone a twin scroll manifold....

Actually its pretty common to just join the two seperate wastegate runners just before the wastegate and still use a single large wastegate. It pollutes the seperate runners slightly but only in so much as the gases are able to go up the wastegate runners and back down. This allows the pressure to equalize between the two sides of the manifold, but the exhaust pulses are still largely seperated.

As for packaging, the room for the extra manifold piping would be to the right(drivers side) of the area for the downpipe anyway. I think by angling one runner down and the other up I can get both runners through the engine mount. Though this would make the mainfold bolts a bit of a bear to get at.

What would you expect to gain from doing this ?

Faster spool. The RX-7 guys are spooling 1.00A/R divided housings as quick as .84A/R undivided housings simply from having a twin scroll housing with one rotor going to each volute while getting higher numbers due to the larger housing. I have yet to see a large enough turbo on this website to warrant all the work to do this with the exception of the one I currently have and even then I went with a 3 into 1 manifold and a undivided .96 housing. A little laggier but not so bad to make me want to divide the center port and make a 4 runner manifold. Space is tight around the right side engine mount....its really tight.

Chris

Wait, you're going to run the downpipe down the drivers side? So it's going to cross in front of the engine? How is it going to join with the rest of the exhaust system?

If you want to do it right, you need two wastegates IMO. There is a reason that top manifold fabricaters like Full Race do it that way.

I'm not trying to say not to do it, just I think this is a little overly ambitious. The room is stupid tight and I don't think the benefit is worth it unless you are running some massive A/R turbine.

My turbo is a T04E 60-1 P trim with 1.00 divided.

I dont know I'll go as far as dividing the shared exhaust port. While it wouldnt be too hard to have a fin protrude from the manifold into the casting to split the port, it would have to be pretty thin to avoid causing a restriction. And then I'd be worried about it staying put when things start glowing :Eyecrazy: Making a custom engine mount isnt beyond me, but only if I thought the benefits justified the work.
I honestly decided to turbo the car out of shear boredom. I was looking for an excuse to do some welding and machine work, so I'm not afraid to try something different just for the heck of it :)

Currently though, I think I'd probably just merge the front and center ports and then run a seperate for the rear port. I know this is slightly polluting the seperate pulses, but since the shared port exhaust flow is less than the mains there should still be some benefit to singling out the rear pulse. If I can even split the diffierence in spool time between a divided and undivided manifold I'd call it a win.

Nah, its going down the passenger side. Was just saying once I get the manifold pipes out from under the engine there is plenty of room ahead of the engine for the dual pipes without taking any of the space for my downpipe. Its not like the downpipe has to pass through the engine mount with the mainifold. There is room to run it over it or under it.

It's not the motor mount area that is your biggest hurdle, it's fitting 3" diameter downpipe to the motor mount in the first place....you have a small space the manifold up-pipe and downpipe both need to run through, along with a radiator hose, AST hose, OMP, OMP lines, and wiring harnesses.

I"m going to try to run downpipe over all that and then go down behind the motor mount and manifold. The way I'm eyeballing it the manifold and downpipe will never be on the same plane.

hmmmm, I can't visualize that right now. Over the radiator hose? There isn't enough room, and you'll run into other stuff.

I was thinking about this the other day, but don't really have the know how so I kinda dropped it. If it works I want to see it, and maybe buy this manifold from you.

It would go under the radiator hoses, but still be above the level of the manifold.

Gonna have clearance issues with the OMP and APV (not to mention cooking them if you did manage to squish the pipes up enough to get them through).
Forget about using the Sohn adapter at that point (which is far more important than a divided housing).

Modern turbos just don't need this kind of help.

It would just be easiest and best on this engine to just collect them into 1 port and not use a divided manifold. Keep it simple. The RX-7 guys can do it differently because it's easy. They have 2 runners. The peripheral exhaust ports also open far more abruptly and do very well when they stay separated through a divided housing. Divided housings on 13B are a performance gain over a single. I just don't see the advantage on the Renesis though.

hmm..so MM and rotarygod say dont bother. Hard to argue :)
Maybe I'll keep it simple this time around but take some measurements so I can tinker with building a more exotic manifold to install at a later time.

Thanks for all the input guys :)