Bellmouth vs Divorced Flow Turbo Elbow?

[NoFlex]

Wondering which O2 housing will get better results on an sr20 with a BB t28 turbo. Bellmouth or divorced flow?

[Mile High Silvia]

I run the bell mouth style, just seems like it would flow better.

I'm running s15 bb turbo with gtx28 billet compressor wheel from Pure.

[NoFlex]

Originally Posted by Mile High Silvia

I run the bell mouth style, just seems like it would flow better.

I'm running s15 bb turbo with gtx28 billet compressor wheel from Pure.

I would think so, but i see a lot of people saying dovorced flow is better

[kyle1a2]

Originally Posted by Mile High Silvia

I run the bell mouth style, just seems like it would flow better.

I'm running s15 bb turbo with gtx28 billet compressor wheel from Pure.

What kind of set up are you running with that turbo and what kind of power is it making? I've been thinking about having mine upgraded.

[Mile High Silvia]

Originally Posted by kyle1a2

What kind of set up are you running with that turbo and what kind of power is it making? I've been thinking about having mine upgraded.

I'm running a Isis manifold, tomei outlet pipe, and apex'i exhaust. Aem standalone, map conversion, 18ish psi. Not sure what power I'm making but I'd say atleast 350 with really fast spool. I'm also running water meth injection with a pre turbo nozzle.

[fatduece]

I think you need divorced for internal waste gate and bell mouth for external waste gate. Hopefully somebody who has experience can chime in

[jedi03]

Yup...that is correct...I use bellmouth regardless tho due to strength of the welds and heat soaking

[Mile High Silvia]

I'd say go with the Bellmouth, because the size of the piping is much bigger and will allow better flow. Some divided designs are better than the pic you posted, that one looks like total crap in my opinion

[jr_ss]

Divorced is better. It keeps the wastegate flow from causing turbulence in the exhaust stream. In an ideal world, wastegate flow would be introduced farther down in the exhaust stream.

[5280VertDET]

Originally Posted by jr_ss

Divorced is better. It keeps the wastegate flow from causing turbulence in the exhaust stream. In an ideal world, wastegate flow would be introduced farther down in the exhaust stream.

The OEM S15 turbo is divorced, if that gives you any help. Since Nissan did this, I would assume that if you are using a internal WG you should keep it as well.

[NoFlex]

Originally Posted by 5280VertDET

The OEM S15 turbo is divorced, if that gives you any help. Since Nissan did this, I would assume that if you are using a internal WG you should keep it as well.

Yeah the s15 turbo has a little divorce plate in tge exhaust housing and yes im using the stock internal wg. Should i get a bellmouth since the turbo already has a divorce plate?

[Mile High Silvia]

Originally Posted by NoFlex

Yeah the s15 turbo has a little divorce plate in tge exhaust housing and yes im using the stock internal wg. Should i get a bellmouth since the turbo already has a divorce plate?

Get the Bellmouth, look around and find one that has the biggest piping because turbos need room to breath!


The tomei unit pictured on the left is one of the best in my opinion! I have the same one on my coupe, with a Megan down pipe since it has the flex section. The greddy unit I had before was a Bitch to fit with the solid piping

[Croustibat]

Originally Posted by Mile High Silvia

find one that has the biggest piping because turbos need room to breath!

It is a T28, have you seen how small the wheels are ?

[Mile High Silvia]

I noticed better top end power with my "Bellmouth" style and better spool.

[PoorMans180SX]

Parts Shop MAX has the only proper divided wastegate donwpipe that I've seen.



You need to separate the flow for 10-12in to get a good result. But it WILL improve flow exiting the turbine. I'd say ideally the wastegate would never rejoin the rest of the exhaust.

If you want to buy one of those cheap, shitty, hack parts you posted, get the bell mouth one.

[yzrider450f]

Do we even bring this up?

[fatduece]

Tomei makes a very nice bellmouth. Very cheap too!















I dont mean to hijack your thread op, but doesn anyone know if these outlets are okay to use with aftermarket exhaust manifolds? Just wondering if its gonna hit anything.

[Chernobyl]

Originally Posted by fatduece

Tomei makes a very nice bellmouth. Very cheap too!

Probably not everyone's definition of "cheap", but I really like the Tomei unit I have. High quality part. Recommended.

[Croustibat]

Internally gated turbo = bellmouth. The divorced design you show is crap anyway, it will leak from each side and it joins too soon. Divorced design on that kind of internally gated turbo is idiotic, it really is an item created to steal money from people.

Use a divorced design when the turbo has a divorced design only (like externally gated turbos), and dump either as a screamer or way further in the exhaust.

[Mile High Silvia]

There ya go crustybat! Some people's children.....

[dorkidori_s13]

That divorced outlet shown in the original photo is shit anyways just looking at how it is designed to dump exhaust gasses into the piping itself. The wastegate side enters at a hard angle and would divert wastegate pressure to where it actually creates MORE turbulence due to the outlet being pointed directly at the opposing wall of the piping (causing a direct flow interference).

The Parts Shop Max design keeps the exhaust gasses flowing evenly at the same angle and same direction (basically a proper 2:1 design).

But if you're worried about getting the most out of your T2 series turbo, you're better off upgrading to a smaller T3x series turbo... Pushing 300+whp out of a larger turbo is much easier than pushing it out of a T2x series turbo... Better CFM at lower boost pressure with less wear to the turbo yada yada yada

[Croustibat]

Yeah, big turbos, losts of boost, i get it. gt2560r ? Nope. I run one, i also have a free flowing 3" exhaust, a shiney elbow and a 3" flex downpipe, but it just is overkill. And it takes room; i bet a 2.5" one would flow better as the bends could be smoother...

[Mile High Silvia]

Originally Posted by Croustibat

Yeah, big turbos, losts of boost, i get it. gt2560r ? Nope. I run one, i also have a free flowing 3" exhaust, a shiney elbow and a 3" flex downpipe, but it just is overkill. And it takes room; i bet a 2.5" one would flow better as the bends could be smoother...

My system is super smooth, not too many bends after the downpipe and there's no way 2.5" is better than 3". Just not even a question in my mind. I've owned a few turbo cars that I built myself and I can assure you that the larger piping is the way to go. I'm sure I can find some dyno videos on YouTube somewhere comparing down pipes or exhaust systems. I don't have any dyno comparisons myself but it's just a matter of efficiency. The easier a turbo can breath The better it will perform with less stress from back pressure

[codyace]

In the grand scheme of things, neither setup is going to affect power *that much* to make me go out of my way for one design or the other. Either way you're using a crappy internal wastegate.

IMO the bigger thing, and MOST important thing, is to get the best quality option, as changing that thing is the single biggest PITA in the world. The PBM setup looks nice, but that big ass single piece downpipe/j pipe would annoy me. I'd go as far as to put a v band midway on it on it just to make install easier.


I'm still personally a fan of the OG Greddy J pipes, with divorced housing for guys wanting to stay internal. Never had an issue with them cracking ever, and we've proven to have made some of the better performing setups utilizing them too (at least on the gt28rs/gt2871r/gtx28 setups)

However the 'best' setup IMO would be one of the newer Tomei bellmouths, and then putting an external wastegate atop the factory manifold. This way you eliminate the biggest issue, and that is controlling the stupid internal gate.

[PoorMans180SX]

Originally Posted by codyace

In the grand scheme of things, neither setup is going to affect power *that much* to make me go out of my way for one design or the other. Either way you're using a crappy internal wastegate.

However the 'best' setup IMO would be one of the newer Tomei bellmouths, and then putting an external wastegate atop the factory manifold. This way you eliminate the biggest issue, and that is controlling the stupid internal gate.

Or just buy an EFR and have an awesome internal gate and a V-band downpipe.

[Mile High Silvia]

[PoorMans180SX]

Just an FYI, pre-turbo meth injection doesn't do anything different than post intercooler meth injection, besides corrode everything.

[Mile High Silvia]

Originally Posted by PoorMans180SX

Just an FYI, pre-turbo meth injection doesn't do anything different than post intercooler meth injection, besides corrode everything.

It actually cools the intake air,making it more dense, and thus working the turbo less. It's working great for me and a ton of other people on YouTube.


Check this video out! These guys are like the pioneers of pre turbo water injection!
https://youtu.be/VaKpzgL4b9o

[kyle1a2]

Nice, I might give them a call. Ive got injectors, poncams, tomei manifold and elbow, Power FC and before the car runs, head studs and gaskets. Id like to hit around 325.

[PoorMans180SX]

That is my friend Paul's video, and it did nothing more for IAT's than post intercooler did...