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Bord Warner S200SXE DIY twin scroll questions

5K views 4 replies 3 participants last post by  titter 
#1 ·
Hey guys,

I'm itching to do more advanced custom fabrication this spring/summer (all of it: twin scroll EL header, rotated up pipe, downpipe, intake, mating with my WAIC system). I just wanted to get some input to make sure that I have supporting mods and won't shoot myself in the foot with turbo selection.

Please don't give me the "why not just get a twin scroll setup" or "why not use a normal Subaru turbo". As I said, this is for a real fabrication challenge and to prove to myself that I can do it. Not to mention I'm not down with dropping 3k+ for a twin scroll rotated setup not even including the turbo when I can do it all for <$1.5k.

I'm eye-balling the Borg Warner S200SXE turbo because it has terrific reviews and a LOT of people using them successfully in other cars. Other people who have done this type of setup report having full boost at <3600rpm which is not much worse than the VF39 I have and with nearly 100whp more and a much better torque / hp graph all around. They're cheap too at <$700 for the ones I'm looking at.

Compressor Map:
Text Line art Drawing Triangle Parallel


Core Options:
Text Font


Turbine Housings:
Text Font Line Number


My setup:
-08 WRX
-Stage 2 IAG Shortblock
-Stock Heads (to be ported)
-Stock fuel (I realize this will need to be upgraded, but how far?)
-Water to Air Intercooler setup
-EBCS
-Turbo Back (3" to quad tip)
-TGV/EGR/Air Pump deletes
-EWG (obviously will have two)
-Stock Gears
-Stock Clutch

My setup is free flowing to/from the engine with a short intake path with no heat soak due to WAIC.

I'm looking to keep building my daily driver and although I don't mind spooling a little bit later, I'd prefer to stay in the <3800k area. I drive hard, but smoothly and don't do stupid shit like launch regularly/downshift abruptly or drop the clutch on gear changes. I do my best to rev match and take care of my car but do hit the red line from time to time and accelerate rapidly.

1). What things is my setup lacking to safely run 350-375 whp (with a low boost, safe tune and eventually work from there)?
2). Am I going to run into issues with the Turbine wheel size. I realize it's a bigger turbo but even the TD05-20G type turbos have one that's 10mm smaller in diameter (albeit this is a twin scroll setup which spools better).
3). How do I go about picking the core? (one has a larger compressor than the other, but how to weigh against what it will do in my car?)
4). How would one pick the Turbine Housing? I have an understanding of what A/R means and how it affects flow, but have no idea how to connect those concepts to my Subie to pick the best option?
5). How much wood could a woodchuck chuck If a woodchuck could chuck wood?

Thanks in advance! ;)
 
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#2 ·
1) youll need injectors and fuel pump. pump doesnt matter. go as big as your budget allows providing it will fit in your tank obviously. the walbro 255 (GSS342) will get you there. 1000cc or 1300cc injectors depening on whether you want E85 or not. you can go bigger if you plan to chase more power in the future. stay oem clutch and trans. most people will go right ahead and grab a new clutch to hold the extra power but this is what in turn usually breaks the tranmission. the new clutch grabs extra hard and sends all the force through the gears thus breaking them. you are 2008 so your fine. the 05-08 LGT got a beefy 5 speed and 2008 onward they gave the wrx the same one. so its stronger than the 02-07 wrx 5MT which break all the time from adding too much power. maybe use those fab skills to make yourself some blast plates. its just essentially some steel plates and grade 10 case bolts.

2)what issues do you think you would run into? do you mean like tuning issues? or mechanical issues? are you putting a bigger wheel into a smaller hosuing? are you making some frakenstein turbo? as a generailzed statement: bigger wheel = more lag but more power up top, little wheel = less lag but more power down low. there shouldnt really be any "issues" if you are buying a new turbo. if its a used turbo... well then you could have multiple issues like an unbalanced shaft.

3) i am not familliar enough with BW turbos to help you pick the core. i can tell you though a 62lbs/min turbo is pretty big. you are only a little smaller than a GTX3576 according to the measurements. honestly i would be suprized if that SXE200 can reach full spool before 4000rpm. actually the bigger core (part# 12769905003) seems to be about the same size. the Gen 2 GTX3576 is 67lbs/min, 58mm inducer, 76mm exducer & 68mm turbine. it can push waaay more then 400whp.

4) twinscroll? out of those 4 choices... go with 1.00 for a nice balance. essentially, the smaller the A/R the more spool and transient response. since its a DD dont go any bigger than 1.00. the blouch domintors are 1.02 a/r and we all know how amazing their twin scroll dominators are on the street.

5) 12
 
#3 ·
Hey titter, I'll comment below. Thank you for your response!

--------------------------------------------------------
1) youll need injectors and fuel pump. pump doesnt matter. go as big as your budget allows providing it will fit in your tank obviously. the walbro 255 (GSS342) will get you there. 1000cc or 1300cc injectors depening on whether you want E85 or not. you can go bigger if you plan to chase more power in the future. stay oem clutch and trans. most people will go right ahead and grab a new clutch to hold the extra power but this is what in turn usually breaks the tranmission. the new clutch grabs extra hard and sends all the force through the gears thus breaking them. you are 2008 so your fine. the 05-08 LGT got a beefy 5 speed and 2008 onward they gave the wrx the same one. so its stronger than the 02-07 wrx 5MT which break all the time from adding too much power. maybe use those fab skills to make yourself some blast plates. its just essentially some steel plates and grade 10 case bolts.
No e85 where I live so that's not an option. Not sure I would want to run it either, I will likely build a meth injection system eventually not to make significantly more power but to make safer power under WOT.

2)what issues do you think you would run into? do you mean like tuning issues? or mechanical issues? are you putting a bigger wheel into a smaller hosuing? are you making some frakenstein turbo? as a generailzed statement: bigger wheel = more lag but more power up top, little wheel = less lag but more power down low. there shouldnt really be any "issues" if you are buying a new turbo. if its a used turbo... well then you could have multiple issues like an unbalanced shaft.
All those options are for purchasing the same new turbo. It comes with several core/housing options and I'm struggling to pick a direction. My worry is the turbine size in terms of spool, I mean the fact that all normal location turbos have an exducer that's I believe 51mm or so for the big ones, this one is quite a bit bigger (almost 10mm) my worry is my motor being able to spool it effectively. I'm not worried about tuning, been there, done that, will do again (and better).

3) i am not familliar enough with BW turbos to help you pick the core. i can tell you though a 62lbs/min turbo is pretty big. you are only a little smaller than a GTX3576 according to the measurements. honestly i would be suprized if that SXE200 can reach full spool before 4000rpm. actually the bigger core (part# 12769905003) seems to be about the same size. the Gen 2 GTX3576 is 67lbs/min, 58mm inducer, 76mm exducer & 68mm turbine. it can push waaay more then 400whp.
Keep in mind it's a twin scroll turbo, so 1). It spools quite a bit faster and 2). Very high torque numbers are happening long before target boost is reached.
Also I got the 3600-3800 number based on other people who have ran this turbo on a Subie.

Once again, keep in mind, this is a full blown Equal Length setup with Individual uppipes that mate to a T4 twin scroll flange to the turbo (not like a regular Subaru divorced up pipe).

I'm leaning toward the smaller size, I am not so sure I want to go above 400whp, I'd rather run safely at lower boost levels (the benefits of a colder charge and less pressure on the internals with still a lot of flow sound nice). Of course this might eventually change, but this turbo will certainly let me go from a lot of power, to A LOT more power if I wanted to in the future (or if I want to play at a track for example).


4) twinscroll? out of those 4 choices... go with 1.00 for a nice balance. essentially, the smaller the A/R the more spool and transient response. since its a DD dont go any bigger than 1.00. the blouch domintors are 1.02 a/r and we all know how amazing their twin scroll dominators are on the street.
Thanks! I was thinking that or the smallest one to help with boost, but if the slightly higher a/r ones are effective on the street I will lean that way for a better balance.

5) 12
 
#4 ·
Seeing as you'll be utilizing a generally large hotside and are going twin-ewg I would say go smaller than you might think. EWG will allow those excess gasses to bypass the smaller hotside and prevent overboosting, especially with twin 44/45mm EWGs.

For fueling I'd stay away from the Bosch 044 and DW parts as I keep reading horror stories about how they fail while driving, and even with a fuel pressure gauge has caused failure to the engine. I second Titter about running a Walbro 255, or if you want a twin pumper for extra headroom. My engine builder said when I shoot for 400whp I may need a bigger pump or a twin 255 for a daily monster, but highly suggested new lines and rails on top of ID1000/1300. The twin pumper may not be for you at those levels depending how you want power to come on (I wanted full boost before 3800, and holding it to redline ~8k). Also unless you can tolerate a VERY loud pump, stay away from the Aeromotive pump. One last thing on the fuel side is have you thought about hardwiring your pump, aka bypassing the FPC? A Fuel Pressure Gauge is highly recommended when modifying the fuel system regardless of the path you choose, in case your pump fails or whatever.

As for the turbo build itself, you know the rule of thumb, larger = slower spool. But if you know the casting is overly thick with a smaller wheel then you could machine the compressor housing to fit the slightly larger wheel inside thus creating tighter tolerances, more efficiency, and save some turbo weight. Have you thought about a custom compressor wheel? I've gone through a handful of turbo mags/articles/etc and read that in drag racing they changed out a 11 blade wheel for a 9 blade that flowed the same in that custom housing I mentioned and bam, same power but it came on sooner and flowed up top the same. Yes it's probably more than you may want to get into but I thought you might want to check it out. I do not have links as I was in school for engine building at the time and my memory for names can be horrific lol.

*EDIT: Just found and it sounds like a very similar build path. I'd recommend Speed Density as well as it's more forgiving than Speed Velocity (MAF). Not sure how read up you are on the blending of MAF/MAP but it's something I'd definitely check out.
 
#5 ·
you'll need to commit to water/meth before choosing your turbo. if your wanting to get close to 400whp only on pump gas, you might want the bigger core. if your 100% going with WMI then the smaller core could get you there maybe (again not 100% sure as im not familiar with BW). underworking a big turbo is no more useless than overworking a smaller turbo. using your wastegates to bleed off the extra boost from the big turbo is more of a bandaid then an actual fix. you want your turbo to operate within its efficiency range for maximum smiles :)
 
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