Gauging Interest: External Wastegate Header

[GTEASER]

Ah okay. I'll probably save up for the ets header then and have one of the wg blocked off if possible. I love the sound haha

 

I think there is a good engineering reason why you don't just want to block off one and use only a single wastegate on that header, but I can't remember right now. Talk to ETS about that.

[Sm00veM00ve]

I think there is a good engineering reason why you don't just want to block off one and use only a single wastegate on that header, but I can't remember right now. Talk to ETS about that.

Oh okay I'll definitely be emailing/talking them then just to get all the facts straight before I make my decision, thanks G

[Rutchard]

Considering each wastegate controls the exhaust coming out of half the exhaust ports, blocking off one would probably lead to a lot of boost control issues. I can't imagine it working well at all.

[s2baru]

THIS^. Being equal length is unique for us and its more of a push&pull of exhaust exits 1-3, 2-4

Stopping one side would in my mind ruins effiency that's why the 6star .ake me scratch my head slightly when you see 6star one how its exits each cylinder but then runs into one tube to reach the turbo then the kickout for the wastegate.

[fahr_side]

The stock header is pretty nice all things considered. When you look at how small the stock turbine and housing are, it's well-sized for the job. The only times I have run into boost creep issues has been with our TD05H-18G and 20G conversions using the stock housings (as BNR does). Coupled with a free-flowing catback exhaust we see boost running away at higher rpms as the wastegate doesn't flow enough to keep turbine speed down.

In most of these cases we were able to improve things a great deal by porting the exhaust housing aggressively. In one case the owner had an exhaust with active (valved) mufflers, so he could keep boost at our S mode targets (1bar) by closing the valve. In S# where target was 1.3bar he could open the valve up and not creep.

 

The ETS header above is a nice improvement on the stock item with moderately sized primary tubes, and it maintains the 1.5-scroll arrangement of the original. This would be great for an owner with (say) a BNR 18G or 20G turbo who doesn't mind either some extra noise at higher loads or extra work plumbing the twin gates back into the midpipe. You cannot block the exhaust flow from two cylinders and wastegate only the other two. Boost control would be a nightmare, EGT would skyrocket on the cylinders that aren't wastegated, and they would make less power than the other two, which would put some nasty torsional loads on the crankshaft. Bad things would happen.

 

The 6-star item below does drop the number of gates required to one, but introduces some pretty awful compromises. For scavenging and even pulses at the turbine, you want to combine the exhaust flow from cylinders 1 and 2, then 3 and 4, as they are in phase with each other. The 6-star item joins 1 with 3, and 2 with 4, which are out of phase. Then there is the issue of the extremely short primary tube length, which in a way mimics the cast manifolds from previous generations. IMO this is a step backwards, would cause higher EGTs and require more EGBP to drive the turbo to the same pressure ratio.

[Sm00veM00ve]

Yup that is what I was starting to figure out and that makes sense. Didn't think about how it could effect the exhaust flow to that extent.Thank you all for all the information. I do plan on getting a 20g so this header wouldn't just be For a stock turbo. I honestly haven't really heard of that 6star header.. but sounds like it would be best to stay away from that option.

[fahr_side]

Yup that is what I was starting to figure out and that makes sense. Didn't think about how it could effect the exhaust flow to that extent.Thank you all for all the information. I do plan on getting a 20g so this header wouldn't just be For a stock turbo. I honestly haven't really heard of that 6star header.. but sounds like it would be best to stay away from that option.

 

The stock VF-54 exhaust housing is I think more of a restriction than the manifold, so until you move to something bigger, replacing the manifold is something of a band-aid to a boost control problem you may or may not run into.

 

Just FYI, the stumbling blocks to power in this platform are a little different from the 4th gen that preceded it.

 

1. The turbine housing is a P18, about the same as the earlier VF-40 item in having a roughly 7.5cm2 nozzle area. Where on the 4th gen the housing is a universal Subaru fitment, common to the Impreza platform and with OEM and aftermarket housings available up to 10cm2, the VF-54 flanges are unique. Not even the new WRX shares these flanges. The largest turbine that fits 'nicely' into this housing is a TD05H or maybe a 'small' GT30 wheel, AKA the GT29 wheel. Beyond that the geometry is horrible and leads to poor spool and not much better flow.

 

2. The exhaust cams on the 5th gen LGT motor are 1mm shorter on lift than on all other 2.5 liter turbo Subaru motors. They are more like oldskool EJ205 cams in profile. If you've ever read about oldskool 'hybrid' engines, built from EJ255 blocks and EJ205 heads, and how they fall down at high revs, you know what that means.

 

The above two factors mean that fitting larger compressors, that flow more air than the exhaust flow can cope with, only decreases efficiency and increases both EGBP and EGT. Cramming more air into the engine does not help when there is so much restriction to exhaust flow. I have tried both 18G and 20G compressors on the same car, with the same TD05H hotside, and gotten exactly the same airflow, power and 100~200kph times out of both. For this reason I would advise you to stick with an 18G wheel, to enjoy the same power as the 20G with better response. At this sort of power level you will not see much if any improvement from an aftermarket catback, and using the stock catback will pretty much obviate any boost creep problems.

 

If that's not enough power then go to a combination of larger manifold with non-stock flange, larger exhaust housing, larger turbine, and at least the STi exhaust cam. Since you need to pull the motor to swap the cams, this is point you build the shortblock.

[Sm00veM00ve]

Yeah I'm not quiet ready to build the motor haha. I'll be looking into all that as the year goes on,however. I have heard about the 18 vs 20g route and you're right. The gains between both aren't that significant..

This was my plan: full nameless tbe, bigger tmic (hopefully grimspeed comes out with their big tmic that will hopefully fit..), 1000cc injectors, dw (or other) fuel pump, and a 20g. I was directed to BNR's page and they have a billet 20g with the td05 turbine wheel that's a direct bolt on for stock location. This was pretty appealing seeing as I wouldn't have to send out my own and it has pretty similar flow rates to the dom 1.5xtr which is a common upgrade for the sti's (my friend went this route..turbo was very impressive..) I am however still looking into turbos to learn more about them and what would be best.

I guess the tldr would be I'm looking to do most of the main bolt-ons I can without building the motor. Later on down the road when i have more money I'll probably go full retard with a built motor,and bigger turbo

[fahr_side]

Don't get me wrong, on a 4th gen or WRX the 20G usually does about 20hp more than the 18G. The 5th gen is held back from that by the short cams and lack of available 8cm2 housing. An 18G does really well on this car. Typically we will see around 300whp on 98RON or 330whp with meth from the billet wheel or just slightly less with the cast one.

 

The other factor I forgot to mention is the small hood scoop. Even with an 18G the stock one heatsoaks badly on prolonged pulls and the RacerX intercooler efficiency is not vastly superior because the flow through the scoop is so restricted. Going larger you really need a FMIC.

 

A Dom 1.5XTR is a bit of a step up from a 20G btw. Full 71mm compressor that flows at least 2lb/min more and superior, though similarly sized turbine. If I upgrade from my billet 18G, that's where I'm going.

 

Sent from some electronic device.

[GTEASER]

I'm glad I bought that motor a few months back, all this info is helping me formulate my build. Thanks guys!

[fahr_side]

I'm glad I bought that motor a few months back, all this info is helping me formulate my build. Thanks guys!

 

 

Feel free to ask questions!

 

 

Sent from some electronic device.

[legaced]

I've had an ewg on my last turbo car and i have to say, it s fun as hell at first but it does get old quite fast.

[Deadrick20]

I can go an entire day without getting into enough boost to engage the EWG. Doesn't really get old if you drive somewhat sensible. I don't need 100% throttle while driving through town. I think people forget that the EWG is controlled by boost. Currently my EWG doesn't open until 17psi, my right foot can accelerate the car and keep it at around 15psi and all you hear is the exhaust. I swear some people think that the EWG just screams with any touch of the gas.

[GTEASER]

^^Great knowledge to share. You may have changed my mind on EWG's.

[m1cha3l]

^^Great knowledge to share. You may have changed my mind on EWG's.

 

Speaking from personal experience.

 

- Plumbing ewg back in to muffle the noise makes it less likely to open up.

 

However;

 

- EWG opens up a lot quicker with a lwfw even when its plumbed back in.

 

- Cold weather speeds things up too.

[Sm00veM00ve]

Sorry wrong thread

[acumenhokie]

Speaking from personal experience.

 

- Plumbing ewg back in to muffle the noise makes it less likely to open up.

 

However;

 

- EWG opens up a lot quicker with a lwfw even when its plumbed back in.

 

- Cold weather speeds things up too.

 

and when you switch to e85 it becomes almost impossible to keep it closed.

[Kb1Legend]

Is there any interest in these turbo manifolds? I'm thinking about making one myself for a friend of mine.

[jackal8788]

There was not enough interest previously to justify a custom run, which was my original intent with initiating the thread. I ended up just purchasing one from Six Star Motorsports in Illinois. If you have some fabrication skills though, making one might be a good option because the Six Star design leave some things to be desired in terms of flow characteristics and the ETS dual WG manifold doesn't seem to be available and was not cheap.