Turbo Compatibility

[dr20t]

See this is the thing that often perplexed with when people (on this forum and others) say the vf52 supports ~20psi to redline on 98 fuel.

The turbine wheels share the same dimensions on the vf37/36/48/52. And the comp wheel from the size should do about 350hp max. Without having a compressor map, its hard to say definitively, but the turbine wheel itself should not theoretically be able to keep up with the exhaust flow of the 2.5 litre engine at higher rpm.

Would be keen to see a log from someone who has a vf52 on a ej255 to see what the airflow curve looks like. I'm still not convinced the vf52 could actually hold to redline on a 2.5 like so many claim.

The twin scroll housing will be better than the single scroll as its the larger a/r internally. The separated exhaust pulses will also help with reducing some of the inefficiency.

Don't get me wrong - still a good turbo for very very little change (on a post face GT). So not knocking them - just confused over the claims.

One idea I have that would definitely assist in managin this backpressure on a vf52 sized turbine wheel - weld the internal wastegate shut and run an ewg of at least 44mm size (or at least dual 38mms for twin scroll).

What does this have to do with choking the turbo? Everything. By sizing the ewg(s) large enough that you can control the amount of exhaust flow that moves around the turbine wheel, you are more effectively able to control pre turbo back pressure (to a point of course). This means you could extend the theoretical flow limit of the turbine wheel at a certain boost pressure by modulating the pre turbo back presure through one (or two in the case of twin scrolls) large orifices pre turbo.

Infact this is one way to also maximise efficiency of a given turbine housing without going up to the next size (if someone is worried about losing spool for example). Something I'm toying with at the moment

Mick

Mick

[andy_mac]

Not a bad idea actually. Would like to see the difference an ewg makes. Seems to be semi common over in the states
Been toying with the idea of just moving up to a real turbo but kinda like the challenge of getting a good result out of what i've already got sitting around. But then if going to the effort of swapping in a new block and all that its probably better to just get a real sized one.

[dr20t]

Not a bad idea actually. Would like to see the difference an ewg makes. Seems to be semi common over in the states
Been toying with the idea of just moving up to a real turbo but kinda like the challenge of getting a good result out of what i've already got sitting around. But then if going to the effort of swapping in a new block and all that its probably better to just get a real sized one.

Totally see your point and I respect that. Just be prepared for some headaches and swearing if you want this.

Its a tough one as sometimes experimenting is more fun and yields better results once you get it right.

From memory you were looking at a holset turbo? I reckon go down that path. A hx35 or hy35 or hc35i will be a great combo in twin scroll on a 257. Use a big twin scroll housing like at least 14cm^2 for efficient use o that holset turbine wheel.

[dr20t]

Also I doubt most people in the states moving to ewg are doing it for the reasons I mentioned. Particularly given the low boost pressure they tend to run on the vf's

For comparison, vf37's and 36's are generally run at 22-24psi on ej207's but only 20psi on the 2.5's. this plays to my theory around backpressure choking the 52mm turbine wheel with the larger displacement.

I'm a big fan of lower backpressure, bigger cams and more boost.

[andy_mac]

Yea its pretty much this one or a holset. Like the challenge of getting good numbers out of something small but fitting a holset is a pretty cool project too, a good challenge for the old welding/fabbing skills atleast.

We get HRC ones over in NZ. HRC 35-2 is what i've been looking at. Same guy that made the hybrid one i've got now does them. Think from memory he uses the standard turbine, turbine cover and maybe the comp cover and works some wizardry on the rest of it, just released his prototype for the next stage of them with his own chra and comp cover. Another guy over on CS reckons he was easily hitting 20psi by 3k with it on a fairly standard 2.5 motor. Probably not wise for engine longetivity but pretty impressive nonetheless.

[shav]

Hey lads, been following on this little discussion for a while now.

Out of curiosity, what is the next best turbo after VF52 that will make a tad more power than the 52 will, works well enough with the auto trans, and is bolt on for a stock 2.5L with supporting mods like TMIC, 3 port, TBE etc?

[andy_mac]

TD05-16g/18g seem to be what the US lot go to after the 52.

BNR make some cool ones that keep the OEM compressor outlet for those that need it.

http://legacygt.com/forums/showthread.p ... 19177.html

[shav]

TD05-16g/18g seem to be what the US lot go to after the 52.

BNR make some cool ones that keep the OEM compressor outlet for those that need it.

http://legacygt.com/forums/showthread.p ... 19177.html

Thanks Andy. As far as what I want out of it, I was hoping it would give me much stronger mid to top end without sacrificing too much bottom end. I can handle a bit of extra lag but yeah, it needs to still be drive-able.

[dr20t]

Kinugawa Td05-16g for up to 200awkw

18g for up to 220awkw

[vinshonz]

interesting thread, got a td05-18g in my wrx 20psi makes 198.5kw (i think different dyno gives different results)

[mpoli]

Personally Ive been using this thread to learn about turbos for subaru.
It maybe a bit old and miss a few but has a huge list of turbos that would suit 2.5l boxers.
http://www.wrxtuners.com/forums/f95/wha ... ing-20013/

A decent 16G should be enough ie Blouch Big TD05H-16G. I know with my AVO450 i get plenty of boost at high rpm but spool time suks.
I would be choosing the turbo based on driving style first. Aim to get more lb/min flow but try to keep close to stock spool rpm.

[dr20t]

interesting thread, got a td05-18g in my wrx 20psi makes 198.5kw (i think different dyno gives different results)

18g wheel is good for at least another 3psi - that's where the additional 20awkw comes from

Personally Ive been using this thread to learn about turbos for subaru.
It maybe a bit old and miss a few but has a huge list of turbos that would suit 2.5l boxers.
http://www.wrxtuners.com/forums/f95/wha ... ing-20013/

A decent 16G should be enough ie Blouch Big TD05H-16G. I know with my AVO450 i get plenty of boost at high rpm but spool time suks.
I would be choosing the turbo based on driving style first. Aim to get more lb/min flow but try to keep close to stock spool rpm.

Haven't read the thread but turbo tech has alot of misinfo out there. With advancement in technology and tuning over the last few years, alot of the old "rules" or norms have been debunked.

There is a hell of alot that goes into choosing the right turbo for your application and its not as easy as picking a hp number and going for it. Alot of variables.

However with oem turbos now able to support close to 200awkw on Subaru's (and up to 250awkw on evo's for example), with very little if any mods to make them fit, there is often no point in changing to aftermarket turbos unless you're chasing big power.

There are multiple turbo myths and rumours that I can personally disprove - example - a larger turbo will add lag. I can guarantee to get a td05-16g spooling better than a stock vf46 on a post facelift GT a still make 30-40 more awkw. Guaranteed. On either 98 or e85 but with 98 would be a minor spool improvement and it would be substantial on e85.

Comes down to the setup and tune. And that is why I'm hesitant to recommend a turbo until I know someone's goals or aims. In most cases though, I'd suggest the smallest turbo that would achieve the desired power level without the risk of choke, surge, or preturbo egbp.

[jarrenowen]

i've been following this too and on the same boat as shav, want something a little bit more than the vf52? Maybe to push 250-260kw tops, ball bearing and billet wheel, but has to bolt up to factory topmount location, in looking i've found billet wheels for vf52 rebuilds and possibly ball bearing vf52 as well, i think BNR looks like good turbo's without compromise of spool, as i still want low end spool, any other alternatives?

[vinshonz]

interesting thread, got a td05-18g in my wrx 20psi makes 198.5kw (i think different dyno gives different results)

18g wheel is good for at least another 3psi - that's where the additional 20awkw comes from

im not game enough to try 23psi on a stock ej255
well its been 3 years of trouble free driving

[shav]

Love the way you talk turbo's Mick. Gets me all moist....

I've seen the Kinugawa TD-05 16g's on ebay for a decent price. Would you recommend there or elsewhere? Also 7cm or 8cm?