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Discussion Starter #42 (Edited)
I recently had the car fined tuned to suit this awesome replacement panel air filter called Sprint Filter and here is the current boost pressure on 93 Oct.



I got a feeling this turbo likes an intake upgrade.

OEM filter tune vs Sprint Filter tune:


The only intake modifications I've done are:
Tomei turbo inlet
AVO airbox hose (this does improve the boost a bit, but I lost the graph)
Sprint Filter replacement panel filter
 

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Nice, thanks for sharing!

For comparison, below is a vdyno and boost curve from my previous '16 WRX with the FA20DIT (twin scroll, ball bearing turbo). The only real power mods were a flex fuel tune, GS TMIC & GS EBCS. This is with the stock intake, downpipe, & exhaust.



This run was in 3rd gear on E50 fuel (~96 octane) because of the poor quality 91 octane here in California. The 91 tune has the same boost curve, but is significantly down on power. The ethanol allows for more aggressive timing thanks to its added knock resistance and cooling properties.

The boost could come on even sooner (especially with an aftermarket downpipe). However, the tune was conservative, intentionally limiting torque/boost below 3,000 rpm, to help preserve the weak rods. Direct injection turbo engines are notoriously prone to bending rods at lower rpms thanks to excessive cylinder pressure combined with knock & pre-ignition (LSPI) susceptibility during low speed, high load conditions. The tune begins ramping boost & torque up around ~3,500 rpm.

The FA20's tiny Garrett MGT2259S turbo certainly runs out of steam sooner than the VF56.

I made a gallery of a few stock block, turbo, and fuel system FA20s pushing 400+ whp on ~E50-E60 fuel. Very impressive for just bolt-ons. Shows a promising future for the next gen STI.

400+ whp stock block & turbo FA20s
 

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Discussion Starter #44
I am sure it must be nice to run on ethanol, afterall timing makes a responsive engine and certainly helps out at the top when boost tapers down.
 

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I am sure it must be nice to run on ethanol, after all timing makes a responsive engine and certainly helps out at the top when boost tapers down.
The timing up top is key to making power on the FA20.

Unfortunately, it's rumored that 91 octane here in California is closer to 89-90 and it has little knock resistance. I was down at least 80 peak hp on 91 and the power drops off a lot sooner :(

You can see the huge power difference at the same boost levels.



The great thing about the FA is that the stock fuel system is capable of supporting up to E60. The HPFP starts to stick at higher ethanol contents due to lack of lubrication. All that's required for flex fuel on the FA is Cobb's $600 flex fuel sensor. The stock fuel pump and injectors are fine.

Despite that, I still ended up with an STI with the old EJ257 :lol:
 

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So, which do you prefer? The FA20DIT or the EJ257?
I 100% prefer the FA20DIT with a tune because I have access to ethanol fuel. The stock tune or aftermarket tune on 91 octane leaves a lot to be desired.

It's hard to beat new technology and the response offered by the direct injection, higher compression ratio, and low mounted, twin scroll ball bearing turbo. The FA20 also improves the electronics (wideband O2 sensor, intake manifold temp sensor, oil temp sensor, fuel pressure sensor, 2 knock sensors placed for "better" detection along with an improved knock control strategy, etc.). Not to mention the added bonus of 30+ mpgs on regular fuel. I managed better fuel economy on E50 with the FA20 than I do on 91 in the STI.

The FA20 isn't perfect though and doesn't do well on 91 octane. So if you're stuck with < 93 octane fuel then the EJ257 is probably the better choice. The EJ257 also has higher power limits at this time due to the forged rods and port injection. But like you, I prefer more streetable, responsive builds that maximize the area under the curve. I'm not one to seek monster power numbers. I prefer a nice flat torque curve.

To be a fair comparison though, I'd really like to see how the EJ257 does with a twin scroll setup like yours. That could potentially sway my decision in the other direction given the added displacement.

I also wouldn't mind driving an EJ207 powered car that revs to 8k rpm :) I imagine that would be my choice (EJ207 > FA20 > EJ257). I'm interested to see what the next gen STI offers.

Obviously, the rest of the STI is better than the WRX (drivetrain, brakes, steering, suspension, etc.), which is what ultimately brought me to the EJ257.
 

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Discussion Starter #48
I 100% prefer the FA20DIT with a tune because I have access to ethanol fuel. The stock tune or aftermarket tune on 91 octane leaves a lot to be desired.

It's hard to beat new technology and the response offered by the direct injection, higher compression ratio, and low mounted, twin scroll ball bearing turbo. The FA20 also improves the electronics (wideband O2 sensor, intake manifold temp sensor, oil temp sensor, fuel pressure sensor, 2 knock sensors placed for "better" detection along with an improved knock control strategy, etc.). Not to mention the added bonus of 30+ mpgs on regular fuel. I managed better fuel economy on E50 with the FA20 than I do on 91 in the STI.

The FA20 isn't perfect though and doesn't do well on 91 octane. So if you're stuck with < 93 octane fuel then the EJ257 is probably the better choice. The EJ257 also has higher power limits at this time due to the forged rods and port injection. But like you, I prefer more streetable, responsive builds that maximize the area under the curve. I'm not one to seek monster power numbers. I prefer a nice flat torque curve.

To be a fair comparison though, I'd really like to see how the EJ257 does with a twin scroll setup like yours. That could potentially sway my decision in the other direction given the added displacement.

I also wouldn't mind driving an EJ207 powered car that revs to 8k rpm :) I imagine that would be my choice (EJ207 > FA20 > EJ257). I'm interested to see what the next gen STI offers.

Obviously, the rest of the STI is better than the WRX (drivetrain, brakes, steering, suspension, etc.), which is what ultimately brought me to the EJ257.
Yeah, I agree with you there. FA20DIT feels nicer to me.

And I look forward for your own EJ257 twinscroll setup. There are many options out there, but you can probably see now why the VF56/58 are appealing (more than just being rare).

That being said, the easiest way to go twinscroll is to get Blouch XTR 1.5 twinscroll. I had a talk with Wlliam Knose (Delicious Tuning) and he told me the turbo will make good power and its fine on stock shortblock - but we have to keep the torque down to protect short block. He also told me, it will be less responsive too - but that's the trade off and maybe it isn't an issue at all especially if Ethanol is accessible. If I have a built short block, then it makes sense to give 1.5 twinscroll a go. If that's not enough, well, there is always that Owen Development twinscroll turbo (which I am sure will be epic expensive) - if stock location is favored over rotated.

EFR twinscroll looks tempting though.
 

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Another VF48 vs VF49 comparison I found:



EJ257's VF48 - single scroll, journal bearing
EJ207's VF49 - twin scroll, journal bearing
 

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Discussion Starter #50
Another VF48 vs VF49 comparison I found:

Image Link


EJ257's VF48 - single scroll, journal bearing
EJ207's VF49 - twin scroll, journal bearing
Ahahahaha. You've been looking at Advanced Sports Engineering Lab facebook page eh?

Yes, the VF48 is a pathetic display.

And Subaru knows it.
 

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Discussion Starter #51
A good and interesting watch comparing the 2.5L WRX STI, S208 and the RA-R by Top Gear Hong Kong.

 

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A good and interesting watch comparing the 2.5L WRX STI, S208 and the RA-R by Top Gear Hong Kong.
Thanks for sharing. I enjoyed the video, but my only complaint is that there's not enough engine/exhaust sound! Too much talking and not enough driving.

It's really too bad that we didn't get a better version of the EJ257 to send it off.. hand-built & balanced , forged pistons, EJ207 heads/cams, ELH, twin scroll ball bearing turbo, etc. We can dream..
 

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Discussion Starter #53
Well, looking at the 2020 STI in another post, looks like there is some tangible upgrade made to the engine.

Yeah the video is about explaining the differences based on what the three journalist experienced driving the three different WRX STI. And I think they did very well in describing the WRX STI and its variants (I know since mine is almost an S206 NBR edition suspension/chassis wise). I also find it true that the STI requires more 'energy' to drive, but that's what made it so involving to drive.

What's interesting is how they feel the EJ257 feels faster low-mid compared to the S208 and RA-R. Also worth knowing, Keiichi Tsuchiya also said if he had to nitpick about the S208 is that he wishes there is more torque down low.

No replacement for displacement.
 

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What's interesting is how they feel the EJ257 feels faster low-mid compared to the S208 and RA-R. Also worth knowing, Keiichi Tsuchiya also said if he had to nitpick about the S208 is that he wishes there is more torque down low.

No replacement for displacement.
I think the extra 463cc of displacement aids in the partial throttle and off-boost responsiveness. As we've seen on many dyno and boost plots, the EJ207 is more responsive with its twin scroll setup once in boost (at WOT). The EJ207 reaches peak torque sooner and for a wider range than the EJ257, however, we're looking at data from WOT pulls. The EJ257's extra displacement gives it a bit more "grunt" in the lower RPM range for daily driving. I believe the UEL also provides an initial "thrust" when tipping into the throttle since it provides a shorter exhaust path to the turbo.. but that advantage quickly drops off compared to the benefits of a twin scroll ELH.

I'm betting it would be hard to notice a difference between the two in the lower gears. Especially since the JDM transmission has even more aggressive gearing. But you would probably notice a difference if you found yourself in 3rd gear at a lower speed. I wish I had an opportunity to drive a S208 to find out :)
 

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Thank you guys for joining our Page and sharing our contents.
You’re welcome.
As far as we know, all existing pictures and graphs of genuine VF58’s available online are taken in our Lab, since it’s one of (if not the) rarest IHI turbocharger ever produced for Subaru twinscroll applications.

Inside our official Facebook Group dedicated to Subaru Motorsports you may find even more useful hints (just type “Advanced Sports Engineering Lab” in the Facebook “search“ field and You will find links to our official Page and Group).

That specific VF58 shown here is inside my own car, so I personally know that turbocharger VERY well.

A huge hug to You all
🤛🏽❤🤜🏽


Giorgio Provinciali
Advanced Sports Engin
founder and CEO
 

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Discussion Starter #57
Ciao Giorgio,

It is good to see you here.

So what is the difference between VF56 and VF58? Is the Vf58 has better top end support?
 

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Ciao Giorgio,

It is good to see you here.

So what is the difference between VF56 and VF58? Is the Vf58 has better top end support?
Hello dlheman,
We had a lot of VF56 and disassembled, tested and flow rated that turbos, too.

Basically the VF58 is an updated version of the VF56 , as they are the same turbocharger except for the straight blades profile seen on the compressor wheel of VF58 and revised, better performing and durable ball bearing configuration.
The VF58 has the “S” marked uprated actuator, too, for better holding boost persistence.

If you‘re the lucky owner of one of the very few VF56’s around here, you’d be very happy of your turbocharger, as it’s one of the best IHI twinscroll turbos ever produced for Subaru application. We did the straight blades mod on Your same turbo, using our billet wheel designed for that specific application.
If you wish to make that kind of upgrade you can send us your unit and we will balance the whole CHRA assy as well as rework the compressor housing for perfect fitting the new wheel and matching the new specs. We can also upgrade the actuator to a new, stronger one.
This way you will have a VF56 capable of the same or better performances of a VF58.

Giorgio Provinciali
Advanced Sports Engineering Lab
founder and CEO
 

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Discussion Starter #59
Thank you for the insight Giorgio. That explainst the stronger performance of S207 and S208. I will definitely keep that in mind to upgrade the turbo :D


Ah, perhaps you can tell me what is the maximum boost the VF56 can handle before it self destruct?
 

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Thank you for the insight Giorgio. That explainst the stronger performance of S207 and S208. I will definitely keep that in mind to upgrade the turbo :D


Ah, perhaps you can tell me what is the maximum boost the VF56 can handle before it self destruct?
hello again dear dlheman,

S207 and S208 have both better too end power as they reach their peak power @7200 rpm instead of the 6400 of R205 equipped w/ VF56 and S206 w/ VF58 because of better balancing and higher blueprint standards of their engines.
Their electronic managements are finer: ECUs are different, using larger memory and more aggressive/refined values not only related to turbo settings but to higher AVCS, too, for example.

To answer you about your last question, the peak boost levels we reached on a R205 are near to 1.6 bars and are held quite stably, w/ no issues.
Please consider that P25 te housings are not comparable to P16/P18/P20 ss ones.

Previously you were also asking about 2019 RA-R’s turbocharger, wondering if it’s a VF56: it’s a VF58 ;)

hugs
 
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