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Old 04-22-2014, 11:49 AM   #51
SeeeeeYa
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Rated Power 220kW@5600rpm
http://garrettbulletin.com/products/...rester-legacy#

This translates to 295.02485955 bhp, the rated output of the JDM unit.

It would seem, therefore, even given this minimum to go on, that there is room for improvement in the USDM FA20DIT's power. Many, including myself, would be content for some time with that degree of additional power.
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Last edited by SeeeeeYa; 04-22-2014 at 12:43 PM.
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Old 04-22-2014, 11:56 AM   #52
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Quote:
Originally Posted by rexblake View Post
So many issues.

AVCS is a huge help in spooling turbos. This has been proven by basically every tune on any motor that has it. If you care to research, you can even look it up yourself in ppb, with out avcs working decent sized turbos (say, 20g) will spool slower, I saw one 20g that spooled a 1000rpm slower than with it working. And that's an example I can think of offhand from ppb. Or, you could call a tuner. Any tuner actually, and have them explain it to ya.

22psi is high... For a Subaru. Otherwise, a ton of modern single turbo engines are pushing that or more. Ford Focus, MB AMG45, Evo, etc.


DI, dual avcs, and the better flowing heads from the FA20, all play a significant roll in better spool and transient response. The twinscroll design and significantly shorter exhaust helps quite a bit as well.

Also, making any claim about future power with mods is beyond speculation at this point. The engine and turbo are new, until we have hard data on both, I don't know why you would even try to speculate. Quite frankly, there is no reason to anyway, we will be seeing modded ones soon enough.
AVCS is not only good for spooling a turbo, it is also good for extending the top end. It took forever to find the combination, but the results were worth the work. This was on an '11 STi.

Given the FA's DI et al, I'm certain the EJ paradigm is no longer adequate. We are all in for some learning, coming soon from a FA20DIT.
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Old 04-22-2014, 01:19 PM   #53
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Old 04-22-2014, 08:25 PM   #54
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Originally Posted by Toys-N-Joys View Post


5. these stock 2015 wrx's push 22psi stock no mods.... thats pretty high for stock... and i see how pushing the tubro from the factory can make a engine look better than it really is.
And where are you getting this 22psi BS? Every article I've found says it's 15.9 psi stock.

http://blog.caranddriver.com/crave-m...l-a-auto-show/

http://www.edmunds.com/subaru/wrx/2015/road-test.html
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Old 04-22-2014, 08:35 PM   #55
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Over boost

It just peaks in the 20s though.
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Old 04-22-2014, 09:13 PM   #56
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Originally Posted by SeeeeeYa View Post
AVCS is not only good for spooling a turbo, it is also good for extending the top end.
Given a fixed set of hardware, the top end improvement comes from somewhat of a different reason than the improvement in spool.

We know overlap helps for scavenging at low speed, under the right conditions (intake pressure higher than exhaust pressure). It helps to think about the particulars of the opening and closing timing of the valves while trying different AVCS settings. So let's start with a set of cams on a DI turbo engine with twin scroll and phasers on the intake and exhaust.



Here's our basic cam lockpin position (assuming intermediate lockpin), before the phasers have moved. X axis is crank angle degrees ATDC firing, where 180 degrees is BDC exhaust, 360 is TDC intake, 540 is BTDC compression. Y axis is valve lift profile assuming some lash. Black line is just a sinusoidal representation of piston position at each crank angle degree. The cam profiles are labeled with their respective centerlines at a given phasing. Centerline here is defined as the number of crank angle degrees between TDC intake and peak lift of the profile.

At low speed lots of spool benefit comes from scavenging. You can go really aggressive on this with a DI engine, because you can set the start of injection to occur after the exhaust valves close. This keeps the fuel from getting thrown out the exhaust. Here's an example of high overlap volume phasing on a DI engine:



There's still the basic effect of earlier intake valve closing timing (more intake cam advance) outside of scavenging. Close the intake valve near bottom dead center for more effective volume at low speeds. That's what the EJ255 and early EJ257 does.



The later you close the valve, the less (geometrically) of the compression stroke you have to fill the cylinder as the piston rises. However you have more time to fill the cylinder. Those are two competing/tradeoff effects that change with rpm.

At low speeds you can open the exhaust valve later for more expansion work and less interference between exhaust pulses, especially on a non-twinscroll engine. This is an additional benefit beyond scavenging. Consider the Audi 2.0T engines with Audi Valve Lift System on the exhaust. They have a low lift exhaust cam profile that's active at low speed high load. The profile results in a very high expansion ratio and late exhaust valve opening right at BDC instead of a twin scroll turbo. So they get the benefits of twin scroll (exhaust pulse interference reduction) without the drawbacks--higher pumping work at high speeds and lower max exhaust temperatures. The profile below shows the same intake centerline, with exhaust cam retard for greater expansion ratio.



At high speed you want a later intake valve closing timing for better cylinder filling (less intake cam advance). This is due to the inertia of the air at high speeds. Even though you have less effective volume (from the piston rising up while intake valve is still open), the inertia of the air overwhelms that and becomes the predominant effect. That's one of the main reasons why high lift/long duration VTEC cams are effective at high speeds on Hondas.

You generally want an earlier exhaust valve opening timing (less exhaust retard) for a stronger blowdown pulse. The earlier blowdown relieves residual gas from the combustion chamber and reduces pumping work, but you get less expansion work. The profile below shows the intake cam retarded from the lockpin position and the exhaust cam advanced. This provides early blowdown and late intake valve closing for reduced effective compression ratio.



So those are some basic principles of AVCS and valve timing in general for performance at full load considering low and high engine speed.
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Old 04-22-2014, 09:13 PM   #57
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I had a hard start this morning. I guess it's a known issue, but it surprised me nonetheless. The first time turning the key it didn't start. The second time turning the key I had to turn it over for three or four seconds, felt like forever, then it fired up fine. It hadn't been sitting for long, drove it to work and back the day before. Anyone else having this issue?
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Old 04-22-2014, 09:28 PM   #58
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Quote:
Originally Posted by Celery GT-5 View Post
Over boost

It just peaks in the 20s though.
Ah, gotcha. I found the logged thread. Sounds like it's a pretty bad stock tune. Sadly.
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Old 04-22-2014, 10:38 PM   #59
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It gives you extra boost for a short period of time, it's supposed to do it. Same with the focus st and some other cars
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Old 04-23-2014, 01:00 AM   #60
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Originally Posted by murrdogg24 View Post
we should make a new website for the new motor !!!
Not the worst idea
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Old 04-23-2014, 08:14 AM   #61
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Originally Posted by SeeeeeYa View Post
http://garrettbulletin.com/products/...rester-legacy#

This translates to 295.02485955 bhp, the rated output of the JDM unit.

It would seem, therefore, even given this minimum to go on, that there is room for improvement in the USDM FA20DIT's power. Many, including myself, would be content for some time with that degree of additional power.
The Legacy JDM unit, right? because I have not yet seen info about the Impreza JDM unit output.
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Old 04-23-2014, 08:16 AM   #62
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The Legacy JDM unit, right? because I have not yet seen info about the Impreza JDM unit output.
Legacy and Forester... i.e., JDM FA20DIT.
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Old 04-23-2014, 08:25 AM   #63
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In the past it was not always the case that whatever turbo and output Legacy and Forester got, Impreza also did.
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Old 04-23-2014, 08:39 AM   #64
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Originally Posted by arghx7 View Post
Given a fixed set of hardware, the top end improvement comes from somewhat of a different reason than the improvement in spool.

<great stuff>

So those are some basic principles of AVCS and valve timing in general for performance at full load considering low and high engine speed.
I'm still digesting what I can of this. Thank you again for information I sincerely wish had been available when all the AVCS talk was going on. Out of that long tortuous thread/conversation only hints, and then from only a couple of participants, provided workable insight. Nothing was directly usable, so after a time of frustration I turned to trial and error, implementing my own ideas... ideas shaped, of course, by all that I'd read and seen. In the end what worked on my STi was a morph of it all, and nothing like I'd seen. But it worked and was obvious despite what seemed to be subtle revisions to existing ideas that did not work. Long story short, however, what you have explained above embraces my results.

Most failed at the overall picture. They got some better spool and called that good. Experiential results most often used too crude an approach and made changes in large chunks of AVCS. But I found the results after hundreds of runs making changes in single and partial degrees until I filled out both the bottom and top ends. It may have helped that I also tuned my STi to a much higher degree of overall acuity by tuning each gear's boost and timing. It all came together after that so it was probably part of the equation.

The main point of this post is to comment/speculate on the FA...
Given the OEM STi AVCS tunes, at least up until this year, and the fact Cobb and others left those OEM AVCS tables untouched in their tunes, the factory never addressed the "big picture" in USDM ECU tuning. This is NOT the same as JDM ECUs, which are obviously far more sophisticated, although the only ones I've seen were 2.0l motor ECUs. Point is, if history is any guide, our USDM FA's ECU will definitely benefit from a "retrofit" of JDM ECU tuning... modified of course to our environment.
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Old 04-23-2014, 09:16 AM   #65
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Nice i am looking forward to getting some info from this thread about the Engines. I picked up my 2015 last saturday. I just hit 400 miles on the way to work this morning I am trying to get it up there quick

It is much quicker then my 06, It is a surprise actually how nice the car gets up to speed with little driver influence. I am still breaking her in but so far its living a dream. Luxury and power.

To me it looks like the engine bay is more clean and space to work. (I dont plan on doing any work though as i want it to stay PERFECT and for now Dealer babied)

But i do want an exhaust system but i would be going through the dealer to have the same style just give me some more noise Even though it sounds very CLEAN and has its OWN unique rumble now.

I don't know a whole lot about this engine compared to the past so i am wanting to learn all i can about it. I knew my 06 VERY well so i intend to get on that level again with my 15.
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Old 04-23-2014, 09:34 AM   #66
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GOOD STUFF thanks ! Learning a lot already
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Old 04-23-2014, 03:41 PM   #67
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Given the OEM STi AVCS tunes, at least up until this year, and the fact Cobb and others left those OEM AVCS tables untouched in their tunes, the factory never addressed the "big picture" in USDM ECU tuning. This is NOT the same as JDM ECUs, which are obviously far more sophisticated, although the only ones I've seen were 2.0l motor ECUs. Point is, if history is any guide, our USDM FA's ECU will definitely benefit from a "retrofit" of JDM ECU tuning... modified of course to our environment.
The thing you've got to be careful with as far as the JDM tunes, is that if they had different cam profiles, different cam lockpin positions, or different phaser authorities it's hard to understand what's really going on. You really need a lift vs crank angle degree plot like the one I provided.

If I have 40 degrees intake cam advance on one engine and 20 degrees on another, if you don't know where the cam is parked for each engine it can be hard to compare.
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Old 04-24-2014, 09:28 AM   #68
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So this engine is also open deck, like the aspirated one, with cast pistons.
Do you guys think that Subaru did away with the throttle body and just kept the two units that look like TGV's?
Those could be TGV/individual bank Idle control solenoids/part time throttle plates.

I am reading that "second-generation" direct injection engines don't t have a throttle unit anymore.
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Old 04-24-2014, 09:35 AM   #69
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how can that be?
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Old 04-24-2014, 11:04 AM   #70
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Originally Posted by Vlad View Post

I am reading that "second-generation" direct injection engines don't t have a throttle unit anymore.
Well they certainly have a throttle, whether it's a single throttle body, or some form of multiple bodies, I don't know.

Introducing the new Subaru throttleless FA20.

"Full Throttle, All the Time."

It's what makes Subaru, a Subaru.
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Old 04-24-2014, 11:31 AM   #71
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Old 04-24-2014, 11:32 AM   #72
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No throttle?
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Old 04-24-2014, 12:01 PM   #73
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Originally Posted by SoapBox View Post
Well they certainly have a throttle, whether it's a single throttle body, or some form of multiple bodies, I don't know.

Introducing the new Subaru throttleless FA20.

"Full Throttle, All the Time."

It's what makes Subaru, a Subaru.
reminds me of the memes that came out after the unintended acceleration lawsuits. It is in collaboration with Toyota

"Toyota: Moving forward > Even if you dont want to"
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Old 04-24-2014, 12:11 PM   #74
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"Toyota: our drivers don't know what neutral, or the key or the engine start/stop button is"
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Old 04-24-2014, 01:21 PM   #75
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Have you seen a diesel in-action?
They are direct-injection.
There is no throttle.
Engine speed is controlled from the injection pump.
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