MY WERD!!! She Breathing Right NOW!!

[Monk BANzai]

Just finished a bit of a hybrid turbo "sidegrade" (dont consider it an upgrade). As you may have known, my original VF38 went "PANG!" some weeks ago due to heavy Impeller and Bearing damage and i had to change it out (the very week I put the car up for sale). Finding a VF38 was like finding a virgin on Murray Street Carnival Friday night. Hopeless.

I also didnt want to do an upgrade of a turbo that wud cost me in excess of 10K in parts and tuning. So I was able to procure an STi Turbo from a Bug eyed car that was doing its own upgrades and was able to machine the back end to bit the larger turbine of the STi unit as well as the larger Impeller of the front end. That way i kept the Twin scroll (pansy i know) piping but got a unit that would spool quicker and give some more power. The total cost (including the STi unit and the machine shop work) came up to less than $6K.

My question is do I have to tune for this sidegrade? I suspect that at higher RPM's//full load the car may run lean. Or should I assume that AFM will comspensate for the increased volume of air and give the necessary fuel?

[Ragnarok]

Virgin lol VF38 aint hard to find just need to check me...
Think you good to go with the upgrade. MAF scale should be the same and injector duty cycle will go up alot but high load should be covered.Boost & wastegate map will need to be adjusted though.

[Monk BANzai]

^^ VF38's aint hard to find i agree...but men calling all kinda $6-7K for a used unit. Plus the timeframe. my car is for sale...i cant be holding back potentials cuz of a turbo that down...


Thanks for the advice. Who wud you suggest i go by to adjust the boost and wastegate maps?

[Ragnarok]

VF38 are to expensive for a little turbo.Check meh i could take a look and see whats need adjusting.

[Glitch]

The turbo will work as is in there...but Ideally you would want to retune as the CFM rates would be different with this turbo.

Small tweaks should be made to the WGDC map maybe Boost Targets as well(if you wanna run a bit more boost) and while you in there Fuel map for our local gas.

You can run 18-20 psi tapering to 15 psi to reline....The Legacy performs very well in this region and safely at that. (tried and tested many many times)

With a retune u will maximize what you have and have the car working much better...plus a retune is not that much for what you get.

[Glitch]

Once you still with your stock airbox and piping you will still be within range for ECU compensation on the MAF scaling....

Hit me a PM for more info

[Jimbo]

So why it hadda be Murray street?

[Monk BANzai]

^^^ LOL....

Glitch....check Inbox...

[Monk BANzai]

gota host of repsonses....but all along these lines

UNkle,

Yes, you will have to tune for the upgrade.

Why? Simple - the STi turbo (which I assume is a VF36 or 37) flows SOME more CFM of air than the std turbo. Actually, if I were you, I'd have gone with larger injectors as well....jsut for safety IF you want be ultra paranoid.

The thing about the Subaru ECU, is that in CL range (closed loop) it's very very picky, and will want to stick to its tables no matter what. To that end, if you start to push the car hard, on high engine load (high engine load = low rpms with max throttle depression), the car may very well pick up knock because of the leaner conditions (for given closed loop fuelling)...and since the boost control will not be "accurate" for this larger turbo. The end result, is that the car shouldl dial back boost etc etc. Or, you could also get unstable boost/boost spikes if you do manage to get the car into high rpm operation.

In OL (open loop mode), while the car may be able to techically adjust, all of your W and possibly inejctor scaling may be off.


The car will work, but it won't work as it should / properly!

It will not be working to its full potential since the car will be oscillating from knock, to no knock and back....limiting the car's performance.


Simply put, ECU retuning for a Legacy (I had a WRX in my case) is too easy NOT to do. There are quite a few options locally, with folks doing both Opensource tuning (which I've used) and Ecutek tuning (which I've also used).

Both work fine....the DIFFERENCE IMHO comes down to the tuner behind the system.....other than the cost of course.

If you aren't familiar with what ECU tuning is....basically the Subaru ECU has a flash-able ECU, with engine rpm/a-f/load tables just like alot of fancy EMS systems out there. So in effect, the ECU is flashed and tuned, with just an OBD2 cable and software (no wiring or cutting), just like an EMS, and can be adjusted as such.

Had it been my car, I wouldn't dream of putting on a larger turbo w/o reflashing (e.g. I did mild "retune" with my tuner - Jason at the time - for a downpipe on the WRX...because I started getting boost spikes with my older map as soon as the larger DPipe was installed).

great advice from a bunch of really good guys!!

going for a road tune today...will update on before and after stuff..

[Jimbo]

^^ sounds about right except I believe he has open loop and closed loop the wrong way.
To my knowledge, open loop means the circuit is "open" and the ECU's outputs are not influenced by the input from the sensors, hence using data from the tables e.g. at WOT or idle
Closed loop is when the circuit is "closed" so the continuous loop between engine sensors and ECU outputs is not interrupted

Feel free to correct me if I'm wrong

[Ragnarok]

CL fueling is the ECU using the output from AF sensor and MAF sensor to adjust the correct amt of fuel needed for a stoichiometric ratio (14.7),The car should not be in boost at this stage.
OL fueling is the ECU using the MAP setting in POLF table to adjust fueling in high load and rpm ranges(boost).Therefore still using the MAF sensor output but not the AF sensor output.
MAF scaling for both CL and OL should be close as possible to spot on else some seroius DET.

[Monk BANzai]

good info here!!! thanks!!!

[VexXx Dogg]

yep, these guys have it down to a science.

I know when I throw in the 37, I'll need to retune because of the increase in CFM. I look at the parts everyday cant wait to install !!
Regarding injector upgrades, I was advised to look at IDC's first - it may not be absolutely necessary with a conservative tune, but if I'm tuning aggressively, I'll probably install some 740's for the overhead.
It probably sucks to do this just to sell now, but at least the next owner will have some sense of security regarding the turbo unit.

[Monk BANzai]

i did a test run last night as i missed my appointment (power steering issues.>>) The car is pulling stronger...took it to like 4500 rpm.... but its lazy down below....you can sense "it wants to go" but doesn't...

then accidentally (honest) PBR 9404 same car like mine..same black same tint everything ran up on me on wrightson Road and i had to "kick down" to navigate traffic...

The car was like "WHOAAAA!!!!" it came alive just like that...and 9404 got stretched.....and then went back to being docile.....

so i need to tune. And fast.

[Ragnarok]

Stay out of boost boy! Till u tune.

[nemesis]

In the words of Sheldon Cooper : "I informed you thusly!"

Anyway, you don't need to change injectors like Mr. Vexx Dogg there. Just tune and you'll be fine.

[Alpha_2nr]

To my knowledge, open loop means the circuit is "open" and the ECU's outputs are not influenced by the input from the sensors, hence using data from the tables e.g. at WOT or idle

Serious? Open Loop at idle???????????????????????

I'm under the impression that the car runs in open loop mode at higher rpm:

http://legacygt.com/forums/showthread.p ... 97928&

In a comment made by Trey Cobb in another post :
"the factory cars stays in closed-loop below 58.04% Throttle up to 4000 RPM after which it automatically switches to open-loop. I retain the same RPM range but lower the Throttle required to begin the open-loop transistion to 40% (as in the USDM WRX STi models).

^^if I interpret Cobb's comments correctly, then car moves from closed loop at low rpm to open loop in higher rpm ranges.

it may not be absolutely necessary with a conservative tune, but if I'm tuning aggressively, I'll probably install some 740's for the overhead.

Exactly. Remember that VF37 is mated to an STi which comes with 550 or is it 565 cc injectors? I don't think Legacy's use those (maybe 380? 440?), so the added headroom of a larger injector (in terms of IDC's) MAY.....MAY prove useful.


/fin.

[Ragnarok]

CL to OL changeover happen mainly when MAF goes above 60g/s and the delay counter is surpassed.

[Monk BANzai]

Good discussion.....question tho.....how wud you pick up signs of detonation or PANG!ness?

[Ragnarok]

If you hear it (metallic rattle) then it really bad.Other than that a LV check will show knock,you may also suffer a loss in power and boost.

[Monk BANzai]

cool....before the sidegrade, in 3rd gear the rpms wud climb to 5000 rpm, then drop off slight, then gain back teh 5000 and continue to climb. After the "grade" i get the boost coming on hard ( the two times I put it in boost), then i "holds back", then picks back up....

all learning experience...the Fuji Heavy Indutries are sooo different from the triple Diamonds.

[VexXx Dogg]

The holding back may be ECU retarding timing because of detonation!

[Ragnarok]

Doubt you can feel that kinda hold back from loss of timing unless you have major DET.
5EAT tranny usually lose rpm around 5300rpm the pick back up you may need to up the requested torque a bit.

[Alpha_2nr]

cool....before the sidegrade, in 3rd gear the rpms wud climb to 5000 rpm, then drop off slight, then gain back teh 5000 and continue to climb. After the "grade" i get the boost coming on hard ( the two times I put it in boost), then i "holds back", then picks back up....

all learning experience...the Fuji Heavy Indutries are sooo different from the triple Diamonds.

As a first check, you could get an idea based on what boost you're running, and how the boost varies (if at all). It's not necessarily due to knock, but it's a rough check so to speak.

e.g. if you're running 7-8 psi boost, then you MAY be pretty much knocking to hell and back, with the engine running a hi-detonation map (and the turbo running at "wastegate pressure" or minimum achievable boost).

I think the figure is 7-8 psi for the Legacy's - other folks would need to confirm that.

Also, if you're getting knock, but not AS much to go into "failsafe" (as per above scenario), the variation of boost to the redline MAY (notice the use of the word "MAY") hint at what may be happening with the car.


All of this guess work however, could be cast away with a purchase of a tactrix data OBD2 cable...for all of 800 or so dollars online. Software is free, and you can log everything....even down to knock correction.....knock tables (tells you when, where...hell, even what throttle you were at) etc etc.

It's an invaluable tool for any Subaru owner IMHO.

http://www.tactrix.com/index.php?page=s ... &Itemid=53

And before you say anything....it's a little more complex (when used with the appropriate software) than what a generic OBD2 reader (like what is commonly sold) can give you.

E.g. a generic OBD2 reader will not give you the detailed knock event and correction values you want, or even tell you about "Ignition advance" in terms of IAM, like what Ragnarok alluded to.

[Monk BANzai]

good stuff.....heading to get that tune tomorrow or tuesday...so i'll keep yall informed. Nice to see the knowledge base here KNOW what they talking bout...

[Alpha_2nr]

^^Sounds good. Keep in mind that you're assuming the turbo and whatever else is working fine. At this point, we can only guess what's up...so for all you know, we may have been assuming the wrong thing about the detonation, or we were totally spot on!

Very curious to see how this turns out.

[Monk BANzai]

yup..me too....given that i'm using the stock piping and twin scroll setup from the Vf38 but then forced a "Mandingo" type internals on it.

[Slayer]

Good discussion.....question tho.....how wud you pick up signs of detonation or PANG!ness?

best way to monitor knock.... buy a cheap VAG data cable, bout 150tt from shift performance in o'meara industrial estate. download romraider and up to date definitions. datalog parameters pertaining to knock. think its the same for LGT and imprezas. feedback knock correction, fine learning knock correction, rough knock correction (IAM).

while u at it, log IDC's before changing injectors to see if its really necessary.

so much parameters to log..... great quantitative way to see the gains from upgrades.

[nemesis]

I think that slight dip in RPM is just due to extremely poor tuning for that turbo. It can't be from timing only since if it got that bad, the car would pull timing across the entire RPM range. And you wouldn't get it back until you drove at that RPM without det in the future and the car adds it back. Meaning you wouldn't get the same symptom everytime. It'd just go through that RPM range slowly next time, not drop.
Yes 7psi is wastegate pressure for a stock Legacy. But with the stronger actuator on the STI turbo?? no idea.
For detonation the car will first try to add a little fuel, which probably won't work well with your small injectors (440 Legacy vs 565 STI), then cut timing, then it just completely drops boost. It doesn't scale the boost for the amount of det you have. So if you have really bad det, you'll see 7psi across the band, in which case you probably shouldn't be trying to redline anyway.
Alpha is quite right in saying we're all just guessing though. Getting your own cable and software is a good idea since you are staying Subaru. But get this car tuned soon.

[Alpha_2nr]

think its the same for LGT and imprezas. feedback knock correction, fine learning knock correction, rough knock correction (IAM).

http://www.romraider.com/forum/topic1840.html

while u at it, log IDC's before changing injectors to see if its really necessary.

Eh? Log IDC's before he tunes? Logging boost and so on, sure. But checking IDC's?

Doesn't make sense, we know the car should be running a little lean.

Additional fuel load requirement is gonna show up FIRST during tuning. Only the TUNER will be able to tell him, while tuning (and adding / manipulating fuelling) whether the injectors have sufficient headroom for what he's trying to achieve with the car.

And how much headroom is desired, is dependent on the tuner, and the owner

Anyhoot, yes, I've heard the VAG cables work with the ECuflash and other software. Never used it...but if it does...it's a mighty economic alternative.

For detonation the car will first try to add a little fuel, which probably won't work well with your small injectors (440 Legacy vs 565 STI), then cut timing, then it just completely drops boost. It doesn't scale the boost for the amount of det you have. So if you have really bad det, you'll see 7psi across the band, in which case you probably shouldn't be trying to redline anyway.

Well said sir.

yup..me too....given that i'm using the stock piping and twin scroll setup from the Vf38 but then forced a "Mandingo" type internals on it.

Meh...you'll be fine.....shouldn't do much harm once everything is connected up right. Maybe after everything is sorted out, and if you decide to keep it, you can look at optimizing the setup further.