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2004 Forester XT
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Discussion Starter #3
Moar boost without moar fuel = BOOM :icon_biggrin:

I don't think either will give you more boost, you'll just reach target boost sooner.

Stan
Haha! Tuning will come, that is why I am asking.

Good answer.

Why do some people go with one method over the other even in reference to target boost?

Some of my searches seem to show that the STI pill/wastegate arm shortening may push boost levels to beyond target boost.

Is that possible or am I reading it the wrong way?

Thanks
 

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2004 Forester XT
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Discussion Starter #4
Beyond this, what I really want to know is if it's possible to exceed target boost and if target boost is exceeded how is that possible if the ECU is completely in control of target boost.

I guess this is more of an ECU question.
 

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Beyond this, what I really want to know is if it's possible to exceed target boost and if target boost is exceeded how is that possible if the ECU is completely in control of target boost.

I guess this is more of an ECU question.
You can't. If you put a manual boost controller in without tuning, it will just turn down wastegate duty iirc. Changing the pill and tightening the wastegate will only let you build boost or hold boost better within the limits set by the ecu, unless you tighten the arm too much in which case it may overboost.
 

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Tightening wastegate arm effectively preloads the spring/diaphram inside which creates additional spring pressure, resulting in higher boost levels.

Negative is that it takes more intial force to open the wastegate and more force to open it fully, and therefore creep tends to be amplified.

Changing the pill dumbs down how much pressure is going to the wastegate and the boost solenoid. This effectively lets the solenoid bleed of a larger % of the air going to the wastegate and you can generate higher boost levels (w/ tuning). Negative is that the amount of dumbed down air coming in is far reduced and therefore isn't there to open the wastegate when it should.

In my experience, making the pill smaller tends to lead to pretty nasty levels of boost spike. However you can achieve higher boost levels w/ the arm tightening.

Ideal method, get yourself an actuator w/ a higher mechanical setting. On that note, I have one sitting around if you're interested...
 

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2004 Forester XT
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Discussion Starter #7
You can't. If you put a manual boost controller in without tuning, it will just turn down wastegate duty iirc. Changing the pill and tightening the wastegate will only let you build boost or hold boost better within the limits set by the ecu, unless you tighten the arm too much in which case it may overboost.
Could you define overboost? Also are you sure that the ECU will turn down the WGDC? I am running a Stage 2 Cobb OTS map? Would the ECU pull it back down to the target boost of that map?

Thanks!
 

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2004 Forester XT
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Discussion Starter #8
Tightening wastegate arm effectively preloads the spring/diaphram inside which creates additional spring pressure, resulting in higher boost levels.

Negative is that it takes more intial force to open the wastegate and more force to open it fully, and therefore creep tends to be amplified.

Changing the pill dumbs down how much pressure is going to the wastegate and the boost solenoid. This effectively lets the solenoid bleed of a larger % of the air going to the wastegate and you can generate higher boost levels (w/ tuning). Negative is that the amount of dumbed down air coming in is far reduced and therefore isn't there to open the wastegate when it should.

In my experience, making the pill smaller tends to lead to pretty nasty levels of boost spike. However you can achieve higher boost levels w/ the arm tightening.

Ideal method, get yourself an actuator w/ a higher mechanical setting. On that note, I have one sitting around if you're interested...
Thanks for the info, I have a WRX wastegate actuator that I purchased off of TheFoos. Using that actuator honestly helped me achieve ALOT closer to target boost in lower gears which is what I am interested in. I am not interested in boost levels past quarter mile speeds.

So from what I am starting to gather, tightening the wastegate arm is really where it is at and the pill is a last resort because of the problems you mentioned above?
 

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2005 Forester XT 4eat
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Thanks for the info, I have a WRX wastegate actuator that I purchased off of TheFoos. Using that actuator honestly helped me achieve ALOT closer to target boost in lower gears which is what I am interested in. I am not interested in boost levels past quarter mile speeds.

So from what I am starting to gather, tightening the wastegate arm is really where it is at and the pill is a last resort because of the problems you mentioned above?
That's how Cobb recommends you do it too. Here's a pretty good article on the subject:

CobbTuning.com - How Subaru’s Factory Boost Control System Works
 

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2004 Forester XT
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Discussion Starter #10
That's how Cobb recommends you do it too. Here's a pretty good article on the subject:

CobbTuning.com - How Subaru’s Factory Boost Control System Works
Becoming pretty clear....thanks!

Really just one thing left...why can't I become a "boost psycho" if all I intend is for my car to be a 0-60 king and perhaps a quarter mile TD04 king?

This is my post in the ECU section because it is starting to become a little bit more ECU related...well then again maybe not.

http://www.subaruforester.org/vbulletin/f95/obtaining-target-boost-lower-speeds-ok-61990/

What I am trying to say is why can't I try to raise boost to pretty damn high levels since I don't care what happens after quarter mile speeds ~ 100 mph...or will this just not happen the way that I want it to because the ECU will pull back WGDC?

I mean, most of us aren't hitting very high boost at all until higher speeds.

Can't I hit like 15 psi at lower speeds using "mechanical deception"? :biggrin:

....or am I just dreaming? :crazy:

Any thoughts?
 

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Becoming pretty clear....thanks!

Really just one thing left...why can't I become a "boost psycho" if all I intend is for my car to be a 0-60 king and perhaps a quarter mile TD04 king?

This is my post in the ECU section because it is starting to become a little bit more ECU related...well then again maybe not.

http://www.subaruforester.org/vbulletin/f95/obtaining-target-boost-lower-speeds-ok-61990/

What I am trying to say is why can't I try to raise boost to pretty damn high levels since I don't care what happens after quarter mile speeds ~ 100 mph...or will this just not happen the way that I want it to because the ECU will pull back WGDC?

I mean, most of us aren't hitting very high boost at all until higher speeds.

Can't I hit like 15 psi at lower speeds using "mechanical deception"? :biggrin:

....or am I just dreaming? :crazy:

Any thoughts?
Engine waste heat is your limiting factor.

The higher the engine load, the more waste heat is generated. The faster you are moving, the higher the engine load. The faster the motor is spinning, the more the engine waste heat you are generating...

There are basic thermodynamic principles that you simply can't overcome.

With that said, I hit 18 psi in every gear in my WRX...its simply a matter of tuning...
 

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There are physical limitations on how early an engine will get boost, you need enough exhaust gas to spin the turbine/compressor assembly fast enough that it stops acting as a restriction and starts boosting, the only way to make this happen lower down the rev ranges is to increase the energy in the exhaust gas stream, so you need either more gas, or the pulses to be stronger (not much you can do on a scoob with it that far from the engine) or it to be hotter.

You can port the manifolds, don't increase volume any more than you have to, and heat wrap it to keep the heat energy in, the downside is that at high revs the turbine will be more restricive as their is a larger volume of exhaust gas to flow, although the engine bay will also be cooler!

Simon
 

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2004 Forester XT
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Discussion Starter #13 (Edited)
Engine waste heat is your limiting factor.

The higher the engine load, the more waste heat is generated. The faster you are moving, the higher the engine load. The faster the motor is spinning, the more the engine waste heat you are generating...

There are basic thermodynamic principles that you simply can't overcome.

With that said, I hit 18 psi in every gear in my WRX...its simply a matter of tuning...
I am bit confused actually, I am talking about low end here (no more than 100 mph). Now short of tuning, am I limited by my Cobb OTS Stage 2 map concerning boost and only boost?

I already know that tuning may be in order, but why would it be in order if target boost is ~15 psi and I probably never be able to achieve it at these relatively low speeds anyways? (Your pm cleared up quite a bit by the way).

I am asking if the OTS map will definitely STOP me from going over target boost if I was to tighten the wastegate arm all the way and/or use the sti pill?.

I am also asking why I would need a new tune if all I care is about boost from 0-100 reaching more or less target boost if EVEN POSSIBLE, using the above methods.

Thanks again
 

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Due to the learning tables, yes, the Cobb OTS map will relearn and turn the boost back to where you are at currently; unless you have it cranked down so far that you are in mechanical boost land versus electronic controlled (but you won't accomplish that on that actuator).
 

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I am bit confused actually, I am talking about low end here (no more than 100 mph). Now short of tuning, am I limited by my Cobb OTS Stage 2 map concerning boost and only boost?

I already know that tuning may be in order, but why would it be in order if target boost is ~15 psi and I probably never be able to achieve it at these relatively low speeds anyways? (Your pm cleared up quite a bit by the way).

I am asking if the OTS map will definitely STOP me from going over target boost if I was to tighten the wastegate arm all the way and/or use the sti pill?.

I am also asking why I would need a new tune if all I care is about boost from 0-100 reaching more or less target boost if EVEN POSSIBLE, using the above methods.

Thanks again
Why are you putting it in terms of mph? I get 18 psi at 20, and 40, and 100 mph. Mph is only one factor. If properly setup and tuned, you should get close to 15 psi, if that is your target, in all gears.

There is a piece of information or knowledge that you're missing that is causing it not to come together. I don't know what it is. Perhaps some reading on turbo dynamics would help...
 

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2004 Forester XT
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Discussion Starter #16 (Edited)
Why are you putting it in terms of mph? I get 18 psi at 20, and 40, and 100 mph. Mph is only one factor. If properly setup and tuned, you should get close to 15 psi, if that is your target, in all gears.

There is a piece of information or knowledge that you're missing that is causing it not to come together. I don't know what it is. Perhaps some reading on turbo dynamics would help...
I am putting it in terms of mph because it is my goal to tune my car to run max boost below ~ 100 mph and it seems that higher boost is built at higher speeds.
I am getting what you mean about the tune. I am just wondering what Cobb's maps are like. If target boost is ~ 15 psi with an OTS then I should be set to reach that boost at any speed.
 
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