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Old 04-07-2006, 12:51 AM   #1
clbd39
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Join Date: Jan 2006
Chapter/Region: MWSOC
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2002 SRP VF43 WRX
P&L Jorge Tuned

Default 3/16 and the AP

I just ordered my AP and it'll be here on the 11th of April

The person i bought my car from put the 3/16 "mod" on it and i'm not sure which piece is the actual "modded" part

does anyone have a picutre of what thing i need to change out to get it back to normal, because i think that's not going to be cool with the AP

or can I just leave it and it won't hurt a thing

if there's a post on these SPECIFIC questions help me out, i searched and couldn't find what i was looking for, otherwise HELP ME!!! i don't want to hurt my car!
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Old 04-07-2006, 02:38 AM   #2
TeknoWhore
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the 3/16 mod is a no no with the AP. It will make your car run like crapola. Go to the dealer and order the new hose connector. Its only like a couple of bucks. I cant remember the part number off hand, but I will look it up.
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Old 04-07-2006, 02:57 AM   #3
CBoldman
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Yes, you are asking for problems if you dont act soon. I cant help you with the original part but please save yourself the headache (and potential Cobb bashing...) and get that sucker back to stock. Good decision with the AP, I am sure you will love it.
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Old 04-07-2006, 09:33 AM   #4
wrxdrvr
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It's the connector between the T and the FBCS. the factory size is 1/8" There's a short 4" vacume line coming off the T and it connects to a longer 12" one going to the solenoid.
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Old 04-12-2006, 01:10 PM   #5
thejean
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I have to do the same to mine as well before I install my Ap, which is supposed to arrive today. Not only do I have the 3/16th but I also extended the line to the wastegate.
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Old 04-12-2006, 01:19 PM   #6
Jaxx
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considering the 3/16 mod is bad idea on stock wrx ..

i know the stock replacement part number is on nasioc somewhere
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Old 04-12-2006, 01:23 PM   #7
thejean
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I still have it kicking around somewhere and I'll put it back to stock before I load up the AP.
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Old 04-12-2006, 01:28 PM   #8
Christian.
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I would highly suggest you use the stock or specified restrictor pill for all of the AccessPORT calibrations. I will post an article we wrote about how the factory boost control system works to help end users better understand why the stock or spedified restrictor pill should be used for our mapping.

How Subaru’s Factory Boost Control System Works


Chapter 1 – Hardware

Turbo - An exhaust driven air compressor which consists of four basic sections or components. The compressor section consists of the compressor housing and the compressor wheel. This section is the inlet or intake for the turbo which compresses the intake charge generating relative pressure (boost). Generally speaking the inlet is always in a vacuum sucking air in and the outlet is pressurized with the intake charge. Next is the center section which contains the bearings, shaft, and the oil and anti-freeze passage ways; the compressor and turbine wheels are also attached to the shaft in this section. The third section is the turbine section which consists of the turbine wheel and turbine housing. This section also contains a machined by-pass for the wastegate valve to seat against. The last component of a turbo charger is the wastegate valve and wastegate actuator which control the wastegate valve’s movement.

Wastegate Actuator - A spring/diaphragm based mechanism which controls the movement of the wastegate valve. A turbo wastegate is normally closed, forced shut by a compressed spring inside the actuator canister. As pressure is applied to the nipple of the canister the wastegate shaft moves away from the actuator, swinging open the wastegate valve.

Wastegate Solenoid Valve - An electromagnetic solenoid which controls the air flow from the wastegate actuator to the turbo inlet. This device is normally closed when no voltage is applied. When DC voltage is applied, by the drivers in the ECM, to the wastegate solenoid valve fully opens allowing air to pass through the device.

Vacuum Lines - Rubberized or silicone tubes attached to various components in the engine assembly. For this article we will be concerned with the 6 attachment point and the four sections of vacuum line plumbing and adapters which we will cover in Chapter 2.

Restrictor Pill - A small pill made of brass which contains a precision machined lengthwise hole in the center.

ECU - Also known as an ECM, PCM, EEC, EMS. Engine Control Unit which contains the processors, drivers, and logic which is calibrated to control the relative pressure (boost) via wastegate solenoid duty cycle.

<Insert picture of components here, sorry I do not have them hosted anywhere>

Chapter 2 – Plumbing

We will break down the plumbing of the factory boost control system into 4 sections of vacuum lines/adapters and 6 attachment points. Please look at the below picture where we have the four basic lengths of vacuum line and the 6 attachment points labeled. Three of these lines are pressurized while the vehicle is under load and the one vacuum line which goes to the turbo inlet tube is under a vacuum which is created by the turbo sucking in air.

<Insert picture of components here, sorry I do not have them hosted anywhere>

Line 1 plumbs the compressor housing to one end of the T-fitting. This line contains the brass restrictor pill.
Line 2 plumbs the wastegate actuator to the opposite on end of the T-fitting.
Line 3 plumbs the middle to the T-fitting to the wastegate solenoid valve.
Line 4 plumbs the other side of the wastegate solenoid valve to the turbo-inlet pipe.

Chapter 3 – Hardware Function

Turbo - The function of a turbo is to compress the intake charge creating a greater volumetric efficiency for the internal combustion motor.

Wastegate Actuator & Wastegate Valve - A wastegate actuator's function is to control the wastegate valve thus the exhaust energy being directed into the turbine housing or by-passing the turbine housing. If the wastegate valve is fully closed, more exhaust energy is directed into the turbine housing the shaft speed of the turbo charger will increase and the relative pressure (boost) will increase, all within the efficiency range of the turbo. If the wastegate valve is open the exhaust energy by-passes the turbine wheel and goes into the downpipe so that the turbo shaft speed decreases or remains constant. This will generally lower relative pressure (boost). Below is a line graph demonstrating the rod movement of the wastegate actuator arm as pressure is applied to the canister nipple.

NOTE: The MORE boost you run the LESS wastegate you need/use. So unless you want to run less pressure than stock and/or have un-tunable boost problems, we suggest you do not port you your wastegate by hand. We suggest you leave your wastegate, the area around it, the turbine housing, etc. alone and tune your boost curve through the proper means.

Wastegate Solenoid Valve - The function of this device is to control the amount of air pressure being bleed away from the wastegate actuator.

Restrictor Pill - The function of this component is to limit the amount of pressurized air flowing from the turbo compressor housing. The air flow is limited by this restrictor pill so the wastegate solenoid valve and wastegate actuator are not overdriven forcing the wastegate valve to open prematurely.

Vacuum Lines - The function of the vacuum lines is to plump the pressurized air to the proper components so the Subaru boost control system works properly.

ECU - This is the master device which controls the slave device, the wastegate solenoid valve, so the targeted relative boost pressure is obtained.

The factory boost control system bleeds pressure away from the wastegate actuator to the intake or turbo inlet pipe. With this device set at 0% wastegate duty cycle through the ECM calibration, all of the air pressure generated at the compressor housing will be applied to the wastegate actuator forcing the wastegate valve to fully open. When the wastegate actuator is fully open, the vehicle will run mechanical boost pressure which can be anything from 7-11psi on OEM turbochargers. With this device set at 100% wastegate duty cycle through the ECM calibration, all of the air pressure generated at the compressor housing will be allowed to by-pass to the wastegate actuator allowing the wastegate valve to close. This flow is limited by the size of the hole in the restrictor pill located in the first vacuum line attached to the turbo compressor housing. The wastegate valve will only close as much as it can (taking into consideration that the exhaust gas pressure between the exhaust port and the turbocharger is generally greater than the manifold pressure the turbo is generating) with this exhaust gas pressure pushing on the wastegate valve.

NOTE: If you run a turbo charger beyond is compressor efficiency range it will turn into a flame thrower.

Chapter 4 – Mechanical Tuning and Boost Control System Calibration Using the AccessECU StreetTUNER Software

Mechanical Tuning
Changing the size of the hole in the restrictor pill; the vacuum lines for the factory boost control system contain a small brass restrictor pill located in the short vacuum line coming off the turbo compressor housing. The middle of this restrictor pill has a lengthwise hole precisely machined to a certain specification so that it works with the factory wastegate actuator and the wastegate duty cycle settings in the stock ECU. The size of this center hole can be changed in order to mechanically assist boost control.

The smaller diameter hole in the center of the brass restrictor pill; the tendency to boost spike will be higher and the less wastegate duty cycle you will need to run higher boost. The larger diameter hole in the center of the restrictor pill; the boost control system will have less of a tendency to boost spike and the greater wastegate duty cycle you will need to run higher boost. If you have a stock turbo and are running an AccessPORT map you have no reason to modify your restrictor pill. If you have installed a new turbocharger and you are using the stock boost control system to tune boost, please verify that the vacuum line coming off the turbo compressor housing (prior to the T-fitting) contains a restrictor pill with a hole machined in the center of pill.

<Insert detailed picture of vacuum lines heree, sorry I do not have them hosted anywhere>

NOTE: The hole in the restrictor pill can always be machined to a larger diameter. Be sure to make very small increases in the diameter of the hole. If the center hole is machined too large you will not be able to hit your boost targets…even with 100% wastegate duty cycle.

<Insert picture of adjustable wastegate actuator arm here, sorry I do not have them hosted anywhere>

Pre-loading the wastegate actuator arm; adjustment of the wastegate actuator rod (is the rod length is not fixed and adjustments can be made) will allow some additional tuning as well. If the rod coming out of the wastegate actuator is shortened it will pre-load the spring inside the wastegate actuator increasing the pressure level at which the actuator will open and total boost pressure that turbo can generate. If the wastegate actuator rod is lengthened the actuator will decrease the load on the spring and decrease the pressure level at which the actuator will open and total boost pressure the turbo can generate will decrease.

NOTE: The larger diameter wastegate valve a turbo has the more difficult it is to stabilize boost pressure as the valve initially opens. This is also true for greater exhaust gas back pressures created by a smaller A/R on the turbine housing.

Electronic Tuning Through ECU Calibration – Currently being composed.

The stock boost control system can be used to tune properly designed internal and external wastegate systems.

If you are increasing or holding wastegate duty cycles steady and boost is dropping then you have most likely reached the threshold of the mechanical efficiency of the turbo or your exhaust gas back pressure prior to the turbo is too high and is forcing the wastegate valve to open.

NOTE: With porting a wastegate, you are trying and make the wastegate valve function potentially work better which means that your turbo is going to lower boost super fast when the wastegate door/valve opens or not run as much boost as it was engineered to. If you make your wastegate react quicker then boost will be very difficult to stabilize and reach peak #s at an earlier RPM. If you make the wastegate flow better, then the exhaust energy your turbo needs to make and maintain boost will have less opportunity to flow across the turbine wheel. Generally speaking, air/pressure/exhaust gases will always flow along the path of least resistance. Not bashing, just trying to give you a different perspective.

Take care,
Christian.
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Old 04-12-2006, 03:40 PM   #9
parker/slc/gc8fan
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Theres Christian Jamming our heads with too much information again.

Go Mullet Man!!!
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Old 06-12-2007, 03:45 PM   #10
Iansstud
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Default newbie question here...

so i have a 02 wrx with only cold air intake and exhaust done to it... The 3/16 mod is bad for the car? why is it soo bad if the stock bov pops off at 13.5 psi anyways? it just gets there quicker dosent it?
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Old 06-13-2007, 12:05 AM   #11
thejean
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^^^^The 3/16 mod will not hurt your car if you are stock. With an AP there is no need for it. But on a stock it can give you slightly faster boost response with a small boost spike as a result. Harmful? I'd have to say no as I ran that way for almost 5 years without a single issue related to boost control.
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