Fitzauto
Fitzauto Dork
12/4/17 10:06 a.m.

Hello everybody. I just got a new to me daily in the form of an 02 WRX wagon. Its 100% stock except for a boost gauge and I want to make sure its reading right.

Currently it will max out at .05 Mpa. Is that about right for a stock wrx with 154xxx miles?

sachilles
sachilles UltraDork
12/4/17 10:16 a.m.

should be 13-14 psi indicated.

fanfoy
fanfoy Dork
12/4/17 10:17 a.m.

There is an 02 WRX still running stock boost???? surprise

Fitzauto
Fitzauto Dork
12/4/17 10:23 a.m.

In reply to sachilles :

.05 Mpa works out to about 7.2 psi according to my conversion calc. What could be causing the low boost?

Robbie
Robbie PowerDork
12/4/17 10:28 a.m.

Should we ask why it has a boost gauge in Mpa?

Easy and cheap to throw even a hf boost gauge on the line and double check the gauge for accuracy.

EvanB
EvanB UltimaDork
12/4/17 10:33 a.m.

The Subaru optional boost gauge was in MPa. 

Fitzauto
Fitzauto Dork
12/4/17 10:46 a.m.

In reply to EvanB :

Good to know it is the Subaru gauge. I was confused why someone would put in an Mpa gauge.

sachilles
sachilles UltraDork
12/4/17 10:59 a.m.
Fitzauto said:

In reply to sachilles :

.05 Mpa works out to about 7.2 psi according to my conversion calc. What could be causing the low boost?

Lots of things.

at it's age, my guess is boost line is cracked somewhere. Spray some carb cleaner around the intake manifold/intercooler and see if the idle will bump up as a result. If it does, the lines have started to crack and go bad.

No idea if the tune is bad from a the previous owner, but I can't imagine someone would intentionally cut the boost in half.

NickD
NickD UltraDork
12/4/17 11:33 a.m.
sachilles said:
Fitzauto said:

In reply to sachilles :

.05 Mpa works out to about 7.2 psi according to my conversion calc. What could be causing the low boost?

Lots of things.

at it's age, my guess is boost line is cracked somewhere. Spray some carb cleaner around the intake manifold/intercooler and see if the idle will bump up as a result. If it does, the lines have started to crack and go bad.

No idea if the tune is bad from a the previous owner, but I can't imagine someone would intentionally cut the boost in half.

I've seen where people have a WRX (or any other boost buggy) that they have cranked to the moon and hurt something, then put it back to stock and turn down the boost to mask that and sell it

lastsnare
lastsnare Reader
12/4/17 11:55 a.m.

if the car was modified at some point and then reverted to stock, it might be missing the restrictor pill inside one of the vacuum lines going into the turbo.  without a pill in there (brass ball with a specially sized hole in it), it will run at wastegate spring pressure (which is probably the 7psi).  

I did this once when swapping turbos, and had that exact problem.  So, just one possibility if it's not a leaking/cracked vacuum line or tune-related/ECU problem.

Fitzauto
Fitzauto Dork
12/4/17 4:06 p.m.

Ill be checking for the restrictor once the car cools down from my drive home.

Fitzauto
Fitzauto Dork
12/4/17 4:44 p.m.

Restrictor pill is in place and the vacuum lines all look decent. My uncle (person I bought it from) replaced them about 100 miles ago.

Patrick
Patrick MegaDork
12/4/17 4:50 p.m.
fanfoy said:

There is an 02 WRX still running stock boost???? surprise

I have an unmolested 02 as well.  

freetors
freetors New Reader
12/4/17 4:55 p.m.

7-8 psi is running strictly at wastegate boost. So for some reason your wastegate actuator is not actuating. Perhaps the rod is stuck or your diaphragm is torn. There could also be a problem with the wastegate solenoid. It could be improperly hooked up, faulty wiring, or it could have just gone bad. They do die on occasion.

Fitzauto
Fitzauto Dork
12/5/17 12:59 p.m.

In reply to freetors :

Is there a way to free up the arm?

freetors
freetors New Reader
12/5/17 5:41 p.m.

I'm not sure exactly. I haven't had it happen to me. Back when I had my wrx the boost solenoid died and caused it. Is your boost response reasonably quick or does it  build slowly? With a factory tune and functioning parts it should be able to get to wastegate boost pretty quickly, like anytime you're above 2000 rpm IIRC.

Also this is semi-unrelated, but the factory and Cobb OTS tuning maps have their wastegate duty cycle maps set such that they basically try to build full boost all the time at anything above cruising throttle. With a free flowing exhaust it basically causes the boost to evershoot past target and then hit boost cut, then it would fall several psi below target, and then repeat the cycle. It would do this anytime I was in a higher gear/high load. I went in to the accesstune race software and turned the wastegate duty cycle way down. As a result I still reach target boost with fast response, but also got a much more linear throttle response and power delivery with respect to throttle position. Like a drag race engine tune vs an autocross/road race tune.

Fitzauto
Fitzauto Dork
12/6/17 12:39 a.m.

It hits its peak boost around 2500 rpm at wide open.

Blaise
Blaise Reader
12/6/17 5:49 a.m.

You've got a wastegate actuator problem. I'm glad you checked the lines and pill but you're missing something.

As somebody who's owned an '02 WRX (stock as well), and gone down the route of modifying it to hell and back, just trust me on this:

Install a De-catted uppipe. NOW. You don't want to risk losing a turbo.

Install a De-catted downpipe if emissions laws in your area aren't insane. A catted one if they are. Most places just OBD2 test nowadays.

Free-tune. Stage 2. Then just drive it forever. The WRX is a great car and aside from gutting the silly early 2000s emissions stuff that the JDM cars didn't get, they don't need much to be amazing.

Fitzauto
Fitzauto Dork
12/6/17 9:23 p.m.

In reply to Blaise :

Whats the best way to find the problem?

Ill keep that in mind about the up and down pipe. I live in OK so no emission testing at all.

Blaise
Blaise Reader
12/7/17 6:41 a.m.

I'd start with your EBC. The way the system works is by applying vacuum to the actuator to keep the wastegate SHUT, therefor allowing boost to build. No vacuum or unplugged or broken = wastegate pressure.

 

On my 02, I actually ran a hybrid setup with an MBC in parallel with the EBC. The MBC was set to ~19psi (don't do this) while the EBC was set extremely aggressively to build boost very quickly. In this way, no matter how hard I ran the EBC I would never exceed 19psi, so even when the boost came on super fast I wouldn't have to worry about overshoot.

Diagnose the EBC, then get yourself a decatted up/down pipe. Tune and DONE. Enjoy your reliable, ultra-fast-boosting machine :)

Fitzauto
Fitzauto Dork
12/7/17 8:16 a.m.

Sounds good to me. 

Robbie
Robbie PowerDork
12/7/17 8:40 a.m.

Does it apply vacuum or boost to the wastegate to keep it shut?

I'm pretty sure my Saab uses boost to keep the wastegate shut (the actuator is fed boost from the turbo and ambient pressure, and uses a solenoid to blend the two to send a signal between full boost and no boost to the wastegate). Would he similar lines/fittings/etc, but might be worth making the distinction for understanding the system.

 

Edit, I spoke too soon. Need to think more I don't think the above is quite right.

Edit 2, ok, so the boost pushes the wastegate open. On the Saab if you unhook the line to the wastegate, you will get full boost (the wastegate is normally closed), the ecu uses the solenoid to pass a specific amount of boost to the wastegate to push is open. Full boost to the wastegate puts you at wastegate pressure (like 4psi on the Saab). Vacuum would hold the wastegate shut, but you don't have much vacuum around when the engine is under boost.

I'd bet the Subaru is similar since the both use td04 turbos. Full boost to the wastegate is base boost, no boost to the wastegate is full boost, somewhere in between full boost and no boost to the wastegate will get you somewhere in between base boost and full boost to the manifold. Ebc uses a solenoid to mix the full boost and no boost signals to send to the wastegate based on ecu command.

Manual boost controller is simply a bleed valve with adjustable bleed pressure that connects full boost to the wastegate but bleeds some boost in the middle. Tighten (bleed less boost) to decrease manifold boost, loosen (bleed more boost) to increase manifold boost.

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