trinituner.com

I'm new to the Subaru as well as boosted arena so please bear with my seemingly naive questions.

Engine: 1998 WRX STI Version V RA 2.0L EJ207 (Completely stock internals)
ECU: 6S
Turbo: Stock VF28
Exhaust: 3'' Turboback 5zigen exhaust.

I currently have an aftermarket MBC (Halman) installed running approximately 10 psi of boost (its a daily driven car).

1. Are there any issues running such low boost? Research suggests that these engines ran 17-18psi stock.
2. Wastegate pressure (if I remember correctly) is circa 7-9psi. I don't quite understand how I can reconnect the OEM Boost Solenoid, I'll appreciate if anyone can supply me with some images of an engine bay and the appropriate connections etc. Effectively then, will adjusting the MBC to run the desired 18psi be equivalent to reconnecting the OEM Boost Solenoid? IMO reconnecting the OEM solenoid seems safer as proper adjustments can be accurately made by the ECU.

I recently installed an AEM Wideband and A/F ratio at idle was averaged to be 14.7±0.2 and 10.0 at WOT. The WOT A/F ratio seems to be quite rich which prompted my question regarding running LOWER than stock boost pressures and its effect on the ability of the ECU to compensate effectively.

Prompt replies and any knowledgeable insight will be hugely appreciated.

Thanks in advance!

Most ppl suggest going electronic as it works with stock system rather than over ride safety parameters as a manual boost controller would....

To address your question;


Running a lower boost level is okay, it won't damage anything.. even if a engine usually runs "high" boost levels... It would have been an issue if it was designed to run 10psi and you were running 20psi everyday.. You don't even have to drive in boost...and nothing happens.


Is your OEM boost solenoid 3 port or 2 port , then I can answer how you reconnect it.

And the only reason to suggest a electronic boost controller (imo) is to prevent boost spike.

I personally would always use my stock solenoid unless I planned to run higher boost levels not lower.

stick to the electronic controller. you can use the aem, perrin, grimmspeed....seems like your can needs a tune as well.

no the stock boost is not 17-19psi...it is usually around 14psi..ie. 1 bar...

^^ Well he can't tune a stock 6S ecu..he would need to either add a piggy back (emanage) or get a standalone (i.e. powerFC)

So he would need a controller like a HKS / Greddy... unlike newer model subaru's which can wire in a boost solenoid such as the AEM to the ECU and set boost

http://www.proimporttuners.com/parts/19 ... oller.html

aem boost controller

when i meant tune, i meant piggy back as well...

Firstly, thanks alot for the replies. I don't intend to go management anytime soon, as major mods to my vehicle aren't really sensible atm. @JJ16 It's a 2 port boost solenoid. I'll post the images of the current setup. However, I came across an odd senario whereby the line from the MAP sensor (which is also mounted on the strut tower in the vicinity of the Boost Solenoid) is merely dangling. There's also a 'Valve Assembly-Solenoid' (which connects to a tee that links to the manifold) mounted right below and the line from the MAP sensor possesses apt length to just connect to it (the Assembly Solenoid has an 'unused port') so I'm wondering if it connects to there. Hope the attempt at an explanation isn't too abstract, and that the pictures clarify.

And yes I more than likely misquoted that stock PSI @Aaron 2NR. There seems to be no consensus however with some stating 'it peaks at 18 and tapers back to 16' or '17 psi from my untampered 1998 WRX STI' leading to my confusion. http://www.type-ra.com/turbo.htm quotes the Type R as possessing 0.8kg/cm^2 which equates to 11.4PSI. I guess once the solenoid is working properly I'll truly find out.

Actually the plumbing is quite simple for the 2 port solenoid. Hope there's still the boost restrictor pill though. Will still appreciate pics of your setup @JJ16

No problem.. i don't have the pill in though

But i'd try to get some pics later or tomorrow for you... looking kinda overcast at the moment, so if rain falls..wont be able to get them.. if not id get them and post them.. its really simple though

Yeah it is pretty simple, gonna do it shortly. Any opinion regarding the loose vacuum line from the MAP sensor?

I can't remember if i have a similar line so i doh wanna quote, but i believe i have that same exact thing...and it doesn't affect anything..

Reconnected the boost solenoid with the restrictor pill and all. Boost builds quite strong with no hesitation to about 16-17PSI after which it tapers back to to about 15.5-16.0PSI in the higher RPMs. A/F ratio however still stands at about 10.0 on WOT. Another tuner suggested:

'That's quite rich under wot.
It can be a number of things: Dirty MAF, bad tune, boost leaks.
Do you have anyway to datalog the ecu?

Running low boost would not be a problem. If you have a boost leak that is causing you to only run at 10psi then you have a problem. What's happening is that the MAF is measuring the air. If their is a leak somewhere (after the MAF) then the problem arises that the ECU is commanding fuel for MORE air than what is actually in the combustion cycle. Hence rich.

Do simple things first like a boost leak test and clean the maf.
Any mechanic or DIYer with a air compressor can do it easy.'

Troubleshoot by a competent subaru mech asap.
If you're really running too rich for a long period of time, you can actually interfere with the lubricity of the oil and you don't want internal problems.

Im assuming he already tried simple things like the O2 sensors etc.

I have a Perrin EBCS on my Legacy... its as old as the car, 5 years, and it works perfectly in tandem with the ECU...

Problem ever solved ?

He need ah e-boost 2 and rtune