EJ20R Boost problems... SOLVED! 3-26-13

[Dead91silvia]

Ok, most of you know of my BG5 GT-B project. She is running and driving, less a windshield.

The problem I'm encountering is that she is boosting funny.

1st gear boost is how I would expect, push you back in your seat, but when I shift to 2nd, I lose all boost and it's like the turbo(s) says EFF you! If I wait a few seconds, like I let it spool down, I can punch it and it spools/boost's like it should, but then I shift into 3rd and it's flat again.

-At idle it's at negative boost
-any kind of throttle the gauge is at 0
-full boost is just about 0.5/0.6
-after shift is at 0.0

Thought it that it might have a problem with the secondary turbo, but I'm not sure...

I have never had a problem like thie. My Silvia's SR20DET never gave me any problems and the only other problem I have had with a turbo system was a customers 05 XT with a lose coupler.

[hansvonaxion]

lol, Rueben's gonna give you hell!

What RPM are you shifting at? Did it switch to both turbos before shifting? If so then you may just be dropping into VOD when you shift, it just feels dead and takes a while to get back on it.

Have you run it up through to redline to check it's boosting OK on both?

[chuckthefuk]

oh VoD... did u tamper with the magical black vacuum box when you rebuilt the car?

[Dead91silvia]

HAHA! I know, I'm gonna get crap for it... :smt005

Well, I thought it might be the VoD, but after thinking about it, there is no way in hell Subaru would have sold a car like this.

I cant really tell if one turbo is working or the other. I'm wondering if it's just the primary turbo working and the 2nd is not working at all.

I did wonder if it was my shift points, but I have tried a number of different one.

Here is one...
-3/4 throttle is first-full boost
-shift to 2nd at 5K-flat/no boost

try #2
-full throttle in 2nd from rolling start-full boost
-shift to 3rd at 6K-flat/no boost... hold it to the floor from 4k-6K, still no boost.

It's like there is a valve not working or the 2nd turbo is shit. and NO ONE over here knows a damn thing about them! :smt022

[hansvonaxion]

Here is one...
-3/4 throttle is first-full boost
-shift to 2nd at 5K-flat/no boost

try #2
-full throttle in 2nd from rolling start-full boost
-shift to 3rd at 6K-flat/no boost... hold it to the floor from 4k-6K, still no boost.


Well VOD is from about 4K to 5.5K so it sounds like you could well be shifting into it but boost should be building by 6k.

Run it up to 7k and see how much boost you get, make sure the secondary is working as it should.

You may have a problem but better to rule out simple VOD first.

EDIT: Just checked on the quick trip home and 2nd to 3rd shifting at 5-5.5kish it drops into oblivion, at 6k it seemed OK but I have cat back exhaust and ECU which helps shorten/reduce it. Oh and just to be sure it is a 20R and not a 20H, right? (sorry cant double check while typing)

[hansvonaxion]

Well, I thought it might be the VoD, but after thinking about it, there is no way in hell Subaru would have sold a car like this.



To be honest it should never have left the factory like that, or at the very least it should have been fixed in one of the early revisions.

:lol:

[Dead91silvia]

Here is one...
-3/4 throttle is first-full boost
-shift to 2nd at 5K-flat/no boost

try #2
-full throttle in 2nd from rolling start-full boost
-shift to 3rd at 6K-flat/no boost... hold it to the floor from 4k-6K, still no boost.


Well VOD is from about 4K to 5.5K so it sounds like you could well be shifting into it but boost should be building by 6k.

Run it up to 7k and see how much boost you get, make sure the secondary is working as it should.

You may have a problem but better to rule out simple VOD first.

EDIT: Just checked on the quick trip home and 2nd to 3rd shifting at 5-5.5kish it drops into oblivion, at 6k it seemed OK but I have cat back exhaust and ECU which helps shorten/reduce it. Oh and just to be sure it is a 20R and not a 20H, right? (sorry cant double check while typing)

Ok, I'll try shifting at a higher RPM and see if it changes. I still find it hard to believe that, thats the VoD. :smt017

It is an EJ20R. I have an axle back exhaust (muffler), but the rest is stock. Even the intake... haha

[Yamazaki]

Ok, I'll try shifting at a higher RPM and see if it changes. I still find it hard to believe that, thats the VoD. :smt017
Yeah, on all the twin turbo cars you have to shift almost near redline to get out of VoD. Your experience with the S401 kind of discolors your view and expectation of Subaru twin turbos.....

However, reading your descriptions, it sounds like your secondary isn't working. But that's just what I think. I have experience with the twin turbo, but I am not a mechanic.

[Dead91silvia]

Problem was fixed!

I some how got 2 of the vacuum line switched. Easy to do seeming that I didnt take it all apart myself.

I'll take a pic of what one they were later. Car runs great! Now understand the VoD too!

[slaytalera]

With the amount of vacuum tubing im surprised it was only two that got switched up :lol: