Low Boost Issue...
 

Hey guys/gals,

I've had my 91' JDM T2 for a while now, but this still has my stumped.

What would be causing my JDM S5 T2 to be only boosting .32kpa which = to about 5psi? I thought the stock boost for S5 T2's is 7.5psi?

The only performance modifications I have are a 3" catback (stock cat/downpipe). Stock airbox/piping/turbo, etc.

Now, if I turn on my boost controller on it's lowest setting (.60kpa) then it'll spike to 8-8.5lbs which is roughly .63-.65kpa. I don't want to run with my boost controller on just to reach 8lbs with stock fuel management/parts.

Anyone have an idea? As far as I know, no vaccuum leaks, and holds boost just fine. It's had a full tune up, timing and TPS set correctly.

Right now I'm confused and am afraid to run with my boost controller on just to reach slightly above my stock boost pressure. I have no issues with running .33kpa of boost, but knowing that my stock levels are around 7.5psi, this is definitely a bit confusing, especially since with the boost controller off I should be hitting stock boost levels.

Anyone have any insight? Thanks in advanced.

FSM calls peak boost at around 8.2 PSI. If you arent reaching target or at least close, here are some things to think about:

1. Turbocharger worn out (check play on turbo)
2. Exhaust restriction (clogged cat/etc..)
3. Worn/malfunctioning wastegate

Wastegate pressure is still the same between the S4 and S5, if I remember correctly the S5's use a sort of electronic boost control built into the ECU to bump the boost up. I'm thinking that you may have bypassed this when you installed your aftermarket boost controller.

Exactly the reason why you install an aftermarket boost controller.

The stock wastegate is set to open at 5 psi. Did the previous owner of the car happen to port the wastegate?

That would make sense that the stock ECU would be bypassed when the EBS was installed.

As far as I know, the wastegate has not been ported, but it is also still running the stock downpipe, stock cat, stock airbox, stock intake piping, etc. And the exhaust is a 3" with dual mufflers in-line, single exit.

With the stock TMIC, downpipe, cats, and airbox, and the boost controller shut off, you won't see much over 5 psi on a warm day.

Even with it being a 91 S5 T2? Thanks for all the response! I know it's not actually an issue, just a curiosity since I don't mind the power it's at right now.

I'm so glad I read this thread. I've got an s4 using s4 electronics with an s5 engine / turbo swap and have always wondered why my peak boost is only at 5psi too. I didn't know s5's used the ECU to bump up the boost a bit. I always thought I had a boost leak somewhere...

Disregard..

Disregard...meaning false?

No, disregard as i made a mistake.