Obscure issue with late boost

[Entaran]

Hey guys, I'm a tad stumped here.

So the car's got a genuine e316g. I ripped the piping off and doublechecked and it's definately that. Even checked the casting numbers vs the other identity thread we have.

My issue is the car only makes boost around 4000 rpm in any gear.

I know the ISC is shot and needs to be replaced, but still that's FREAKING LATE.
Vehicle has a 2.5 inch turbo back exhaust and the cat is not busted or blocked, neither is the muffler. Ye olde tap test tells me so. (As well as looking up the guts of the muffler)

Side note, the vehicle when it makes boost is making 11psi instead of 7/9psi standard. And if you swap the vac lines around a bit it makes 18 or more psi and hits boost cut so you can't even get the free 4psi upgrade by moving a vac line.

Any ideas on where I can start looking? Turbo spins freely and doesn't have play. Manifold is a GT Pumps item, Dump pipe is e3 or bigger, exhaust is 2.5 inch. Only serious restriction I can see is the factory elbow on the throttlebody, but my silver vr4 made boost at 2600 with a 14b.

 

[CLuTZ]

What kind of controller do you have on it

 

[Entaran]

None. There's no boost controller plumbed into it at all which is what's making me confused. I would understand if it had an el-cheapo controller causing the wastegate to open halfway most of the time or something.

 

[VR-4Squid]

Check the wastegate is closing properly.

I had the same problem when I first swapped to a 16G, wouldn't reach full boost (15psi) until 4500rpm - turns out the bracket for the wastegate actuator was slightly bent causing the wastegate to sit slightly open (about 2mm) - I spaced the bracket out from the comp cover with a pair of washers so the wastegate was held fully closed, with just slight tension on it. Ever since then it's made full boost by 3500rpm.

 

[Entaran]

Ta, will check that when I rip the exhaust off during the cam change

 

[milkandoj]

Check the wastegate is closing properly.

I had the same problem when I first swapped to a 16G, wouldn't reach full boost (15psi) until 4500rpm - turns out the bracket for the wastegate actuator was slightly bent causing the wastegate to sit slightly open (about 2mm) - I spaced the bracket out from the comp cover with a pair of washers so the wastegate was held fully closed, with just slight tension on it. Ever since then it's made full boost by 3500rpm.

Ive done this aswell, makes sure the rod is pre tensioned and the wastegate flap held tightly shut.

The holes on the actuator barcket have a bit of slop in them, so it could have been unbolted and bolted back on and just angled a bit so its not pre tensioning the gate.

Take the actuator rod off the pin on the gate flap, so you can actually move the actuator bracket around a bit when bolting it up to add more or less pre tension on the actuator rod. if the rods off the gate pin it wont pull the bracket around as you do it up.

So bolt it up so it has tension or add the weashers aswell.


If you have to yank the rod back to get it back on the pin connected to the gate, its nice and tight.
Nothings better than tight flaps.

 

[Entaran]

Lol. Ain't that the truth

 

[rob323]

If the wastegate is not the problem, the next things to check would be intake leaks and cam and ignition timing.
Oh, and assuming the exhaust wheel hasn't been clipped.

 

[omad]

was also going to suggest intake leaks. my tb shaft seals were shot causing massive leak and late boost.

intake pressure test!