pointby

So we reset the actuator rod last night on the GT28RS. We put the actuator under pressure causing the rod to extend. Then clipped it on the turbo housing pin so there is preload on teh actuator rod. We forgot to connect up the boost hose to the actuator and went for a test drive.

So guess, how much boost did we see at WOT with no line attached to the actuator?
a) no boost
b) 8-10 lbs of boost
c) normal boost of 20-25 lbs.
d) boost spikes over 25 lbs.

Setup: 1997 A4 1.8T Quattro

Engine: Rebuilt 1.8T with Scat rods, GT28RS Turbo, APR Manifold, 430cc Genesis Injectors, PES software, , shotgun test pipe, Borla cat-back. GenIII SPP Racetec FMIC w/Samco hoses, Mesa oil cooler.

Gldnrkt(GT3076R)

those rods should be set for 8-12psi...iirc.what did you see?

@wesome

if you don't have your wastegate line hooked up your turbo goes nuts,

Mine did the same thing on a k04... i could max out at over 25lbs of boost ( i would hit limp mode) limited to 5 p.s.i.. then it would let me have a bit more.. maybe 15-20.. then it would over boost

other times it wouldn't boost at all and i think that was because i was already out of the usable range of the turbo (keep in mind this is all Imawesome theory)...

I would boost up to 25p.s.i... car would be moving along nicely

would let off the gas, then punch it again... boost would go up to 10... let the car slow down so I was at a lower rpm and punch it again.. i would have normal boost... or a boost spike

all in all i solved the problem by fixing my broken line :P

pointby

Originally, with the rod set from the turbo rebuilder, it made 25 lbs of boost. With the rod reset, and the line disconnected (by mistake) it made 22-23 lbs of boost and it ran great. In traffic, stop and go and then a few full out WOT pulls. No issues. We'll reconnect the line tonite and see what happens.

I figured without the boost line the actuator would stay closed and the car would overboost or be erratic. So it's puzzling to me. But I'm no expert.

Gldnrkt(GT3076R)

before the oncoming exhaust pressure is greater, therefore forcing the WG flapper open anyways.

holy crap...did I just make sense??

2.0GT35

yes you did

Gldnrkt(GT3076R)

woohoo!!!!! *happy dance* my work here is done, back to AWOT.

pointby

So why even bother with an N75 and a wastegate?

Silver Streakin'

for the ECU (software) to control the N75 to control a wastegate

pointby

There are so many systems fighting to control boost on the Audi. Just seems a bit funny that the software, the wastegate and the N75 all get over-ridden by some little brainless flapper valve! And then we have people putting manual boost controllers on top of that.

Just trying to educate myself. But some of this stuff doesn't make a lot of sense... yet.