Question: stock actuator, t28...

[FriedEGs]

First question: How far open should teh wastegate trap door open on a stock t28 turbo/actuator? The full 90 degrees? The FSM shows a picture of the door open 90 degree's. My actuator is NOT opening the door this much. It's maybe opening it about 25 degree's, or a quarter of what the full opening should be.

I did a test using my air compressor and a boost gauge. I pushed 7 psi of air into the wastegate and it opens nicely, but only opens the door a quarter of the way. (about 25 degree's) If I push 20 psi, I get teh same result.

I took off the rod from teh wastegate trap door and noticed that the trap door clearly opens atleast 90 degrees. (again, the actuator is not opening teh door anywhere near this much)

Do I have a bad actuator, or is this not a big prob for the door to open this little for our specific turbo and motor, at stock boost?

*S1 rb25det, stock t28, stock actuator, etc...

My problem is a fuel cut at full boost. . I am waay overboosting, close to 18lbs. of pressure, everything stock. I think I've narrowed the problem down to this wastegate.... I just need second opinions about how far these stock actuator's are supposed to open.

[Fenvy]

it should open the same amount, whether you give it 7 or 70psi

[FriedEGs]

it should open the same amount, whether you give it 7 or 70psi

yea, but, how far? cracked open or full 90 degree opening?

[gawdzilla]

it should open the same amount, whether you give it 7 or 70psi

you sure about that? the actuator is a spring and opens gradually with force. more pressure = more opening force, so more psi will make it open further, at least until it physically stops. but you may be right as in 7 psi = the max it will ever open, and less than 7 psi = partial opening.

i'm not sure how far its supposed to open under 7 psi, but is the arm the rod connects to bent at all? sometimes they can get bent from shipping, etc.

[FriedEGs]

well, teh 25 already has that bend that allows it to fit around the compressor hot pipe. I think it's okay, and really teh problem is the movement.. The rod isn't moving out far enough. Again, the question is, how far should the rod open the valve?

Here's a pic for better reference:

Red line: closed, no pressureYellow line: this is how far the rod is moving with how my actuator is now.Green line: If I disconnect the rod at the pink X, I can easily open the trap door all the way to the green line.

I think it's the actuator not opening the valve enough.. This is what's causing teh overboost, because the boost gas can't escape fast enough from the small opening... This is also why the motor instantly runs fine after I let off from the fuel cut..the pressure equalizes below that point..

[Fenvy]

you sure about that? the actuator is a spring and opens gradually with force. more pressure = more opening force, so more psi will make it open further, at least until it physically stops. but you may be right as in 7 psi = the max it will ever open, and less than 7 psi = partial opening.

i'm not sure how far its supposed to open under 7 psi, but is the arm the rod connects to bent at all? sometimes they can get bent from shipping, etc.

that is true but only until certain psi, when the diaphragm opens all the way (or most of it)

if it opens all the way to the yellow line, it should be fine.

at one point I thought my actuator was broken so I removed it and used my compressor on it, it was about the same around when I input ~10psi of pressure vs ~50psi

[gawdzilla]

seems to look ok.

how is your boost control set up? have you tried running directly off the wastegate actuator? are you getting a good vac/press signal to the actuator?

[FriedEGs]

seems to look ok.

how is your boost control set up? have you tried running directly off the wastegate actuator? are you getting a good vac/press signal to the actuator?

boost control? Do you mean running the boost gauge directly from teh wastegate?

originally, the gauge was hooked up to the intake manifold and read good vacuum.

[digzsublime]

I don't think he's running a boost controller. He said everything is stock.

So, if everything is stock, all lines hooked up correctly, and boost gauge is accurate, I would say that you are probably correct in assuming the actuator is bad. 18psi = bads new for stock turbo.

Like you, I was also under the impression that the valve in the turbo would open up almost a full 90 degrees under full boost. If you don't get it figured out, I'll test my actuator movement when mine comes back from the paint shop next week.

[gawdzilla]

boost control? Do you mean running the boost gauge directly from teh wastegate?

originally, the gauge was hooked up to the intake manifold and read good vacuum.

i just meant... are you sure you hooked up your wastegate actuator correctly?

and have you tried connecting the wastegate actuator with a hose directly to a solid vac/boost source and bypassing the factory solenoid?

could be a defective solenoid if you're using that or some user error when connecting the factory solenoid or boost controller. it's hard to overboost to 18 psi with a partially open wastegate... cuz even if your puck wasn't swinging that far from the actuator, the exhaust gas will be forcing the puck open.
Modified by gawdzilla at 7:53 PM 9/12/2007

[FriedEGs]

I figured out my problem!!

I thought about what gawdzilla said about just putting a straight line from the cold pipe to the actuator. I took teh two hoses that have that T-fitting in teh middle and started attaching them up, with the boost gauge attached to that third point on that 'T'. For some reason I thought about checking to make sure there wasn't anything blocking the airflow.. (seemed far fetched to have happen) So, i pull them off, and shove a long narrow screwdriver all teh way up both of them..

After going through the shorter hose, I get an instant block, half way in. This is what was in there:



I have no idea what this came from.. It almost looks like a Nitro Jet that you use for nitrous setup's.... But, it def didn't come from any of the fittings pictured in that last pic... (nipple from cold pipe, wastegate and T-fitting) What an odd solution to such a weird problem.

Anyway's, the car runs perfectly fine at 5-7 psi now, finally!! She's def ready for some added boost!!! Thanks for everyone's input and help!!

[gawdzilla]

glad you got it figured out.

looks like that could've been a restrictor that just clogged and they might've used a bleeder somewhere down the line.

[Shocker]

nicee

[fly240]

so, have you try running above 12lb boost and see what happen..?

[FriedEGs]

so, have you try running above 12lb boost and see what happen..?

no, not yet.. i just ordered the Nismo FPR and a nice mbc...

[fly240]

let us know how it runs when it runs above 12psi.....