Overboosting, can't figure out why
 

Hi, I just got my turbo set up installed on mt 03 silverado with an LQ9 6.0l, 212/218 cam and it wants to boost much higher then desired. Its an STS kit with a 61 turbo, .80 A/R and has 38mm waist gate. I have everything hooked up correct and with the 5 psi wg spring it will hit 11 psi at 1/2 throttle in first gear. The spring is black with red on one end. It will even hit 2 psi revving it in neutral. I tried two different boost gauges and they read the same.
I'm using a soft spring from a stock 4l60e in the waist gate right now and it will go 6psi in 1st gear and hit 8psi in 2nd and seems to still be climbing up. I took the waist gate apart and everything looks fine, I also cleaned the shaft up. Any ideas ?

Is the waste gate just on the spring or is it boost assisted....ie. do you have a manifold vacuum line hooked up to the WG?

Also, where are you sensing boost from?

Yeah, I would check your reference line if you have one. Make sure there are no leaks.

The waste gate is boost assisted and I have the hose hooked up to the compressor, the hose seems fine, no leaks.
My boost gauge is hooked up to the elbo right before the throttle body.

can you snap a picture of it, and show us how its hooked up, not to be funny but ive seen tons of people put Wastegates on backwards on turboforums

If I think I understand your system correctly, then you should be able to just disconnect your vacuum/boost line to the WG and it should give you a relatively low boost.

If you have it setup as boost assisted, then I'm guessing you have a boost controller in somewhere in that line?

I think the boost gauge (and the WG) need to be connected to the intake manifold directly.

Either way should work.

If it just a simple diaphragm activated WG then a boost reference off of the discharge side of the compressor should work fine - IMO.

Here are a couple picture from under the truck. I'm lost to as of why the boost is so high. I just got back from taking it for a run, its 87F ambient right now so boost came up slower then yesterday at 60F but once in 2nd gear it doesn't seem to quit climbing.

Does the WG actuate away or towards the spring housing in order to open?

I feel your over boosting pain... You could try taking the spring completely out and see if it makes boost,if it does I'd say the wg is too small.

I have to say I think your WG is too small especially considering it is mounted at a 90* angle to the exhaust flow making it not optimal for controlling low boost. That coupled with a small turbo and a big engine = overboost

IMO this.

fix the position of the WG or put a bigger one on.

The wg valve has to move towards the spring to open.
I was wondering if the 61 is a little small for a 6.0l with a small cam ? I could put the wg where the pipe goes up 90* to the turbo so the exhaust has a straight shot at it right before the turbo ?
If I remember right when I had the wg off and looking into the exhaust, the welded on wg flange wasn't centered very well over the drilled hole, at least 1/8 to 1/4in off center. I will port that to match and see what happens.
I have to say I'm not too impressed with STS's kit.... The cold pipe going back up is all steel piping (holds in the heat) The hot side 90* going up to the turbo isn't even mandrel bent. My intake temps cruising today were 127F and a 4.5 second wot pull brought them up to 162F.. Hopefully the e85 holds it own.

Looks like it is hooked up to pop WG open rather early then - so I don't think it is the connection.

If you feel like troublshooting the WG, the next step is to go get a cheapy air regulator from home depot. Grab an air compressor and using the air regulator in series with a hose connected to the lower point of the WG (where you have it connected) determine what pressure you need to actuate the waste gate open while watching through the discharge - careful not to blow the diaphram.

If it is much higher than 5 psi then you know it is the waste gate. If it is right around 5 psi, then you know you may be looking at larger system design issues (WG too small etc...)

If it was boost creep, I would think you could hear the open waste gate rather clearly.

yeah that looks like you are hooked up correctly bottom port and bottom connected to the exhaust, thats only a 38mm gate so that might be too small

If I had on a larger turbo or higher ar would the 38mm gate might work ?

this is wrong, and you will see huge numbers when the throttle closes.

measure boost inside the intake AFTER the tb.

if you are still seeing odd numbers take the wastegate OFF and repeat.