I just tapped into my MAP line and ran a gauge into my cab to see what kind of boost #'s I was getting. I'm kind of confused...i have an edge evo with 80 horse tune, 6637, etc and at WOT I was only registering 20-22 psi. Is this a normal reading or is that a little low for my mods? Also, i'm not getting anything on the gauge until i'm at about half throttle (bout 10-12 psi)...normal as well?? Thanks ahead for the input!

 

well that looks close to what it should be, your ses light pops up about 22# , if you unplug you red line from waistgate you should get more, but not recommended , stock turbo is not efficient beyound 25#,
and is it half way from the dead stop?

 

that # is from a rolling start. I figured i'd see at least 25 with an 80 hp tune. someone from another forum suggested that i might have a kink in the line. i didn't see any but could that be an issue or does 20-22 sound right for what i've got?

 

I think that there might be a pattern failure developing with the turbos on the 7.3.
Disconnect the the wastegate lever, (the one on the top of the exhaust housing) and open and close it. See if it feels like the little head is loose on the lever or not. You will feel the head make contact and then the lever will move a little more toward the closed position as the head flattens out against the seat.

 

ok, i've been told that the wastegate opens at 25 psi anyways and that 21-23 psi is normal...

 

I would agree with the patternt forming theory Dan.

Cowboy Steve

 

problem I had,I could build 24 lbs boost but wouldn't pass about 6lb til over 2000 rpm

 

rbaker...that's how mine is acting. so i should be seeing more than 6 psi at normal acceleration and cruising? if so, what did you do to fix?

 

cruising @ 70 I now get around 8lbs but at lower rpms upon acceleration the boost should start climbing
I finally replaced turbo and everything is fine now,at any speed even with light pedal turbo will start to whistle

 

Y'all seen this picture yet?
The wastegate valve fell off of this VW 1.8t turbocharger and the WG is loose on mine.
I think that's where all the boost loss is happening right now on our trucks.
Rbaker you have a new turbo so everything is nice and tight, no exhaust pressure leaks anywhere so good whistle.



.

 

My recollection is that the wastegate button valve is supposed to have some play relative to the actuator shaft. These pics are my new rebuilt turbo with only 300 miles, when it was removed to install the correct early 99 wheel. I remember playing with the wastegate and seeing that the button is held in the center with a large rivet kind of deal which has a little slop in the junction. It seemed designed so that the button can easily rotate on the shaft, but when the shaft pushes the wastegate closed an outer shoulder that's part of the shaft pushes on and seals the hole in the center of the button valve. I think this slop is so that the button valve will make a good seat on the turbine housing.

One reason an older turbo gradually loses some boost is due to wear on the outer turbine and compressor blade edges which increases the gaps between the outer edges of the blades and the housings. As those gaps widen just a little, the turbine loses some drive pressure, and the compressor wheel can't maintain as high a pressure ratio. Also wear on the leading edges of the blades reduces drive pressure and boost on the compressor side.

 

Gene a little slop is good.
Mine is so sloppy that it feels like it's hanging at a 45* angle and it hits the seat and jams.
It takes some fiddling with the lever to get it to fully close.