Why do I have boost with the boost line disconnected from the ECU?
12-13-2008, 01:33 PM
#1
AudiWorld Member
Thread Starter
Join Date: Sep 2007
Posts: 230
Likes: 0
Received 0 Likes
on
0 Posts
Why do I have boost with the boost line disconnected from the ECU?
My car was running great, then one day it started acting like it was missing under boost. I went through the usual stuff. While chasing a vacuum leak, I disconnected the boost line from the ECU and plugged it. I needed to go buy a new t-fitting for the boost gauge, so I drove the car with the line to the ECU disconnected. The car ran fine but seemed down on power as I would expect if the ECU wasn't getting the boost signal. (I assumed it was only giving me around 6 lbs boost because of the wastegate spring.) Well, I reconnected my boost gauge and the car was giving me 12-15 lbs of boost without the boost line connected to the ECU. What is going on? K75? Wastegate cap is still intact.
12-13-2008, 02:20 PM
#2
Makes no sense. Without the boost/vac line connected to the ECU all you get is WG spring based
boost. Perhaps you have a stronger than normal WG spring.
And it's N75 not K75 for the WGFV (that the ECU controls).
And it's N75 not K75 for the WGFV (that the ECU controls).
12-13-2008, 06:09 PM
#5
AudiWorld Member
Thread Starter
Join Date: Sep 2007
Posts: 230
Likes: 0
Received 0 Likes
on
0 Posts
Any thoughts on what to check next?
When it was running good, it pulled about 15-16 pounds of boost. Isn't it the wastegate spring that determines the maximum boost? Or is it the WGFV. Could the N75 fail and cause the boost to be 15lbs? If the wastegate spring broke, it would have less boost? I also have another ECU.
Trending Topics
12-13-2008, 06:55 PM
#8
AudiWorld Senior Member
Join Date: Dec 2003
Posts: 2,242
Likes: 0
Received 0 Likes
on
0 Posts
Maybe nothing
but it would be possible to program the wgfv to come on at 100kpa (=atmospheric pressure) in an attempt to prevent WG cracking. Certainly not on a stock ecu, though.
12-14-2008, 11:43 AM
#10
Former Vendor
Join Date: May 2003
Location: Fremont, CA
Posts: 1,352
Likes: 0
Received 0 Likes
on
0 Posts
Certainly so on a stock ECU, The WGFV is on as soon as you floor it.
There are pre-set duty cycle targets based on RPM TPS, and boost.
Disconnecting the boost line is a very bad idea, particularly if you're going to be mashing the gas.
Disconnecting the boost line is a very bad idea, particularly if you're going to be mashing the gas.