So charge pressure control pos. deviation doesn't necessarily mean a boost leak? After STFA I found
09-12-2006, 08:22 AM
#1
AudiWorld Member
Thread Starter
Join Date: Nov 2003
Posts: 234
Likes: 0
Received 0 Likes
on
0 Posts
So charge pressure control pos. deviation doesn't necessarily mean a boost leak? After STFA I found
that it can mean overboosting is occuring, which doesn't have to be caused by a boost leak. I only ask becuase I run an MBC @ 15psi with no N75 valve and a TCD. I went to the drag strip and turned the boost up to 17psi--now I have this pos. deviation code so I'm wondering if it's related. I've had 710n's and a samco tbb/f-hose for about a year now so I'd be surprised if those tore. I'm just really worried because if this is actually a boost leak, I want to get my car in ASAP and I'm busy out at school. Some things to note:
- boost doesn't spike, it builds to 15psi and stays.
- even though I have no N75, doesn't the TCD fool the ecu into thinking its running less boost (i.e. why would the ecu think it's overbosting even at 17psi).
- have never had this code running 15psi. Ran 17psi for 2 drag runs and then back to 15psi--now I have a pos. deviation code.
Sorry for the long post but I'm just trying to gauge whether this sounds like a boost leak and I should worry or it sounds like overboosting because I turned up the boost a little and have no N75 (then I guess I could just clear the code and hope it doesn't come back). It's really hard for me to get to a mechanic out here (I think KTR is the closest @ an hour away). I'd really appreciate any advice from you guys!!
- boost doesn't spike, it builds to 15psi and stays.
- even though I have no N75, doesn't the TCD fool the ecu into thinking its running less boost (i.e. why would the ecu think it's overbosting even at 17psi).
- have never had this code running 15psi. Ran 17psi for 2 drag runs and then back to 15psi--now I have a pos. deviation code.
Sorry for the long post but I'm just trying to gauge whether this sounds like a boost leak and I should worry or it sounds like overboosting because I turned up the boost a little and have no N75 (then I guess I could just clear the code and hope it doesn't come back). It's really hard for me to get to a mechanic out here (I think KTR is the closest @ an hour away). I'd really appreciate any advice from you guys!!
09-12-2006, 08:57 AM
#2
AudiWorld Super User
Join Date: Mar 2002
Posts: 17,933
Likes: 0
Received 0 Likes
on
0 Posts
you could be ramping up boost at a quicker rate than x-chip wants to see.....
so before the tcd "kicks in" you're getting deviation from requested boost. If there is anyway to get a log of boost (115) you could see if that is the case.
09-12-2006, 09:00 AM
#3
AudiWorld Super User
Join Date: Feb 2003
Posts: 16,402
Likes: 0
Received 0 Likes
on
0 Posts
All the code means is that the "actual" boost is higher than what the ECU "requests"
This can be caused by a number of things. In your case, it's probably part throttle driving with your MBC. The MBC acts like an on/off switch. It "requests" max boost at all times. They only time you don't reach max boost is when there isn't sufficient exhaust gas energy to provide that boost.
Your X chip on the other hand, may request lower amounts of boost at part throttle. Your MBC will deliver more than the chip requests...and you end up with a deviation code.
Your X chip on the other hand, may request lower amounts of boost at part throttle. Your MBC will deliver more than the chip requests...and you end up with a deviation code.
09-12-2006, 09:20 AM
#7
Member
Join Date: Aug 2006
Posts: 2,686
Likes: 0
Received 0 Likes
on
0 Posts
"It "requests" max boost at all times." More like at 80%+ throttle position.
Is it possible that he doesn't have a TCD and boost tapered a touch on 15 PSI setting enough to not trigger code/TC...and now with higher boost he is throwing a code for boost deviation and unaware of TC occurring?
Just a thought.
Just a thought.
Trending Topics
09-12-2006, 09:21 AM
#8
Member
Join Date: Aug 2006
Posts: 2,686
Likes: 0
Received 0 Likes
on
0 Posts
2nd,3rd,4th...at least this is what I've witnessed on X chip.
For example, I got negative deviation when running XR with TCD...down low requested boost is so much higher than clamped MAP voltage that it freaks out.
