Pages: [1]
Author Topic: 1.8t AWP - Part Throttle Boost Issues  (Read 7471 times)
SB_GLI
Hero Member
*****

Karma: +115/-10
Offline Offline

Posts: 1022


« on: July 27, 2015, 11:44:58 AM »

Trying to help diagnose a part throttle boost issue on a MKIV 1.8t.  This is probably a shot in the dark but maybe someone can help.

It's not an issue with the tune as the issue persists at WOT on a stock file.

It seems as though any boost above wastegate cracking pressure is uncontrollable.  The car is also using a MBC to control boost spikes and then oscillations that would ensue at WOT.  Any attempt to boost above 5psi, and below WOT boost (~20psi) results in wide oscillations of boost between 10 and 20 psi, bucking, and eventual throttle plate slamming and limp mode.  Boost can be controlled at part throttle at around 5-6psi, but anything more results it erratic behavior.

N75 has been replaced with known good N75.  DV has been replaced with known good DV.  Turbo has been replaced.  Pressure tested for boost leaks.  N249 has been bypassed to verify it's not that.  Nothing as made a difference.

Logs of oscillations are included.  Screen shot of problem is also included.  If anyone has feedback it would be greatly appreciated.
« Last Edit: July 27, 2015, 11:47:48 AM by SB_GLI » Logged
nyet
Administrator
Hero Member
*****

Karma: +604/-166
Offline Offline

Posts: 12232


WWW
« Reply #1 on: July 27, 2015, 11:51:38 AM »

http://s4wiki.com/wiki/Tuning#Base_Boost

but i am having difficulties:

http://nefariousmotorsports.com/forum/index.php?topic=4381.msg77163#msg77163
Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
SB_GLI
Hero Member
*****

Karma: +115/-10
Offline Offline

Posts: 1022


« Reply #2 on: July 27, 2015, 12:56:17 PM »


Yeah, it's not even that Nye.  This is a simple stage I tune, stock turbo, stock just about everything...  as mentioned, even a stock tune exhibits the same issue.  It's something hardware, just unsure of what it is.
Logged
nyet
Administrator
Hero Member
*****

Karma: +604/-166
Offline Offline

Posts: 12232


WWW
« Reply #3 on: July 27, 2015, 01:01:30 PM »

Throttle body maybe?
Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
SB_GLI
Hero Member
*****

Karma: +115/-10
Offline Offline

Posts: 1022


« Reply #4 on: July 27, 2015, 03:49:50 PM »

Throttle body maybe?

Was also replaced just replaced.
Logged
10101011
Full Member
***

Karma: +10/-13
Offline Offline

Posts: 161



WWW
« Reply #5 on: July 29, 2015, 12:12:13 PM »

Was also replaced just replaced.

You said you have a MBC ?? . what MBC are you running ?. Why do you have a MBC on a car you can tune ?? Get rid of it !!! The MBC impacts the air to the N75.

Lee
Logged

Poor quality lingers long after the price is forgotten ....
SB_GLI
Hero Member
*****

Karma: +115/-10
Offline Offline

Posts: 1022


« Reply #6 on: July 30, 2015, 04:06:40 PM »

You said you have a MBC ?? . what MBC are you running ?. Why do you have a MBC on a car you can tune ?? Get rid of it !!! The MBC impacts the air to the N75.

Lee
Yes, it has a MBC in there only for overboost protection.  It is run in parallel with the N75.  Needed so that WOT boost doesn't spike to the moon.  No amount of tuning will fix whatever is going on.
Logged
10101011
Full Member
***

Karma: +10/-13
Offline Offline

Posts: 161



WWW
« Reply #7 on: August 03, 2015, 11:17:18 AM »

Yes, it has a MBC in there only for overboost protection.  It is run in parallel with the N75.  Needed so that WOT boost doesn't spike to the moon.  No amount of tuning will fix whatever is going on.

I disagree with you using the MBC for a over boost correction. Unless you have a T3-T4 turbo or a super 60 turbo you should have a large over boost issue. A Ko3 , Ko4 or even a hybrid EO5 turbo will not have over boost spike the N75 could handle. It sounds like you have a plumbing with the n75 issue or  someone has tried to adjust the spring screw in it .

The other thing that can cause the over boost issue is the wastegate  being adjusted incorrectly . Again  you should not have a MBC for boost spiking.

Lee
Logged

Poor quality lingers long after the price is forgotten ....
SB_GLI
Hero Member
*****

Karma: +115/-10
Offline Offline

Posts: 1022


« Reply #8 on: August 04, 2015, 05:26:32 AM »

I disagree with you using the MBC for a over boost correction. Unless you have a T3-T4 turbo or a super 60 turbo you should have a large over boost issue. A Ko3 , Ko4 or even a hybrid EO5 turbo will not have over boost spike the N75 could handle. It sounds like you have a plumbing with the n75 issue or  someone has tried to adjust the spring screw in it .

The other thing that can cause the over boost issue is the wastegate  being adjusted incorrectly . Again  you should not have a MBC for boost spiking.

Lee

I agree with all of this.  MBC is no good, but until the root problem is solved, the MBC will stay in there for overboost.  The N75 is fine, tried other known working ones.  It very well could be plumbing related.  I am having my friend tap his boost gauge into the n75 lines to see if there seems to be a restriction there that is causing this mess.
Logged
Pages: [1]
  Print  
 
Jump to:  

Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Page created in 0.019 seconds with 17 queries. (Pretty URLs adds 0.001s, 0q)