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Title: 1.8t AWP - Part Throttle Boost Issues Post by: SB_GLI 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. Title: Re: 1.8t AWP - Part Throttle Boost Issues Post by: nyet 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 Title: Re: 1.8t AWP - Part Throttle Boost Issues Post by: SB_GLI on July 27, 2015, 12:56:17 PM http://s4wiki.com/wiki/Tuning#Base_Boost but i am having difficulties: http://nefariousmotorsports.com/forum/index.php?topic=4381.msg77163#msg77163 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. Title: Re: 1.8t AWP - Part Throttle Boost Issues Post by: nyet on July 27, 2015, 01:01:30 PM Throttle body maybe?
Title: Re: 1.8t AWP - Part Throttle Boost Issues Post by: SB_GLI on July 27, 2015, 03:49:50 PM Title: Re: 1.8t AWP - Part Throttle Boost Issues Post by: 10101011 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 Title: Re: 1.8t AWP - Part Throttle Boost Issues Post by: SB_GLI 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. 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.Lee Title: Re: 1.8t AWP - Part Throttle Boost Issues Post by: 10101011 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 Title: Re: 1.8t AWP - Part Throttle Boost Issues Post by: SB_GLI 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. |