So I thought I would post this on here to see if there were any thoughts on what could be going on before taking my beast back to the dealer. So today is a nice cold day, which I love because my car is a totally different car and pulls like it's trying to escape earth's gravity. So I am running through the grears 1-3 about 60% throttle and then I nailed it in 4th and see the boost gauge hit 25 and hold solid. Then boom all of the sudden 5 PSI and nothing more. I pull over and check all pipes and clamps and they are all tight. Start her up again and pulls like normal, 20-25 PSI. So back on the frontage road again and running through the gears like before, 1 about 19 PSI to 4500 RPM, 2nd 21 PSI 4500, 3rd 23 PSI 3500, 4th nail it at 3000k and see 25 PSI which it holds for 5 seconds and then bam again, 5 PSI and this time a CEL. A friend and I were thinking fuel cut because of how much more dense the air is now that it's cold and that wasn't it. I have hit fuel cut in my GTO and it's just like I am bouncing off a rev limiter. Then I start to think that maybe the car is holding the throttle closed because it's fly by wire and not letting me boost. I don't know what the CEL is, but any thoughts?
Limp mode will clear by restarting the car, unless you have a loose clampor some other mechanical problem.
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Is because you reach the over spinning of the turbo shaft and the ECM shut you down to conserve the engine.
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The 5 lb boost max is not the turbo over speed protocol bur rather what I refer to as "Limp Mode Minor". This is a protection protocol that the ECM engages when it feels something is wrong, but not really bad like a mechanical failure. This mode will clear on the next key cycle, typically. It can throw a CEL or it may not throw a CEL (known as a silent code). I agree that is most likely being caused by an "over boost" code, if you had advanced the WG. And considering you and I are at about the same elevation, and you were still seeing a solid 25 with the air temp cold, then to coin a phrase, "There's Your Sign". Basically the MAP was reading to much manifold pressure and threw you into Limp Mode Minor. My WG is set real close to stock and with the temps down to 40 degrees, I am only seeing about 22-23 max and usually only 22.
If you hit the "turbo over speed" protocol, then the ECM will just open the WG to bleed off some pressure. There will be no CEL or limp mode. This is possible to observe on a really hot summer day at our altitude, even with stock WG setting (I have seen this referred to as "High Altitude Turbo Syndrome"). But typically you would not notice, unless you have advanced the WG. Because this protocol seems to kick in at about 27-28 PSI. But there is no exact number to go by, because the ECM runs an algorithm to "estimate" turbo speed in any given conditions and also looks at "for how much time" the turbo is running at the excessive speed, before it decides to intervene.
The 5 lb boost max is not the turbo over speed protocol bur rather what I refer to as "Limp Mode Minor". This is a protection protocol that the ECM engages when it feels something is wrong, but not really bad like a mechanical failure. This mode will clear on the next key cycle, typically. It can throw a CEL or it may not throw a CEL (known as a silent code). I agree that is most likely being caused by an "over boost" code, if you had advanced the WG. And considering you and I are at about the same elevation, and you were still seeing a solid 25 with the air temp cold, then to coin a phrase, "There's Your Sign". Basically the MAP was reading to much manifold pressure and threw you into Limp Mode Minor. My WG is set real close to stock and with the temps down to 40 degrees, I am only seeing about 22-23 max and usually only 22.
If you hit the "turbo over speed" protocol, then the ECM will just open the WG to bleed off some pressure. There will be no CEL or limp mode. This is possible to observe on a really hot summer day at our altitude, even with stock WG setting (I have seen this referred to as "High Altitude Turbo Syndrome"). But typically you would not notice, unless you have advanced the WG. Because this protocol seems to kick in at about 27-28 PSI. But there is no exact number to go by, because the ECM runs an algorithm to "estimate" turbo speed in any given conditions and also looks at "for how much time" the turbo is running at the excessive speed, before it decides to intervene.
Excellent information, thank you very much. So the computer can actually open the wastegate?
Excellent information, thank you very much. So the computer can actually open the wastegate?
Yes, there is a "Turbo Control Module" that intercepts the vacuum line to the turbo and allows the ECM to "adjust" the vacuum feed to the turbo WG diaphragm. That is why if you "adjust" the WG rod tighter on a stock LNF you will only see larger boost for a few key cycles. As soon as the ECM figures out it is getting more boost than required to hit it's max target of 260 pounds of torque, it "re-adjusts" the WG by taking away some of the vacuum command, effectively undoing the "adjustment" you manually made on the rod. And that is how it also restricts you to only 5 pounds of boost for "Limp Mode Minor", by reducing the vacuum command a bunch via the Turbo Control Module.
I am pretty sure there was at least one forum member that had a failed Turbo Control Module and started to experience some serious surging problems, but I can't remember which forum it was on.
Yes, there is a "Turbo Control Module" that intercepts the vacuum line to the turbo and allows the ECM to "adjust" the vacuum feed to the turbo WG diaphragm. That is why if you "adjust" the WG rod tighter on a stock LNF you will only see larger boost for a few key cycles. As soon as the ECM figures out it is getting more boost than required to hit it's max target of 260 pounds of torque, it "re-adjusts" the WG by taking away some of the vacuum command, effectively undoing the "adjustment" you manually made on the rod. And that is how it also restricts you to only 5 pounds of boost for "Limp Mode Minor", by reducing the vacuum command a bunch via the Turbo Control Module.
I am pretty sure there was at least one forum member that had a failed Turbo Control Module and started to experience some serious surging problems, but I can't remember which forum it was on.
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Basically the MAP was reading to much manifold pressure and threw you into Limp Mode Minor. My WG is set real close to stock and with the temps down to 40 degrees, I am only seeing about 22-23 max and usually only 22.
Linear Mode
