Hello, I have a problem with my 2015 model year Lexus GS200t (at 100.000 km) turbo boost. It does not related to topic of fluctuation of turbo boost. Before and normally, from 2000 rpm up to 4500 rpm, it boosts up to 1.1-1.2 bar as in first video. But in one day, suddenly, boost vs rpm relation has changed as in second video. It boosts 0.8 bar between 2000-3000rpm , then drops at around 0.6 bar between 3000-3500 rpm, then from 3500 to 4500 rpm it boosts normally as 1.2 bar.
No boost leak can not be find, Vacuum pressure regulator, vacuum hoses, turbo turbine part, engine valve cover and pcv valve have been changed but the problem can not be solved. There is no faulty codes or sign. I tried to remap tuning with ecu flash to increase the boost but no changes up to 3500 rpm.
Also, when I take data from OBD II, the target boost pressure is compatible with measured boost pressure. That is, the target pressure is also low up to 3500 rpm. Fuel pressures and other data I take, they seem all normal range.

 

There are a few different threads in the IS forum about this. If not I would post it there for help.

What Tune/Software did you use to remap tune?

https://www.clublexus.com/forums/per...t-issue-9.html

 

I have read all of the topics in this forum, and tried all of them but my problem couldnt be solved. I have used remaps software in my country which is a reliable company and even if boost limits were increased by software, target and measured boosts are low (below 1 bar gauge) up to 3500 rpm. After 3500 rpm everything is normal.

 

Have you posted this in the IS forum and asked for help?

 

No, I have written only in this section. Ok, I will ask for IS forum.

 

You will likely have 3-4 ppl respond. Some for sure know how to resolve this.

 

Looks like the vacuum regulator is faulty. Does the engine sound differently, like a buzzing noise?

 

I have changed the vacuum regulator valve and vacuum hoses twice, wastegate once but nothing changes. The problem is still in there.