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Message: <blockquote data-quote="nan83" data-source="post: 4122346" data-attributes="member: 6718">not cause yr small turbo you dun have power above 6k... the valve overlap is too big is the main prob... you change to bigger turbo maybe can help.... but if you can low the valve overlap degree, the hi rpm power will increase .... i give you some info :valve overlap = both intake & exhaust valve open at same time..cam duration = how long the valve will open in timecam lift = how long the valve stam will travel...valve overlap degree = (intake opens @ º BTDC) + (Exhaust closes @ º ATDC) so you think... yr engine have big overlap.... mean intake & exhause valve open at same time at long time... yr exhaust pressure higher than intake pressure..... so some of exhaust gases will enter the combustion chamber before the exhaust valve fully close... that cause power loss....huumm... hard for me to expain if you dunno much.... i need to draw it to make you easier to understand...the prob is yr variable valve timing still act like N/A engine.... turbo engine want different setting ...---------- Post added at 12:39 AM ---------- 6 hour anti-bump limit - Previous post was at 12:23 AM ----------Here i copy article for you... hope you can understand... that below setup only have 10' valve overlap degree..... your car 55-98' valve overlap.... cannot like that looo...Camshafts - Why 272 intake /264 exhaust?It has been standard practice to make the exhaust duration longer than the intake duration on a normally aspirated engine. This has been done to promote scavenging and increase cylinder pressure at high RPM because overlap is longer and one can run narrower LSA's (Lobe Separation Angles).Applying the same methods to a turbo charged engine, however, will not have the same desired effect because turbo charged engines do not make use of scavenging and reversion caused by larger overlaps, which can cause havoc.In a turbo charged engine exhaust pressure is almost at all times (99.95%) higher than intake pressure. Reversion, when air flows the opposite direction than what it is suppose to flow, must at all times be prevented in a turbo charged engine. If not compressor surge will occur which can result in serious damage. If we take a set of 264 degrees duration cams we will see that the inlet opens at 4 BTDC and closes at 43 ABDC for LS of 110 degrees. The exhaust opens at 36 BBDC and closes at 10 ATDC for a LS of 103. This gives us an overlap of 14 degrees and a total LSA of 7 degrees. Not good for a smooth idle and even worse when it comes to reversionNow let's increase the exhaust cam to 272 degrees duration. Intake still opens at 4 BTDC and closes at 43 ABDC for a LS of 110 degrees, but exhaust now opens at 45 BBDC and closes at 9 ATDC for a LS of 108. This now gives us an overlap of 13 degrees and a LSA of 3 degrees. Let's now go the opposite way, increase the inlet cam to 272 degrees duration but change the LS for the 264-exhaust cam to 112. Inlet opens at 8 BTDC and closes at 47 ABDC for LS of 110 degrees and the exhaust opens at 44 BBDC and closes at 0 ATDC for a LS of 112. This gives us an overlap of 10 degrees and a LSA of 4 degrees. Less change for reversion and great for cylinder pressures.The following are achieved: 1) longer fill period for a more powerful combustion which in turn will lead to a higher volume of exhaust gases with a higher initial pressure.2) smaller overlap which will prevent reversion.3) longer effective exhaust duration which will help spool faster and stronger because of the higher cylinder pressures.4) larger volume of exhaust gases present when the exhaust valve starts to open.</blockquote>

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