[dellguyz]

Hello~

I just bought a Suabru Legacy 2.0 (with 5 manually gear), it is a sport sedan with turbocharger engine. The car come with a turbo timer for display the boost value and control the turbo cooling time before shut down the engine. I drive my car softly most of the time. For most of the highway, I will keep the car with around 2000rpm at 5th gear to get a 80km/h steady cruise speed, even it is going up-to-the-slope.

Last week when I was driving, I keep the speed at 80km/h @ 2000rpm while going up-slope on a highway, then I wanna accelerate to higher speed during the slope, I just step fully down the throttle. Suddenly I feel the acceleration is "choking"! Just feel like the compressor is going "spinning and slow down" again and again, then the turbo timer alaram with a warning signal. From the reading of the timer, the boost value goes up to 1.3kg/cm2. I know this must be the pre-set limit of boost value to protect the compressor. In normal day-time driving, the boost value always around -5X to 0.x kg/cm2.

According to this condition, I got several question

1. Why the boost will build up to so high level when I step down the throttle fully? Though I step down the throttle fully at the mean time, the engine speed haven't build up quickly, the exhausted gas should not have a big change in flow to make the turbine spin fast which generate much more boost.

2. For the timer the defaul boost limit is around 1.1-1.2kg/cm2, will it a too hidebound or boldness value? How much will be this boost in converting to BAR unit? If I never install this turbo timer, I will never know that it's overboost in this situtation, which will damage the engine, isn't it?

3. In steady speed driving on flat road, the boost value mostly between -40 to -50 kg/cm2, why the pressure will be in negative value?

4. From some of the information from internet, it said the turbine is start spinning when the engine is started, is it true? In my knowledge, if the compressor make the boost reaching limit, pressure will trigger the wastegate to let exhaust gas bypass the turbine and balance the pressure. So if I drive the car in low RPM (cruise on highway at 2000rpm, 80km), the compressor will keep charging and build up pressure, doesn't it will damage the comprees under long time?

Thanks for reading~