Reply to thread

Message: [QUOTE="Charles, post: 1521107, member: 103"] If I put together a setup to roam the streets today and I was willing to fit a second charger, I would run stock compression, partially filled block, 300/200's, 38R and GT55 with GT4718 Compressor.... That last part seems strange, but the turbine is just so efficient in the 55, but the 88mm GT47-88 compressor is sized and trimmed well for the low boost / high flow you need in a first stage.... plus is makes noise. The whistle, while it may seem trivial, or subjective is paramount for safety on a daily driver. With the 55 compressor I couldn't hear anything the motor was doing. Half a dozen times, in a truck I had been driving at the same basic power level for years, I found myself caught off-guard by a sudden onset of power at the wrong time because I could not HEAR the truck coming up on boost. On the track it doesn't matter. So what, you're focused. But driving on the street that little pitch change the 47-88 makes when the back tires lose the pavement with the cruise set on a rainy interstate drive is something you take for granted until it's gone... Or something as simple as not realizing you're under the chargers and for the last half mile you just blotted the sun from the sky behind you because you never heard them lay down. On a turbo diesel you're basically driving a turbo, the engine is just a box that holds pressure, and if you can't hear anything from the turbo, you lose orientation for shift timing and general engine status. Anyway, the turbine in the 47 was the only thing I would have changed about the 38R/47 combo. It was 1:1 (or better) up to ~65psi, then it would start to flip and by 90+ it was over 100psi. With the 55, the boost drive was always positive or even. The 55-94 was functionally great with the 1.12 turbine housing. But without sound, it was very disorienting on the street for anything other than flat -out where you fully knew what you were doing with or without any audible feedback. [/QUOTE]