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When you turn up the boost as high as you can get while still avoiding fuel cuts, you are then on the edge of having those. The MBC-A will produce pressure overshoots. And you peak boost setting will be around 15 PSI minus the magnitude of the overshoots. So the MBC+A lets you get more power. The MBC+A eliminates pressure overshoots.
Pressure overshoots are more severe in cold weather.
You are getting boost taper. The MBC is controlling the pressure at the turbo compressor outlet. The pressure at the TB is that pressure minus the pressure drops across the IC and the pipes etc. At higher flow rates at higher RPMs the pressure losses in the IC get higher. When you feed the MBC from the TB, then it controls pressure at the TB. A MBC-A connected at the TB will tend to increase pressure overshoots all the more. A MBC+A connected at the TB allows you to control boost at the TB and eliminates boost overshoots. This allows for a higher boost setting and more power.
You have a boost guage... when is it tapped in?
At 10PSI of boost, you are around the same peak boost as stock. Any overshoots are not going to cause fuel cuts.
What mods to you have? As you reduce the intake and exhaust restrictions, the turbo will spool faster and this increases the magnitude of boost overshoots. Once you understand how a MBC-A works, it is obvious why there are pressure overshoots.
Jeff in ATL started with a MBC, then did the MBC+A. That was working well. He thought that it was as good at it could be. I sent him a TB adapter hose from my old 95SET, and he hooked that up. He really liked the improvement.
You really need to get to higher boost levels to appreciate these improvements.
Boost taper is worse with the old IC and less so with a Viggen IC.
posted by 66.142.22...
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