Quote:
Originally Posted by BoxerSix
Erics(EJ) MBC pulls its boost signal from the compressor outlet as OEM.
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Wow, not the EBC then. Both configs, boost/vac and boost-only and the same result.
The test car is cam'd with both intake and exhaust. I think that we're seeing the culmination of 2 possible scenarios. Because, as I mentioned, BOVs aren't smart, and at the end of the day, the pressure at the IC pipe pre-throttle is oscillating, which makes the valve cycle open and close. This has been minimized by taking the actuating pressure at the compressor where the flow is consistent. After the intercooler, you have dampening of pressure and flow and pressure signal attenuation, and ultimately, the engine consuming flow pre-throttle.
The 2 co-existing scenarios I see are:
1) Reverse flow through the compressor via compressor surge is generating noisy signals for the MAF which unsettles the car.
2) DV Flutter is due to: Engine air consumption rate at part throttle/high rpm is much higher than stock. Which generates airflow inconsistent with steady compressor discharge flow of the stock turbo. The stock turbo spools so fast to make the pressure ratio, but perhaps doesn't have the flow at that pressure to overcome the demand of the cam. I surmise that you're actually hitting the surge line of the compressor map.
This really comes down to a question of dissonant air flow across the engine. A BOV can potentially band-aid this scenario by regulating the pressures pre-throttle. I had a meeting with a defense contractor recently that was having this type of surge-line limitation with a compressor they had on a piston aero engine and the fix was to shift the surge line over using a DV to bleed compressor flow in order to get the turbo shaft speed to an area of greater efficiency. Their scenario was similar, as it was under load that this was happening.