The Allison/RR 250 fitted to JetRangers, Hughes 500 and the likes doesn't, as far as I remember, have VIGVs. What it does have is a bleed valve on the compressor section which, at start, is fully open.
As the start progresses and pressures build up along the (logical) length of the engine, the bleed valve is closed. If this didn't happen the pressures at low compressor RPMs would lead to compressor stalls. However this mechanism is totally automatic, and the only thing the pilot needs to do is ensure the valve is open before start by physically checking it.