// simple regulator model that clamps smoothly to about 5 inhg
// over a normal rpm range
- double max = 5.39 - 1.0 / ( rpm * 0.00111 );
+ double max = (rpm > 0 ? 5.39 - 1.0 / ( rpm * 0.00111 ) : 0);
if ( suction < 0.0 ) suction = 0.0;
if ( suction > max ) suction = max;
}