The trick I was talking about involves replacing
the 1/4 inch hose with larger diameter hose, a larger diameter tee piece and, of course,
larger tap fittings. The result is that you are still achieving the same effect. ie there
is a pressure drop at the wastegate actuator, but we are using and venting much more air
to atmosphere to achieve this.
On the VL commodore EFI system, the boost air being
vented to atmosphere has already been measured by the Air-Flow-Meter, and so the computer
has already calculated how much fuel is required to mix with that measured air. What we
are doing is releasing some of this air out of this normally closed system. The result is
that the computer "thinks" that (A) amount of air is being mixed with it's
calculated fuel quantity (F), but, in fact, since some of this now pressurised air (A) is
being bled to atmosphere via tee piece, hose and tap (B) we have a higher ratio of
fuel/air.
In a normal system, the formula would look
something like: Fuel/Air Ratio= F/A In the standard sized piping to increase boost we
would have: Fuel/Air Ratio =F/[A-(1*B)] By doubling the 1/4 inch pipe diameter to 1/2 inch
bleed hose: Fuel/Air Ratio =F/[A-(2*B)] The end result is a much richer mixture, helping
to eliminate lean-out when increased boost is present and eliminating pinging.
However, going overboard on hose diameter will
overwork the Turbo and you may find that descent boost levels can't be reached. ie the
turbo runs out of puff, especially in high RPM. The best solution is to have the EFI
modified to richen the mixture.
