Evo Forum

[ghoonk]

Okay guys, need some advice regarding risking rate fuel pressure regulators, e.g. HKS fuel pressure regulator, SARD fuel pressure regulator.

When installing an adjustable fuel pressure regulator (FPR), many people make the mistake of setting the fuel pressure with the vacuum line on the FPR still connected. From what I now understand, the correct way is to set it at a fuel pressure high enough to get the engine running, then disconnect the vacuum hose on the FPR, THEN set the fuel pressure to the 'correct'/desired level before reconnecting the vacuum hose. This will typically cause the fuel pressure to then drop.

For the purpose of this question, let's say we set the fuel pressure to 2.8 bar (40.6 psi)with the vacuum line disconnected.

Now, according to a number of online references from FPR manufacturers, this means that the fuel pressure at WOT is 2.8 bar, and the idling fuel pressure should be lower. In many cases, this would be irrelevant since we should only be concerned with fuel pressure under throttle.

Now, with the understanding that

a. fuel pressure should be set in accordance with the target peak boost level (i.e. to provide the right level of fuel pressure at max boost), and

b. this seems to be consistent with the description of the purpose of the differential pressure warning lamp in the Defi Link Control Unit II,

what is the 'correct' fuel pressure to set (with the vacuum hose off) if I am running 1.5/1.6 (21.7-23.2 psi) bars of peak boost, assuming that I am using stock fuel injectors and a Walbro 255 lph fuel pump?