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Turbo NC Vacuum lines

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Why and what are we doing?

So lets clarify from a strategic point of view. What components need vacuum-reference to operate in total. First the fuel setup has changed. To an aftermarket fuel-rail by Radium Engineering. This fuel-rail has Radium Engineering’s fuel-pressure-regulator and fuel-pulse-damper mounted directly to the fuel-rail. Both of which need vacuum-reference to operate. Let’s focus on the FPR (fuel-pressure-regulator). The FPR is a “rising-rate” regulator.

To do this we need to clarify some common terms relating to the fuel rail setup.

“Base fuel pressure” – This is is set when the FPR’s vacuum-port is open to atmospheric-pressure. During initial first start-up. Typically this is set at 43.5PSI but can vary from vehicle to vehicle.

“Rising rate” This term is used to describe a common type of FPR. The regulator has a vacuum-port. This is so as the vacuum-source-of-origin increases pressure from negative-pressure (vacuum) to positive-pressure (boost) the FPR can compensate by that value. So to conclude if the base-fuel-pressure is set at 43.5PSI and your intake-manifold has 10psi of boost-pressure then the fuel-pressure increases from 43.5PSI to 53.5PSI under boost conditions.

This is why the FPR needs to be connected to vacuum-reference. I should clarify when we use the term “vacuum” when speaking about engines. This can mean the hose, fitting, part etc can be under vacuum and also under certain conditions be under boost-pressure. So the term vacuum with engines is a sort of loose term as it also refers to boost-pressure. The fuel-pulse-damper (FPD) is used in fuel injection systems to absorb pressure pulsations generated by the fuel-pump operating and by the injectors opening/closing. In our case the vacuum-port needs to be hooked up preferably to the same vacuum-line as the FPR. So a Y-fitting is installed above the fuel-rail to link the FPR and FPR to one common line.

Before we jump ahead we must first understand how we get vacuum-reference to all our components under the bonnet. We do this with a vacuum manifold. It would be worth noting my vehicle is RHD so placement of the vacuum manifold may need to be altered if your using on a LHD vehicle. So lets start at the vacuum chain. First we originate from the intake-manifold, then using the original brake-booster plastic barb we take a short stab of reinforced airbrake hose to a plastic tee. Continuing through the tee we take another stab and connect to the BOFI Racing branded vacuum-manifold via a 90degree 12mm barb to AN6 female fitting, then attached to a AN6 to M20x1.5mm straight fitting with an O-ring. These generic style manifolds can be picked up cheap and they are ideal. However do not listen to the seller about specifications, the large end ports are not 1/2″NPT. They are once again, M20x1.5mm straight-thread and you’ll need a 20mm I.D. 2mm C.S. O-ring to create the proper seal into the aluminium manifolds chamfer. The smaller nipples are 1/8″NPT. You’ll need to use something like Permatex high-temperature thread-sealant to create the seal. Do not use PTFE-tape. Thread-sealant today is preferred. Working away from tee-fitting we take another short stab of hose to connect to the original 3/8″ brake-booster hardline.

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