SPA Turbo FPR

Description

Brand new Rising Rate Fuel Pressure Regulator (FPR) – to suit turbo or supercharged blow through carb applications.

Designed for use with EFI fuel pumps and other high-pressure pumps whilst fully adjustable to regulate fuel pressure down to carb levels. 

FPR delivers a 1.2:1 rise in fuel pressure as boost pressure increases.  For example, if set at a base fuel pressure of 5psi, and running 10psi of boost, the FPR will deliver 5psi fuel pressure off boost, and 17psi fuel pressure at full boost. 

This can help overcome restrictive needle and seat.

This FPR has 3 x 5/16” (8mm) hose tail barb fittings and includes a mounting stud/nut. These fittings are for inlet, outlet and return to tank. The boost port fitting is 5.5mm.

These are the FPRs that we use in our blow through turbo kits, they work great and you can’t beat the price.

A blow through turbo/supercharger application requires a special fuel system that has to stick to a very important rule: The fuel pressure must remain above the engine boost pressure at all times.  Otherwise, the boost pressure generated from the turbo or supercharger will stop fuel flowing into the carb fuel bowl, starving the carb of fuel.

Allowing the carb to starve of fuel not only makes the engine die in the bum, (like you’ve just run out of fuel obviously), but it’s also dangerous to your engine, as low fuel pressure can cause a lean running condition that will allow detonation/pre-ignition to destroy your pistons, head gasket or head/engine itself.

For the fuel pressure to remain above the boost pressure, you need two components.

1. A fuel pump that will deliver enough flow and more fuel pressure than the boost pressure you plan to run.
2. A Fuel Pressure Regulator (FPR) that will control the fuel pressure and make sure it always stays above boost pressure, but not so far above that you flood the carb.

This FPR is designed to allow the base fuel pressure to be adjusted in the range of 2psi to 10psi, (depends on pump output, return line back pressure, etc. – 2-10psi has been tested with our 070 EFI pumps).   This base fuel pressure is adjustable to suit your carb, as different carbs require different fuel pressure to operate properly.  FPR has a lock nut to stop accidental changes.

4-6psi of fuel pressure is ideal for most downdraught Weber carbs like the 32/36 DGV and the 38 DGS.  Any more fuel pressure than this and you will overpower the needle and seat resulting in a high fuel level or a flooded fuel bowl.  Holley carbs can handle about 7psi of fuel pressure, whilst other carbs such as Edelbrock, Rochester or Carter will all have a maximum base fuel pressure that they can run up to.  This depends mostly on the brand of carb and the needle and seat fitted.

We’ve run many different blow through turbo setups using downdraught Weber carbs like the 32/36 DGV, so we know what’s required, and know what works and what doesn’t.  We modify and test these FPRs ourselves to make sure they operate correctly and will do the job right.

The FPR utilizes a return line to allow the use of a high-pressure pump, such as a typical EFI pump or an off the shelf high pressure carb pump like a Holley Blue or Carter, whilst still delivering low enough fuel pressure to allow adjustment in the 4-6psi base fuel pressure range.

A small, barbed fitting allows connection of boost pressure.  The fuel pressure will be increased by approximately 1.2psi for every 1psi of boost pressure.  This gives a 1.2:1 rate rise in fuel pressure vs. boost pressure.  For example, if you set your base fuel pressure at 5psi and you want to run 10psi of boost, this regulator will deliver 5psi fuel pressure off boost, and approx 17psi of fuel pressure when on 10psi of boost.  Keep in mind you need a fuel pump capable of delivering at least 17psi of fuel pressure, at enough flow to keep your engine fed with fuel at full noise.