Fuel System

[eschaider]

Originally Posted by bobcowan

Ohhh, look what I found! I'm liking this.

https://www.holley.com/products/fuel...s/parts/12-133

Who knew shopping could be so much fun?

Bob,

Here is a larger pic of a current production dual pump Fore fuel hat, click here => Fore Hat Top View. By clicking on the photo it will cycle through other views.

The bottom gasket surface is machined flat. The left circular opening on the top of your tank I suspect is your fuel level sensor. The larger one on the right appears to be an access port. If you built a flat plate that bolted to the existing BDR bolt circle there and had the Ford OEM bolt circle that Fore uses then, the Fore hat bolts right up to your existing tank.

Morris asked an important question about placing multiple pumps on opposite sides of the tank, I suspect for fuel control during cornering. EFI systems and EFI pumps do not like the pump pickups to be uncovered. They require continual submersion. Uncovering either of them will introduce air bubbles into the fuel delivery line that will minimally cause popping and occasional backfiring. Under power with a supercharged engine it will burn a piston.

The fix for the problem is building a diamond shaped baffle (like an oil pickup oil control baffle) around the pump pickup with sufficient depth (~2 -3 inches) that it will keep the pump inlets covered during cornering and less than full tank conditions.

The Hollry system is one of those popular systems that has a few rough edges. One of them is their 60 psi relief valve built into their fuel hat. Injectors are flow rated at 3BAR (43.5 psi). Everyone except Ford runs their base fuel pressure at or above 3BAR. For supercharged applications in particular, you want your fuel pressure regulator to be boost referenced. That means you will end up buying a separate boost referenced regulator to be used down stream from the pumps.

With a boost referenced regulator, as manifold pressure rises and falls so to does fuel rail pressure. The idea is to maintain a constant delta pressure across the injector nozzle to make injector pulse width calculation more precise and AFR more steady — a good thing on a supercharged engine.

If you have 20 psi of manifold pressure you will need 43.5 psi (3BAR) of base pressure plus 20 more psi of fuel pressure to restore the injector delta pressure to 43.5psi. If your system uses a higher base pressure than 43.5 psi then you need to add that to the 20 psi boost pressure in the manifold to get back to your constant delta pressure across the injectors.

A base fuel pressure of 43.5psi and a 20 psi manifold boost pressure puts the fuel rail pressure at 63.5 psi. Remember that 60 psi blow off valve in the Holley hat? It is not only already open but the story gets even worse. If you put a pressure sensor on your fuel rail and another back at the pump and then data logged the two you would see a 10 psi or higher pressure differential between the two test points.

The 10 psi difference between the two test points means that your fuel system has been leaking fuel back to the tank for a long time. EFI systems are constant pressure variable injector pulse width systems. That means that at low speeds, leak not withstanding, you would be OK because your primary fuel pressure regulator would just bypass less fuel.

At high engine speeds, under power, your engine would go lean and you would literally kill one or more pistons in an engine that for all intents and purposes looked to be properly tuned.

Fore has been making those fuel hats for a decade longer than anyone else. He literally invented the methodology for supercharged Fords when his company was called Fore Precision. This is a 12 or thirteen year old Fore hat that I bought when I first built my engine.



In some ways the selection was pretty easy because at that time he was the only game in town. When others saw his success with the product, suddenly there were many competitive alternatives. The sales pitch in the beginning frequently was something to the effect the competitive offering was "as good as a Fore."

Many of the copycat providers have faded away, some have remained. Today the EFI companies have embraced the same fuel hat style for their in-tank pump offerings. The in-tank pumps are almost exclusively built by Walbro, Bosch or TI Automotive. They are the best performing, most reliable fuel pump alternatives available today and they are cooled by the fuel they are submerged in.

Don't get me wrong I have no association with Fore other than to use his products, just like the Walbro, Bosch etc fuel pumps. I have built many supercharged modular engines and these parts simply work without drama — and drama on blown motors turn out to be burnt pistons, heads and yes even blocks.

In the end it is your build and your motor and no one is more qualified to decide what goes in there than your are. Supercharging ups the ante at the check writing table for engine parts. I'm trying to give you enough experience based knowledge so you have a better than average chance of keeping those expensive pieces operating and inside your engine where they belong.


Ed