quote:
I was just looking for feedback on what Tennessee Tims fuel plumbing design does.
but then I have had SO MANY issues with Holleys I worry about them also.
Tennessee Tims fuel system set up is essentially the same set up as for fuel injectors.
In injection you have a pump feeding two fuel rails, then these rails are connected to a regulator (or pressure relief valve) that once a preset pressure (say 50 psi) is reached in the rails allows the extra fuel to escape back to the tank thus maintaining the preset pressure very accurately in the rails and to the injectors.
Tennessee Tim has a pump feeding a fuel line that delivers fuel to each carb (like injector rails deliver fuel to injectors) and then at the end of that line he has the regulator (or pressure relief valve) that allows the pressure in that line to only reach 2.5 psi and then allows the extra fuel to flow back to the tank.
This type of setup can cope with a much larger quantity of fuel being delivered from the pump and still maintain the pressure setting very accurately.
So if you have a very large pump to supply huge amounts of fuel to a engine that requires huge amounts at WOT (maximum speed, maximumum load) then that very large amount of fuel can be hard to regulate accurately when engine demand for fuel is low, like idle or cruising.
But if your pump is variable volume, such as controlled electronically to vary it's speed with actual fuel demands, then the pressure relief valve system with the return line back to tank is less necessary and the more simple system of a pressure regulator with no return line can work ok.
There is a trap here for the unwary.
In the Fuel injection system and Tennessee Tim's system the "regulator" is in fact misnamed, it is actually a pressure relief valve because it maintains the system pressure by allowing excess fuel to escape the fuel system and return unimpeded to the tank. This works like the pressure relief valve in a hydraulic system.
A regulator works a completely different way.
It creates a restriction to flow from the pump to drop the pressure on the outlet side of the regulator to the preset level. Like the regulator on a gas cylinder.
This basically deadheads the pump so the pump needs it's own mechanism to prevent over pressure, ie it's own internal pressure relief valve. Such as in Holley or Carter electric pumps.
Pressure relief valves work best with liquids and regulators work best with gases.
What tends to happen when you use a regulator with liquids is at high flow rates the liquid will flash off into vapor as it passes through the restriction that produces the pressure drop. Like the expansion valve in a refrigeration system. Minute bubbles of vaporized fuel in the fuel going to the carburettors may not be very desirable. The pressure relief valve set up does not produce that problem.
Holley carbs ?? I have had SO MANY issues with them too. That's why i went to EFI.
