Does anyone know it the SC430 has a fuel system that uses a returnless or return setup?
Thanks

 

I believe it is a return fuel system. I'll check my book tonight to be sure.

 

It's a returnless fuel system. All of the VVT-I engine adopt these system. There is a pressure regulator located in the tank. Fuel pump ecu regulate the amount voltage going to the pump.
JPI

 

What was the purpose of the question in the first place? What does this mean? How might this knowledge benefit us?

 

Thanks for the correction JPI....I believe the question would benefit anyone who would want to enhance the performance of the engine.

 

...or anyone going FI. A return system has a fuel pressure regulator placed after the injectors that opens & closes, depending on vacuum, to alow more or less fuel to flow through. The less fuel it lets through the more the fuel backs up and fuel pressure rises which forces more fuel through the injectors into the motor. The fuel that passes through then "RETURNS" to the fuel tank. That is why its called a return fuel system. The returnless system works as described above by JPI. It just alters voltage to control pressure. Its easier (IMHO) to control fuel delivery in a return setup.

 

As stated if one is considering FI fuel management is a big issue. If you try to trick the car's ECU with a piggyback system it often re-learns due to its feedback system (closed loop). A return system can be adapted easier by having a parallel system. Here is an article; http://autospeed.com/cms/A_2636/article.html

 

Sorry I couldn't reply to this thread earlier because I went out of town. Back to the returnless fuel sytem. The returnless fuel delivery system was adopted because it lowers evaporative emissions since no heated fuel is returned to the fuel tank. On the return fuel delivery system, fuel heated by by the engine returns o the fuel tank and has warmer fuel craeting more fuel vapors.
Let's move into fuel pump speed and it works. When the ignition key move to the ON position, Fuel pump will continue to run if the NE signal(Crank shaft sensor signal. This crank shaft procket mounted on the crankshaft). If the NE signal is lost at any time after starting, the ECM(Electronic Control Module) turns the fuel pump off.
There are a couple of designs of pump control, and here they are:
- ON/OFF Control by ECM
- ON/OFF Control by fuel pump switch
- ON/OFF Two speed control with a resistor
- ON/OFF TWo speed control with Fuel pump ECU
- ON/OFF Three speed control with Fuel pump ECU
I don't have the time to go into details for all of these pump control but into a little further details on the, ON/OFF Three speed control with Fuel pump ECU because that is what came with the SC430.

With this system, Your fuel pump is controlled in 3 steps(High speed, medium speed,and low speed)
High speed When the engine is running under a heavy load at high rpm and starting up, The ECM sends a 5 volt signal to the fuel pump ECU. The fuel pump ECU then applies battery power to the fuel pump causing the fuel pump to operate at this high. This is consider open loop.
Medium speed Under heavy loads at low speed, the ECM sends a 2.5 volt signal to the fuel pump control. The fuel pump ECU applies about around 10 volts to the fuel pump.
Low speed When the vehicle is idling or under light loads, the ECM sends a 1.3 volt signal to the fuel pump ECU. The fuel pump ECU applies 8.5 volts to the fuel pump, preventing excessive noise and decreasing power comsumption.
Returnless fuel system maintained at a constant and higher pressure, 44-50 psi of fuel pressure.
I will continue with the part 2 tomorrow. Mod the returnless fuel system

 

This is very interesting. I didn't realise that the system was so involved in this car.

 

When the system is in "open loop", ie in the 3rd stage, does anyone know what gal/hr rate can the stock pump put out at around 50 psi? Also can a series booster pump be placed inline?