The heart of the fuel system is the fuel pump. It must deliver the volume of fuel needed at the require pressure for the rest of the fuel system to do its job. If the pump is not up to the job, then nothing else is going to matter.
Some dispute that an upgraded pump is needed. Let them dispute it if they want, we at UNDERDOG RACING DEVELOPMENT have seen a fuel pressure loss whenever we try to get enough fuel into the engine to meet the needs of the supercharger. The stock pump is fine when used with the stock injectors, but the stock injectors do not flow the required amount of fuel. When the proper size injectors are installed the stock pump CANNOT flow enough fuel to feed the injectors and meet the demands of the supercharger. That results in a loss of fuel pressure. A loss of fuel pressure on a forced induction engine is just a disaster waiting to happen.
If you want to see for yourself what we are talking about here, watch this video. This test was done on a 97 Supercharged 4Runner with 305cc injectors and a stock pump. The left gauge is the Exhaust Gas Temperature, the center is fuel pressure, and right is oil pressure. Watch the center gauge. As the RPMs build at full throttle, you will see the fuel pressure drop off and at the same time the EGT spikes up from the lean out. Keep in mind that this truck only had 12,000 miles on it at the time of the test. Convinced yet??
Gadget has done a lot of fuel pump testing over the years. He first started with the Kenne-Bell Boost-A-Pump. This is a voltage amplifier that increases the voltage to the stock pump to make of flow more fuel then it normally would. This worked well, but it does increase wear on the stock pump and is more expensive the replacing the pump itself with the proper size. So, what is the proper size pump?
Gadget acquired several different fuel pumps and had them professionally flow tested at different pressures and voltages and tested them in the truck. All of this finally led to the perfect fuel pump, the Walbro 190 LPH fuel pump.
When used with the proper size fuel injectors, this fuel pump flows the fuel needed by the supercharged engine at about 80% of its total capacity and has a low current draw. It fits into the stock pump bracket in the fuel tank and is easy to install.
If you are not planning on increasing the size of your injectors it is unlikely that installing this pump will be of any benefit to you and we suggest that you do not waste your money. The stock pump is capable of flowing all the fuel that those little stock injectors can flow. Also, if you are planning on running a pressure increasing Fuel Management Unit (FMU) this is not the pump for you. This particular model 190 LPH pump will suffer from reduced flow over 60 PSI. If you are going to run a FMU that is going to increase the fuel pressure above 60 PSI, then you should seek out and purchase the ï¿½High Pressureï¿½ version of the 190 LPH pump. That will maintain flow as the pressure increases. UNDERDOG will not be carrying the high pressure version, or any FMUs as we feel that approach is an ineffective ï¿½Band Aidï¿½ fix and we want no part of it.