[V8] Fuel Pump Noise

[Professor GT gmail]

Al,

In spite of what's already been stated, I have to point out that that some other manufacturers have developed a circuit which uses a 5-pin relay to REDUCE fuel pump voltage below approx 75% throttle, to spin the pump slower and reduce NOISE. They did this because of noise complaints, and found that unless the throttle is at WOT max pump volume wasn't necessary, BUT the pump has to be designed to handle running on lower voltage reliably. Basically a dropping resistor was used through the relay on the normally closed contact, and then when the engine ecu sees WOT it switches the relay to the normally open contact which gives the pump full voltage, so it supplies max volume to meet the demand.
So, I guess, the bottom line on your pump is that if you are getting proper voltage drop across the pump, then other than the way it's mounted, or an issue with the pickup sock, the pump is the culprit. BUT that may just wind up being the nature of the beast, as one of our other members (sorry I forgot his  name) so aptly pointed out as is the case with some Bosch pumps.

A quick look at the schematic will tell you if the fuel pump is voltage controlled as I mentioned earlier. Some ecus even employed current controlled output drivers for this same reason.

It's also interesting to see what has transpired with fuel return systems. They have basically been eliminated due to evaporative emissions. By having a return line the fuel is heated and agitated, causing more evap emissions. So, the return line was eliminated (saves lots of cost in vehicle production). This however also eliminated the ability of the return line to carry away the heat the fuel absorbed from the injectors, etc. So, to prevent possible vapor lock issues (remember that from carburetor days?) the fuel pressure was bumped to at least 50psi. (increased pressure raises the boiling point - same reason cooling systems have a pressurized system).

Well, okay maybe you are too young to remember Carburetors - damn, I'm gettin OLD!, but you get the idea.

Hmmm, can't say I'll have the V8 ready for Sfest, but I'm sire as heck gonna try! 

Thanks,

ProfessorGT
(Sent from my iPhone4)