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Fuel Pump and Current Draw

General Tuning Discussion

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For a fuel return system,

does the current draw from the fuel pump change with engine load and fuel requirements?

How many amps can an ABS require when activated?


Sure the current draw changes with fuel pressure/flow

Here is AEM 320 LPH diagram

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  • Fuel-Pumps-Pressure-vs-Flow-Current-50-1000.jpg
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So running a lower fuel pressure gives us a higher rate of flow, that's gotta be good.

keep in mind that if you reduce the fuel pressure you also reduce the injector flow and the atomisation.

Yes, so how do we determine the "sweet spot" when putting a fuel supply system together, if we account for drop in flow as we increase rail pressure, determine what pressure the injectors require under max load to operate at their most efficient, and supplying requirements for expected HP, we should be right? So your Walbro 450 E85 "compatible" pump for example, is it affected by the density of the liter it flows ?

eg, 745 / 782, and I guess we shouldn't forget about at what temp..

I like that "Fuel-Pumps-Pressure-vs-Flow-Current" graph have you seen those for specific brand/model of pumps?

I cant wait for the webinar, when all will be revealed, or maybe it should be a module in the Course, "Practical Real Life Wiring",

The 'sweet spot' as you put it, will depend on what you're doing and how much flow you need at your injectors. This in turn comes down to how much power you're trying to support. Most injector manufacturers will provide you with data that relates fuel pressure to injector flow. Within reason, as the fuel pressure is increased, so does the injector flow and hence the amount of power they can support. An aside to this is that often with increased fuel pressure comes improved atomisation of the fuel.

It's common for OEMs to use 3 bar differential pressure on a return-style fuel system and 4 bar on a returnless. On the other hand for high output drag motors its common to run 5.5 bar differential pressure. You would struggle to run 5.5 bar with an electric pump though and most of the guys running these sort of setups are using mechanical pumps.

Once you've decided on fuel pressure, this will let you know what sort of current draw you can expect - Provided of course you have this data from the pump supplier. If your engine is boosted though, remember that under boost the pressure will increase and hence current draw will also increase.