@Fullthrottleguy just mentioned this to me in my engine swap post. I'm sure he has more info on this.
well since you asked ...
All this related to 500HP and up -- But let me explain what I have learned on the bigger HP cars ... probably gonna be long - I apologize upfront ..
Lately I have been doing more and more e95 High HP cars. E85 uses ~ 1.5x the amount of fuel as race gas, but in turbo or SC engine the fuel consumption is of course far greater during boost as is the pressure (boost referenced pressure). The problem most pumps have is that you start with a non boost 60PSI base pressure and if you are running say an SC with 20Lbs of boost now your Fuel pressure in boost is 80Lbs - Most Pumps are generally designed to deliver the highest volume at 43psi and tend to drop off fast over 60psi and when you are making 1200-1400HP, you are using a lot of fuel. So to get around that generally you run a big pump with big volume.
Or maybe you are just that "bigger is better" kinda person ... Unlimited wallet size ...
If you go that route, you are likely running -10 or -12 line and a big pump like an Aeromotive Eliminator which can feed a 2500HP engine, and without a motor controller you are pumping a ton of fuel all the time and using very little at idle and part throttle , and while those pumps cool by having fuel run around them (internally) they will not usually overheat and shut down, but they heat the fuel which is generally bad, But what is worse is that you are returning a ton a fuel back to the tank .... a few issues here. Also using a fuel regulator it's just suppose to regulate the "pressure" not the volume - but if you push too much volume to a regulator that can't handle that much volume you will be pushing back on the pump causing the pump to work way harder against the back flow (its like hitting a wall for the pump) and the pump will draw more current and run hotter trying to meet the demand, and hotter pumps heat fuel and have less life.
The big issues not using a motor controller and a big pump are:
1. You are making lots of gas fumes- which by itself is fire hazard and it also wastes fuel and if you don't have a big enough vent you also put back-pressure on the regulator
**** Vents are also really important if you have -10 feed you need -10 vent etc. If the vent is not bringing air to replace the fuel going out of the tank you will either cavitate the pump or just cut down the volume (collapse the line) I have seen guys run the hill at G and car pops and sputters and the guy goes home spends $2K on a new fuel system and its Worse - I pull the Tank cap off and have them try again and the car is rocket - problem - vent too small....
2. You are heating the fuel pushing it through the lines
3. You are causing aireation of the fuel - this is really bad because you put bubbles in the fuel - and enough bubbles and pump cavitates and ruin the pump and or lean out the engine - even though your pump could power a fire truck ...
4. You are banging really hard on the regulator - its either going to fail or your fuel pressure is going surge up and down and that is worse than having low fuel pressure -
5. You alternator is working really hard to keep up with the fuel pump current draw (and all your Baller LEDs and 10,000 watt stereo) that 30AMP fuel pump relay is likely to burn up too - time to go 70amp
The motor controller does a fuel things - One thing it does NOT do is turn down the pressure - it just turns down volume - but what it does ...
1. It adds life to pump and the regulator - they are not working as hard
2. It guarantees you are not getting any of the three things mentioned above
3. It guarantees fuel is there on demand when you need because its PWM (Pulse width modulated) so the pump does not strain coming back up to speed
4. It guarantees the Fuel Pressure is always the same - since it just varies the Volume ...
5. Puts less strain on your electrical system
an added bonus is the pump is way quieter until you romp on the engine
The Aeromotive controllers are dead reliable from my experience, and have not done alot of others, but you Must match the pump and controller brand since its PWM and depends on a number of factors that are specific to the pump
One exception is used the opposite way and thats the Keene Bell BAP (boost a pump) that actually increases the PWM and Voltage to a pump to make it pump more - thjey are pretty universal and work great - but cost more than a new pump in most cases.... so its really only good for factory cars you don't want to tear up.
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You also need to size the Fuel filters to the pump - they can either restrict fuel flow or you can with a big enough push actually blow the filter element apart in the filter - I have seen that on 100LPH filters on a 1000LPH pump (Eliminator)
Before motor controllers got really good and if someone is on a budget, I would use 2 pumps in parallel with check valves on each pump, and run one pump until we got into boost and then either turn the second on with Hobbs switch or programmatically through the ECU (MAP Input)
That works really well except check valves always restrict flow - so its not as efficient, but it usually way more affordable and way more flexible than a big pump
On my personal SC car I run two AEM 400LPH's that way using the Holley to trigger the second under boost. What is also nice is that if your primary pump fails, you move the wires over and just "try" to stay out of heavy boost, but you aren't stuck.. Hardly antyone is carrying around and $800 Eliminator pump spare ...
BTW thew AEM is the only pump I found other the Aeromotive's that actually have a good output curve in higher PSI so for SC and Turbo cars they work great
On a 500HP engine it's pretty common to run a 200LPH - 340LPH pump like a Weldon or Bosch 044 and those pumps like the AEM don't have the volume or raw pressure to need to a motor controller as long as your bypass regulator can handle the flow (so don't use a Chinese A1000 knock off regulator)
The charts I have seen from RC and others for the 340-400 category by output curve vs pressure - rank the AEM at the top, the Aeromotive 340 second, the weldon A-600 tied with the Aeromotive , the Bosch 044 next (real not counterfeit) and far behind the Aeromotive Tsunami.
They are all pretty equal in reliability as long as you feed them enough current so they stay cool and don't run them dry.
Having a equally as well flowing regulator is really important. when I run into someone Not running and Aeromotive, Fuel Lab, magnafuel or Weldon regulator I test them down to 40lbs to see if they can maintain there with one of the good pumps and I run the return through a clear hose back to the tank - if I see bubbles or pulsing in the stream - I will not guarantee the tune I out in the car - I know its gonna lean out and burn down the engine - regulators and pumos are important.
IMO anything that runs over ~ 850HP at the crank either needs dual pumps in parallel or a BIg A$$ pump and motor controller - Back before site meltdown I posted a couple build HP Fuel systems I did - I need to find those pics again
But for me if run an Aeromotive Eliminator, Weldon 1100 or bigger, or bada$$ Magnafuel Prostar or the Aeromotibe gear pumps (copies of the prostar basically..) you will do yourself a favor if you run a motor controller. Most of the brushless pumps require a motor controller, and its hard to justify the spend although they draw way less current and should last forever...FWIW
