Return Style system

[crcpdx]

Hi Guys,
My Lethal return system is arriving today and had some questions for you guys. Its a dual pump for now since I'm only around 750whp. I was thinking of running only 1 pump constantly and putting the second pump on the switch as soon as boost comes in. I know there are some concerns with pump failure, but is that really a big concern? Also will I get enough fuel on E85 with just 1 pump when not in boost? My thought process is the car is mostly street driven and I would like to avoid the extra heat (especially when running 93) and also unnecessarily sending extra fuel around in circles.

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[80FoxCoupe]

You will be fine with the staged setup.

 

[Andrew@Lethal]

Hi Guys,
My Lethal return system is arriving today and had some questions for you guys. Its a dual pump for now since I'm only around 750whp. I was thinking of running only 1 pump constantly and putting the second pump on the switch as soon as boost comes in. I know there are some concerns with pump failure, but is that really a big concern? Also will I get enough fuel on E85 with just 1 pump when not in boost? My thought process is the car is mostly street driven and I would like to avoid the extra heat (especially when running 93) and also unnecessarily sending extra fuel around in circles.

I would run both pumps constant. Hobbs switch wouldn't be needed unless you were running a triple pump system.

 

[FastCarFanBoy]

I would just run them both on full time, less complicated and no downside.

 

[Angrey]

I would just run them both on full time, less complicated and no downside.

The downside is running both pumps wide open full time. It's wear and tear on the pumps, added heat and unnecessary churn of the fuel back to the tank, etc. It's also more wear and tear and load on the electrical system (depending on the pumps, you're talking about 40 or more amps consistently running). You run a further increased risk from vapor lock as the tank depletes and the thermal heat sink capacity of the partially filled fuel tank diminishes. (i.e. 16 gallons can soak up more heat than 4).

The benefits are some semblance of safety (although I'd submit to you that if one pump burns out, it's not that much safer both running than staged. If he mashes and only one pump is available, there goes the motor. (regardless of whether it was supposed to come on or not). If he mashes with a staged system and the second pump isn't available, there goes the motor.

The other minor benefit would be that full boogie on both pumps would be constantly sucking max value out of the syphon from the passenger saddle.

In fact, by staging, depending on which pump fries, which would probably be more often the "base load" or pimary pump, it may save his motor because it'll take a dump at lower load. If he runs both all the time, and one goes out, he's not going to know one's out until he mashes and boom.

I guess someone could add an indicator light that either lights full time when both pumps are running (and goes out if either is faulty) or lights up if one of the pumps is dead.

 

[Dominant1]

I just got my Fore system from beefcake today, its a dual pump set up with the fc3 controller with hobbs switch for the 2nd pump. The Difference is i’m running gas only and race fuel so i don’t need the highflow 465’s that you have. I have 2 walbro gss 342 g3’s.. less flow = less heat and draw. It will be perfect for my set up. I’m gonna see if my tuner can give me a second pump indicator light , that would be nice..

 

[crcpdx]

I would run both pumps constant. Hobbs switch wouldn't be needed unless you were running a triple pump system.

So I know that is what Lethal recommended, but I haven't really heard a good reason. Do you know why I should run both?

 

[BlackandBlue]

So I know that is what Lethal recommended, but I haven't really heard a good reason. Do you know why I should run both?

You eliminate another point of failure by running them all the time. Fuel pumps are pretty reliable. A separate system adds failure points.

All it takes is running lean one time.

It’s also less work.

 

[Dominant1]

Im currently running the stock pump with a bap @ 750 whp..on pump 93 + octane booster in every tankful & if that bap was to fail during a wot pull i’m done. I’d rather be second pump dependent then bap dependent. The single walbro pump that will be running during normal driving flows more fuel then the stock pump with bap would flow at wot. The second pump turning on at the given boost level is insurance. If your running both 465’s all the time, your current draw will be high and the heat those pumps generate, especially on a hot day with a long drive could become problematic. I would talk to your tuner, he’s the one that knows whats best for your set up..

 

[Angrey]

As I've said guys, if the problem is a concern about a pump going out, then running both of them at the same time isn't really addressing the issue. If it's that much of a concern, then a simple wire with a status light would serve better.

Returnless systems are much more efficient. Return style systems attempt to mitigate the disparity by staging.

Running a return style with multiple pumps screaming full load all the time because you're worried about running out of fuel is like leaving your shower on hot full blast all the time because you never know when you might want to take a shower and you want hot water to be there when you decide.

Or driving around at WOT all the time because you're not sure when you're gonna want torque so you just leave the pedal smashed and manage with the clutch and the brake.

Does it work? Sure. Is it less risky than shutting the water off and on only when you need it? That's debatable.

And the argument that a hobb switch is another point of failure is no different than any other component of the system.

And just to be clear and put it into perspective, a typical residential 4 burner oven uses a 40 amp circuit breaker (meaning that by design it's never meant to draw more than 40 amps without tripping the breaker as a safety measure to ensure the circuits don't overheat and cause a fire). 40 AMPs constantly on an electrical system isn't trivial.

 

[Angrey]

In fairness, I looked up a typical TI 267 and TI 274 pump curve chart(s)

Assuming that the vehicle electrical system is somewhere between 12.0 volts and 13.5 volts (with the smart system we have) and assuming the pumps will run between 55 and 75 psi on the adjustable regulator, the 267 will operate at between 16.5 amps and 18 amps (55-70 psi, 13.5v) and the 274 will operate about the same.

So not 40 amps, but about 30-32 amps. Better, but still.

 

[olaosunt]

I would ask your tuner but I know Lund prefers to have pumps on all the time.

 

[olaosunt]

It is also easier to check if a pump is down by pulling fuses to each pump if they are both on .

 

[Angrey]

It is also easier to check if a pump is down by pulling fuses to each pump if they are both on .

Kinda hard to do when you're in the car driving about to do a WOT pull.

Rather than run both pumps wide open, it would SEEM better to have a status light and have one staged. But that's just me. And I agree, tuners are going to prefer what's simple and easiest for them and currently the market doesn't have a good product/engineering solution to these needs. But that's changing soon.

 

[olaosunt]

Kinda hard to do when you're in the car driving about to do a WOT pull.

Rather than run both pumps wide open, it would SEEM better to have a status light and have one staged. But that's just me. And I agree, tuners are going to prefer what's simple and easiest for them and currently the market doesn't have a good product/engineering solution to these needs. But that's changing soon.

LOL
If you pull the fuses one at a time , if one pump is down the car won’t start .
You can’t check the pump on a Hobbs switch that way .

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