I would disagree that heat is a major issue in a dead end system, the very design has the big advantage of not returning fuel heated in the rails from the hot engine back to the tank, the plastic components transferring less heat than metal would IMO.

And for you to say it's a fallacy that fuel cools the pumps, almost seems a total contradiction to saying the pumps impart heat into the fuel through word done by the pump. Surely only one of those statements can be true ?

As for daily driven etc, no reason why daily driven cars that encounter all sorts of conditions will not run perfectly and totally reliably with both pumps all the time. Every car I've done it in has, whether it's a 1 mile journey or 500 mile journey.

Keep it Simple...it always works. I'm not saying yours doesn't work, or a hobs switch or other approach doesn't work, but simple always works too.

People often just want to complicate things for no real reason.

 

Well said, true with so many things...

 

What do you all recommend on the Hobbs for a meth inj system? Are there a good adjustable switch you could use for a meth system and also use the same for a secondary pump? I'm talking a separate switch for both, but having the same kind for both so you could keep 1 spare in case one failed. I was going to run 1 areomotive but have a frame mount Walbro for the second pump. I don't really want it to run all the time. This will also be a street car and I figured if you ever did have the main pump to fail, you could jumper the second one to get home.

 

The "controllers" take care of all switching for the meth pumps.

 

So true. Either the pump imparts heat on the fuel and cools down while simultaneously heating the fuel, or no heat transfer happens at all. Cant be both

 

I use the racetronix hobbs switches which are adjustable a few lbs either way of the rating. This way I can fine tune exactly where my pumps kick in. They are mounted side by side so that if one switch or pump would fail, I can always keep at least one running, just by switching over the connection.
The meth usually runs either off the map or maf, and not off a hobbs.

 

EDIT:

Heat is a major issue in today's non-return fuel systems with heat-retaining plastic components and non-recirculating fuel modules. New fuel pump modules use turbine pumps and other components to help reduce heating and gassing of the fuel. HP in-tank pumps spin considerably faster than factory pumps and use very powerful motors to produce flow that is many times that of a factory pump in a package of the same size. This translates to increased heat in the fuel system. since fuel is used to cool and lubricate the pump. It is a fallacy often posted on these forums that fuel surrounding the outside of a pump contributes to cooling in any significant way

Perhaps the verbiage above was a bit confusing? In other words HP pumps generate a considerable amount more heat which is transferred to the fuel passing through the pump. Fuel passing through the pump is critical to pump cooling and lubrication not the fuel in contact with the outer skin of the pump.

This may be an over simplification but an analogy people here can relate to is:

A turbine fuel pump in some ways is the same as a torque converter. It has vanes (blades) which push fuel to generate pressure. When a gas or a liquid is pumped it introduces heat just like in a transmission. The armature in the pump has copper wire which also generates heat from resistive losses as not all energy is converted to mechanical energy. This heat is also transferred to the fuel. All one has to do is take a 5 gallon container of fuel and circulate two 340LPH pumps running it 58PSI. The temperature rise is quite significant even when done in an open-air environment. Heated fuel is bad for many reasons but that is a subject for another discussion.

For those with an engineering background please consider reading about hydraulic, mechanical and volumetric loss / efficiencies relating to fuel pumps. SAE is a good place to start.

A good fuel system has to be designed from the ground up. Incorporating proven technology to enhance a fuel system’s performance is the goal of every engineer and educated consumer. Check valves, pump controllers, jet pumps and many other fuel system components have been reliably used as OEM parts for decades.

We encourage customers to embrace new technology and learn how to take advantage of its benefits. With direct injection becoming mainstream customers are going to be forced to gain a better understanding of fuel systems if they hope to successfully implement upgrades.

Everything we have posted here is based on scientific fact, sound engineering and field testing. Hopefully some forum members will appreciate and benefit from what we have posted.

 

Pretty much the very test I did, albeit with 2x044's which are roller vanes as far as I know, not turbines.

I tested them in the car, completely as installed for 20 minutes at 60psi ( got bored waiting after that ). Tank would probably have had around 30 litres in it. Temperature rise over that time period was barely 5degF


I wouldnt argue that heated fuel is bad...but I've also yet to find anyone give any details about how hot is bad and what effects it will actually have. Other than a guy who is a R&D guy at Aston Martin who pretty much said even very hot fuel isnt a big deal at all.

Most people who say hot fuel is so bad, or pumps heat fuel too much etc...have never actually monitored fuel temps in the first place.

Even dead end turbine setups you describe have a regulator at the rear in tank, so fuel does still circulate locally so there should never be any hot fuel worth talking about passing up the line to the front. Likewise with modern closed loop PWM controlled setups, as the pump basically runs on-demand at all times so always doing the least work needed.

 

Let's just say that there are many interrelated and overlooked issues here which have not been addressed. Although some of your statements may be valid when looked at on an individual / isolated basis they may not be valid when they are part of a larger more complex system. There are many documents and formulas online for those who wish to become fluid engineers.

This thread can become ever more technically involved and beyond the scope of what we were trying to get across.

The majority of customers just want to know what is simple to install, reliable, and provides good value for their hard-earned money. We have put together PnP DIY dual-pump packages which offer excellent performance and value. Our DP systems have been reliably run on V8 and V6 cars running deep in to the 8-second ¼ mile range. For those who would rather purchase an assembled bench-tested solution they may contact Lonnie’s Performance. Lonnie has assembled thousands of custom DP systems over the years.

All the best with your project.