The concept of a surge tank is not new.  Surge tanks that are mounted external to the fuel tank have been used in purpose-built racing applications for years, and are extremely effective at preventing fuel starvation and the associated problems. 

The main issue with external surge tanks is that there isn't usually enough space to install one under the car, requiring mounting in the passenger compartment.  This isn't desirable, but there wasn't an alternative until now . . .

The Internal Surge Tank (IST) is an innovative application of this technology that mounts inside the fuel tank, allowing cars to reap the benefits of a surge tank without the liabilities.


Advantages of an IST vs. a traditional external surge tank:

Engine Protection
Catastrophic engine failure can be very painful -- emotionally and monetarily.  The IST prevents this in two ways:

    1. It prevents fuel starvation during normal operation, as explained earlier.

    2. In the event the IST malfunctions, it provides a fault signal when the internal fuel level drops below a pre-set threshold.   The signal can be used to actively protect the engine.  This is an important feature and added insurance that other surge tanks don't offer.   

Since the IST installs inside the fuel tank, a separate mounting solution isn't required.

The external and internal appearance of the vehicle are unaltered.

Fuel Cooling
High performance fuel pumps can add a significant amount of heat to the fuel.  This issue is significant enough that some setups require fuel coolers.  The IST is made of highly thermally conductive aluminum, which is immersed in the cool surrounding fuel, resolving this issue.

The lift pump in the IST is housed within a fuel-filled reservoir, which is itself encased in the fuel tank.  This arrangement effectively quells pump noise.

Cost / Complexity
Assuming it's mounted inside the passenger compartment, an external surge tank requires the following additional plumbing and mounting.  This is a significant hidden cost, both in parts and labor:

  • Low Pressure Circuit                
    • Supply Line, Fuel tank to Bulkhead Fitting
    • Supply Bulkhead Fitting
    • Supply Line, Bulkhead Fitting to Surge Tank
    • Return Line, Surge Tank to Bulkhead Fitting
    • Return Bulkhead Fitting
    • Return Line, Bulkhead Fitting to Fuel Tank
  • High Pressure Circuit
    • Supply Line, Surge Tank to Pressure Pump
    • Inlet Fitting, Pressure Pump
    • Mounting Bracket, Pressure Pump
    • Outlet Fitting, Pressure Pump
    • Supply Line, Pressure Pump to Bulkhead Fitting
    • Supply Bulkhead Fitting
    • Return Bulkhead Fitting
    • Return Line, Bulkhead Fitting to Surge Tank

Leak Avoidance / Occupant Safety
Each of the connections listed above is a potential leak path, and many of them are inside the passenger compartment!  Since the IST is located inside the fuel tank, these leaks are no longer a concern or safety risk.