Internal Surge Tank (IST)

The Problem

During aggressive maneuvers such as high-G cornering, the fuel in the main tank may slosh or "surge" away from the fuel pickup, creating a dangerous lean condition.

Below is the rear view of a typical fuel tank during the above right hand corner at 1 G lateral acceleration and 1/4 fuel level.  The fuel migrates to the left, uncovering the fuel pickup.

 

When the pickup is uncovered, it sets off a chain reaction of bad events:

1. Air is ingested into the fuel system
2. The air displaces fuel in the high pressure, decreasing the volume of fuel
3. The ECU can't compensate, and the mixture in the combustion chambers goes lean
4. The lean condition causes loss of power, increased combustion temps, and potentially detonation
5. Increased temps and detonation can damage engine components. 
   Boosted engines (turbocharged or supercharged) are especially vulnerable.

 

_________________________________________________________________________________________


The Solution

A surge tank (more accurately an "anti-surge tank") is a solution for the fuel starvation illustrated above.  It functions by scavenging fuel from the primary fuel tank and depositing it in a secondary reservoir, known as the surge tank .  The high pressure fuel system draws from the surge tank, which is tall and narrow in design to resist slosh and interruption in fuel supply.  A well designed surge tank will prevent fuel starvation down to near empty levels in the primary tank.

The Internal Surge Tank is a variation on this concept. It is fully housed within the confines of the fuel tank or fuel cell, resulting in a safer, cheaper, and more reliable solution.

_________________________________________________________________________________________

Note 1:  The term "swirl pot" is commonly used for a class of surge tanks that are cylindrical in design to promote a vortex inside the unit.  The swirling action aids in mixing and de-aeration of fuel.  While there may be some slight benefit to this concept, we feel that the oval design of the IST offers significant advantages that outweigh those of a swirl pot:

• Provides adequate space for inclusion of the Fuel Level Switch, while keeping the overall package compact enough to fit in most fuel tanks
• A Fuel Level Swtich may not fit or function properly in a vortex design
• The tall, narrow design of the IST provides more than sufficient conditions for fuel de-aeration
• The fuel mixing created in a swirl pot is required primarily to keep fuel temps under control; this is not required in the IST, since the basic design rejects heat

Note 2:  The Internal Surge Tank is designed for use in off-road and racing applications.  It has not been certified to comply with emissions requirements in any vehicle appication, in any state.