Evolution of Aeromotive Ultra 4/KOH Fuel Systems

Evolution of Aeromotive Ultra 4/KOH Fuel Systems

With the Chili Bowl and 24 hours of Daytona behind us, race season is well underway and it gets another boost this week with NHRA Pomona and King of the Hammers kicking off in California.  If you are not familiar with King of the Hammers, or KOH as it is commonly called, then we need to chat. 

One of the most unique events in the motorsports universe, it also creates unique challenges for manufacturers as well, including fuel systems.  The 9 day event combines high speed desert racing and rock crawling, and now has numerous classes that include bikes, UTVs, trucks and Ultra 4, which are the vehicles that compete to be crowned King of the Hammers.  The actual KOH race comprises 3 laps totaling over 200 miles, with several mandatory colorfully-named obstacles, which racers are free to attempt on any of the 3 laps and creates some unique opportunities for timing and strategy.  It also has a 14 hour time limit, and the finish rate is typically 25% of the roughly 100 qualified competitors.

With 100 plus MPH speeds across the desert, 100:1 (or lower) crawl ratios, and 40” tires, the typical Ultra 4 is an LS based EFI combination with 600-800 horsepower.  As fuel systems go the horsepower requirement is the easy part. The challenge becomes controlling the fuel in very large tanks (40-60 gallons) with vehicles nearly vertical while crawling or laying on their side.  Many vehicles at some point will end up on their side, tipped back over and continue competing.

Almost every racer utilizes a dual pump (redundant) system that incorporates 2 pumps with check valves installed, and typically dual ball valve fuel filters (PN 12331) to make system maintenance easier, and to prevent a catastrophic fuel dump in the event the vehicle becomes inverted (turtled as they say!).  With KOH being a 3 lap race, I know of at least 1 racer that runs lap 1 on pump A, lap 2 on pump B, and then back to pump A for lap 3 to take full advantage of the redundant system.

In our training seminars, we emphasize that the suction side of the fuel system is the most important, and with very large fuel tanks, and the extreme angles and attitudes Ultra 4 vehicles encounter while competing, they present a daunting challenge for the suction side of the fuel system.

The first event was held in 2007, and early Ultra 4 racers utilized dual inline A1000s (PN 11101) mounted in front of the tank in various locations, sometimes  shoulder high near the top of the fuel cell. As you can imagine, drawing fuel from the bottom of a fuel cell that may be up to 3 feet in depth, and keeping the in-tank pickup covered at all times requires  great execution of everything on the suction side, including the collector box and other baffling. The unfortunate reality was that at low fuel levels the in-tank pickup could potentially suck air, impacting not only vehicle performance, but also pump durability due to the hot pumping mechanism running dry.

Fuel pumps would rather push than pull, and through the process of education of the competitors and in conjunction with various fuel cell manufacturers, we were able to convince racers that our in-tank solutions would improve both performance and reliability.

Current state-of-the art Ultra 4 vehicles utilize 2 ea. in-tank A1000s (PN 18010) which ultimately solves a lot of performance issues and enhances reliability by being submerged in the fuel, i.e. pushing the fuel not pulling it.  Going forward, you will see our True Variable Speed Brushless A1000 (PN 18050 – released 2/1/2020) become very popular due to the fact that we can match the cycle rate of the fuel system to engine demand while also reducing amperage draw.  In other words, without affecting system pressure, we can slow the pump down to about 30% of maximum flow when the engine is at low rpm, and then climb to maximum flow as engine rpm increases.

 I also believe that the in-tank configuration helps dampen some of the vibration and severe harmonics that are unavoidable in this type of vehicle, and I believe that helps enhance fuel pump reliability.  Whether in-tank or inline, another key element is suction side filtration. We recommend a 100 micron stainless steel element with nothing less than 60 square inches of filter media, such as Aeromotive PN 12604.  The surface area is critical to minimize suction side restriction. Keep in mind that anytime you put fuel under a vacuum you reduce the boiling point.

Some competitors and off-road enthusiasts spectating and recreating at KOH also use our Dual Phantom (PN 18309).  Utilizing two 340 lph pumps, it is the easiest and least expensive way to create a “redundant” system. Racers can utilize the patented Aeromotive baffle and sump, or with custom fuel cells they often extend the pumps down into the collector box built into the fuel cell bladder.   If they use the Aeromotive baffle and sump, they can add bladder baffles (PN 18021) and our Phantom Apex (PN 18706) for the ultimate fuel system. The Apex Phantom is a jet siphon operates off of the pressure side of the pump, and will pull 1 gpm from any location in the tank to keep the sump full at all times.

So now you know a little bit about King of the Hammers, and how Aeromotive fuels some of the most unique vehicles in the motorsports universe.For more information on these and other Aeromotive products, visit, or call 913-647-7300.