Saturday, June 1, 2013

Fuel Systems and Heat

Few people think about the heat in their fuel system. The truth is, heat has a substantial affect on how long your fuel pumps live. OEM fuel systems have controls to reduce the heat in the fuel systems; but what about your aftermarket fuel system? High performance aftermarket fuel systems move a LOT of fuel...even our lower end systems may double the OEM capacity...and a high end system may churn out six times the fuel of the original pump(s).

A pair of 450 lph Walbro F90000267s running at 13.5 volts and 60 psi makes over 450 watts of heat. To put that in perspective, think about four 100 watt light bulbs sitting in your fuel tank!

Our typical 1200 rwhp fuel system will reach 170º F when operated in five gallons of fuel exposed to 70º atmosphere for two hours. (where evaporation helps cool the fuel)  A fuel tank in the summer under your hot car WILL get hotter, unless you do something about it. This elevated temperature makes your fuel pump internals wear faster and any chemical reactions happen a LOT faster...especially if you're running E85. (which is laden with additives and contaminants)

Now that I have your attention, let's talk about the OEM and aftermarket approaches to fuel heat management.


Many high performance vehicles come with high capacity fuel systems that require some sort of provisions to reduce the heat. Vehicle manufacturers have the added burden of minimizing fuel heat for evaporative emissions.  Here are some of the methods vehicle manufacturers use to keep fuel cool:

POWER RESISTORS:  An old school technique used on Ford Lightnings and Subaru WRX have used power resistors to slow down the fuel pumps when under low loads. These power resistors have large heat sinks that absorb and dissipate the energy (heat) that would normally go into the fuel under most operating conditions.

MODULATION:  Electronic returnless systems such as those found in certain model Mustangs and late model Camaros modulate the fuel pump(s) based on demand from the engine using a fuel pump controller. When you're cruising around, the pumps simply run slower (and cooler).

HYBRID MODULATED/REGULATED:  Coyote based Mustangs use a fuel pump controller AND a static mechanical regulator to deliver fuel.  Under low load conditions, the fuel pump is operated at a lower voltage (slower and cooler); under load, the fuel pump voltage is "stepped" up to full voltage. Meanwhile, the mechanical regulator bypasses the excess fuel to keep fuel pressure constant.

PUMP DEACTIVATED:  The Nissan GT-R R35 has two fuel pumps. One is simply disabled when not required.


The nature of a comprehensive fuel system upgrade eliminates nearly all factory controls, so the easy solution is to simply omit any heat reducing measures.  In many cases this may be fine, especially where the car will only be run for short periods. However, some circumstances could be deadly for your fuel pumps. Here are some free and inexpensive methods to keep your fuel cooler and pumps healthy:

DEACTIVATE UNUSED PUMPS:  You don't need 1200-1800 rwhp of fuel pump blasting away while you putt around town, so opt for our FC3 controller and have that extra supply only on demand. You can trigger the other pumps however you like. Popular methods are via pressure switch, windows switch, nitrous controller, or boost controller's aux outputs.

FREQUENT INLINE FILTER CHANGES:  Some people think a drop in fuel pressure (at idle/cruising) is an indicator to change their filter. However, the fuel pressure regulator automatically compensates for a dirty filter, and the expected fuel pressure drop never happens. In the meantime, the fuel pump is working overtime (and running hotter and slower) to push past the dirty filter. If installing a fuel pressure gauge prior to the filter is too much trouble, at least change your filter every six months.  (more often for E85)  Our reusable stainless replacement element will pay for itself in three changes.

USE SMALLER FUEL PUMPS:  If you have a 800 rwhp centri blown high compression motor, you don't need nearly as much fuel as your neighbor's 800 rwhp low compression twinscrew setup. You can use the F10000302 pump that makes 35% less heat than what your neighbor needs. The general idea is to use only as much pump as you can always upgrade later to a bigger pump.

KEEP MORE FUEL IN THE TANK:  The more fuel you have on board, the more of a thermal "reservoir" you have. If you have enough power that requires an upgraded fuel system, accept that you're not driving a Camry and your car requires additional precautions and considerations...and one of those is the life of your fuel pumps.  Keep your fuel levels high if you run the car for a long period of time.

ROAD TRIPS:  If you insist on a road trip with your beast, disconnect or disable the pump(s) you don't need. While you're at it, fill up with 87, put a sticky note on your tach, and forget about teaching any "lessons" along the way.

RUN PROPER BASE FUEL PRESSURE:  A factory GT500 spins the stock Eaton to 9 psi of boost. When you bolt on an aftermarket supercharger, do you pulley the blower for 9 psi? I bet you don't...and the same thing applies with your fuel system: the original fuel pressure means nothing. If you are running a standalone return style fuel system, set the fuel pressure to the rating of your injectors. (usually between 39-43 psi) We've heard the rationale from some tuners...and we can agree to disagree. We'll leave it alone since your tuner is ultimately responsible for how your car behaves, but keep in mind, the higher your fuel pressure, the fuel pumps will generate MORE heat with LESS output and live a SHORTER life.

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