Tuesday, July 22, 2014

Upgrading Coyote Fuel Systems

The 2011-2014 Coyote powered Mustang GT and Boss 302 are popular platforms for upgrades, and some owners eventually get to the point of needing a fuel upgrade.  The most basic fuel upgrade is large injectors with a pump voltage booster, which is perfectly adequate for mild builds.  More extreme builds require a properly planned fuel system.



In order to plan a proper fuel system, a basic understanding of the OEM system is required.  Let's get one thing straight...the Coyote fuel system is NOT an electronic returnless fuel system like the GT500.  Yes, there is a Fuel Pump Driver Module (FPDM)...and yes, there is not a return line.  However, fuel pump speed is NOT modulated to maintain a target fuel pressure...instead the FPDM is only used to reduce pump voltage during low load conditions...the rest of the fuel is simply "blown off" inside the fuel tank by a fuel pressure regulator.  We classify this type of fuel system as mechanical returnless, since it is mechanically regulated and there is not a return line.

In order to accommodate this functionality, the OEM (driver side) pump module is configured to stuff the following components in a relatively small package:
  • fuel pump (Delphi T-23)
  • coarse pre-filter (to protect the fuel pump)
  • fine post-filter (to protect the injectors)
  • venturi transfer pump
  • level sender
  • fuel pressure regulator (static)
  • suction tube connector
  • check valve



The in-tank components of the Coyote Mustang were engineered to work together.  Incremental upgrades such as voltage boosting the pump are generally not substantial enough to exploit the weakness of the other components.  However, a substantial upgrade such as multiple upgraded fuel pumps requires high capacity filtration, and upgraded regulation with the additional functionality of manifold pressure (boost) reference, upgraded electrical system, and larger fittings and feed/return lines.

Additionally, some E85 conversions require additional E85 enhancements, such as stainless filtration media, filter loss monitoring, ethanol content monitoring, etc.  ...none of which are possible with the OEM fuel system.


Our high end customers use our fuel pump modules that can deliver up to 4.5 times the pump capacity of the OEM module.  As you can imagine, this needs appropriate support components so the entire system can function properly.  Here is a quick rundown of how we spec out a built Coyote fuel system:

Our module retains the OEM level sender and has it's own venturi jet pumps so you don't lose any functionality of the original fuel tank.  However, our module can hold two or three big pumps that can deliver more fuel than any single electric external pump.  Needless to say, these pumps don't leave enough room to install the rest of the necessary [upgraded] components, so they have to go outside the tank.

Unlike the OEM filter, which is inside the tank, we provide a large, external, serviceable fuel filter that can be equipped with stainless steel filter element for E85 compatibility.  Additionally, placing the filter outside the tank allows pressure monitoring before the filter, which we consider necessary with E85 builds.  BTW, the OEM Coyote filter is not E85 compatible.

More flow requires a larger check valve.  Our check valve is simply too large to fit inside the fuel tank, so we simple install it on the end of our external filter

Engines that sip fuel at idle, but guzzle massive amounts of fuel at WOT need a larger regulator that can accurately deliver fuel throughout the entire range of fuel consumption.  Additionally, most tuners prefer a "boost referenced" fuel pressure regulator for forced induction motors.

The factory electrical system is simply not sized properly to handle high current aftermarket pumps, nor does it separate the individual pumps into isolated circuits so that pumps may be properly "staged" to maximize reliability.  A proper electrical upgrade is the most overlooked aspect of a high capacity fuel system.

Properly sized fuel lines are necessary to delivery the planned supply flowrate.  Undersized fuel line will create increased backpressure at the fuel pumps and reduced flowrate to the injectors, resulting in excess wear on fuel pumps and reduced fuel system capacity.

If you have a high capacity fuel system and want to monitor the ethanol content of your alcohol blended fuel, the preferred way is to intercept the RETURN line with a GM flex fuel sensor.  Our built Coyote fuel systems have return line access for easy installation of this sensor.  (and it's an option in our kits)


When it's all said and done, if you have a mildly built Coyote, a pump voltage booster and large injectors may be all you need....but once your hunger for power and ETs exceeds these mild upgrades, a proper fuel system for your Coyote does not follow in the same footsteps as the OEM system.

Friday, April 25, 2014

Restrictive Flex Fuel Sensor?

Flex fuel sensors are becoming more popular in the aftermarket. Naturally, performance enthusiasts speculate these "OEM" style sensors could be a flow restriction when used with a built fuel system.

There is plenty of internet chatter about sensor "flow rates" and some companies are even selling elaborate sensor bypass arrangements because of the "restriction" in these sensors. However, nobody provides any test data to validate the effectiveness of their product.

We called one of the leading suppliers and integrators of these sensors and asked for performance data. Surprisingly, they didn't have any data either, but they assured me that plenty of "high power" cars run their sensors. To validate their claim, we decided to test ourselves. Test results follow (GM #13577394)


Looking at the results, we can see that a fuel system delivering 600 lph will have a ~1.5psi loss across the sensor. For perspective, 600 lph of fuel is similar to (actually less than) maxing out eight ID1300s and/or two TI Auto F90000267s on a fuel system providing 43 psi base pressure with 30 psi of boost.

Question:  How will a 1.5psi loss affect the 600 lph fuel system?
Answer:  Less than 10 liters/hour...and this car is probably putting down four digits to the wheels.

Affect on Returnless Fuel Systems

It is reasonable to say any returnless fuel system (mechanical or electronic) is not going to max perform eight ID1300s and dual F90000267s. In fact, most returnless cars probably use less than 400 lph, which barely registers a loss on the sensor we tested. If you fit this criteria, don't waste your time and money with y-blocks and bypass lines...there is nothing to gain.

From an installation flexibility standpoint, you may install the sensor in one of the distribution lines that goes to one of the fuel rails with no detrimental affects. (flow through the sensor is cut in half)

One warning here--many returnless cars have in-tank filters, which are usually not E85 compatible, so check before you think about running E85 in your returnless fuel system.

Affect on Return Fuel Systems

Built return fuel systems take a "ground up" approach to maximizing fuel delivery, and the measured losses are definitely a problem if used in the feed line on our high end fuel systems. The alternate sensor location is the return line, which could potentially induce a regulation error. Good news: we tested this sensor on the return line from an F2i regulator and picked up zero additional regulator error over a 240-1200 lph bypass range. FYI, here is the regulation error of our F2i, which is excellent. (don't expect these results from other brand regulators)

Thursday, February 20, 2014

Increase Fuel Pump Capacity 50% for Free.

Okay, this article doesn't apply to everyone, but we all love risky, warranty voiding modifications to squeeze unintended performance out of a product. Don't worry, this doesn't involve fancy five axis CNC port work...while this modification can be performed by anybody with a drill and hammer, we suggest you leave this modification to an expert.

As of this writing, the TI Automotive F90000267 is the standard fuel pump to run on high boost street/strip cars running ethanol blended fuel. While this is currently one of the highest performing electric pumps available, the safety relief valve is a weakness that needs to be considered if you're pushing your fuel pressure past 80 psi.

TI Automotive publishes the following performance curve for a new F90000267. Detailed performance data between 80-90 psi is not provided, but the change in the slope of the performance graph indicates the relief valve may actuate anywhere in between 80-90 psi and still be in specification.

Broken-in pumps perform better than new pumps; however, repeated actuation of the relief valve causes degradation in the relief spring. In order to find out "which one" wins, we took a used pump (that had spent some time at high pressures) and tested before / after the modification. As you can see, performance before relief valve actuation is better than the new pump, but performance after the relief valve could be unsafe for some cars...especially if the valve is allowed to degrade under repeated actuation after the initial tune.


Thanks to Tony and his crew at T1 Race Development for pushing us to get more out of these pumps and proving out the effectiveness of these changes. He was gracious enough to provide the following screen before/after captures from a couple R35s at his shop:


First off, you have to completely remove the fuel pump from the hanger/module. If you are using one of our cartridge based modules, it is best to plan ahead an purchase an o-ring kit for reassembly...the o-rings will likely tear when you take everything apart.

Drill a 4.5mm hole as shown...(but try to do a better job of getting the hole on center...CNC is our thing...not necessarily hand tools):

Use a M4 screw to find the depth of the spring seat, then adjust the jam nuts so you can press the spring seat down another 1.5mm.  (FYI, two turns on a M4 screw = 1.4mm)  Done.

Here's what you did.  There is a spring behind the ball...you simply pressed down the spring so that the ball doesn't spring open at 80-90 psi.


This won't help everybody...this is only valid if you're pushing the pumps beyond 80 psi. Remember, in a boost referenced application, the fuel pump operates at base pressure + boost pressure + system losses.  (do you monitor the loss across your fuel filter...like this?)


Absolutely forget a pump warranty...but you're probably used to hearing that if you're using 80 psi of fuel pressure. By the way, TI Automotive is planning a future revision in the F90000267 to increase the blowoff pressure to 110 psi. Until then, this is the best way to accommodate high base+boost cars.