AEM Fuel Pressure Sensor Explained & Installed
Everyone seems to want a “daily driven race car” these days and who can blame them? Making at least 100+HP per cylinder has become the new standard. The question is how do you double, triple or even quadruple the stock power output while maintaining reliability?
We will be publishing a series of blogs that lay out the basic blue prints to building, owning and servicing a highly modified “daily driven race car”. The first series of posts will cover ECU/sensor set up, tuning and data analysis. We have decided to start the blog series here rather than with engine builds. Remember a stock engine and a “built” engine both need to be correctly tuned, monitored and serviced to ensure a long happy life making the power you expect.
One of the most overlooked sensors these days has to be the Fuel Pressure sensor. Monitoring fuel pressure via a gauge is good but adding the fuel pressure sensor to your ECU is one of the most effective ways to increase the reliability and safety margin for your engine.
Explanation: Fuel injectors flow a given amount at a set fuel pressure; more pressure - more flow, less pressure - less flow (for the same given injector open time). If your engine has been tuned with 50psi fuel pressure/injector pressure and 6 months later your dirty fuel pump starts to die fuel pressure will fall off first at high RPM/high engine load. This is where the pump needs to flow the most fuel, this is also the most vulnerable operating range for an engine so any loss in fuel will quickly cause a lean condition leading to damage. Tuning@brewedmotorsports.com or call 888-290-3213
Solution: Assuming your car is using a proper motorsports ECU such as; Motec M1, AEM Infinity, Haltech, Bosch, Pectel, etc we would incorporate a 3 wire fuel pressure sensor into your calibration aka “ecu tune” in a number of helpful ways listed below.
-Injector flow calculation- The ecu is set up to monitor the fuel pressure sensor full time adjusting fueling to the engine based on any fuel pressure/injector differential pressure changes. This “closed loop” system means that if pressure drops from a faulty pump or leak the ECU already knows that the injectors will need to be held open longer to flow the same amount of fuel at the lower fuel pressure. This helps to ensure the ecu hits the target AFR without relying on the o2 sensor feedback.
-Fuel pressure fail safes- One of the best features for forced induction engines is using the fuel pressure/injector pressure differential to dictate target boost pressure and or RPM limit. If fuel pressure drops for any reason this feature will effectively lower the target boost pressure and or RPM limit for the engine keeping it safe from a faulty fuel system/dropping fuel pressure. There are a number of other fuel pressure based fail safe options but boost and rpm limits are the most effective when combined with the “injector flow calculation” explained above.
-Fuel pressure warnings- This one is simple, if the fuel pressure/injector pressure drops below the target for any reason it is very important the system be serviced and faulty parts replaced right away. Because the ECU does such a good job of compensating for the dropping pressure unless the ECU sends a warning message to the dash the driver may never know about the problem. Adding a simple warning message to the dash combined with regular analysis of data logs are both critical to catching a fuel pressure problem before it starts to effect engine performance or reliability. We recommend reviewing engine data logs on a monthly basis at minimum. For customers that do not want to analyze their own engine data we offer extended tuning/data analysis services as required for many of our customers with track cars or street cars that need extra attention.
***Best BANG for the BUCK*** fuel pressure sensor and display combination is the AEM X series fuel pressure gauge. This gauge uses the same sensor you see below on our BMW, it also comes with an easy to read display that can be set up with warnings as well as communicate with the ECU through the CANbus system which keeps ECU pins open for other sensors.
Now for the fun get your hands dirty action, installing the FPS (fuel pressure sensor). Here you can see the BrewedCrew SR20DET powered BMW E30 running an AEM Infinity getting a 150psi stainless fuel pressure sensor fitted to the fuel rail.
Lucky for us the engine wiring harness from Velocity Element came pre wired for the FPS. In the case your engine harness did not come pre wired for a fuel pressure senor you can easily make up your own harness. 95% of all the fuel pressure sensors we sell are a 3 wire design (5 volt power, sensor ground and signal wire) ALL fuel pressure sensors purchased from Brewed Motors will also come with a detailed wiring diagram for EASY install.
After removing the fuel rail and injectors it is always a good idea to carefully inspect all the parts before reassembly. The Injector Dynamics injectors use a small aluminum top hat (purple piece) that features a slick little pre injector filter.
This filter is a great "last defence" preventing sh*t from getting into the injectors internals keeps them happy and healthy. Carefully inspect the filters for any damage, gunk and corrosion, if any corrosion is present on the tip or injector internals the injectors will not flow the same and must be serviced to retain the precisely matched flow ratings between the other injectors/cylinders. **if your injectors need serviced email email@example.com and we can get them all sorted out.
With the injectors set safely to the side we remove the ¼” npt plug from the fuel rail. Because the AEM 150psi sensor is a 1/8” npt thread we also need to use an adapter fitting. Both the fitting and the sensor are NPT thread so Teflon tape is a must.
After wrapping both threads screw the sensor into the fitting and then the fitting/sensor assembly into the fuel rail. **be careful not to apply to much Teflon tape! The excess tape will find its way into the small filters on top of the injectors and cause you big problems.
Sensor installed, re fit the injectors to the fuel rail; be careful to ensure all O rings are in good condition (soft, no cracks or cuts). Bolt the rail, injector and sensor assembly back into place, plug in your injectors and prime the fuel system to check for leaks. **It is best to leave the engine off for this first test, just turn on the fuel pump for a few seconds to check for any fuel leaks.**
Now that your hardware is installed the only thing left to do is incorporate the new sensor into your ECU calibration/tune. In our next article we will go through in detail the basic ECU set up and tuning options described above. If you want to learn ECU tuning secrets keep your eyes peeled for our next article!
Do you need a fuel pressure gauge, sensor, injectors, pump or even just fuel filter? Check out the links below for our top picks of quality parts that will deliver the performance you need while saving you money!
Not exaclty sure what parts you need? Give us a call or email any time: 888-290-3213 or firstname.lastname@example.org our team is happy to help explain exaclty what your build needs and why it needs it.
AEM Electronics - Huge selcection of affordable ECUs, gauges, sensors and pumps
Radium Engineering - Fuel rails, filters, dampers and regulators
Injector Dynamics - The best injectors money can buy **All Brewed builds use ID injectors