Sensor 101: The Basics Of Sensors For EFI Systems

Electronic Fuel Injection (EFI) has become a common way of feeding an engine fuel in many high-performance builds. Enthusiasts use everything from the OEM-style EFI systems to high-end aftermarket setups for high-horsepower builds. All of these systems need sensors to function, and if you’re thinking of moving to EFI, we’re going to cover what you need to look for when it comes to those sensors.

In simple terms, EFI sensors are tasked with measuring something and relaying that information back to the Engine Control Unit (ECU). The ECU will then take that information, do some math, and tell the engine what it needs to run and not blow up. That means you need the right sensors in the right places to get the most accurate information to the ECU so everything runs smoothly.

It can be easy to get confused when it comes to the sensors you'll need for an EFI system of any kind.

The Basics Of Sensors

Your average EFI system is fairly complex, and different systems will use different sensors. An OEM EFI system is going to have a lot more sensors since it has to account for emissions and other electronic systems. For this article, we’re going to look more at the basics you’ll need for an aftermarket setup that won’t use emissions or the other electronic systems a modern vehicle might use.

At a bare minimum, an EFI system will need a Manifold Absolute Pressure (MAP), or Mass Air Flow (MAF) sensor, a Throttle Position Sensor (TPS), oil pressure, fuel pressure sensors, intake air temperature, and coolant temperature sensors, as well as at least one oxygen sensor, preferably a wideband. This list might change slightly based on the engine, ECU, software, and other factors. You can always add more sensors based on your application, or if you want to have even more data to look at and help tune your EFI engine.

At a minimum you'll need a MAP sensor along with various temperature and pressure sensors for your EFI system to function.

Before you go out and start buying sensors, you need to make sure you look at the fittings they are going into. Not every type of sensor uses the same type of fittings. Andrew DiMartino from Haltech explains why this is an important detail.

“OEM sensors and aftermarket sensors are going to have different thread pitches. Make sure that if you need to have an adapter it will actually work. Some of these adapters, like the one you’d use for a standard AN adaptor might not be deep enough for the sensor. That could lead to incorrect readings or even leaks.”

Brandon Doller, owner of Lowdoller Motorsports knows a thing or two about EFI systems and sensors. Doller’s company offers numerous types of sensors that can be used in just about any application you can dream up. When it comes to what sensors to use, Doller has a pretty common sense approach.

“I will typically tell customers to use what’s readily available based on their application. Let’s say your combo is set up for a stock-style GM sensor, go ahead and use that GM sensor for your coolant sensor. Different aftermarket EFI systems will still be able to recognize and use that sensor too. Now, for other sensors in the system, you’re going to want to make sure they match what you’re trying to do. This means you might need an aftermarket sensor that has a higher temperature or pressure range.”

There are going to be areas where you can’t use an OEM-style sensor based on your combination. True and accurate readings are important when it comes to EFI sensors, but the sensors also need to be able to handle what you’re going to ask them to do. This is where you need to start looking at aftermarket sensors that are designed to work in unique situations.

“So, let’s look at a fuel pressure sensor. You want to use a sensor that’s high quality and can hold up to whatever type of fuel you plan to run. The sensor should have an FKM-style seal that can work with most fuels. These seals are a must-have for oxygenated fuels, ethanol, and methanol. You also need these critical sensors to be extremely accurate, especially if you’re running a high-horsepower application. If that sensor is giving bad data to the ECU, it’s going to cause tuning issues,” Doller says.

Using the right sensor in the right place is critical.

Accurate sensors are extremely important to an EFI system. The majority of the aftermarket sensors that are available will be very accurate and have been tested before they’re sold.

“For a sensor to be acceptable, it needs to be within 1/2-percent on our testing machines, that’s what we’re really looking for. The sensors also need to show repeatability of what they’re measuring. If the sensor is all over the place, it’s not very accurate,” Doller explains.

Sensors have different temperature and pressure ranges they can read. This is important to keep in mind when you’re trying to select a sensor for a specific task. If you don’t use a sensor with the correct range, the data it provides won’t match what’s needed for the ECU to do its job.

Not all sensors have the same abilities when it comes to what they can read. You need to make sure the sensor you're using has a broad enough range so it can correctly read the pressure or temperature levels that are required for a task.

“So, let’s say you need a temperature sensor for your transmission,” DiMartino explains.“That’s a situation where you’ll want a sensor that has a higher range than what you would use for coolant, otherwise, it might not give you the right information. The same goes for pressure sensors. If you’re starting with a base pressure of 80 psi and installing a 0-150 psi sensor, you only have 60 psi of range, or less than half of a 0-150 psi sensor’s range.”

Keeping Sensors Happy

The most accurate sensors on earth are going to be useless if they’re not installed correctly. You need to keep in mind what’s around a sensor and what it’s mounted to when you’re setting up an EFI system. The environment under the hood of a vehicle is very harsh and it can easily damage sensors if you’re not careful.

“If you wouldn’t want to make a dyno pull with your hand in a location where a sensor is, there’s a good chance that location is bad for the sensor. Most sensors don’t like heat. It doesn’t matter how expensive the sensor is, you need to mount sensors in safe locations. If you’re building a street car, this is really important since the vehicle is going to be running for extended periods of time and generating a lot of ambient heat,” Doller states.

Remotely mounting sensors will keep them out of areas that could damage them, and make it easier connect them to the wiring harness.

Another thing that needs to be on your radar as you mount sensors is the amount of vibration they’ll be exposed to. Sensors are precision pieces of electronics, so if you start hitting them with a lot of vibration they’re not going to be happy. A little bit of planning can go a long way to avoid shoving a lot of vibrations through your sensors.

“You can always remote mount sensors to keep them out of harm’s way. That will give you the ability to not only limit their exposure to heat and vibration, but it will also provide more wiring and plumbing options for the sensors. If you’re running an aftermarket ECU there’s even more options available for setting up a remote mounting system for your sensors,” Doller says.

Adding Advanced Sensors

There are so many options out there if you’re planning on building a vehicle that will use an EFI system. A restomod that’s rocking a pullout engine and transmission can use an OEM ECU, wiring harness, and sensors to run and will be just fine. If you’re building something a bit more extreme and using an aftermarket ECU, you might need some additional sensors.

Project Red Dragon evolved past needing an OEM ECU, so it got an R3 VCU from Haltech. This meant the entire EFI system on the car would be removed and replaced with aftermarket parts and pieces.

A driveshaft sensor can be used for multiple things.

The car could no longer use its factory speedometer wiring with the aftermarket dash we installed, so we had to create a solution for that.

“A driveshaft sensor is a great addition to a vehicle that will be going to the track. It’s another data set you can use to help see what the vehicle is doing, and in Project Red Dragon’s case, can be used to monitor how fast the car is going on the street. The best part is, this type of sensor is easy to install, you just need to mount the Hall-Effect sensor in a spot that it can read the collar on the driveshaft,” Doller states.

An affordable coolant pressure sensor could save your expensive engine.

We also wanted to add a coolant pressure sensor as a safeguard since the engine would be making a lot more horsepower thanks to the turbo system it received. A coolant pressure sensor is great insurance to add to your EFI system if you plan on running the vehicle hard. The coolant pressure sensor is going to be mounted in line with the cooling system, either on a cylinder head, or one of the system’s hoses. This sensor is used to monitor just how much pressure the cooling system is seeing.

“The coolant pressure sensor is going to be able to see a problem in the engine before you feel it. You can set up a specific value in the ECU’s software to alert you to the issue, or put the engine in safe mode if the pressure hits a certain level. The sensor is a great insurance policy to have in place for high horsepower engines that are running hard,” Dollar explains.

What kind of issues are we looking for with a coolant pressure sensor? The biggest thing is a spike in coolant pressure. When the sensor starts to read a high amount of coolant pressure, that usually means something very bad is about to happen, or has already happened. We’ve set up parameters within our Haltech VCU that keep an eye on this sensor and what it’s seeing. If the pressure goes above a certain value, the VCU will shut the engine down to prevent any serious damage.

If you’re moving to an EFI system, don’t make the mistake of using the wrong sensors for your application. A sensor needs to be designed for what you’re going to use it for and be accurate as well. Spending money on the right sensors the first time will save you from having issues later on down the line.

Article Sources

About the author

Brian Wagner

Spending his childhood at different race tracks around Ohio with his family’s 1967 Nova, Brian developed a true love for drag racing. Brian enjoys anything loud, fast, and fun.
Read My Articles