Exhaust Gas Recirculation: Don't Delete Your Diesel Engine EGR Valve

Have you put much thought into why you need your EGR system? Oftentimes people choose to delete it because of problems it can cause. But, this can actually end up costing you even more money in the long run!

We're going to take you through how this system works and why it's important to keep it functioning on your diesel engine. 

You can learn more by checking out our video: 



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How Does a Diesel Engine EGR System Work?


egr system exhust manifold | Highway & Heavy Parts


Briefly, everything starts at the exhaust manifold. The majority of your exhaust gas is going to go to spinning your turbo. Looking at the front side of your manifold, you've got an elbow bend. This is going to feed that 500 or 600 degree exhaust gas into your EGR cooler. The EGR cooler has an inlet that is going to give you coolant flow through the cooler and the flow from the coolant is going out the back end of the block where the exhaust gas is going to continue to travel on through this crossover pipe and back out the EGR valve. 

The EGR valve sits on this side and that's going to control how much exhaust gas is going to be flowing into the intake. As you come up into the intake manifold, you have a venturi mixer that allows the exhaust gas to get pulled in with the charge air that is coming from your charge air cooler. The turbo feeds the charge air cooler, and the charge air cooler puts clean air into the intake manifold. 


egr system venturi mixer | Highway & Heavy Parts


The venturi has a couple of ports on it and a differential pressure sensor. Those two are connected. That will tell the ECM how much flow is coming through this venturi so we know exactly how much exhaust gas is mixing with the clean gas to make the combustion temperature ideal. 


egr system intake manifold pressure and temperature sensor | Highway & Heavy Parts


The intake manifold pressure and temperature sensor checks out everything right before it goes into the engine. Everything on the engine is designed to work with this system intacteverything from the timing to the compression ratio. It all works in unison to make sure that this works as good as it possibly can. You run into problems when you delete.

Curious about this system? Get even more details in our blog about the advantages of VGT turbos!


Why You Shouldn't Delete Your Diesel Engine EGR System

There are quite a few issues that come up if you choose to delete part of this system.

For one, when you delete, you're not legal anymore.

Two, there are certain states that won't allow you to even run in them.

When you delete, you typically end up getting rid of your variable geometry turbo. Getting rid of this causes you to lose engine braking and you lose that real nice flat torque curve. The torque that you enjoy at real low rpm is helped out significantly by the variable geometry turbo.

The next thing you lose is the coolant path from the water pump that comes in the front of the EGR cooler to the back of the engine by the number five and six cylinder. When people delete, they often notice scoring at the number six cylinder. Well, the coolant path from the water pump to the back of the engine without the EGR cooler is problematic and will lead to those types of problems.

The next thing that you're going to find is when you come back over to the intake side and you have it all blocked off, now you're putting in 100% clean air. Clean air is good to make power with it, but everything in the engine is designed to work when the two are mixing. When you put clean air in, it burns hotter. You end up having an engine that has pistons that are designed to run with the EGR system, and now we're putting all this clean air in and it's burning very hot compared to what it was previously. So, you're really having to rely on your VGT gauges to make sure that you're not going to burn this thing down.

Combustion temperatures can go anywhere from 500, 600, 700 degrees with the EGR. Now we're talking without the EGR, maybe you're running 1100, 1200, 1300 degrees. You're pushing the limit of what you can withstand within the combustion chamberthat goes from everything from pistons to valves. Do you want to burn the engine up? Most people don't. Now you've got a deleted engine that you've saved a few bucks on an EGR cooler, but it's cost you a cylinder head, an overhaul kit, and then putting it back together.


You can learn more about EGR systems by reading our blog post, Problems with EGR Systems in Diesel Engines.


It's cheaper in the long run to learn the system than it is to burn out the engine a couple of times because we didn't get it nailed down just right. 


Have a problem with your EGR system or any other part of your diesel engine? Our ASE Certified Technicians are here to help! Call us at 844-304-7688, or request a quote online!