EGR Delete or Catch Can; what’s better?

With environmental standards getting more stringent each year, its hard to find a diesel engine today that doesn’t make use of an EGR, and often a DPF. If you aren’t familiar with these, they are Exhaust Gas Recirculation systems, and a Diesel Particulate Filter.

The issue with meeting environmental constraints is it often comes at the cost of engine reliability, and today we take a deep dive into some of the common ways people try to get some of that reliability back.

Some options are completely legal, and some are not, so its important you understand the benefits and downsides of each choice.

Provent 200 catch can
Should you go with a catch can, or an EGR Delete?

What’s the problem?

The main problem with an EGR is the carbon particles mixing with the oil mist from your engine, causing build up on the intake manifold. This eventually restricts the air flow and causes your vehicle to work harder, struggle to suck air and use more fuel.

The intention between fitting an EGR delete or catch can is to reduce the build up, and wear and tear on your motor from having particles go through that it was never designed to handle.

What is an EGR?

Put simply, an Exhaust Gas Recirculation System takes a portion of your exhaust gasses, and feeds them back into the engine.

The primary intention of an EGR system is to reduce harmful gasses that are created by the motor. It has some other benefits like slowing the burn, reducing combustion temperature temperatures and producing a cleaner exhaust stream.

Dmax and Hybrid Camper
All modern diesels come with complicated environmental controls

What’s the downside of an Exhaust Gas Recirculation system?

Whilst an EGR might seem like a good idea, it comes at the cost of pumping carbon back into your engine which is not a good thing in terms of reliability.

Carbon is abrasive, and can become a significant problem when it mixes with the oil mist that your engine naturally generates over time. Ultimately you end up with a build up of black muck, like vegemite on the intake of your engine and it suffers significantly as a result.

EGR modifications

Due to the extensive reliability issues that an EGR can cause, people take it upon themselves to make modifications to the EGR. You should know that any of these modifications are illegal, and the fines if you are caught are significant.

You should also know that thousands of people do it every day, and I’ve never heard of any individual being caught and fined badly for doing so, but its still a potential.

EGR Delete

The most common way to deal with an EGR is to stop it working completely. This can be done in a number of ways. EGR Blanking plates were very common initially, where you’d install a plate that physically stopped the air flow.

In many cases this would cause the vehicle to go into limp mode, and people would get around it by drilling a small hole in the plate (which partially defeats the idea!).

Alternatively, you can electronically disable the EGR. This can be done by most tuning and diesel businesses, and the EGR valve will simply stop working.

Another option is to use an EGR delete cable, which tricks the engine into keeping the EGR valve closed at all times. Some of these are as simple as a resistor which tells the engine the ambient temperature is too cold, and it stops the valve from ever opening.

What’s the benefits of an EGR delete?

There’s lots of benefits from doing an EGR delete. For starters, you are guaranteed that no carbon can make its way into your engine, which is a good thing in terms of reliability.

What’s the downsides of an EGR delete?

It’s illegal

When we built our Dmax, I made a commitment to ensure it was a legal 4WD. The ramifications for a vehicle that isn’t insured are just too high, especially if you get into an accident.

However, it can go beyond this. I have heard a number of times recently of finance companies and insurance companies refusing to deal with customers after an engine remap, because its taken the vehicle outside of its recommended operating parameters. 

You might just find that the fine print on your finance or 4WD insurance requires you to have a roadworthy vehicle, and if you’ve modified the emission control systems you could be on your own.

It’s not good for the environment

The whole idea behind an EGR is to improve the environmental emissions.

Now, I’m not qualified to comment on how much difference this makes, and perhaps with the reliability issues and extra fuel used when the build up occurs its all null and void, but they were designed and installed by engineers with the intention of helping the environment.

It can trick your ECU

Some EGR deletes tell your vehicles computer that the ambient temperature is 0 degrees, and this puts them in a state where the EGR doesn’t open.

However if your ECU thinks its 0 degrees and its actually 40, and you are slogging your vehicle up a hill towing a trailer, surely there must be some risk of doing engine damage.

Ultragauge in our Dmax
There’s a number of ways of ‘deleting’ an EGR, and some feed false data to your ECU

What is a catch can?

Moving onto the next very common modification to assist with the build up is a catch can. By the very nature of an engine, you have some blow by that escapes past the pistons, and is pushed out of the motor.

This blow by has an oil mist, along with minor traces of fuel and carbon, and it goes through a PCV (Positive Crankcase Ventilation) system before being returned into the intake.

Without a catch can this oil mist mixes with the carbon from your EGR, and creates essentially vegemite on your intake, and slowly builds up until its a major restriction.

A catch can goes between the PCV, and is designed to separate the oil mist and send pure, clean air back to the intake. Without the oil mist, you get much less build up occurring.

Provent 200 filter
The filter from our Provent 200 Catch Can

Catch cans are not equal

Before you purchase a catch can, you need to know that they are very, very different in terms of actual performance.

I know this all too well, after running a HPD catch can for about 30,000km, and then swapping to a Provent 200. The latter caught as much oil in 5000km as the HPD did in 30,000km, and you can read a full, in depth report here; HPD vs Provent Catch Cans.

This is a huge point to consider; if you go to the effort to mitigate build up and you fit a rubbish catch can, you may as well have done nothing.

HPD Catch can inside
I removed our HPD catch can, after finding out they are very bad at collecting oil

What’s the benefits of a catch can?

There’s a reason so many people fit catch cans. They are literally the only legal way to reduce the build up from happening in your engine. They are also easy to install and maintain, and do a good job.

What’s the downsides of a catch can?

Like everything in life you’ll always have a cost of doing something, and fitting a catch can is no different. To start with, you have to pay for the catch can, and then install it, or pay someone to do it.

A good catch can kit to suit a specific model 4WD will cost you about $350, and then you have to pay to get it fitted (if you can’t).

From there, you have to replace the filters every 20 – 40k, and they can be around $80. Catch cans require regular draining too, and that means you’ll be kneeling down next to, or climbing under your vehicle every 3000 – 10,000km to empty the build up of oil.

Catch cans are not 100% efficient either (even the best), and the problem worsens when you buy a poorly engineered product. That means despite your best efforts, you will still be letting some oil go through, and build up will eventually occur. 

Catch cans can also create additional back pressure, which can result in seals or gaskets leaking, and it can create additional maintenance related problems.

Provent 200 oil collection
We drain our Provent catch can every 1500km or so, and it gets tiring

Other good practices

Diesel engines today are very different to their predecessors, and there’s a few things you should be doing to make your vehicle last.

Work it hard from time to time

If you baby your 4WD, and idle everywhere, you will have more issues than someone who makes the engine work hard from time to time. Now, lets be clear here; I don’t mean flogging the living guts out of it.

I mean putting your foot flat to the floor from time to time, and allowing the revs to climb up towards redline (but not too far!). Diesels like to work, and babying them everywhere does not help with keeping the engines clear and happy.

If you are regularly towing something heavy you’ll be doing this anyway, but don’t be afraid to give it some every now and again!

Bypassing the salt water
Diesel engines that get worked tend to have less build up

Don’t do short trips

I still see people buying brand spanking new diesel vehicles to drive 6km to work and back each day. This will be the demise of your vehicle; they are not meant to do short trips often.

The engine will not get to temperature, and you will absolutely have DPF issues in the future as they aren’t able to burn the build up off.

Do some long distance driving

The best treatment for a diesel is long distance driving. If you do a lot of short trips, make sure you do a decent drive at higher speed at least a couple of times a month.

That means at least 30 minutes to an hour at 80 – 100km/h, non stop. Take your family on an adventure somewhere, and give the vehicle a decent run.

What options do you really have?

Ultimately, you have 5 choices. 4 options are completely viable, and done by a huge number of people. The 5th, and last option is a poor choice in our opinion, and we don’t recommend it at all.

1 ) Do nothing

If you are doing regular, long trips and you turn your vehicle over reasonably regularly, you will probably get away with this option with no problem at all. You will end up with build up in the motor, but with longer trips it will be reduced and you’ll likely turn the vehicle over before it becomes a problem.

Alternatively, you just clean the intake out every 100,000km or when your vehicle needs it. This is normally around $1000 to do it properly (physically removing the intake and cleaning it out).

2) Install a quality catch can

If you want to keep the vehicle legal, and hold onto it for some time you are probably better off installing a catch can, but this comes at a financial cost to install it and maintain the filters too.

I’m going to do a comparison on this soon, as the Provent 200 filters are not cheap. Make sure you understand the downsides too.

Provent 200 install
If you are getting a catch can, get a reputable one (Provent or Ryco)

3) Get your EGR deleted

Lastly, a lot of people just get their EGR disabled, or deleted, and this works very well. It is illegal, and you might face other ramifications, but it certainly stops the problem as oil going through your motor without the exhaust gasses is far more friendly.

4) Fit a catch can and an EGR delete

Some people choose to fit an EGR delete and a catch can. This is less common as its the most expensive option and in most cases unnecessary. Oil going through your motor without the carbon is much less of a problem. Yes, you’ll end up with pipework covered in oil and the intercooler will be less efficient, but its much less of an issue.

5) Run the PCV to the chassis

Some people just take their PCV vent hose and run it into the chassis, and cap the suction side off. This means any oil coming from the motor ends up in your chassis, and cannot go back to the motor.

The issue with doing this is you end up with oil in your chassis which eventually leaks out, and on a wet day you’ll probably kill a motorbike rider. Don’t do this.

There’s no perfect solution

Unfortunately, there is no perfect way forward here. Pick the most suitable option for yourself, weigh the pro’s and con’s and roll with it. 

We’ve gone with a good quality catch can (Provent 200) and left the rest of the engine stock. Will it eliminate the build up? Probably not, but it should reduce it enough that we never have to play intake cleans again.

4JJ1 motor in our Dmax
Hopefully the Provent 200 removes the need to clean the intake

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  1. Hey Ray,

    The EGR circulates a portion of the engine air back into the motor. The DPF filters particles exiting the exhaust pipe, and then burns them off periodically. The two are not interlinked directly, but I believe that by blocking or turning off the EGR you may have issues with your DPF.

    I’d talk to an engine tuner who deals with these before you do anything.

    All the best

  2. Ray Saunders says:

    Hi Aaron
    I have a 2023 Pajero Sports that is fitted with a DPF. My question is if I have an EGR delete cable fitted, how does it effect the DPF. Will there stilll be a soot buildup in the DPF?
    Thanks in advance for any comments.