Fuso FG84 EGR Blocking

[SkiFreak]

For anyone that's been living in a cave and missed the memo, vehicles these days are usually fitted with emission reducing devices. The concept is obviously sound, but the implementation is sometimes questionable.
A case in point are exhaust gas recirculation (EGR) systems.

The basic theory behind an EGR system is that by reducing the amount of oxygen that enters the combustion chamber, Nitrogen Oxide (NOx) emissions are reduced. To do this, some of the exhaust gasses are redirected back into the intake manifold via a computerised valve.

Yes, EGRs do reduce NOx emissions, but at what cost?

• Mixing hot exhaust gasses with the intake air reduces engine efficiency. The primary reason for using an intercooler is to lower the temperature of the intake air. This makes the air more dense, so you get more air into the engine. The way an EGR works effectively negates the function of the intercooler.

• Burnt fuel contains contaminates that used to go straight out the exhaust pipe. Now, some of these contaminates (including soot) are being redirected back into the combustion chamber. Engines experience varying levels of piston blow-by, where some of the exhaust will go past the rings and into the engine sump. The more contaminates there are in the exhaust gasses, the more contaminates end up in the engine oil. Contaminated oil can have very detrimental effects on engine parts.

• The positive crankcase ventilation (PCV) valve can vent a small amount of oily mist into the intake manifold. When this oily mist comes into contact with the soot from the exhaust gas it can form deposits on the walls of the intake manifold. Over time these deposits get baked into a solid mass which can seriously affect air flow through the manifold.

So, the EGR will make you use more fuel, give you less power, cause carbon build-up in the intake manifold and ultimately reduce your engine life. But it does reduce NOx emissions, so all is forgiven, right?

Well... if I'm honest about this... I'd have to say that I care a bit more about my engine than I do about the NOx emissions.
I did lots of research and asked quite a few people about blocking my EGR. The only real concern was that the ECU would know something had changed and throw up some error codes, making the engine warning light come on.

I could not find any other FG84 owner that had attempted to block their EGR, but that did not deter me. About a month ago I took the plunge and removed the crossover pipe between the exhaust manifold and the EGR heat exchanger. After doing that I measured up the flanges and made blanking plates for the two holes. I chose to do it this way as the crossover pipe was a little difficult to get off on my truck. It was easier to make two blanking plates, opposed to taking the crossover pipe on and off.
With the two ports blocked I started the engine and idled the truck for about 15 minutes. This did not produce any error codes, but I was not too surprised about that, as I don’t think the EGR has much, if any, effect at idle. I then took the truck for a short run of about 25Km, trying to keep the engine at low to mid range load, where the EGR should be working. Again, no error codes were displayed. The following day re-installed the crossover pipe, leaving the manifold blanking plate in place. I then went for a longer drive (about 130Km) and put the truck under different loads. The EGR valve should be fully closed at wide open throttle (WOT), but I tested this any scenario anyway. Still no error codes...
I have done about 250Km now with the EGR blocked off and I have not generated any EGR related error codes so far. I figure that if the ECU was going to complain it would have done so by now, but it hasn't.

I should mention that changing/disabling any vehicle emission control systems is illegal. Be it on your own head, should you choose to do this.
Having said that... I am confident that with the EGR disabled, the engine will be more reliable and should be more efficient. That is my justification for going down this path.

Just thought that I would share...

 

[mog]

Nice write-up, thanks.
When did Fusos get the EGRs added, 2005?

 

[gait]

right conclusion - explanation a bit suss!

the efficiency of a diesel is proportional to the combustion temperature and inversely proportional to the inlet air temperature. Also a function of compression ratio. Its a variation of the carnot cycle.

The theory behind EGR is that reduced combustion temperature reduces the formation of nitrogen oxides. Reduce combustion temperature reduce efficiency.

Air and fuel are such that complete combustion occurs. If there's more air there needs to be more fuel (or vice versa. Otherwise efficiency falls as all we are doing is heating excess air.

There's always a little excess air, otherwise complete combustion doesn't occur. Exhaust gas analysis should (does?) look at oxygen as well as carbon dioxide and carbon monoxide.

Petrol engines work with less excess air (nearly none).

More air (with appropriate fuel) increases power not efficiency.

I used to tune industrial furnaces and internal combustion engines are only a little more complicated!

As for quantifying the efficiency loss with various rates of EGR (anything up to 20% recirculation), in some studies its been considered marginal. There's probably an effect on power.

Sorry, I'm the sort of person that prefers trees to plastic bags. My whimpy excuse for driving something that consumes so much fuel and emits so much carbon dioxide is that driving to Europe from Malaysia was less damaging than two people flying. I struggle with the potential effect of not setting off.

In the current scheme of things Aus may be considered by other countries as somewhat backward in respect of pollution awareness and action. A couple of days ago the Aus Climate Change Authority suggested that if Australia were simply to match the US fuel economy standards for new cars we'd save 59m tonnes of CO2 and save consumers $8500 on fuel over the life of the average car.

I guess I'm looking forward to the day when I can have a 4wd vehicle carrying a 4m x 2m 600kg box for living, a couple of spare tyres, a bit of water and a bit of fuel that is less than the starting 2.6mt of my current cab chassis.

In the cool of the evening it doesn't make rational sense to me to have a converted delivery truck capable of 6.5mt GVM.

 

[SkiFreak]

right conclusion - explanation a bit suss!

My intent was not to write a technical article on EGR systems, just to point out that they do have negative effects on an engine.
Also... letting anyone that has an FG84 know, blocking the EGR does not throw up error codes.

The primary reason for wanting to block the EGR was to make my engine more reliable. I will leave all of the ethical stuff to others.

 

[gait]

I understand Owen,

there's a lot of misinformation on the internet, and a world of difference between efficiency and power,

nice to know how to block the EGR,

explanation of the effect was very suss

 

[1aquaholic]

So it's been 4 years, to those who have done this mod I have three questions. Still no problems? Do you think a US FG140 would also not have a code issue? Finally has anyone pulled the heat exchanger under the driver's side of the EGR as I'm assuming it would no longer have a function.

Thanks

Sent from my SM-G955U using Tapatalk

 

[SkiFreak]

Since doing the mod I have only driven a few thousand kilometres, but I have never encountered any error codes or other issues.
The FG140 has the same 4M50 engine as my FG84, so I see no reason why there would be any issues, but there's an easy way to find out... All you are doing is replacing a gasket with a plate, so if it does go pear shaped it is a very simple process to revert back to how it was.

Yes, you could remove the heat exchanger completely, but in doing so you would also make it very obvious that you have bypassed parts of the emissions system.
I don't know how it is in the US, but here it would likely be a problem, as trucks over 4.5T need to have inspections on a regular basis (every year or two, depending on the State) in order to maintain registration.
The "stealth" approach is a simpler option, in my opinion.

I should add... I don't know why I used that photo, as that was how I did my initial testing, not how I ended up doing the modification.
As it is now, the crossover pipe is still in place and there is no blanking plate on the heat exchanger. The only change was replacing the original triangular gasket on the exhaust manifold with an equally sized stainless steel blanking plate.
Unless you look very closely, everything looks like it is a standard OEM setup.

 

[Amesz00]

Yep. 10k km and no issues. Didn't notice anything different about it at all tbh, but at least it's not pumping soot into the intake now..

 

[1aquaholic]

Great thanks for all the info!

Sent from my SM-G955U using Tapatalk

 

[pugslyyy]

So it's been 4 years, to those who have done this mod I have three questions. Still no problems? Do you think a US FG140 would also not have a code issue? Finally has anyone pulled the heat exchanger under the driver's side of the EGR as I'm assuming it would no longer have a function.

Thanks

Sent from my SM-G955U using Tapatalk

I have had no problems, completely pulled everything off and installed blanking plates. You will need to retain the EGR valve actuator/position sensor but it does not need to be attached to the motor.