Combustion, exhaust temperatures and emissions

by | Jun 17, 2023

Recently we were asked by a client to explain how Aderco products affect exhaust temperatures and emissions. This was the explanation with case studies we presented.

How do Aderco products influence combustion and exhaust temperatures?

When fuel is treated with Aderco it has an impact on the engine exhaust temperatures. I have put this paper together for a client who wanted to understand exactly what the Aderco fuel treatment effects are.

Below is a real field trial on a Sydney Ferry on the harbour, these Caterpillar engines are similar to ones used on trucks for transport and mining. The fuel is an Australian Standards automotive grade distillate, with a maximum of 10ppm in sulphur. A real field test on water is a safe method to operate on all loads, whilst taking emission measurements.

The above graphs are the results of “before and after – Aderco fuel treatment” for both N0x and PM in the same engine, they were measured and certified by Coal Mines Technical Services.

Left graph;

N0x – Nitric Oxides are a direct indicator of the combustion heat temperature, production of N0x gases begins at approximately 1600 ̊C.

Right graph;

PM – Particulate Matter is un-burnt hydrocarbon residue in the form of soot. Indicating an incomplete and inefficient combustion.

Generally, when there is an increase in fuel, rpm and loads, there is higher heat emitted at combustion. Therefore when we look at the untreated fuel, the green line on the left graph we see lower N0x values at lower loads (0-20%) and higher N0x values at higher loads (80-100%).

However, when the combustion temperature is not sufficiently high a number of hydrocarbons are left un-burnt as seen on the green line of the PM graph between 0-20% loads.

This is common with un-treated fuels and has left the industry with a general perception that diesel engines should not operate at low loads, but this isn’t entirely true or fair on the engine manufacturers, as it is in fact the fuel that is letting the engine down.

In this trial, the changes in NOx and PM values between the untreated fuel (green lines) and treated fuel (blue lines) was already a clear indication the fuel had molecular agglomerations (discussed below). Essentially making the fuel heavier than it was intended to be and unless treated more difficult to deliver a complete combustion in this engine.

We wanted to confirm this and decided to count the agglomerations before and after treatment with the help of this INTERTEK Lab ASTM D7619 particle count below.

This table shows the number of hydrocarbon chains in 1ml of fuel. Hydrocarbons with 4 microns or less came to a total of 2613 particles before treatment and after treatment, that number increased by 30% to 3588.

* It is important to note the ASTM DT619 counts each agglomeration as one particle.

This ASTM D7619 test verified the hydrocarbons had already begun to agglomerate and the chamber required more heat then the engine was designed for, in order to completely combust all the fuel. Therefore, it was leaving unburnt fuel and producing a high value in PM (green line PM graph).

Once treated, the agglomerations were dispersed, and the number of hydrocarbons particles increased, returning the fuel back to the refineries intended composition (Polymeric detergent additives discussed – Chevron diesel-fuel-tech-review. Page 87)

The blue line (after treatment) on the left graph indicates a rise in temperatures (N0x) at loads 0-20%, which could be perceived as a negative value – but only if the PM (un-burnt hydrocarbons) remained at the same level.

In this case, the PM value dropped by approximately 30% – indicating the combustion is now optimal and efficient at the lower 0-20% loads. Here the increase in NOx (temperature) is actually a benefit as it leaves less PM (unburnt fuel), improving fuel efficiency and reducing soot/smoke.

This is also the source of the diesel scandal and why all modern diesel engines with DPF’s should work in theory, but don’t in practice.

As the loads increase the Aderco treated fuel (blue line) flattens and N0x’s drop, this is because the engine’s performance improves and fewer rpm’s are required to deliver the same torque, decreasing the heat produced in the chamber and exhaust – TAFE SWSI dyno test below.

Lowering the NOx at higher loads without increasing PM again indicates the optimal combustion for this fuel and this engine.


Exhaust gas temperatures are derived from combustion temperatures.

The line on the left graph is naturally lower at the low load end and higher at the high load end.

The key objective of a good combustion is to flatten the NOx line, without increasing the PM to achieve an optimal efficiency and performance.

The lowering of exhaust temperatures must be balanced to avoid leaving unburnt hydrocarbons (PM) resulting in smoke and soot in older engines and choked up DPFs in modern diesel engines.

When fuel is treated with Aderco we unfold the agglomerated hydrocarbons, returning the fuel to it’s originally intended composition to deliver a complete combustion at the right time.

Fuel instabilities are why the automotive industry today have difficulties balancing the EGR with the DPF. As the EGR lowers N0x (heat) the combustion produce excess PM (soot) that then requires an unreasonable amount of DPF regeneration. This involves long drives at high rpm’s which is difficult in city driving and without it, vehicles end up with blocked DPFs.

With the fuel treated, an engine will perform as it was designed, avoiding a great deal of overworked DPF issues and delivering the fuel efficiencies the manufacturer intended.

Further evidence – TAFE SWSI DYNO 2015

Further “before and after” dyno test example with exhaust temp/torque/rpm/fuel :





CONCLUSION: This testing shows that there was a decrease in fuel usage of 4.9%. There was a substantial reduction in the black smoke emitted from the exhaust over the duration of the testing. Some consideration was given to the changing environmental conditions over the testing period, ambient air temperatures started at 24 degree Celsius and at the finish of testing were at 31 degree Celsius. The changes reinforce the findings as efficiency continued to improve as the test progressed into hotter conditions. This confirms the manufactures claims and other testing carried out elsewhere. (Neale David –Instructor)

This test was performed at 70% load. The evidence of reduced combustion temperature is the rpm’s dropping without torque being lost, just as we can decipher from the NOx graph at higher loads. The fuel consumption dropping in this test is again similar to the PM graph on the first test.

The exhaust temperatures also drop, but the real importance is in combustion temperature and those indicators. 

Supporting documents available on request for clients and qualified prospective clients;

By Francisco Malta

Aderco – Sustainable Fuel Treatment Solutions


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