Apr 11, 2019
Posted by Keith Howard, Strategic Technology Manager, Ping Zhu, Director of Technology, Asia
In previous articles, we’ve mentioned the increasing importance of fuel quality as emissions limits tighten. This is particularly so for China 6, with its added focus on maintaining efficient and low emissions operation across vehicle lifetimes. High quality fuels help ensure correct combustion, not only from new, but also as vehicles age. Without both, air quality is adversely impacted.
The short-term behavior of a fuel is normally addressed through the fuel standards GB 17930-2016 for gasoline and GB 19147-2016 for diesel. These use rapid tests on all fuel sold, to ensure quality. They assure the correct nature in terms of ignition, stability and volatility. They can control potential contaminants that could cause exhaust aftertreatment deterioration, and the general chemical nature of the fuel. Getting these right for a successful China 6 implementation is important.
However, such specifications can’t fully control another aspect of deterioration in otherwise well-maintained vehicles—deposit accumulation. Engine tests are necessary to fully assess this; they show deposit control can be achieved through fuel additive treatments—often at parts per million level. Due to their cost and complexity, though, these tests can’t be run on every batch of fuel sold. However, the fast pace of change in engine technology is potentially altering appetites for deposit control. Keeping deposit tests up-to-date for the modern engine requires development.
Take gasoline engines. There has been a switch from port fuel injection to direct injection, something likely to be reinforced by China 6. With intake valves no longer being cleaned by fuels, and fuel injectors now directly exposed to fuel combustion, deposit control needs are clearly changing. Established tests can’t reflect this, so new procedures are needed. These are still under development, but it’s important that standards and practice deployed in China reflect this changing need.
Historically, there has been a lot of skepticism about the need for deposit control in China. Indeed, this has gone as far as a ban on such additives previously, possibly reaction to a past history of overstated claims. The lack of modern, effective deposit formation testing procedures makes their control harder.
There is a link between some types of deposit formation and emissions deterioration. In the context of China 6 legislation, where OEMs face the prospect of being held accountable for deterioration in emissions and losses in efficiency through vehicle lifetimes, this makes deposit control important. This link can be seen in Figure 1 below, where particulate number concentration appears to respond to fouling, as shown by an increase in fuel injection duration.
A well justified and balanced case for fuel additization for deposit control can therefore be made, but legislators need to be convinced and buy in. It’s in their interest, because without emissions control across vehicle life, they won’t deliver good air quality. It’s also important for OEMs, because China 6 makes them accountable for this going forward. They need effective solutions deployed.
OEMs can ensure deposit control, through fuel additives in three ways:
- Request the required fuel quality in the generally available bulk fuel.
- Offer their own preventative treatments, under their control. Though they will need to take care these are applied consistently.
- Offer their own workshop-based treatments that deliver deposit remediation more cost effectively than engine dismantling.
Controlling deposit formation through bulk fuel standards is difficult. Fuel additives can be prequalified, but ensuring that works for every OEM and user can be difficult. Testing protocols require relevance to emerging engine technology, and enough severity to assure real-world effectiveness.
Preventative OEM-prescribed aftermarket additives can work if bulk fuel treatments lack consistent effectiveness. The problem with these is their consistency of usage. Can you always persuade an end user to put an additive from a bottle in the fuel tank every time they fill up? OEMs could counter this through automated on-board dosing of fuel additives, much as is already used to assist diesel particulate filter regeneration and SCR function.
Where a vehicle is brought into a workshop for remediative work, then professionally applied, rapid deposit remediation treatments, potentially under OEM control may be particularly effective. We see this in Figure 2, where there has been a reduction across a high-speed drive cycle of 64% in the concentration of particulate after applying cleaning treatments to a gasoline direct injection vehicle. With increased use of on-board diagnostics and in use conformity under China 6, this might be necessary more often in the future.
Undoubtedly China 6 presents challenges to fuel quality. However, the solutions outlined can aid improved compliance. That’s key to the success of a serious and admirable legislative effort to deliver a prosperous high mobility future for China, with good air quality in its cities, and health for its citizens.
If you would like additional information on China 6,visit the China 6 section, or contact your Lubrizol representative