CGI offers boost for small diesels

Development of small-displacement diesel engines using compacted graphite iron (CGI) and offering over 100 bhp/litre is under way.

Dr. Steve Dawson, SinterCast’s president and chief executive officer, confirmed the company is supporting development of small-displacement diesel engines offering over 100 bhp/litre. SinterCast specialises in process control technology for the manufacture of compacted graphite iron (CGI).

 “In addition, many of the new horizontal opposed-piston engines have specified CGI for the block and/or liner,” notes Dawson. “There are growth opportunities in new technology as well as conventional technology.”

“Commercial vehicles and industrial power applications are obvious growth opportunities for CGI.  The material is proven and there is a clear trend for more performance from smaller engine packages,” added Dawson. “Our current production split is approximately 60 per cent passenger vehicle, 35 per cent commercial vehicle, and 5 per cent industrial power.  Our production started with diesel engines because higher combustion pressures required stronger materials.”

For passenger vehicles, CGI has effectively become the standard material for vee-diesels with the Mercedes-Benz 3-litre V6 (aluminum) and the V8 Duramax (grey iron) engine from General Motors (GM) being the only remaining passenger vehicle vee-diesels that are not produced in CGI. 

“It is very significant that the Mercedes-Benz aluminum V6 is 125 mm longer and 15 kg heavier than Audi's  3-litre V6 diesel produced with a CGI block,” said Dawson.

“We received our first gasoline breakthrough in 2014,” noted Dawson. “The Ford 2.7- litre V6 gasoline engine (below) with fracture-split main bearings was launched as the world’s first high-volume CGI gasoline engine.  It is used in Ford F-150 pick-up truck, and Ford Edge and Focus passenger cars.  A 3-litre derivative with 400 bhp appears in the new Lincoln Continental and we expect more gasoline engines will come as the trend toward downsizing and direct injection continues.” 

“In contrast to passenger vehicles where, until now, we only have production of vee-engine cylinder blocks, commercial vehicles have adopted CGI for blocks and heads in both in-line and V-configurations,” noted Dawson. “CGI has made good inroads in commercial vehicles and most western OEMs now have at least one CGI offering in their line-ups.  If we think of new designs in the US and Europe, perhaps 25 or 30 per cent of new designs have either block or head in CGI, sometimes both.  As the demand for more performance from smaller packages continues, the application of CGI will grow.”

“We are at the stage where we have credible high volume references in every sector, and these references provide competitive benchmarks that help CGI to secure additional applications.  We are most proud of the fact that no OEM has made one SinterCast-CGI engine and then stopped,” Dawson stated.

“If we look back to the uphill playing field of the 1990’s, there were many reasons why CGI couldn’t be used:  too difficult in the foundry; too difficult to machine; too expensive.  But, when an OEM produces its first CGI engine, the engineers see the benefits and they apply CGI in more engines.  For example, Ford has nine CGI engines while Audi and Hyundai both have six.  Our challenge is to get the first engine – if we can get one, there is a strong probability that the growth will be self-fulfilling,” Dawson added. 

The SinterCast process control technology has been installed on 44 foundry production lines in 13 different countries.  The major benefit is that CGI can be cast in existing cylinder block foundries using the same melting and molding techniques.

                                               The CGI company

Dr Dawson’s primary focus is that of defining SinterCast as The CGI Company,

“Our engineers frequently generate new ideas, and therefore, we investigate a variety of different concepts,” noted Dawson. “But when we consider developing these concepts into products, our ambition is that new products should be unique to SinterCast and they should improve efficiency in the foundry as well as reinforce the image of SinterCast as a foundry technology leader.”

“We don’t want to be a second source for ordinary products,” Dawson emphasised. “There will be new products, but I expect the new products will be contributors to our business rather than competitors to our core CGI attentions and revenues.  We will continue to investigate and develop new technologies, but the best thing we can do is to be the best at CGI.”

“Our progress shows that we have good OEM uptake in the US, Europe and Korea, which leaves Japan, China, India and other OEM countries as future growth opportunities,” he points out.  “We do have three foundry installations in Japan and 10 installations in China, so we do have a local footprint.  Three of our installations in China are already exporting CGI components, but we are still waiting for the domestic demand for CGI.  The applications for CGI are clear and the growth opportunities are well defined.  We don’t need to do anything different, we just need to do more.”

As to the thorny question of what competitive technologies does CGI face in the next 10 years, Dawson replies: “On the passenger vehicle side, aluminium is an obvious competitor.  But iron has a good story; we just need to get better at telling the story.” 

He notes that legislation has focused on CO₂ tailpipe emissions, prompting some passenger vehicle OEMs to adopt aluminium cylinder blocks to reduce weight. 

“But aluminium production is significantly more energy-intensive than iron,” points out Dawson.  “Each kilogram of aluminium produces 9-12 kg of CO₂, depending on the energy source.  It is not clear that the reduced weight (about 10 kg for a typical 1.6 litre passenger vehicle aluminum engine) will ever payback the up-front CO₂ penalty.  Most studies indicate a CO₂ payback requirement of more than 10 years of driving. “

“On the commercial vehicle side, CGI has been well embraced as the ‘next’ material and we do not see anything else in the pipeline” states Dawson.  “The higher peak firing pressures (230 bar for heavy duty diesels against 175 bar for passenger vehicle diesels) and the larger bore diameters (130 mm for heavy duty compared with 90 mm for passenger vehicles) mean that aluminium simply is not strong enough for the durability requirements.” 

“We need to consider costs too,” he adds.  “The off-road sector is very cost-sensitive and aluminium is significantly more expensive than iron.  For heavy duty engines and even for smaller off-road engines, iron has a favourable profile for specific performance, durability, package size, life-cycle energy and cost.”

It is Dawson’s view that the company is still at the early stages of the core CGI market development. 

                                      Support and foster CGI

“The most important thing we can do with our resources is to support and foster the CGI development, both in technical functionality and market awareness,” he points out.  “Our clear ambition, and our commitment to our shareholders, is to be the global CGI leader. So we are solidly focussed on CGI solutions and CGI applications.”

“The good news is that the benefits of CGI are fairly obvious, so we can always discuss the opportunities with the design engineers and start the ball rolling.  Now that the CGI market has become established, our strongest sales messages are the engines that are running on the roads,” he declares. 

In flushing out the metallurgical benefits of CGI, Dawson explains: “The elongated graphite flakes in grey iron provide good heat transfer but reduce strength.  The individual spheres in ductile iron provide strength but impair thermal conductivity.  It is the coral-like compacted graphite microstructure that provide both strength and heat transfer.”

And it is this fundamental characteristic that paves the way forward for CGI n engine technology.

Compared to grey iron, CGI is 75 per cent stronger, 45 per cent stiffer and provides double the fatigue strength.  This increase in strength allows for increased peak firing pressure (P_max) and improved specific performance – horsepower per litre.  

In off-road applications, CGI is used to increase performance while ensuring durability, for example, to increase the power of an existing engine or, in a new design, to get the performance of a 15-litre engine from a 13-litre package. 

“Most engines are operating near the durability limit, so it isn’t possible to make significant steps without resorting to stronger materials,” notes Dawson.  “We have production examples in the off-road sector where grey iron is used for the base engine and CGI is substituted for the high power versions of the engine.”

Explains Dawson: “The OEM uses the same foundry tooling and the same machining line, but substitutes CGI to improve durability.  This is particularly true of cylinder heads in marine engines where the duty cycle is severe.  In the standardized thermal fatigue bench test developed by AVL of Austria, CGI provides approximately double the fatigue life of grey iron.  This improvement translates to field experience with heavily loaded cylinder heads.” 

The main driver in off-road applications is downsizing and power-up while ensuring durability.  In parent-bore applications, CGI will also have 20-30 per cent less bore distortion, allowing for reduced ring tension and reduced friction losses (particularly at cold start); less oil consumption; and, less blow-by. 

“Engine designers can also expect 1.0-1.5 dB reduced noise due to the higher stiffness, and operators can expect longer service life and extended service intervals,” points out Dawson. “If you give engine designers a free hand to choose materials, they will always choose the stronger material.”