Monday 16 December 2013

Hotfire gets a boost from Ricardo

Ricardo’s Syner-D programme gives a pointer to how JaguarLandRover’s next-generation Hotfire engine could progress towards meeting Euro 6 emissions requirements and CO2 reductions of over 30 per cent.

The Syner-D project, partly funded by the Technology Strategy Board, the UK’s innovation agency, had as its main aim: to deliver a premium vehicle demonstration vehicle offering a CO2 reduction of 30 per cent, Euro 6 tailpipe emissions and suffering no compromise in transient variability and overall performance.

The three-year programme included input from JLR, Valeo, SKF, Shell and Lontra.

Crucially, the programme revolved around a Jaguar XF saloon powered by a Euro 5 3-litre V6 diesel engine and as a first step the project would be downsized to a 2.2-litre  DW12 in-line four-cylinder diesel unit calibrated to Euro 6 emissions levels.

This latter unit fits within the broad engine capacity range of the new JLR Hotfire engine (which is expected to be in the range of 1.5 to 2.5 litres) that will be manufactured at the company new state-of-the-art manufacturing centre on the i54 industrial complex near Wolverhampton. The plant will make both gasoline and diesel power units using the latest machine tools from MAG.

“The objective was to achieve comparable transient performance, and going from a 3-litre to a 2.2-litre goes against that,” explained Andy Ward, head of Ricardo’s light duty diesel engine.

“So we had to add some technology to increase the performance beyond the baseline 2.2-litre engine,” added Ward. “We selected an advanced boost system comprising a low-pressure turbocharger and a high-pressure mechanical supercharger, which is quite a novel approach.”

The low-pressure turbo was retained from the larger engine, while a Roots type belt-driven supercharger was added. The supercharger is declutched to minimise losses when not required. In this situation, the air path is bypassed around the supercharger.

In addition to the advanced boosting, a low-pressure EGR circuit is used in combination with an SCR after-treatment giving more capability than is required to meet Euro 6.

As a result, this enables re-optimisation of the engine calibration for more efficient operation and hence provides a further fuel consumption benefit.

Ricardo could have selected a two-stage boosting set-up as this technology is already on the market,

“But our approach presented a more interesting research and development proposition,” explained Ward.

It is highly unlikely that Hotfire will embrace the complex arrangement adopted for the Syner-D programme, if only because of packaging and cost issues. But the genes of the research give a strong pointer to how Hotfire could evolve if it is to deliver (in some modes) the power and torque characteristics of the well-established Ford 3-litre V6 diesel engine built at Dagenham, UK.

                                    Phasing out

JLR’s long-term aim will be to phase out purchase of the V6 diesel engine, once it has brought its own Hotfire engine programme to the stage that downsizing from the chunky V6 becomes a formality.

Ward notes too that the target of Euro 6 emissions (which Hotfire will have to meet - Ed) could not be ignored.

“If we had used two-stage turbo boosting, adding NOx after-treatment would have caused temperature issues from the two turbines because of the temperature drop along longer pipe lengths, this in turn would mean the NOx after-treatment would be less effective.”

“Having a supercharger at the high-pressure stage means the exhaust system layout is unaffected,” added Ward. “You are left with the same high temperature as you would get on a standard, single-stage turbo variant. Basically, while there are some synergies between supercharging and NOx after-treatment, you do not find the same synergy between two-stage boosting and NOx after-treatment.”

In their down-sizing work, Ricardo engineers maintained 500Nm of torque across both engines, as well as zero to 100km/h acceleration of 8.8s. The original engine put out 236bhp but by the time Ricardo engineers’ down-sizing efforts were complete the I4 engine delivered 188bhp.

The all-important CO2 figure fell from 179gm/km in the case of the 3-litre to 125g/km for the 2.2-litre engine, and the emissions standard was raised from Euro 5 to Euro 6 in the process. The measured CO2 reduction achieved was 32.5 per cent.

Also forming part of the Syner-D programme were such important issues as thermal management and reducing friction.

Predicted Ward carefully: “While it is perhaps unlikely that a vehicle of precisely the configuration of Syner-D will appear on the market very soon, I believe many of the constituent technologies that it demonstrates may well prove attractive in the short to medium term.”

Significantly, from the point of view of the upcoming Hotfire engine, JLR engineers will be anxious not to be out of step with the current trend that edges towards CO2 outputs of under 100g/km, if for no other reason than customer expectations by the time the engines come to market. 


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