Diesel beats hybrids

Your article about hybrid car technology (

) was very interesting. This subject deserves greater coverage due to the massive impact this technology can have on fossil fuel usage and global emissions.

In my previous job I investigated the application of motor/ generators to replace flywheels in diesel engines for non-automotive applications.

This ‘semi-hybrid’ technology is simple, reliable, low cost and can be easily integrated in existing platforms. It can therefore have an immediate impact on fuel consumption and emissions. But semi-hybrid technology is not glamorous and does not qualify for government subsidies.

The full hybrid system used by Toyota is expensive, complicated and therefore liable to failure. The first problems are already appearing in north America (‘Hybrid on the hard shoulder').

The emissions and fuel consumption figures quoted in the article are based on on a combination of urban and extra-urban driving cycles. I could not find figures in Toyota’s literature for extra-urban driving only, but I believe emissions and fuel consumption will be much worse during long motorway journeys, when there is little energy input from regenerative braking.

Torque from the Prius petrol engine is also very low: 85lb/ft against 180 for the Peugeot 307. And what happens with acceleration when the battery power in the Prius is low?

I believe a semi-hybrid system using a low-emission diesel engine with a particulate filter can produce virtually identical fuel consumption and emissions figures without the complexity and expense of the Toyota system.

Particulates, a bugbear of diesel engines, are cut to 0.02g/km with the particulate filter and common rail injection. By adding a flywheel/generator to the Peugeot 307 the fuel consumption and emissions figures could be improved by at least 10 per cent.

The development of direct inline common rail diesel engines is continuing apace and the next generation will further improve fuel consumption and emissions.

Until fuel cells become truly cost effective and reliable I believe a propulsion technology based on modern diesel engines provides the best method to reduce car emissions and fuel consumption.

Mike Antonis, Director

InspecVision

Larne,

Co Antrim