I4H coach: Hybrid commuter saves 20% fuel in UK first

I4H coach: Hybrid commuter saves 20% fuel in UK first

Irizar’s new i4H brings fuel-saving hybrid driveline technology to the commuter coach market in a UK first.


The driveline combines a reliable, HVO bio-fuel capable Cummins ISBe 6.7-litre Euro VI engine with an advanced Eaton PHP hybrid transmission, incorporating an electric inverter and traction motor-generator, together with a conventional six-speed automated manual gearbox.


Combined electrical and internal combustion power, together with energy recovered using the electric motor/generator as a retarder, helps to reduce fuel consumption by over 20 per cent in mixed ‘real-life’ conditions, where relatively high-speed running on major roads is interspersed with stop-start urban traffic. An automated stop-start system also shuts down the diesel engine (if temperatures and battery condition allows) when the parking brake is applied, further reducing unnecessary exhaust emissions. The engine restarts automatically when the brake is released.


On a 13-metre length, the Irizar i4H can typically seat 57 people, or 53 with additional spaces for a wheelchair user and luggage stowage.


At low speeds, the Irizar i4H is propelled by electricity only (although the diesel engine still idles to power auxiliary systems such as air-conditioning), taking advantage of the low-speed torque provided by the three-phase 346V motor/generator. If the coach is accelerating or cruising, then the diesel engine revs up to combine with the electric motor to provide the optimum blend of power for the conditions. When the Irizar i4H slows, the diesel engine disengages and returns to idle, while the vehicle’s momentum turns the motor/generator to replenish the batteries. An added bonus is reduced load on the coach’s foundation brakes, which aids safety, reduces wear and cuts particulate emissions, as the motor/generator acts as a retarder.


Care has been taken to make the Irizar i4H as safe and simple to work on as possible: there are only five cables carrying high-voltage current, and they are all clearly colour-coded and continued within the engine bay. The engine bay itself is the same size as that of a conventional coach, and full luggage capacity is retained.


An advanced temperature-management system segregates air-conditioning, and engine and battery cooling functions, with separate radiators independently cooled by dedicated electric fans which only operate as required. The fans can reverse to remove air-borne debris that might otherwise clog the system. Drive for the saloon air-conditioning system is taken directly from the diesel engine: utilising the power take-off that would normally drive the engine cooling fan; reducing parasitic losses.


The Cummins ISBe 6.7-litre, 300-hp diesel engine has genuine multi-fuel capability. It can run, without modification, on the renewable synthetic diesel fuel HVO which is made from bio-waste, or conventional diesel, or any blend of the two fuels. Use of pure HVO will reduce engine CO2 output by up to 90 per cent.


Engineered specifically for commuter and inter-urban work where a mixture of unrestricted and congested roads are encountered, the Irizar i4H will be undergoing real-world operational trials with selected UK operators as immediately after the show closes.