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No turbos for Ford V8
Ford says its V8 doesn’t need turbochargers to meet emissions standards
29 Sep 2014
By DANIEL GARDNER in LOS ANGELES
ONE of Ford's top engine designers says its iconic normally aspirated V8 will not have to resort to turbocharging to meet increasingly tight emissions regulation.
Where many manufacturers have turned to turbos, the Blue Oval says developments in direct fuel injection, intake geometry, camshaft and ignition timing have allowed significant improvements without the side effects of turbocharging.
In many applications, turbochargers are known for robbing exhaust note and character, while producing undesirable power-lag, but with natural aspiration Ford's V8-powered 2015 Mustang GT, will retain the soundtrack for which it is known, says Ford.
Speaking at the international launch of the 2015 Mustang, Ford V8 engine specialist Adam Christian said that during the most polluting stage of engine operation – cold-start – turbochargers actually prolong higher emissions.
“In some ways it's more difficult to get good emissions on turbocharged engines because for us emissions is the first 30 seconds and cold-start is everything,” he said.
“The turbocharger absorbs a lot of heat and we are trying to put out as much heat to the exhaust system as possible to warm the catalyst (catalytic converter). The turbocharger actually sucks up a lot of that heat.”
Instead of turbos, Ford's approach aims to increase exhaust gas temperature as fast as possible allowing the emissions-cutting catalytic converter to reach its 'light-off' temperature sooner.
Ford's rapid exhaust heating process makes the V8 work more like an oil-burning stove, holding the throttle wide open to allow very hot and efficient combustion of fuel, while maintaining idle speed by severely retarding ignition timing.
“For your traditional spark timing you want to be around 30 degrees before top-dead centre. These engines run 10 to 30 degrees after top-dead centre,” Mr Christian said.
“A wide open throttle sends almost all of the combustion energy into the exhaust system.
“Fortunately with direct injection we can do a stratified charge at cold-start and have better combustion stability.”
Variable induction geometry has also been developed for the new V8 and a bank of 'charge motion control valves' alter the flow of intake air to further reduce cold-start pollution.
“The way we have made our cold-start even better is with the CMCV valves - by bringing in charge motion and stirring up the fuel and air much better, our combustion improves, and we are able to run very retarded ignition, and that is what has allowed us to meet the emissions standards of the future,” said Mr Christian.
The V8's variable camshaft timing also aids in rapid catalytic converter light-off, but the same technology has also reduced fuel consumption when up to operating temperature as well.
“We have found a way to make the intake camshaft go to an advanced position and lock there. Its not fully advanced and not fully retarded - called mid-lock and in that position gives the the best cold start.”“What that allows us to do is add 20 more degrees of intake retard and that allows us to have better light load fuel economy.”
Under the bonnet of the new Mustang, Ford's V8 is similar to the engine of the previous generation model, and carries some of the components that powered the higher-performance Boss 302 variant.
Its conrods and exhaust camshafts are identical and 1mm of lift has been added to the inlet camshaft, but its cylinder heads are drastically different.
Each of the Boss 302 heads required a marathon five hours of machining, but the new components provide the same flow with far less intensive manufacturing.
“We made the cylinder head flow as good as the Boss 302 but the Boss was 100 per cent CNC-ed. We build one of these babies every 15 seconds but it flows as good,” said Mr Christian.
The extensive changes have boosted output by 11kW over the outgoing standard Mustang V8, while cutting fuel consumption and emissions, however Ford is yet to confirm an official combined cycle figure.
In American guise, the new Mustang GT produces 325kW and 542Nm of torque, while returning fuel consumption of between 15.6 litres per 100km and 9.4L/100km on urban and freeway driving respectively.
Ford has not confirmed power or performance figures for the Australian specification Mustang, which touches down about the middle of next year.
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