Gas burner, rallying and a BMW vs Merc question
I’ve noticed that many manufacturers are moving to direct-injection engines. Can you clarify how direct injection works and what the benefits are? Are there any drawbacks to this technology?
Question sent in by Travis Pilten, Woodmead
Direct injection is not new technology but, because of the costs involved, it hasn’t enjoyed a lot of popularity until now.
Traditional fuel injection systems pre-mix fuel and air in the inlet manifold from injectors positioned on a common fuel rail.
In direct injection motors, the fuel is sprayed directly into each cylinder where it mixes with the air – the injector placed at the opening of the inlet valve. This results in a better fuel spray pattern and a more complete fuel combustion. Direct injection produces more power, less waste.
The upshot of this is that carbon emissions are reduced by about 15%. Similar figures for fuel consumption have been recorded. In fact, Mercedes’ new range of direct injection engines are some 20%-25% more fuel efficient. Direct injection also works with diesel engines.
The downside to direct injection is its tendency to build up excess soot and carbon around the intake valve. But overall, the pros far outweigh the cons.
You said that Toyota and Imperial are preparing to enter the Dakar Rally with the Hilux. I was surprised that there was no mention of another rally car that was present at the Johannesburg International Motor Show – the Volkswagen (VW) Polo R.
So when can we expect to see this car compete in the World Rally Championship (WRC)?
I would also like to know why the rules changed to smaller 1.6-litre engines. Is it because of cost or to meet new emission standards? – Steve Kruger, Boksburg
The car is expected to make its debut in the WRC next year but we’re still waiting for confirmation as to who the driver and co-driver will be. All that can be speculated on right now is that VW want to make it an all-German partnership.
Last year people lamented the move to 1.6-litre engines as a step backwards but from what we have seen already these smaller motors produce the same power as the defunct 2.0-litre turbo motors.
The move to smaller engines also suits the philosophy of VW (and many others) of green motoring powered by efficient and economical engines. That is one of the reasons VW has entered the WRC.
Downsizing is part of the Fédération Internationale de l’Automobile’s (FIA’s) global plan to introduce smaller turbo motors across all forms of motorsport; in 2014 Formula One cars will use 1.6-litre V6 turbo-charged engines.
How can the Mercedes SLK 350 cost R200,000 more than the BMW 135i?
I currently drive a BMW 135i convertible and I can’t see how the SLK can justify that difference in price. – Ryan, Rustenburg
If you judge the cars on performance alone the 135i is better, especially at the Reef’s altitude where non-turbo charged cars suffer the most.
That said, the SLK 350 is more competitive compared to the Z4 sDrive35i or the Porsche Boxster S than with the BMW 135i convertible. Here the pricing is consistent.
If you’re after performance, agility and speed-induced thrills, the 135i is a dynamite package.
The SLK is more sophisticated inside and out. It’s a more intelligent drive, is softer around town and is easier to drive on the limit. It looks better too and the sound of the engine will resonate through your bones long after you’ve parked it.
For something a little more affordable you could consider the SLK 200 with its four-cylinder 2.0-litre engine that retails at about R555,700.