Tue Sep 26 16:31:06 SAST 2017

Gas burner, rallying and a BMW vs Merc question

2011-10-23 13:15:04.0 | Ask Morgan |

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

Morgan replies:

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.


To Morgan,

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

Dear Steve,

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.


Dear Morgan,

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

Dear Ryan,

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.

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