12 February 2006: Fuel

 
 


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’m going to discuss Hoshi’s fuel consumption.  When we were shopping for a replacement for Kermy, fuel consumption had a lower priority than ever before.  Sure, on the one hand, I wanted a modern turbodiesel - but this was because of how they drive rather than for consumption reasons.  Okay, don’t get me wrong, a more economical car is certainly handy... but Charlie and I are planning on moving somewhere closer to my work so my commute will cost less.  If we move too close we’ll never make up the difference between (say) running a Passat TDI and a Passat 1·8T.

This written, the Accord is not a natural choice for somebody concerned about fuel consumption because on paper they’re thirsty compared with the vast majority of what may be considered peers.  Going on standard fuel consumption figures the Accord should use around 25% more fuel compared to our Ka.

So far Hoshi’s fuel consumption figures have been between 32·4 and 35·6 miles per gallon.  This included my usual commute, some city driving and one trip to Lincolnshire.

Now the Accord has a low fuel warning light.  The handbook reckons that the tank has a capacity of sixty five litres and the low fuel warning light comes on with nine litres remaining.  One of these figures is inaccurate: I’ve filled when the low fuel light has just flicked on and put fifty one litres into the tank.  I’ve no intention of finding out the inaccuracy because I really don’t want to run out of petrol.  Running out of fuel is no fun.

There are a few compromises associated with the Accord compared to the Ka.  One is flexibility, both from an engine and boot space perspective.  I’ll talk about the boot later in CruiseControl but I can at least discuss that Honda VTEC donk.  The engine is almost as flexible as the Ka’s Endura-E, although the more I get used to it the more of a difference I feel.

The key difference is that the Endura-E’s power band is different.  With the Ka, the engine is either idling, labouring or driving.  It’ll labour if, for example, you accelerate from 20 in fourth, or moving off from rest in third.  Otherwise it’ll drive along.  There’s lots of torque from under 2,000 rpm, which means at forty five indicated in top it picks up nicely.

Compare this with the Honda, which has almost identical overall gearing to the Ka but taller interim ratios.  Compare this to the Accord.  We have idling, we have labouring, we have driving and we have screaming (the nice form of screaming).  The Accord’s engine labour at engine speeds where the Endura-E is driving and the interim gears are higher, so there’s another difference here.  It’s driving along from 2,000 rpm in the upper two gears but it will pull from 1,750 rpm on flat ground in fourth.  However, if one tries to accelerate with under 2,500 rpm on the tachometer you get very little happening bar the odd tumbleweed.

This means in fifth gear the car has limited acceleration until the speedometer is around 55 mph.  From this speed, there’s a sharp increase in available acceleration.

This trait is apparent in all of the gears, which means moving off relatively smartly causes a surge in acceleration as the tachometer sweeps past 2,500 rpm.

Further up in the rev range, the power increases quite dramatically from 4,000 rpm.  From 4,000 to the limiter at 6,700 rpm the engine is pulling very well indeed as it’s working with the higher lift camshaft profile.  Here’s it’s screaming along.  IF I wish to remain inside the motorway speed limit, I’ll only be listening to this noise in the lower three gears.

Thus, we have an engine that needs 2,500 rpm on the tacho to pull well and 4,000 rpm for proper acceleration.

Now if I left it at that, readers might think that the Honda engine represents a typical multivalve unit - it needs plenty of revs to perform.  However, VTEC means that, whilst I find the engine a little lacking in flexibility it’s a whole lot better than most alternatives.  The key benefit of VTEC is flattening the torque curve.

But it is thirsty.  Perhaps switching to a diet of super unleaded (or Optimax) will help this?