BEHIND THE WHEEL: Let’s talk about choosing the right engine size

What you need to know:

  • I had a manual 1.5 litre Mazda Demio Sport, 5-speed. In 5th gear, at 100km/h, the engine would be turning nicely at a steady 3200rpm.
  • This car was replaced by a 2.0 litre Subaru, similarly a 5-speed manual, which does a hair short of 2800 rpm in 5th at 100km/h.
  • You can see the bigger engine needs lower engine speeds to achieve the same road speeds, which, theoretically is good for consumption but in practice makes for a smoother, quieter, fuss-free drive.

I am a great fan of your motoring column. Thank you for the advice. Now, I have two questions:

1.) I am torn between what engine size car to buy between 1500cc, 1800cc and 2000cc.  I mostly intended to use the car to commute from home (approx 25km) to work here in Nairobi and a few occasional runs upcountry, approximately 250km. Which one would you recommend?

2.) My friend normally spends most of his time driving along highways at an average speed between 90-120km/h. What would be the most appropriate and efficient engine size for him among the above three? 

 

Hello Martin,

1. The recommended engine size depends on a variety of factors. All three will serve the listed purposes: 50km town-bound round trip and the occasional 250km jaunt to the village. The 1500 will be the cheapest to buy and probably run, the 2.0 litre will be the costliest to buy and run, with the 1.8 falling somewhere in the middle. However, the differences in running costs are not that big. The biggest difference may lie in buying price. That said, if you have even the slightest hint of petrolhead in you, then you could take the plunge and splurge on the 2.0 liter if the price difference will not have guilt gnawing at the cockles of your heart. If, on the other hand, you believe a car is nothing more than a convenient alternative to a horse, then just get the 1.5 and save oodles of shekels and get bored out of your mind...

2. This will depend on the gearing in question. All three cars will do 90-100km/h easily; the question is at what rpm in top does the car do it in? Again, the differences will be slight and I will use my own cars in comparison. I had a manual 1.5 litre Mazda

Demio Sport, 5-speed. In 5th gear, at 100km/h, the engine would be turning nicely at a steady 3200rpm. This car was replaced by a 2.0 litre Subaru, similarly a 5-speed manual, which does a hair short of 2800 rpm in 5th at 100km/h. You can see the bigger

engine needs lower engine speeds to achieve the same road speeds, which, theoretically is good for consumption but in practice makes for a smoother, quieter, fuss-free drive.

A car fitted with a 6-speed transmission will do 100 at even lower rpm than quoted above.

 

Hi JM,

I have a 2008 Merc A Class 169 with a 1690cc engine capacity. I have two questions:

1. After an average of about 3,500kms, I have done an average consumption rate of 11.3 km/l. Is this normal for a car of such low engine capacity? 

2. After about 3,000kms, I am experiencing a jerking action immediately I release the fuel pedal (the car is an automatic). This is especially chronic while I drive in sport mode. My mechanic seems to ignore this problem and insists it just needs service. The engine runs smoothly while in acceleration, but the jerking gets very distinct when I rev between 2,000-3,000 rms. 

During my last service (which was not actually due!), I noted that my plugs had burnt out and I suspect that my oil could be the problem. Currently, my service is still not due but my oil seems to have darkened completely. What would you advise on the above issues?

3. Why is it so hard to get parts for Mercedes A class models? I recently cracked my windshield and a certain car dealer is asking me to cough Sh78,000 for a windshield (minus repair!).

 

Salutations, Jones,

1. I have written this statement so many times, I think my computer now has an auto-complete option for it: fuel consumption depends mostly on where and how you drive, closely followed by the mechanical condition of your car. If you are always caught up in gridlock driving a car firing on only three cylinders and compensate for the time wasted by trying to send your right foot through the firewall, then yes; 11.3km/l is your lot. Otherwise, no; 11.3 is a wee bit high for the wee Merc.

2. There are several conclusions I’m drawing from your description and I hope they are accurate. a) this jerking started after 3000km of driving and was not there before. b) this is not the first time you are engaging Sport Mode c) the mechanic did not specify what particular aspect of service it required urgently. So now,

You may have a case of bad driveline joints. For a front-drive hatch like the A, these are constant-velocity joints, more famously known as CV joints. Replace them. When lifting off, the load on the powertrain is suddenly reduced, which means that there will

be shock, which will jar or shake up anything that is not properly secured; in this case, your CV joints. This is manifest either as an audible clunk or even a jerk if the looseness is severe. It also won’t hurt to check the level and quality of ATF just to rule out

any other possible suspects. Also, there is a strong likelihood that the clutches are damaged or the bands are out of adjustment. Unfortunately, I can’t explain this further without diagrams and at least 5,000 more words, so... ahem... if all other diagnoses

show nothing, then you may have to take apart your transmission, a very expensive and risky exercise. Just to be sure: how does the car behave when NOT in Sport mode? The jerk could be from a software glitch unique to Sport mode only, in which case

maybe you need to flush/reset your control modules. As for the oil, change it immediately. The plugs too.

 

Hi Baraza

Thank you for your wise answers to everything automobile. My unsolicited advice as to why we have so many cars on our roads is the predictable numbering which singles out fairly new cars as old.

My Toyota Carib s/wagon is perfect but because it’s KAR... it feels old. Even KBR feels old. Why can’t the government demystify car registration like it did with motorcycle and tractors and solve the unending congestion on our roads?

Two questions for you now:

1.Why do vehicle manufacturers change perfectly good cars and bring in New models every five years or so? Is there anything substantial they add apart from looks and a hike in prices? Does this trend augur well for availability of spares?

Why can’t they stick with one model and shape like the Landrover defender and Peugeot 504?

2. Which is the best transmission out there between manual, automatic, selectable automatic and the CVT( continuously variable transmission)?

           

Hello Donald (Trump?),

I thought the current motor vehicle registration protocol is as predictable as predictable gets. If there is a format that seems randomly wild (or wildly random), it is that of motorcycles, auto-rickshaws (tuk-tuks) and tractors. I have no idea what is going on there.

1. The biggest determining factor of constant updates is competition, especially in lucrative segments such as performance and pseudo-utility. People like us, and by that I mean self-proclaimed judges and juries on matters motoring, have empowered car buyers with a wealth of information that has transformed what would otherwise have been a casual client into a not-picking maniac armed with a magnet and tape measure ready to tap bodywork to affirm its solidity and gauge clearances, tolerances and various “-rooms” such as headroom, legroom, shoulder room and knee-room.

Once upon a time,  these words had no meaning and manufacturers would shift metal on the basis of string ad campaigns and dominance in motorsport. Nowadays, a BMW 3 Series will be released with various parameters, after which Mercedes-Benz will release their C Class with a slightly bigger boot, or slightly better rear headroom or something.

This will force BMW back to their design sketches to stretch the car a little to match the C’s interior dimensions, because in today’s world where having an Instagram account is more important than having a worthy opinion, a difference of 5mm rear legroom could spell disaster in sales.

Having stretched the 3er to match the C, Audi will then launch a new A4 that offers better economy or better driving dynamics or better features as standard, which will send both BMW and Mercedes scampering back to their design studios and /or engineering workshops to “update” their vehicles to match or better Audi’s output; which will subsequently displace Audi from first to last in this automotive game of one-upmanship; which in turn means they will go back to their drawing board to improve their car in an never-ending cycle of marginal improvements.

 Besides competition, there is the bottom line to look out for. Accountants are clever people and they know how to squeeze money out of unwitting customers. Buying a brand new car is more of an ego trip and desire to dominate the Joneses than an actual need for transportation.

So if I sell you a car now, say a BMW M3; come next year the car will still be relatively new so you won’t need a new one. But I can make you want a new one; by simply improving on what you have. Suddenly, your “dominant” M3 is no longer king of the hill; there is a better one available, and if anyone else buys it, you don’t get to rule the roost. You want it because you have to have the best, nothing less. So you get rid of your newish one-year old M3 and shell out more money for the latest. For you, you get bragging rights. For me, I make two sales, rather than one; from the same person. See where I’m going with this?  Ferrari is notorious for this kind of thing: they have been accused of releasing a limp-wristed version of a car at launch then charging people more a year later for something better with evocative suffixes like “Scuderia” or “TdF” in their names.

Yet another contributing factor is legislation, particularly on safety and emissions. The standards for these two are getting increasingly stringent; and the penalties meted out for failure to meet expectations can quickly drain one’s kitty and hurt one’s reputation; so manufacturers have to keep up. This explains your two examples: the Land River Defender and the Peugeot 504. Lovely cars, these, but they are inefficient and unsafe, and are therefore obsolete, rabid dinosaurs that have no place in the current motoring landscape of frolicky puppies and fluffy kittens. This is all the more important to some friends of mine who, to date, still lament the passing on of the Scania F330. Let me explain.

I belong to a group of enthusiastic bus-spotters. Over the past few years, there has been a Scania F330 bus on sale, an 11-liter, 6-cylinder beast fitted with an 8-speed manual transmission good for 330hp and the most charismatic engine note if you are into that kind of thing.

The bus was phased out in favour of the current F310, a 9-liter, 5-clylinder creation with a 6-speed transmission making 310hp that doesn’t quite sound right, turbo whine notwithstanding.

Well, my fellow bus fans were up in arms; and their lack of affection for the F310 was immediately made apparent. They did not want to believe that something as abstract and arbitrary as “Euro 4 emissions standards” could lead to the death of their favourite workhorse, but unfortunately for them, it did. You see, the F330 developed 1350Nm of torque, while the F310, with its lower power figure, actually makes MORE torque: 1550Nm. In the world of commercial vehicles, torque is everything.

Economy is also everything: the F310 is more economical than the F330, and is cheaper. That may explain why despite the F330’s popularity, the F310 has outsold it several times over and is (and has been) the best-selling full-size bus model in the country.

2. Is there really an answer to this question? “Best” is relative: the manual is the “best” for hardened petrolheads for whom driving sensations matter. It is terrible, though, quite the dinosaur in fact, in almost all other aspects.

The CVT is the “best” from a scientific and engineering point of view, such is its simplicity (relatively) and efficiency of operation; but drive a car with a pukka CVT and you might park it at the side of the road and complete your journey on foot.

They are boring and counterintuitive, and should be killed with fire while humans are still allowed to drive their own cars. Automatics have few fans and from an engineer’s eye view, they currently lack justification.

They are heavy, inefficient and complex; but they are the best for towing, for off-roading and are the recommended transmission type for those who care little about driving as an activity, but are still wary about Skynet taking over through the automotive

singularity that is currently being initiated by the advent of autonomous cars. If you do not understand that last statement, then you missed some of my articles from earlier in the year.