Hello Baraza,
Kindly enlighten me on the difference between the ordinary super petrol and the V-Power fuel sold by Shell. I drive a supercharged Vitz — RS 1600cc — and have tried using both fuel types and experienced no difference at all in terms of speed, performance and kilometres per litre. Let me hear from you on this.
Nawaz Omar.
Shell were very careful when pointing this out. Much as the ads starred a Ferrari road car (and an F1 racer too, if I recall), it did not mean that putting V-Power in a Vitz will turn it into a 458 Italia. Nor did it mean that the fuel economy of a small car will be changed from the incredible to the scarcely believable.
Shell V-Power contains extra cleaning agents that will wipe away all the dirty sins, sorry, dirty deposits from your engine and fuel system, just like Christians insist Jesus will if you call out to Him.
Even more importantly (for those of us who love performance engines), it also contains octane levels high enough to allow high compression engines to run on it: engines such as those with forced induction (turbocharged/supercharged) or even… yes, a Ferrari F1 racer.
So Nawaz, take note: V-Power will clean the engine of your Vitz, not transform it.
Hi Baraza,
I enjoy reading your column every week. Good work! I would like to know the relationship between engine size and fuel consumption. Basically, what is the relationship between the fuel injected into the combustion chamber and engine size?
Thank you,
Kiama.
If we were in the year 1930, there would be a clear-cut answer to your question, but it is 2012 and we have with us technologies like Variable Valve Timing and Direct Injection which make things very hard to explain without pictures.
Anyway, I will try to make things as simple as possible, and, before I start, I hope you know the basic physiology of an engine.
For normal running, we have what we call the stoichiometric intake charge ratio, which is simply referred to as air-fuel ratio, and stands at 14.7:1. If it goes lower, it is called a rich mixture (such as 10:1 or 5:1). If it goes higher, it is called a lean mixture.
Now, if it was the year 1930, the calculation would be simple: for every 15 metric units of air sucked into the engine, the fuel levels would drop by just a shade more than 1 metric unit.
So for a 2.0 litre engine operating at a constant 1,500rpm, you have four cylinders, which go through 1500 revolutions in one minute, consuming fuel in one stroke out of every four, and two strokes make one revolution (0.5×1500=750 fuel-intensive strokes). Since the cylinders occupy 2,000cc, 750 strokes of 2,000cc would be 1,500,000cc worth of intake charge.
I talked about metric units, and it is here that you have to pay attention because it ties in with all the economy advise I give people about filling up early in the morning.
While at the dispenser down at the petrol station you will buy fuel by VOLUME, the injection system of a car measures it by MASS for the intake charge ratio.
The density of air at 25 degrees Celcius (RTP — room temperature and pressure) is about 1.2 kg/cubic metre. So 1.5 cubic metres (1,500,000cc) will weigh 3.6 kg, which constitutes 14.7/15.7 (93.6%) of the intake charge, with fuel covering the remaining 1/15.7 (6.4%), which by simple arithmetic translates to about 0.25 kg of fuel.
Fuel has a density of 0.74 kg/L, so 0.25 kg of petrol will translate to roughly 338 ml of the stuff, or about 1/3 of a litre.
This is for the 2.0 litre engine running at a steady 1,500rpm for exactly one minute under the stoichiometric intake charge ratio. In the year 1930.
Nowadays, with electronic engine management, direct injection and variable valve timing, the cars can run lean and the effective volume of the cylinder changed in real time, so it is not that easy to calculate the consumption by hand like I just did.
Hello JM,
I drive the new-model Caldina and whenever I encounter dusty roads or wade through muddy waters, the brakes become a gamble. Recently, I noticed the same on my friend’s Subaru Outback. Is it a manufacturer’s error or just the pads? I almost rammed another car because of this.
Sam.
No, Sam, that is not a manufacturers’ mistake. It is your mistake. What you are telling me is: “Look, I drove over a police spike strip and now all my tyres are flat. The manufacturer must be really useless.”
When wet or dirty, brakes don’t work as well as they should because the foreign material interferes with the friction surfaces that convert your kinetic energy into heat energy; and that is why at the driving school they told you to increase your braking distance by at least half if you are driving on a wet surface.
Just to prove my point, tell me, honestly, really truthfully, with a straight face: When clean and dry, the brakes work fine, don’t they?
Hi Baraza,
I imported a Subaru Imprezza GG2, 2004 model late last year and the mileage on the odometer at the time was around 82,000km. I had a small accident with it along Valley Road, Nairobi a month ago and the insurance company fixed the car, but since then there’s a “wheezing” sound that comes from the back as I drive.
Two mechanics have independently confirmed to me that the rear right bearing is the source of the noise and that, for this particular model, the bearing and the hub are sold together as one component. Could you confirm this? What would be the risk of driving it that way before I get it fixed? Can the rear right wheel come off as I’m driving?
Secondly, having done that mileage, what particular parts or components should I replace? Do I need to change the timing belt or any other particular thing? Kindly advise.
You could go to a shop and ask to buy a bearing. If they tell you that it sold with the hub as a unit, then there’s your answer.
I went through a similar case with a Peugeot 405 I had: the fourth gear synchroniser unit was damaged, and when I went to buy a new one, they handed over the unit, to which was attached a gear, and they quoted an unfriendly price. Told them the gear in my car was fine: lose the cog and drop the price. Can’t do, they said; the synchro is the one that costs that much, the gear is actually free. I wanted to weep.
The rear wheel will not necessarily come off, at first, but the bearing could collapse and this might lead to the studs in the hub breaking when the wheel wobbles. Then the wheel will come off.
You could pre-empt breakages by replacing parts such as the timing belt, but the Kenyan way is to drive a car until it stalls, right at the moment when you are at the front of a queue in a heavy traffic jam and the lights turn green or a traffic policeman waves you off.
A physical check will let you know what to replace before your dashboard lights up like a gaudy neon sign, but look at tyres, brakes, the timing belt and the transmission. The suspension too, the shocks especially.
Hi Baraza,
On a trip abroad I had a taste of the great Lexus LS400 and the Chevrolet Lumina SS, though I fell in love with the Lexus as it had a huge, all-leather interior and that ‘cruise feeling’ to it.
You wouldn’t want to go to work in that car, it makes you feel rich and lazy. The consumption, I was told, is on the higher side, but wouldn’t that depend on how heavy your foot is?
Then came the Lumina. She is a beauty, though fitted with plastic interior. I couldn’t help but feel the car had that ‘I’m gonna fall apart soon’ look. I mean, it looks like it wouldn’t survive a head-on with a Vitz. Fuel consumption was much the same.
Considering I can afford the two cars, which one would you suggest I go for?
Wilson.
Buy the Lexus and feel like you have arrived.
The SS is not meant for driving to the office through heavy traffic (the Lexus will shine here), it is meant to go through corners while facing the wrong way, executing massive powerslides and doing great big drifts in the process. It is a car for having fun in.
Your wife will not take it kindly if you show up one day exclaiming: “Honey, we are broke, but at least we have a 6.0 litre V8 car to show why.” The massive spoiler, fat tyres and unsubtle body kits will not tickle her fancy as it would yours. The SS is a sports car. Buy the Lexus.
Hi Baraza,
The ‘check engine’ light on my Nissan Wingroad 2001 model is permanently on. I did an OBD and the fault detected was the primary ignition coil, which I replaced. The plugs were also checked and found sound and of correct specification, but the engine light has refused to go off. I have tried four other OBDs and the result is the same. My mechanic is advising that I change the computer unit. Are the units repairable? Kindly advise.
Isaac.
You should have flushed the ECU after replacing the coil, especially if that cured the problem. It has to be done to most cars. The recommended method is using the same OBD scanner or a PC with the appropriate software and hardware links. Another method is to disconnect the battery overnight.
Dear Baraza,
I drive a 2002 Toyota Corolla station wagon EE103, 1490cc. It has served me diligently, but I would like to sell it to another financially challenged Kenyan and upgrade myself. I like fancy cars but I’m afraid of the cost implications.
I have made many visits to garages manned by thieving mechanics and would like my next car to guarantee me few mechanical breakdowns.
So help me make the big leap. Of the following, which one should I go for: Toyota Mark X, Mitsubishi Lancer, Mitsubishi Diamante, Nissan Wingroad or Toyota Wish? If I remember, you likened the Wish to a bicycle, but still….
Hassan Mahat
The only fancy cars in that list are the Mark X (lovely machine) and the Diamante (dodgy ancestry — Diamantes of old were unreliable). The rest are common fare, especially among the “financially challenged”.
The Wingroad feels — and is — cheap, and ages fast. The Lancer is pretty but suffers from wonky powertrains, especially as an auto. The Wish is aimed at those who have little interest in cars (and from the seating capacity, little control over their loins too).
Hi Baraza
I am 29 and want to buy my first car. I have sampled what’s on offer and this is the fare that has caught my attention: VW Golf, VW Polo, Toyota RunX, Mazda Demio, Toyota Cami, Toyota Opa, Suzuki Maruti and Suzuki Swift.
I’m looking for a second-hand car priced between Sh500,000 and Sh750,000, a car that can do long-distance drives twice a month (Nairobi-Mombasa), a car that is not a ‘Kenyan uniform’ and would still have a good resale value after four or five years. What should I go for?
Second, where is the best place to buy a car? Is it okay to trawl through the classifieds?
Job.
Job, maintenance and consumption aside, what you want is the Golf if you are serious about doing the Nairobi-Mombasa run once in a while. The rest of the cars will prove to be a heavy cross to bear. For economy, get a diesel Golf.
On where to get it, cars can be bought from anywhere, but do not commit yourself to anything until you see the car itself. I know of some people who have been sold non-existent vehicles after following newspaper and Internet ads.
Hi Baraza,
I want to buy a car for the first time and I’m so much interested in the Subaru Forester. But after enquiring about it from various people, I’m beginning to get confused. Those who own it swear it’s the best car on Kenyan roads today, while those who don’t feel nothing for it. Kindly tell me more about this car, especially the 2000cc model.
Also, between the turbo-charged and non-turbo, 4WD and 2WD, which one is better in terms of fuel consumption, availability of spare parts, durability and performance.
In addition, what is the difference between these two Foresters: the 2.0XT and the 2.0XS?
Thank you.
I had no idea 2WD Foresters existed, but if they do, then they should have lower consumption but lose out on performance to their 4WD compadres. Turbo cars are faster, thirstier, harder to repair and a touch fragile compared to NA versions of the same vehicle. Generally.
The XS model is naturally aspirated (non-turbo) and has auto levelling rear suspension, 16-inch alloy wheels, fog lamps, climate control and a CD Stacker (six-disc in-dash).
The XT is turbocharged and shares features with the the XS, but additionally, also has 17-inch alloy wheels, high-intensity discharge (HID) headlights, a Momo steering wheel and a seven-speaker stereo.
Hi Baraza,
1. I recently came across and advertisement for a motorcycle that can do 70 kilometres per litre. Is this practical?
2. VW have developing a car called the 1L and claim it can do 100 kilometres per litre, thus 10 litres will take you from Nairobi to Mombasa and back. Kindly shed more light on this.
Chris.
1. Yes, especially if it’s engine is of 50cc or less.
2. The reality remains to be seen, because the self-same Volkswagen had a “three-litre car” (3L/100km) which I have discussed before, the Lupo/SEAT Arosa/Audi A2. It might have done the 33kpl, but not exactly daily. Our roads, diesel quality and traffic conditions may hamper drivers from easily attaining this kind of mileage.
Practicality will depend on the intensity of engineering genius behind it: how many passengers, how much luggage, whether or not it can sustain highway speeds, how easy it is to live with, and so on.
