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I’m moving back to Kenya, what car should I buy?

Hi Baraza,
Your column is like a special motoring university. Kudos! I am moving back to Kenya from the UK at the end of the year and intend to reward myself with a car after my studies.

I have identified the following used cars based on how much I want to spend (both cost here and tax in Kenya), age, and appeal: Toyota Avensis (most abundant but with unappealing dashboard), Mazda6, Vauxhall Insignia (gorgeous), Volkswagen Passat, Honda Accord, Dodge Caliber, Chevrolet Epica, Hyundai Sonata, and Tucson.

I want to spend about Sh10,000 a month on the car and do a maximum of 100 kilometres a week. Which would you recommend for consideration in terms of fuel efficiency, spares availability, Kenyan roads, my monthly budget, and being my first self-owned car?

NB: I do try to read the Daily Nation every day, but sometimes, as a student, I am sure you understand that the schedule just throws one off. So kindly copy me the response on e-mail.

Kind regards,

James.

Leave the Insignia, the Caliber, and the Epica alone if you want any form of confident support from this side. I can bet a large number of people do not even know what those are, let alone have the know-how to fix them when the need arises.

The Sonata, Accord, Passat, and Avensis are a better choice, but the problem is that you do not specify what model year these vehicles are.

Only the Passat will get support for the past three models, the Sonata and the Accord have only recently been formally introduced and it is my guess that current and future models will receive priority in support terms from the respective franchises, while past models may be overlooked.

If you choose backstreet Mr Fix-Its, well, good luck. My pick here would be the Passat B6 or B7. Not the B5, though. If you want to buy the Tucson, get the new one. The old one looked funny.

Hi Baraza,

Thanks for the informative articles. Please help me understand one issue. What is the relationship between the engine size (cc) and the gearbox? In other words, if I was able to put a jet engine in a tractor, would the tractor out-pace most cars on the road, not withstanding the aerodynamics?

Regards,

Ronald

With a jet engine on a tractor, you would not need a gearbox. All you would need is a reliable steering system and very good brakes (an added parachute has been found to be invaluable when stopping jet-powered ground vehicles).

This is because the jet engine works by pushing the entire vehicle using Newton’s Third Law of Motion: for every action there is a reaction equal in magnitude and opposite in direction. So the plasma stream of hot gases exiting the rear of the jet engine creates a force that pushes the jet/tractor in the opposite direction, enabling it to go forward.

Motor vehicle engines, the regular ones rather, exert force through the wheels of the vehicle through a transmission system of sorts. The whole setup is called the power-train and usually incorporates drive-shafts, transmissions, gearboxes, the engine itself, and the tyres. This is where you need a gearbox because the torque developed by the engine sometimes needs multiplication when the load increases.

Now, between the engine size and gearbox, there is definitely a relationship but the variables involved are numerous. The power and torque curves of the engine are the primary determinants of the ratios one uses in the gearbox.

Then there is application: are you designing a gearbox for a tractor that pulls tree stumps out of the ground or is the gearbox for a road car that is designed to break speed records? Engine size may or may not apply.

Here is an example American cars have very huge engines, typically in the 5.7-litre range. But these massive engines are built to drive everywhere at 88km/h while spooling lazily and effortlessly, sometimes towing a caravan or a speedboat if the 88 km/h drive is headed towards a holiday destination.

Then take a McLaren Mercedes SLR sports car, 5.5 litres (with a supercharger), which is smaller than the American equivalent, but will do almost four times the speed. Clearly, the gear ratios are dissimilar. At 88 km/h the SLR is going to be still in first gear.

Application and engine output characteristics (torque and power curves) directly determine the gear ratios in a gearbox more than engine size itself does. It is just that engine size again determines the torque and power, if everything else is kept constant, so that is how they are related. Indirectly.

Hi Baraza,

I would like you to shed some light on the interaction between brake horse power, torque, and engine rating. I am curious as to why a 2,000cc Evolution MR produces 400bhp yet a much bigger Mercedes Actros (2546) does 460bhp.

If a 2.0-litre engine can develop such a high HP, why do Mercedes, Ferrari, Lamborghini, and other super cars go to the length of making behemoth engines of 6,300cc and above that produce only 500bhp?

I once raced a Mercedes CLS 3500 CC (270bhp)) in a VW Golf GTI 2,000cc (200 bhp) and won. What do you attribute this to? Torque? A Range Rover Sport (2.7-litre) with 188bhp and 324.5lbs of torque easily wins against a GTI.

Thanks,

Anthony Mugo.

Brake horse power is the power of the car developed by an engine before losses occur in the transmission and peripherals (alternators, pumps, mufflers). It is not a very accurate way of determining the outright performance of a car. Wheel horse power is a much better indicator.

Torque is force applied over a certain distance, but to make it clear, it is what GETS you going. The effort needed to move a certain load, and determines the magnitude of load one can move as opposed to power, which is what keeps you going, the rate at which the force is applied and determines the absolute speed at which one can move.

For engine rating, see brake horse power. Now, the power output of an engine is directly related to the torque. An engine develops torque naturally. The power output is determined by how high that torque can be carried before the torque curve drops off.

That is the amount of rpm the engine keeps pulling with maximum force. An Actros develops massive torque, say 3000Nm or even more, but it revs to only 2500rpm. So power output is pegged at 460hp (this is still a lot, by the way).

The Evo, on the other hand, makes about 550Nm, but revs to 8,000rpm, hence the power is higher. I know of an Evo that makes, or made 820whp WITH A SLIPPING CLUTCH, but this particular Evo could rev to a stratospheric 9,000rpm.

Big engines with low-ish power outputs are unstressed and last longer. That is in direct contrast to small, high-strung engines with high outputs. They do not go far. That is why race cars go an engine a race.

About that VW vs CLS thing you are talking about: either the CLS driver was inept or he was concerned about wrecking his expensive saloon racing a hatchback. If he had chosen to open the taps on that CLS, you would have been blown out of the water.

Hello Baraza,

I am a fan of your articles and would like to figure out the problem with my car. It is Toyota RunX VVTi, a 2003 model that I have been driving for two years now. However, I started experiencing a problem when I changed tyres from the original ones (imported with the car).

I drive on two new front tyres and the original ones at the rear. The car vibration increases when the speed exceeds 80km/hr. The vibrations reduces when the new tyres are taken to the rear. I have done wheel balancing/alignment and the situation has not improved. What could be the problem?

Okomoli B.O.

You could be having directional tyres. Switching them front to back reduces the vibrations, right? So how about you switch them right to left? Some tyres are designed for use on one side of the car only, so placing them on the “wrong” side of the car creates an unpleasant driving experience.

I would also like to know what is the brand and size of the new tyres.

Hi,

My father has an S320 diesel import from UK registered in 2008. When you hit the 120kph mark, a hazard light appears on the speedometer. It says the ABS is not functioning. We have taken it to DT Dobie for diagnosis twice but it keeps coming back on and they keep charging him every time. He does not mind this, but I do. Do you have any idea what the issue is?

For a few months my father did not drive the car but the on-board computer says the car was due to be serviced, considering it has only travelled around 1,000km. Will anything happen to the car if he keeps driving it?

On a final note, when my father was importing the car, many of his friends, including DT Dobie staff, told him not to buy a diesel Mercedes, or a small diesel car for that matter, because the diesel in Kenya is not as pure as that in Europe. Is this true? For the past two years the car has been running smoothly, I think it is a myth.

Regards,

Victor.

Mercedes cars, more so the top-of-the-range S Class uber-saloon, cannot and should not be fixed by amateurs, driveway grease monkeys, or backstreet opportunists. Only approved dealers and franchises are supposed to handle the car.

So this is my advice: Go back to DT Dobie. Ask them to fix the car, if they cannot, let them be honest enough to say so. If they attempt to fix it and the results are unsatisfactory, inform them that you will not be paying, because why pay when the service you requested has not been delivered?

I do not know what usually happens when your Benz tells you it is due for service and you do not service it. Jeremy Clarkson of BBC Top Gear jokes a lot about that warning, but he has never said what will actually happen to the car. He just says “kooler, sree veeks” (three weeks in the cooler a.k.a jail), which is not very helpful. So I do not know. Service your car when it asks you to. It knows best when it needs attention.

The diesel allegation is mostly true, especially when it applies to Mercedes cars. But this is usually for small engines. The S320 CDI does not have a small engine, this is the same engine used in the ML320 CDI, a 3.2l 6-cylinder engine. It should not be much of a problem

Dear Baraza,

Kindly help me to choose between the new Honda CRV (2006-2007 model), Toyota RAV 4, and Mitsubishi Outlander in terms of price, availability of spare parts, durability/dependability, and fuel consumption.
Thanks,

Moses Mwanjala.

This is what my research yielded:

Price: I visited that website I keep mentioning, autobazaar.co.ke, and this is what I found. A 2007 CRV that costs Sh1.83 million on the lower side, and a 2006 (eh??) CRV that costs Sh2.5 million on the upper side. Actually there were two of these.

Toyota RAV4: As low as Sh1.49 million for a 2006 car, as high as Sh2.87 million for another car of similar vintage. Most were going for Sh2.5 million. Mitsubishi Outlander: As low as Sh2 million, as high as Sh 2.1 million. Most of them had “Contact Seller” on the price tag, and contact them you will. Autobazaar.co.ke not only gives you the cars available, there is also a map below the search results that shows you exactly where the car is at that moment. Nifty, eh?

Availability of spares: I did not do research on this because none of these cars is limited edition or custom made. They are mass produced by Japan. The answer to this is fairly obvious.

Reliability and durability: Honda’s V-TEC line of engines are nicknamed “Terminator” by foreign journalists because they never suffer engine failure. This is unlike Toyota’s D4 and Mitsubishi’s GDI, which are fickle by comparison. The RAV4 also seems to age a bit fast compared to the Honda. The Outlanders I have seen are mostly pampered vehicles, so it is hard to tell what would happen if one gets abused.

Fuel economy: This is where Toyota and Mitsubishi get their revenge. D4 and GDI yield astonishing economy figures, the D4 more so. But would you rather save fuel or suffer engine failure?

Dear Baraza,

As we speak, I am stuck between a rock and a hard place because I am planning to buy an expedition vehicle (something tough enough to withstand the harsh off-road world).

I have been looking at expedition vehicle videos and I realised that most of them go for vehicles with solid axles (Land Rover Defender, Toyota Landcruiser 70 series) as compared to independent suspension (Discovery 3, Hummer).

a) Why is this? b) What would you advise me to buy? Thanks.

Sunus.

First, solid axles are tougher, more robust, simpler in design, and consequently cheaper to buy, instal, and repair. In actual terms, you are better off with independent suspension because this helps in wheel articulation, increases stroke room per wheel (up and down travel), and helps keep the car balanced even in extreme situations.

However, independent suspensions are a bit more delicate, so they break easily and they cost more. So it is wiser to just grin and bear it with the solid axles if you are going to participate in the Rhino Charge.

Second, it depends on the extremity of your off-road activities and the wherewithal available to you. I could suggest you buy a Series III Land Rover 109 and raise its suspension only to find out I am talking to a billionaire who rarely goes over anything taller than a tree stump and is better off in the 2013 Range Rover.

Then again I may suggest you buy the Landcruiser 200 V8 but it turns out Sh15 million is too much money to splash on a new off-road car, and your budget can only stretch to a clapped out J70 pick-up from a police auction. So, how extreme is your off-roading and how much are you ready to spend on your off-roader?

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The Avensis is just another bland Toyota

Hi Baraza,

I have shipped in a Toyota Avensis from the UK and have been told of certain concerns regarding the car:

1. That parts are not locally available; I will have to get some spares, such as suspensions and ball joints, from Dubai.

2. That body parts can only be found upon placing a special order to the auto spares dealer shops along Kirinyaga Road. Are these concerns real?

Also, please comment on the performance, maintenance, as well as the merits and demerits. It is a 1.8-litre automatic model.

John

1. Visit Toyota Kenya and ask if they have the parts you seek. They sold the car under franchise, they should be able to offer support for that model.

2. I repeat, visit Toyota Kenya and ask.

The performance of this car is not exciting, maintenance is typical of pseudo-executive Toyota saloons and, being a Toyota, it is hard to come up with legitimate demerits without resorting to nit-picking.

Also, being a Toyota from the early 21st century, it is hard to come up with particular strong points that stand out versus other vehicles (maybe fuel economy in the D4-D diesel version).

In other words, it is just another bland Toyota that will do everything a family saloon is supposed to. That is why I have never reviewed it; there is nothing to say without boring the hell out of my readers.

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Hi Baraza,

What is the difference between a restricted and unrestricted exhaust system in a car and how do the systems affect performance and fuel consumption?

Also, what are the pros and cons of low-profile tyres? Do they make a car more stable as compared to the “normal” tyres?

Restricted exhausts are what you would find in any normal car, complete with catalytic converters, back boxes, silencers and such.

Unrestricted exhausts have all these removed and are just one straight pipe from manifold to tip (hence the name straight-thru exhaust), which, more often than not, is of a larger diameter than stock (factory spec).

The effect is to improve performance, but you will not make your car faster by removing the silencer and the cat, you also have to map the ECU, in effect telling the engine that there is lower back pressure as compared to before, so adjust your timing accordingly.

Also, the real purpose of straight-thru exhaust comes after engine modifications are done; such modifications will make the engine rev higher, faster and with greater volume/mass of intake charge/exhaust products, such as by forced induction or using bigger and highly polished intakes.

The exhaust is rarely, if ever, Step 1 in making a car go faster.

About low-profile tyres; Pros: better handling since most low-profile tyres are also wide-section and offer better grip. Also, the thinner side walls are stiffer and so reduce body roll and the tendency to flip over.

Cons: They are expensive, and they make the car uncomfortable. They also are unsuitable for less-than-perfect road conditions as the impact from constant bumping makes them swell.

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JM,

What would be your advice in regard to driving on roads that have been damaged by heavy trailers such as the section near Eldoret?

Is there any damage to the wheels/suspension if one drives on the raised “rails” now that this seems to be the only way out for low cars (else their under-carriage will scrape the road)?

I know the place you are referring to: not too far from the Equator crossing and just next to the turn-off into Kapsabet, right?

The trick is to keep the tyres on either side of the car on top of the bumps (or “rails” as you call them).

Avoid slipping into the troughs as you might bend your steering arms, scrape off the sump or even knock out the diff in a rear-drive car if it is low enough. Keep your speed low to guarantee control and avoid skidding under hard braking (downhill plus slippery road surface).

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Baraza,

I previously owned a Toyota 110 but recently disposed of it. I now want to buy another car and, owing to the market prices, I have decided to go for a Subaru Impreza.

I would like to know the consumption of this car verses Toyotas of the same engine capacity (1500cc) and why people don’t like Subarus as much as they do Toyotas.

Njoroge.

The fuel economy figures for Subarus and Toyotas should not be too disparate, if we keep turbos out of the picture.

The Subs may be a touch thirstier owing to the AWD transmission, but this is not something you cannot recover with a little common sense.

After all, Subarus are built and developed by Toyota (in a way).

The disregard for Subaru cars stems from several avenues.

First, are the turbocharged versions; they are thirsty, especially when pushed, so people generally assume (after buying the wrong Subaru once) that all Subs are dipsomaniacs.

Second, is the STi clique, the Impreza WRX fan club.

While not all of them exhibit anti-social behaviour on the roads, there are one or two bad cards that will overtake you while driving on the pavement or wake you up at 3am as they pass outside your bedroom window in a car equipped with an aftermarket exhaust system and ALS (anti-lag system), sounding like a small army is invading your neighbourhood with automatic weapons.

But they are not all evil, sleep-depriving, rule-flouting louts in the STi club. Just as not all Subarus are turbocharged, and so not all will deplete your disposable income. Feel free to get an Impreza, even an STi if you are up to the task, but please don’t drive like an idiot.

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JM,

My friend and I are re-engineering the petrol engine of a saloon car so that it uses hydrogen; don’t be bewildered, great inventions come from mundane ideas.

We have built a hydrogen cell that uses water and electric current to produce hydrogen. The hydrogen, we presume, can be combusted to produce the driving power to the pistons. The hydrogen cell is already working and the hydrogen being produced is igniting.

Now, what are the challenges we may face in using hydrogen as a fuel? By the way, hydrogen burns at much lower temperatures than fossil fuels, and the by-product is water only, so we save on the environment. Do you think we are headed anywhere?

I hope we live through the process to enjoy the car. If we succeed, we will bring you the car for a road test… if the oil multinationals don’t smoke us out.

Harold.

You have managed to isolate hydrogen gas from water? At what cost?

Anyway, I am glad the cell is working, and yes, hydrogen does combust (with a “pop” sound, according to our Chemistry teachers; in reality, it burns with a loud bang/explosion, as the operators of air-ships will tearfully testify). The question is: how does it burn in the engine?

How are you storing it in the car? What injection system will you use? Will it have to be first liquefied? Have you studied the combustion properties of hydrogen? This will assist in variable valve timing and direct injection.

What of additives? If the by-product is water (which it is), and there is a bit of blow-by in the cylinders (which there will be), water will get into the sump and mix with the oil, forming sludge.

Exhaust gas re-circulation? Will you re-circulate steam into the engine? How much energy will the combustion process release? If the explosion is too violent, how will you control it? Is there stratified intake charge combustion? Will the engine block and heads need bolstering to prevent pre-mature failures?

I am not watering down your hard work, these are just guidelines on areas to pay attention to. You may be on to something here, who knows?

What you need is funding for feasibility studies of your project, because I have not even started on infrastructure: plants and factories for extracting hydrogen, storage facilities, dispensers…

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Hi Baraza,

I am a physically challenged person (paraplegic) who is planning to buy a second-hand car. My budget is between Sh300,000 and Sh400,000. Kindly advice on the following:

1. Type i.e. Toyota, Nissan, etc.

2. To import or buy locally assembled.

3. If it is to import, the right/proper procedure of doing it. Please note that I am tax-exempted.

4. Where can I learn to drive the same?

Mwangi.

1. This mostly depends on personal taste, though for that kind of money, a Nissan may be a better bet. The demand for Toyotas rarely wanes, so getting a good one that cheap is not easy.

2. For reliability, a locally assembled version is the smarter choice. Also, the car can be modified for use by paraplegics by the same people who sold it.

3. I have never known the exact procedure that will ensure you get the car you want without risking theft, fraud or short-selling.

4. The AA, or any reputable driving school, should be able to help you out. First of all, the car has to be modified to transfer the foot controls (pedals and parking for some models) from the floor and site them within arms reach. From there, it is just practice.

I know of someone who has had his Caldina modified with a “foot-free” kit, so to speak. He, like you, is paraplegic.

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Hi JM,

Thanks for your article on the Scania (DN2, July 25, 2012). I have driven the Scania 380 once and for sure it’s a good machine. I would like you to help me out on these two questions:

1. What brings about the “big” difference in speed between the Scania and the Mercedes Actros? That is, the Scania outdoes the Benz when climbing a hill, but when cruising on flat/level ground, the Scania is outdone.

2. Why do truck drivers raise the wheels that are just before the rear driving wheels. That is, those that have no torque?

1. The amazing climbing power comes from the incredible torque that the engine develops (about 2500 Nm in the R420).

This torque in itself comes from the turbocharger, intercooler, intelligent engine programming, and of course the turbocompound setup, which acts as a complement to the turbocharger (it increases the speed of exhaust gases going through the exhaust turbine in the turbo).

The lower speed on flat ground stems from the fact that Scanias are programmed (and built) to last and offer good performance (in lugging loads) while returning good fuel economy, so their close-ratio gearboxes are not engineered for outright top speed.

The presence of a retarder along the drive-line also makes high speeds hard to achieve. And lastly, they come fitted with speed governors.

2. The raising of the tag axle (that is what it is called) is sometimes automatic, when the vehicle senses the load does not warrant the use of the extra axle.

It can also be raised manually, if the vehicle is so equipped.

It is usually raised to save the tyres: if the tag axle is not needed, you can save tyres (and money) by getting the two tyres off the ground, at which point they are essentially spare wheels.

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If you like the prison feel, go Russian

Hi Baraza,
I understand the Russians make some of the best war planes and tanks, but rarely do we see Russian products on our roads, like the Niva, or the Kamaz, which I understand has won the Dakar Rally nine times in a row. Tell me about the Lada Niva and the Mazda 6
Joe

The percentage of clients who buy trucks in order to win the Dakar Rally or a similar event is too small to be calculated, so a Dakar Championship is not necessarily a bragging right for lorry manufacturers.

In all other respects, Russian trucks are about as good as their prisons in usability: the Spartan level of build and kit is what we motoring hacks call “crudely effective”.

In comparison, a Mercedes Actros is a high-powered R93 Blaser Jagdwaffen sniper rifle while a Kamaz is a wooden club with nails driven into its head. Both will kill with only one blow but the cost difference is huge and the degrees of sophistication are poles apart.

The Lada Niva was a good seller in the ‘90s because it could do all that the Defender 90 could at a fraction of the cost, so it was a farmer’s favourite. It also attracted the off-road enthusiast with a small bank balance. But the prison cell passenger environment, 0-100 km/h in 22 seconds and the fearsome thirst from its 1.9-litre (and very unrefined) engine meant only the really desperate needed apply. For a harsher and more unforgiving analysis of cars from eastern Europe, please watch BBC Top Gear. You might die laughing.

The Mazda 6 is a very good car. I have been in one recently, the 2011 model, and it is exceptional to drive. Build quality is a step ahead of most of its rivals, as is its performance, and yet it costs less than its major rivals (the Hyundai Sonata costs about Sh4.5 million, the Camry a whopping Sh8 million, the Legacy Sh5.5 million.

The Mazda? Only Sh4.1 million). It is also quite practical: it can seat five and the boot is massive, large enough to accommodate a magazine editor and leave enough room for one of his writers to fit in there with him — pictorial evidence of this unusual test technique coming soon to a social network near you.

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Hi
In a past article in the Daily Nation, Shell had put up the final figures of their fuel challenge conducted over a distance between Nairobi and Naivasha. What astonished me is that a certain lady driver took her car over 181 km with only 3.32 litres, achieving an enviable consumption of 54.52 kpl. If this is achievable, then what is the magic, other than the fact that she is a salonist?
Kioko

There is no magic, there is only skill, patience and a set of cojones bigger than most other people’s. To achieve that kind of consumption figure requires some pretty oddball driving techniques, some of which include turning off the engine while in motion (no power assistance for the steering, no servo assistance for the brakes, you cannot accelerate should the need arise) and the risk of warping some delicate drive-shafts due to low-rev high-gear manoeuvres.

And the fact that she was salonist has nothing to do with her abilities. That lady is damn good behind the wheel, period.

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Dear Baraza,
I want to buy a vehicle that is a bit high from the ground due to my rural terrain but which is also stable and comfortable. I have in mind an 1800cc Honda CRV year 2000 and a 1600cc Suzuki Vitara year 1998. Please advise me in respect to consumption, spares, resale value and stability. And do we have old model CRVs with 4WD locally?

Yes, there are old CRVs with 4WD. The CRV is comfier and more economical than the Vitara, but the Suzuki can climb a wall with the right driver behind the wheel.
Spares are not a problem for either; resale value favours the CRV, as does stability (I presume we are referring to the absence of wobbling on the highway).

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Baraza,
A friend of mine wants to purchase a saloon car. His preference is a 2000cc to 2500cc Nissan, year 2005. After checking around, the car that comes to mind is the Nissan Teana, which comes with initials such as 230JK, 230JM, J31, etc, and a VQ23, with a 2300cc engine with CVTC technology and a compression ratio of 9.8:1. The model is said to produce 173PS (127Kw, 171hp) at 6000 rpm and 166ft.lbf (225 Nm) at 4400 rpm.
Kindly shed some light on the following:
1. The VQ23 engine compared to other engines in terms of performance and durability.
2. The CVTC technology in terms of fuel consumption and whether this is the same as the VVT-i technology used in most Toyotas.
3. What is a compression ratio and how does it determine fuel consumption in a vehicle? What is the difference, for example, between an engine with a compression ratio of 9.8:1 and one with 10.8:1?
4. With the power produced by this car as shown indicated, how many kilometres can it cover per litre on a highway and in traffic?
David

1. Nissan’s VQ line of engines are commonly used in sporty vehicles, so performance is not a worry. The most famous version is the VQ35 3.5-litre NA V6 engine, as used in the Nissan 350 Z/ Fairlady Z and the Murano. Durability is not a cause for concern if you stay away from bashing against the red line on a daily basis, and make your oil changes right on cue.

2. The variable valve timing system gives an engine two personalities, one for performance and one for economy, so you could say it does improve economy. It is similar to VVT-i and MIVEC and what not.

3. Compression ratio is the ratio of volume of all the air in the cylinder when the piston is at BDC (bottom dead centre, the lower most point of piston travel) to the volume with the piston at TDC (top dead centre, the uppermost point of piston travel), that is, the volume of the cylinder (V1) + volume of combustion chamber (V2) divided by the volume of the combustion chamber (V2), or (V1 + V2) / V2. It has no direct effect on fuel consumption, but it does affect torque and piston speed, which in itself determines power output.
High compression ratios create more torque and increase power output, but require higher octane fuels to prevent pre-ignition. An engine operation with a 9.8-to-1 compression ratio means the intake charge (air-fuel mixture) is not compressed as much as much as it is in the 10.8-to-1 engine.

While from my explanation it would be easy to assume that the latter engine develops more power than the former, it is not as simple as that. Sometimes the compression ratio is adjusted to allow an engine to run on a different type of fuel without adversely affecting power output.

The commonest way would be to use different pistons (with either concave or convex crowns, depending on whether you want to raise or lower the compression ratio) or replacing the cylinder head.

4. A 2.3-litre modern engine should return 8 to 9 kpl in the city and up to 14 kpl on the highway, though these figures are subject to driving style.

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JM,
I would like you to comment on the new technology that has been developed by Mazda called SkyActiv. Using this technology, the new Mazda Demio can achieve a consumption of up to 28 kpl. Also, what is your opinion of the turbocharged Mazda Axela with manual transmission? In some reviews on the Internet, it beats the Subaru Impreza hands down.
Derek

The SkyActiv tech covers a wide range of parameters, from engines (G: a type of direct injection for petrol engines that uses extremely high compression ratios and D: diesel engines that use two-stage turbos to widen the boost operating range); transmissions (DRIVE: an ordinary automatic with features from CVT and DSG and a wider lockup range for more efficient torque transfer and MT: a manual gearbox with lighter components and more compact dimensions); and platforms (body and chassis).

So I guess combining all this SkyActiv stuff in a tiny car like the Demio can result in 20 kpl, though I smell a lawsuit here. Ask Honda what happened when they took liberties with fuel economy figures and one lady driver failed to achieve said figures. Another issue is our fuel. Part of the reason you don’t see high performance cars on our roads is that even though we could afford them, our fuel couldn’t run them.

Cars with high-pressure turbos or high compression ratios require high octane fuel to run. A compression ratio of 11.0:1 is already very high: Mazda’s SkyActiv G boffinry boasts of 14.0:1, so for those who don’t follow the jargon, this means an engine with that kind of compression should run on something closer to paraffin or aviation fuel than to regular petrol. Let the SkyActiv cars get here first then we will see what is what.

In other news, I can bet that Impreza was not an STi. I am not an Impreza fan, but I know what the flagship car in the range can do and I highly doubt if the Axela is in that league. The closest Mazda came to the 280hp-4-cylinder-turbo-intercooler-4WD rally car formula was with the Mazda 6 MPS, and even that was not able to unseat the usual pair of tarmac terrorists: the Evo and the WRX Sti.

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Hello Baraza,
I want to buy a second-hand 1820cc Subaru Legacy Station Wagon STI, year 1996, petrol. What should I check for to ensure I’m getting a good deal? I’m a bit lame with cars.
Peter

You claim to be “a bit lame” with motor vehicles, but the car you are asking about is an enthusiast’s car. Interesting.

It is not a common car, this one, so my guess is you are getting one from Japan, in which case by the time it gets here a physical check will be too late. Anyway, with such performance-oriented cars, it is best to look at brakes and suspension mostly. Test the brakes to see if they work, and the car should not sag or lean on one side.

Then the tyres: check for bald spots, which suggest hard use or abuse. Finally, check the engine and gearbox (the oil especially, and the sounds). Any suspicious clinks, pings or rattles from the engine and/or transmission suggest that either something is broken or is about to. Go to one of the local tuning houses (they are almost always run by guys with names such as Singh, some of whom are my friends) for a checkup on the turbo, to see if it is boosting properly.

If you can afford it, also have the car checked for chassis straightness. Some may have been involved in a big accident then the evidence cleverly concealed underneath a fancy paint job.

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Hi Baraza,
I drive a manual 1998 Starlet EP 91, which has the following problems:
1. The engine vibrates excessively when idling.
2. It has reduced speed over time, even after replacing the plugs.
3. A mechanic removed the thermostat, is this in order?
4. Can the fuel consumption improve from 16 kpl?

1. Check engine mounts or the IAC (idle air control). From what you say in question two, it most likely is the IAC.
2. See 1 above.
3. It is not fatal, if that is what you are asking. But now that the water pump and the fans have to be connected directly to the car’s electrical power system since there is no switch, the car will overheat before going too far.
4. It can but why would you want to? Attaining a better economy figure than 16 kpl involves some unusual and extra-legal driving techniques, some of which I would not recommend.

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Hi Baraza,
My car is a Nissan Bluebird EU-12 (SR 18), and for sometime it has really been misbehaving. It slows down like it is about to stall, then suddenly picks up like a jet on the runway. It is now stripped down for repairs. My mechanic told me that the carburettor is faulty, and because he believes I cannot get its model in our shops (something to do with a CI model), I can only replace it with another model, meaning modification will be needed.
Because I believe in originality, I decided to consult another mechanic who said my carburettor isn’t the problem rather it is the computer that is faulty. He also believes that I cannot get its computer and advises me to get a carburettor of another vehicle and forget about the computer. Please advise me on the following as my financial status cannot allow my mind to dream of a new toy yet I need to be mobile as soon possible.
1. What was the cause of the stalling and picking up?
2. The computer and “CI carburettor” analysis by my two mechanics, what do you have to say?
3. If the mechanics are right about unavailability of both the computer and the carburettor, which I think may be true because of the age of the vehicle, what would you suggest I should get that will fit?
4. What do you think I should do to put this vehicle back on the road?

Both reasons are legitimate for a car that is not running smoothly. Other reasons could include wiring problems, fuel delivery issues (pumps, lines, filters, dirt in the fuel), and a lot more, so I cannot tell you why exactly your car is not running.

However, one of the two mechanics knows not of what he speaks, and my prime suspect is the chap who started the talk on computers. What year model is your car? Is he sure there is an ECU?

And incredible as it sounds, there are still carburettors on sale. While some are model specific, others are built to be installed on almost any engine (after-market Weber and SU), especially for those seeking to modify performance on their cars.

My advice: Get another mechanic. Even if I was to help you, I cannot begin describing here how to tune your carburettor, it will take at least 25,000 words just to explain what is what.

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Hi JM,
I would like to know more about the Chevy Aveo in terms of fuel consumption, spares availability, and performance. Would you advise one to acquire it?

Consumption: 10 kpl urban, 14 kpl extra-urban.

Spares: General Motors should still have parts for the car as they sold some not too long ago.

Performance: Nothing near a Ferrari if that’s what you are asking. It is a 1.5-litre naturally aspirated engine fitted into a small saloon car, so what do you expect?

Advice? It depends. How badly do you want an Aveo? If the answer is “very”, then get an Aveo. If the answer is “not very”, then shop around some more for something else. Anything I say beyond this point will amount to what someone once called “de-marketing”.