The ‘cc’ is engine capacity, usually expressed in cubic centimetres

Dear Baraza,

Please enlighten me on the 1500cc and 1800cc capacity of a car. I want to choose between a Toyota Wish, a Fielder, a Premio and an Allion. My question is, what does the cc of a car translate to?

I have been told an 1800cc car consumes more fuel than a 1500cc. But is there a benefit I would derive from the 1800cc? Does the car “perform” better? Is it “stronger/more powerful”?

I live in Kikuyu and currently drive a 1500cc NZE. On a rainy day, a 200m stretch of a dirt road takes a lot of prayers as I skid through the mud. A 4 x 4 is not within my budget at the moment.

Caro

The “cc” of a car is called the engine displacement, which in layman’s terms means the engine size. In a nutshell, an engine works like this: air goes into the engine, this air is mixed with fuel in a particular ratio then this air-fuel mixture (called the intake charge) is fed into the engine cylinders where it is set on fire by spark plugs through electrical arcing.

Petrol is explosive, so when mixed with air and set on fire, it explodes.

This is the basic set-up of a cylinder: at the top are two sets of valves, one set called the inlet valves which allow the intake charge to enter the cylinder, and another set called the exhaust valves that allow the burnt gases (exhaust) to leave the cylinder. The cylinder is basically a tube with a tight-fitting but movable piston within it.

When the intake charge enters the cylinder, it is set on fire and explodes. This explosion forces the piston downwards, in what we call the power stroke.

The effect of this explosion pushing the piston downwards is equivalent to that of your leg pushing downwards when pedalling a bicycle. It provides the torque that gives rotating motion and movement.

This is where we pause for a moment. The piston goes down, but how does it come back up? Just like a bicycle, when the pedal goes down, it is brought back up by the downward push of the opposite pedal.

The main sprocket (the big-toothed wheel to which the chain and pedals are attached on a bicycle) has its equivalent as the crankshaft in a vehicle engine. It translates reciprocating motion (up and down or back and forth movement) into rotating motion (circular movement).

Therefore, the piston in an engine is brought upwards by the downward motion of other pistons (a typical engine has several pistons: 3, 4, 5, 6, 8, 10, 12 or even 16, but the commonest number is four).

For single-cylinder engines like motorcycles and chainsaws, the momentum gained by the downward push is what brings the piston up.

So, back to the cylinder: Primary school mathematics taught us that cylinders have volume, got by the base area (pi multiplied by the square of the radius) multiplied by the length/height of the cylinder.

The length of the cylinder is determined by the limits of piston travel, that is, from the topmost limit that the piston reaches before starting to head back downwards, to the lowest limit it reaches before going back up.

This cylinder volume, multiplied by the number of cylinders, is what gives us the engine capacity, commonly expressed in cc (actually cubic centimeters) such as 1500cc or 1800cc; and in litres as 3,0-litre engine or 4.7-litre engine.

More cc means more swept volume by the cylinders, right? More swept volume means more intake charge going into the engine, right? More intake charge means more air and more petrol, and therefore, bigger explosions which create more downward force on the piston crowns.

So yes: a bigger engine develops more power. An 1800cc car is “stronger/more powerful” than a 1500cc one and it performs better.

I also live in Kikuyu, but I will not specify where exactly for obvious reasons. It can get quite unbecoming in the rainy season, I know, and now that you cannot buy an SUV, your options are a little limited.

You could buy a 4WD version of the listed vehicles (they do come with 4WD as an option, these cars) which will offer increased directional stability and better traction, and/or (especially and) buy deeply treaded tyres which have better grip in the mud.

You will be surprised at how well they hold the muddy ground. The payoff is that they are not very good on tarmac, but then again, they are not disastrous either.

I don’t think you spend your time cornering at the limit or hunting STI Subarus, so the reduced tarmac-gripping ability will go unnoticed. Just buy the treaded tyres.

Hi Baraza,

Good work you’re doing.

I bought a non-turbo Imprezza in February last year. Towards the end of the year, it developed a clunky noise at the front right wheel, which I suspect to be a worn out bush.

As I organise my finances, please tell me what risk(s) I run if I delay replacement of the same.

Lastly, which exhaust configuration would you recommend for a non-turbo to gain slightly more pick up speed?

Ndung’u Ngaruiya

Hello,

A late replacement of the bush means you first have to put up with the clunky noise a bit longer.

The steering might also feel a little unusual with time and the bush gets eaten away some more, losing part of the geometry in the process. And the ride will become a little thumpy and rattly over bumps and ruts.

You need to get what is called a through-pipe (straight exhaust, no cat) if you want better engine response.

Without the restrictions caused by the kinks, catalytic converter and silencer, exhaust gases flow faster out of the engine and offer reduced back pressure, leading to what I’d call a “zingy” response: a slightly increased “revviness” of the engine.

Hi,
I am an ardent reader of your column. I recently bought an automatic Toyota Fielder 1500cc, new model.

Note that I have never had an automatic car before, and that during my driving classes in 2003, I did not use an automatic car. If I was taught anything about automatic cars, I must have forgotten it all. So, kindly explain:

1. Why is it that when I am driving slowly, the ECO light appears on the screen/dash board but disappears as I increase speed?

2. The gear has the letters N, P, R and D-S (not arranged according to how they appear in the vehicle) marked at different points, except D and S, which are side by side.

What does S stand for and when is it supposed to be used. Also, explain fuel consumption when driving on S in comparison to driving on D.

3. If you don’t mind, explain the meanings of those D, P, R, S, D1, D2 in automatic vehicles and when one is supposed to engage them. This is what I know so far: D-Drive, P-Parking, R-Reverse and S-Speed/Screed, not sure which.

(Last but not the least, I don’t want my questions to appear in the newspaper).

Too bad for you, it looks like you made it into the paper anyway! We will not divulge your identity though, so don’t worry.

1. The ECO light comes on when the vehicle is in economy mode, meaning it is burning very little fuel, if any.

Common in most Japanese saloons, especially those equipped with automatic transmissions, the mode is activated by a driving style that epitomises hypermiling; in the instances that I witnessed this light glowing (while driving the Toyotas Vista and Premio, but of course not both at the same time), the accelerator pedal was either depressed very lightly or not at all.

Invariably, I was rolling downhill in both, at moderate speeds, meaning the engine was doing no work and probably the injectors were shut off in turn, meaning the vehicles were consuming little or no fuel, hence economy mode, ergo the ECO light.

2. Those are a lot of things you have listed: are you sure they are all in the same car? Anyway, here goes. P is for Park, a selector position that locks the transmission in both forward and reverse, acting as a static brake.

The vehicle cannot move in either direction as both directions are engaged. R is for Reverse, and is used if you want to go backwards. N is for Neutral, the exact opposite of Park.

Whereas in Park both forward and reverse gears are selected, in Neutral no gear is selected, so the vehicle is in freewheel mode.

This is mostly used when towing, but as I have come to learn, certain people take the things I say rigidly so I will issue a disclaimer: A vehicle can only be towed when it is in Neutral, however, Neutral is not only for towing.

I hope I’m clear on that. D is for Drive, which is the opposite of Reverse. Select it if you want to go forward.

S is Sport mode, a selection in which the transmission holds onto gears for longer, changing up and down at higher revs than in Drive (Normal mode). The positions 1 (or L), 2 and 3 — where available — lock the transmission in those gears, disallowing upshifts beyond the respective selector position but allowing downshifts.

Lastly, what, in the name of burnt clutches, is Screed?

Thanks for the very informative Car Clinic story on October 29, 2014.  

I have a similar situation. My car has four options; N, 4H, 4L, 2L. Whenever I select N, the car makes the same noise on the dash board.

When I drive the car on 4H, the consumption is quite high; recently I monitored the consumption with this selection and noted that 18 litres took me 136km, which translated to 7.5km local running.

The other two selections are quite heavy for the car, with even worse consumption. My car’s consumption is currently very high. I expected it to be relatively low, considering that it is a VVT.  I have reached out to local dealer CMC, to no avail.\

Please advise. 

George

What car is this? By mentioning CMC and VVT (not VVTi), I’ll hazard a guess and say it is a Suzuki of some sort, possibly a Grand Vitara.

For starters, what engine does it have? You might say 7.5km/l is quite high, but if you have the 2.7 litre V6 engine, that is not high. After all, it is an SUV, isn’t it?

The other two selections give worse economy figures, and they should. This is because they constitute the low-range section of the transfer case, meaning extra low gearing for the sake of torque multiplication, which in turn means the engine revs a lot but the corresponding motion is snail-like, just like a tractor. It is very hard on fuel, so again, the high consumption is to be expected.

Yes, you need help; help in the form of advice. Drive in High range only, unless you are doing some pretty hardcore off-road stuff that would warrant the use of Low range. Just one quick question: what dashboard noise does the car make in N (Neutral)?

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