Don’t drive in Neutral gear, it makes no sense at all

Hello Braza,

Thank you very much for your advice on tyre size. It worked perfectly. I have one other question. Somebody advised me to be changing my gear selection to N (Neutral) when going downhill in order to save fuel. Is this true?

Does it have any adverse effect on the vehicle, especially when I change from D to N and vice-versa when the vehicle is in motion?

Please help, and God bless you.

Lisa

Don’t do it, Lisa. There may not be an “adverse effect” per se, but it is risky in that you may bump the lever into R instead of D when going out of N, though this is heavily dependent on the design of the car in question.

Also, it is self-defeating, in that most of the time before going into N most people accelerate hard in D (or whatever gear for a manual transmission) to gain the momentum they think they are preserving in neutral.

If you want to save fuel, drive like this: accelerate gently, but not so slowly as to be a nuisance to me when I come up behind you in a powerful car. Do it within reason.

As a driver, use your discretion as to what “within reason” means. Don’t crawl like an old woman.

Also, don’t stomp the accelerator to the bulk-head, unless under special circumstances... like when stuck at a railway crossing and a freight train is bearing down on you, but this is an unlikely occurrence. We don’t have freight trains any more.

Avoid braking as much as possible, but again within reason. I once said that to someone who offered to drive me from point A to point B, then the joker proceeded to drive into a crowd of people saying “Baraza said not to brake”.

Were it not for the cat-like reactions of the subsequently insanely furious bystanders, there might have been some injuries. No, no, no: brake when necessary, but only when necessary. This is because braking wastes precious energy in the form of momentum, which energy was expended getting up to speed.

Try this: rather than braking hard, try and lose speed with the throttle closed (foot off the accelerator) first, then when you have lost enough momentum and are ready to stop (or the car ahead of you is REALLY close now)... stop.

When going downhill, instead of going into N, simply take your foot off the accelerator. Gravity will still pull your car downhill, so you won’t stop. The compression in the engine will create a retardation effect, so you won’t have to keep braking to prevent your car from behaving like a runaway bicycle. And with modern engines, once the sensors tell that there is no load on the engine, fuel is cut off completely, so you use zero fuel. In neutral, some fuel is used for idling. Which is better?

Economy driving at first seemed fairly obvious to me, but over the nearly-three years of doing this column I have come to realise it is more of an art: not everybody understands it, not everybody can do it, or knows when to do it.

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Dear Baraza,

I have been driving a 1990 Nissan Primera (1838cc) for the past five years. The car has given me no problems at all — until recently, when it started emitting black smoke and guzzling petrol such that I had to ground it. My questions are:

1. What might be the problem, and what is the solution?

2. If I were to replace the engine with a second-hand 1500cc or 1600cc EFI or VVTI one from, which one would you recommend, and how much should I expect to pay for it?

3. What are the things that a layman should look out for when buying a replacement engine?

Luvembe

1. Your car is running rich, very rich, and these are the probable causes: Oxygen sensors, a leak in the intake or exhaust before the oxygen sensors, cracked or disconnected vacuum hoses, faulty fuel system, and clogged fuel lines, among others. The best way to determine the cause is to get an OBD (On Board Diagnostics) scanner that gives you feedback in real time.

2. Be specific. Almost all engines nowadays are EFI (Electronic Fuel Injection), and have some form of variable valve timing. My recommendation would be to buy an engine from that model range (Primera), but newer. It will be easier to install than trying to shoe-horn a Toyota engine into a Nissan engine bay.

3. You can’t. That is why it is advisable you have a reliable and trustworthy mechanic who can help you with such analyses. Either that or someone who knows his way around a car engine. Even I sometimes have to seek help from some of my friends on some matters.

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Hi Baraza,

I have been reading your articles for some time now and I must say I find them interesting.

I would like you to do some research on the Kenyan Traffic Act because I feel police officers have been making their own laws. For instance, who said driving without a driving licence in your car amounts to an offence?

The offence should only apply to those who have never been issued with a driving licence, not those who do not carry it around in person. If you have a licence but have not carried it with you, the law is specific that you should be allowed to produce it within 24 hours at the nearest police station. A lot of drivers continue to be harassed on the road simply because they do not know the provisions of the law.

Finally, I seek your advice on an unrelated matter. Which is the most ideal car to drive between an automatic and a manual one?

Thanks,

Peter Wachira.

I will study the Traffic Act (the full Act, not just the recent Amendments) and do something thorough about it. In the meantime, let me ask you this: if you get into an argument with a traffic policeman, who do you think will win?

If stopped at a road-block and you show signs of being hard-headed (kichwa ngumu) or extremely knowledgeable (mjuaji sana), your day will not go well, I assure you. Most of the time when the police stop you it will be for a legitimate reason. If not, then it is just to let you know that they are watching.

If you start getting argumentative, you are letting them know that you have plenty of time on your hands, and they will help you to occupy this time. Traffic policemen are experts at using time up.

On the second issue: manual or auto. Which one do you prefer? That is the better one. One man’s preferred gearbox could be another man’s accident-in-waiting.

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Dear Baraza,

Please tell me what, in engine sizes and configurations, does the number of valves in an engine mean? I have an example below to illustrate this:

How different is a 2006 6V 2.7-litre Hyundai Tuscon (JM-Japanese version) from a 2007 Toyota Rav-4 with 16V 2.4-litre, VVT-i engine? In terms of maintenance, is there anything peculiar these vehicles require regarding service intervals and requirements, given the different engine configurations?

Many thanks,

Josh.

The number of valves, simply, is the number of valves. There are two types in an engine, according to function: inlet and exhaust. The inlet valves open to allow air into the cylinders. All valves are closed during the compression and power strokes, then the exhaust valves open for the burnt air to be scavenged from the cylinders.

In a nut-shell, the higher the number of valves, the better the engine ‘breathes’ — takes in fresh air and expels exhaust. Still, there are several key constraints, one of which is cylinder head design and the increase in number of moving parts (increases friction and rotating inertia moments of the new masses). So sometimes instead of having many valves it might be better to make the few bigger.

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Hello Baraza,

Your article on hydro cars was a thriller. I’d like to share what seems like a rare find. I read about a Swiss inventor who’s patented square pistons for reciprocating engines... with reason.

Yes, you heard me right. They’re true squares, viewed from top. The square profile enables the piston to tilt with the rod on strokes, eliminating the gudgeon pin. A lighter reciprocating assembly is created by directly welding the piston to the rod or by forging one compact assembly.

Reciprocating masses reduced mean a harder revving, more powerful engine. I did a paper model of it and found it true. It can work. The problem was designing rings that can seal the wide cavities arising. You may consider getting a paper model of it from me absolutely FREE (I’m gifted in craft!) to see how true this is if you haven’t come across it.

I’ve since tried to look for it on the Internet in vain. But I’m not complaining; even more ambitious engine projects like Kauertz are in books but not online.

Lawrence Mutisya.

The problem with square pistons is that the corners create problems. This is how:

1. Lines of weakness. The high pressures and extreme stress caused by combustion will weaken the engine block along those corners first.

This is also the reason why water and fuel tankers have cylindrical containers rather than the cuboids used to transport TVs and other stuff.

The weight of the water will act on the edges first and weaken the structure. A round container has no definite stress point, so pressure is distributed evenly all over

2. The corners look like potential ‘hot spots’, places where pockets of heat form and these could cause detonation and or pre-ignition.

3. As you mentioned: sealing the corner gaps will not be easy.

4. The rotary engine, though clever, never really managed to oust the reciprocating engine. Lack of torque, high fuel consumption, high oil consumption and frequent replacement of rotor tips made them impractical. Mazda struggled to keep the rotary engine alive with the RX-8 sports car but even they had to give it up as a lost cause.

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Dear Baraza,

I work in Rift Valley and reside in Nairobi’s Eastlands. I have an automatic Toyota Fielder X, 1500cc that has proved very reliable. My only problem with it is that, when it rains, I get stuck all over the place, even on flat surfaces.

I am now thinking of replacing it with a good family car with adequate space for cargo. Which, among, the following, would you recommend: Toyota Noah/Voxy, ‘Nissan E-Trail’, Subaru Forester or Honda CRV? Fuel economy is of utmost importance to me, as is automatic transmission.

Thanks,

Zacheus Karimi.

Cargo Space: There is a five-seat option on the Voxy (two rows of seats instead of three), which leaves an entire warehouse of space where typically the other passenger bench would be. That particular configuration leaves the cross-over cars biting the dust in terms of capacious cargo holds. I don’t even want or need to give figures as proof; it is so obvious.

The Nissan X-trail comes second with 603 litres of space with the rear seats up and 1,773 litres with the seats down. This, however, you did not ask about, which leads me to ask a question of my own: what is a Nissan E-Trail?

The Subaru Forester comes at last place, with 450 litres if you don’t drop the rear seats and 1,660 litres if you do. The Honda CRV, according to my research, was quoted in cubic feet: 37.2 with the seats up and 70.9 with them down.

Further research resulted in this being an astonishing (and frankly unbelievable) 1,053.4 litres with the seats up and 2,008 litres with them down. This places it second, especially if you also remove the middle row of seats in the Voxy. It then turns into a pickup. (All figures quoted are for the latest versions of these cars. Next time be more specific about vintage).

Automatic transmissions: All these vehicles have them. The Subaru and the Nissan X-trail also have CVT options, which I’d encourage you to explore, if only to get more people into the world of CVT. I don’t know about the Nissan E-Trail (if such a thing even exists).

Again, these vehicles have some form or other of 4WD, which some would call AWD (Subaru). It is always on in the five-star Fuji product (stars on the logo, not its overall ranking), the Nissan X-Trail has deselectable 4WD via an electronic system (which turns it into a FWD), the CRV is predominantly front-drive until grip runs out fore then power is sent aft (an adaptive system, you could call it), while the drivetrain configuration of the Nissan E-Trail is unknown because the vehicle itself is unknown.

Fuel economy: All these cars rank somewhere in the 9l/100km zone, which translates to about 11kpl. The van can be thirsty if provoked. A way into even better economy would be to acquire a Forester diesel with a manual gearbox (for the 2013 model such a thing does exist), but then again you say you want an automatic car, so... too bad. Also, Subaru Kenya does not sell diesel Foresters. Given Subaru’s past output, it is highly likely they have never even seen a diesel engine over there.

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Dear Baraza,

I have a Nissan Sunny, B15 2002 which is in a good condition. The problem with the car is that I cannot read the odometer clock because it only shows half the digits. When I start the car in the morning I can barely see the whole mileage, and, as the car warms up, the numbers fade off. What could be the problem?

Titus Musyoka

The problem is that your digital odometer read-out is on the fritz, which is just what you have told me. What you want to know are probable causes.

It is unlikely to be temperature-related because engine heat has to go through a veritable buffer zone before it gets to the odo’. That buffer zone has a plethora of insulators within it (insulator in this case is not necessarily the dressing on heat or electricity-bearing components, but rather is any material that does not conduct heat... or electricity.

The opposite of the word “conductor”, in other words). My guess is a loose connection somewhere. The vibrations from the running engine slowly work loose some tiny little wires that feed the digital read-out, so half of it gets blurry or disappears.

That is my best guess. Whether or not I am right is immaterial here: either way you will have to see an electrical expert to sort you out. It may require pushing a wire back in place, soldering it or maybe replacing the whole readout.

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