Planning to get a diesel? Expect to spend more on maintenance

Baraza, thank you for supporting Kenyans by educating them on motoring issues.

I’m a regular reader of your articles and this is the third time I’m seeking your advice, having received useful answers from you twice.

Now, there seems to be a revolution in diesel technology in cars, especially in  Europe. Lately, I have realised that they are creeping into the US, a market that was previously shy to embrace torqued cars, preferring gasoline instead. These cars seem to be very fuel economical. Kindly delve into this issue and if possible, challenge Japanese manufacturers who most Kenyans buy from to produce more diesels cars.

Tell us about the reliability, pricing, durability and so on. Why aren’t we seeing many of these cars on our roads?

Are Kenyans still sceptical about this technology while European engineers believe it’s the future because of the many advantages of these engines?

Maybe it is high time we conquered misplaced fears in order to benefit.

Give us any other relevant information on this subject.

Kenneth Murithi Itonga.

 

Kenneth, despite what many might think, diesel power is a bit of an oddity in the motoring world.

Diesel stinks, it is not volatile (despite what Hollywood may present in a Transformers film), its combustion cycle is difficult to understand and hard to properly control, it is oily ­— in fact it is oil

and is actually called diesel oil — and diesel-powered cars are inappropriately named because diesel cars have no power at all (what they have is torque) and they are slow.

Turbos are to diesel engines what the discovery of fire was to Early Man: an opening into a whole other world of advancement and improvement.

These absurd qualities of diesel oil are what led to the great American dislike for diesel engine road vehicles. You see, American manufacturers in the ’70s decided to experiment with diesel engines, but the problem was, at that time not many people understood diesel properly and R&D was not taken very seriously.

The result was crap. The cars were worse than terrible: they smoked badly, had no power, were unreliable and were not as economical as the makers thought they were because the only way (at the

time) of getting more power out of an engine was to burn more fuel, which is self-defeating when discussing diesel.

It doesn’t exactly work like that with diesel: burning more fuel without increasing the amount of air (overfuelling, it is called in the tuning community) doesn’t help much with a diesel engine.

In addition, one of the quirks with a diesel engine is that the accelerator only varies the fuel delivered into the engine but the mass of air going into the engine always remains constant, unlike a petrol

engine where the air entering is controlled by a butterfly valve (to which the accelerator is connected) and the fuel used is metered accordingly.

The American diesel cars of the ’70s were so bad the Yanks swore off them completely and wouldn’t touch one with a 10-foot pole. It has taken more than 40 years to have them even consider diesel again, and they are still not fully convinced. This is where the Europeans come in.

They, on the other hand, looked at diesel and decided to make it work for them. No power from a diesel engine, right? Well, adding more fuel doesn’t really work, so we’ll add more air. No butterfly valves, eh? No problem, we have this little magic trick  called turbocharging, let’s see if it works.

Ahh, it does. Good. Now what? Turbo lag? Narrow torque bands? Hmm, Oh wait, how about using two turbos: one for low rpm and another for high rpm? That works too. If only we could fiddle with the injector pulses, valve timing and use direct injection.

To cut a  long story short, the Europeans developed diesel engines to the point where they became the must-have accessory for the thinking motorist.

The turbos added useable power while not only maintaining, but also boosting, the naturally high torque characteristics of the diesel engine and the outstanding fuel economy.

Small diesel cars are more economical than the hateful Toyota Prius. They became as good as — and in some cases better than — petrol engines. These engines became so good, now more than half

the cars sold in Europe run on diesel. So now?

The three qualities you list are actually the three biggest weaknesses of diesel engines.

  1. Reliability: it is not exactly poor, but repairs and maintenance are more common with a diesel engine compared with a petrol one. The service intervals are also noticeably shorter. This is for the same reason as the next two:
  2. Pricing: diesel engines are generally more expensive than their equivalent petrol units. This also applies to parts.
  3. Durability: diesel engines have shorter life spans than petrol ones. Poor care will trim down these life spans even further.

This is why; the explosive properties of diesel (when you finally get it to burn, not by setting fire to it using a spark plug but by atomising it first then mixing it with hot compressed air) tend to

generate very high torque in discrete bursts, which places a lot of stress on engine and transmission components. This affects reliability and durability.

As such, these engines and transmissions have to be built stronger and more robust, which in turn affects pricing. You can’t win.

This is further exacerbated by the fact that diesel oil is more viscous than most fluids and is notoriously difficult to vapourise.

This calls for an extremely high-pressure fuel delivery system — be it common-rail or direct injection — which is expensive to develop and is still somewhat tortured by the high pressure; and this

high pressure fuel rail has to terminate in a very fine injector nozzle for proper atomisation to occur: again costly and susceptible to pressure-related distress.

You can see why the Americans never bothered to follow up on it; it is too much work and they were too busy developing desktop computers to care.

There are other downsides. The engines are gruff, they don’t sound right (who wants a Mercedes that sounds like a posho mill wrapped in a thin mattress?), the vibrations are difficult to tame and

emissions control via DPF (diesel particulate filter) is something akin to a Chinese fire drill, a vicious circle that looks self-defeating.

The DPF is meant to filter out sulphur from the exhaust fumes. Over time, these deposits start clogging up the DPF, which sends an SOS to the ECU (engine management computer) to do

something, that something being to declog the DPF. Declogging the DPF uses heat, so to generate more heat, the engine burns more fuel, which in turn causes the deposits to form faster, further

clogging the DPF, which keeps telling the engine to help by providing heat, which is… you can see where this is going.

To this quandary, add a stench that makes everything around it reek of an old bus’ exhaust fumes. That is why European diesel engines are a nightmare to run on these shores: the DPF won’t last. And replacing it is tear-jerkingly hard on the pocket.

The advantages are attractive, though. Endless torque and outstanding fuel economy are the main ones; while turbocharging introduces wider power bands and the oomph that naturally aspirated units sorely lacked. A lot more could be said, but I can’t due to lack of space.

***

Baraza, can there be a better compact SUV other than the Subaru Forrester for  a mid-size family that  also has to run busy errands on- and off-road?

Anonymous

 

Yes. But just because there can be does not necessarily mean there actually is. It all boils down to what exactly a mid-size family is, and your stand on Subaru vehicles.

There are those who view them as a source of distraction for the emotionally unintelligent sociopath and would thus prefer to avoid guilt by association. I am talking about those who hear the name

Subaru and immediately start quoting Njoki Chege. Then there are those (like you) who believe Subaru is the answer to the question, “What is the meaning of life?”

In objective terms, yes, there are better compact SUVs. The RAV4 is more practical. The X-Trail is prettier. The Honda has a better engine*. The Vitara is better off-road.

The Sportage and/or Tucson indicate that you watch CNN early in the morning and are very easily swayed by advertisements. The question is: if you were to draw a Venn diagram of all these things,

guess which car would lie in the centre, right at the point of confluence? Yes, the Subaru Forester. It might not dominate any one field (except performance if turbocharged, and maybe handling) but

it does strike a somewhat fine balance of the rest of the qualities.

*Subaru fans, I know the Fozzie’s mill won the Engine of The Year Award some time back… shut up. The Honda’s i-VTEC plant is revvier and more refined, so there.

 

Baraza, I enjoy your illuminating articles on cars. I am a young man looking to buy my first ride,  and I particularly like the Nissan Skyline GT-R R34. How is this car in terms of spare parts

availability, fuel consumption, handling and reliability? I know it’s an iconic car in the world of petrolheads but I want an overall assessment, to help me avoid making a mistake.

William

 

Spare Parts Availability: establish a contact in Japan. If not, forget about Godzilla.

Fuel consumption: poor, if you use it like it is meant to be used. If not, forget about Godzilla.

Handling: epic. No other word for it; simply epic. Nothing handles like an R34, not even the later R35 (which actually handles better but is not as engaging). This was a car built specifically to murder exotics and set lap records. If not, forget about Godzilla.

Reliability: ranges between excellent and shaky, depending on how many changes you make from its stock format. 700hp is just about as far as you want to push that RB26DETT 6-cylinder without compromise. Beyond that and you are venturing into tricky waters. If not, forget about Godzilla.

You know what? Just forget about Godzilla. It went out of production 13 years ago, so importing one is out of the question.

If you know of someone selling one locally, let me have his or her contacts so that I can buy it from them, in which case you really will have to forget about Godzilla.Baraza, I own a 2006 Toyota Caldina ZT with a D4 Engine( 2000cc).

The car served me well, until sometime in February (mileage was 100,000km at the time), when I noticed that the engine oil level always drops significantly when I drive for long distances (400km) or more.  I always top up the oil with a litre or 1.5 litres.

I have also noticed a smell akin to burning oil every time I hit the accelerator pedal hard, or when the car is straining on steep inclines. I have been to numerous garages, but none of the mechanics seems has been able to tell what the problem is.

I have changed the plugs twice at intervals of 40,000km (I bought the plugs from Toyota Kenya) and tried various engine oil brands but the problem persists. What could be the problem?

***

I am considering buying a new engine but would appreciate your advice before I commit. Also, a friend suggests I flush the engine. Could this help?

Lawrence

 

If the vehicle is burning oil a surefire troubleshooting symptom is clouds of blue smoke emanating from the tailpipe. No smoke, no oil burning.

This is clearly a leak of sorts, so a thorough check of the engine is called for. Pay special attention to the valve train, more so the seals — but also the oil sump, pump and filter. These are notorious leaking points.

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