Is water in my car's exhaust pipe steam or just vapour?

What you need to know:

  • Water is a by-product of combustion, yes, and as such, water vapour is one of the components of the exhaust gas mixture.
  • The mistake most people make is mistaking steam for water vapour. In reality, water vapour is invisible; it is a gas

Dear Baraza,
A few weeks ago someone asked about water coming out from the tailpipe of certain cars. My understanding is that fuel is a hydrocarbon and when it burns in the presence of oxygen the result is H2O+CO2.

Of course this happens when the air fuel mixture is in the right ratios — 14:1, hence the theory that if you see water coming out of the tailpipe then the engine is perfectly tuned. I object to your condensation theory.

Please prove me wrong.

Kihara.

I am not going to prove you wrong; what I will tell you is that you and I are debating from the same side of the table. Water is a by-product of combustion, yes, and as such, water vapour is one of the components of the exhaust gas mixture.

The mistake most people make is mistaking steam for water vapour. In reality, water vapour is invisible; it is a gas. What you see as steam is the water vapour when it condenses.

Steam is actually just water (which is why steam makes things wet). So, when the water vapour in the hot exhaust gases encounters the cold morning air, super cooling occurs (super cooling is the rapid drop in temperature of any matter), leading to condensation, irrespective of actual temperature.

This also explains the contrails visible in the wake of a jet-powered aircraft. It is a result of supercooling of exhaust gases.

Dear Baraza,

Some time ago, I had asked for your advise on buying a Toyota Prado SX turbo and you told me it is a good choice with the only negative being that it does not corner well. I went ahead and sold the petrol-guzzling Isuzu Trooper and aquired the Toyota. I travel from Nairobi to Limuru, a distance of about 40km and I was told it could do at least 10km/litre but to no avail.

I changed the pump to a manual, bought new pistons and rings, a new head and gasket, a new set of nozzles, and even consulted a pump calibration and nozzles expert, but it still does not do the 10km/litre. In fact, the turbo ceased and I bought another one so I am sure the turbo is fine. I am wondering, is that not the recommended consumption? Am I driving it wrong or do you have an insight on how we should handle these cars?

Please advise me because I want to travel to Kapenguria and I do not want it to be like the trip I took in the Isuzu Trooper to Mombasa with my eyes constantly on the fuel gauge. Last but not least, I am a military guy and in operation quite a lot. Can I find your past articles online and if so, what is the link?

Thouffs.

I am beginning to think your driving style might be in question here. How hard do you push the vehicle? What rev range does the engine mostly operate in when you are piloting the vehicle?

Then also, you say you cannot attain 10 kpl with your Prado box. What figure do you achieve? If it is 9km/litre then you are not so far off the actual consumption.

Remember the J70’s Prado’s shape. It is aerodynamically unfriendly, what with the near vertical surfaces of the windscreen and front grille. Such shapes are an enemy to high speed driving because drag causes the engine to work too hard trying to push that blocky shape through the air, which offers more resistance the faster you move.

It must be diesel powered, that Prado of yours, isn’t it? Keep the engine speed at or below 3,000rpm (revs per mintue), you should be fine. By the way, what led to the turbo failure?

Hey Baraza,

I am planning on buying a double cabin but I am not sure which one to go with. My sons are suggesting I take a Ford Ranger but they are not well versed about its performance. I am a Toyota guy, so I was thinking of the Toyota Hilux, which seems massive. How does it compare with the Nissan Navara in terms of performance?

Charles.

If it is performance you are after, then the Navara is plenty fast, if we are talking 2.5 litre turbo-charged diesel engines all round. The Hilux is also available with a 3.0 litre, as is the Ranger, which tilts the scale in the Ranger’s favour (the Hilux really

underperforms in double-cab form, it is not pleasing). However, unavailable for this market is a 4.0 litre petrol V6 for the Navara, which makes the Nissan go like a bat out of hell. This engine variant is available from South Africa.

Dear Baraza,

I am about to spend Sh500,000 on a Toyota since I am looking for a car that is cheap to maintain and not thirsty. Do you think I am making the right choice? If not, what other options do you recommend?
Anonymous.

Painless maintenance and excellent fuel economy, you say? The Toyota IST fits the bill perfectly.

Dear Baraza,
Recently, I visited a mechanic to have a few things checked. I found a huge fellow there having his car checked and we had a chat. I learned that he was there to have his brake pads, wheel studs, battery, and windscreen wipers changed. He was charged about Sh2,000 for this and I really pitied him.

I think Kenyans need to know that there are some petty issues that should never take you to a mechanic. I mean, I can change anything that needs changing (brake pads, plugs, lubricants, lights, car stereo, and a lot of other things).

I have not touched the engine but I will try soon. I have no mechanical training; it is just common sense and the willingness to get soiled rather than waste time waiting at dusty and noisy garages.

The reason I am writing today is because I need your advice. I am a recovering spinal cord injury patient and I have had some challenges with the little car I drive (Nissan Sylphy).

The seat is very uncomfortable. Kindly let me know the best car in terms of comfort both on and off road since I do 500kms every weekend. Secondly, when should I engage the overdrive? Does it have any effect on fuel consumption? My car seems to be a little faster and I have to disengage whenever I remember the mobile roadside courts. Finally, why do you call yourself “petrolhead”? Why not “Dieselhead” or “Electricityhead”?

Martin.


When you say the Sylphy seat is uncomfortable, what exactly do you mean? Is it too hard? I did not find it any harder than those in other vehicles of the same category. Is there insufficient lumbar support? Side support? Cars with highly adjustable seat shapes occupy a much higher rung on the cost scale: You might be looking at the likes of Range Rovers or Mercedes. My sympathies about your back injury, by the way.

As for the overdrive, just leave it on. It will save you fuel and you are very unlikely to wind up in a situation where you will need to turn it off. Lastly, I do not call myself “petrolhead”.

My editors started it, then it was taken up by someone in marketing... next thing I know it has become a pseudo-official title here at NMG. At least it sounds better than the other two, and it is easier to say out loud, and it also conveys a fairly accurate description of my interests.

“Diesel head” sounds like a truck-specific enthusiast while “electricity-head” sounds just a little bit sociopathic. It sounds like someone who walks around electrocuting people just for the fun of it. I do not do that, at least not knowingly.


Dear Baraza,

I am considering buying a Subaru Forester. Should I go for turbo or non-turbo, considering fuel economy and maintenance cost? And what is the fuel consumption per 100km for either of them? Please advise. Thanks.
Charles.

Naturally aspirated wins on both counts. The exact consumption figures will vary greatly depending on various parameters, but expect as good as 8L/100km for the NA Forester and as bad as 15L/100km for the turbo STi. The Cross Sports Turbo lies somewhere in between

Hi Baraza,

I barely know anything about cars, but I am considering buying one and various options, based on my price quote, have been thrown at me by friends and family.

Appreciating that Toyota is the most expensive brand in the Kenyan market I have tried to steer clear of it. I am looking for a really low maintenance, easily disposable saloon car. The options presently thrown at me are: Nissan Sylphy, Honda Civic, Honda Accord, Mazda Axela, Toyota Carina. Should I consider any of these? What other alternatives should I consider?

Nyawira.

You are right, you barely know anything about cars if you are of the opinion that Toyota is the most expensive brand in the country. That is not the matter at hand, though, so let us get down to work.

The list of cars you present is actually a good one, with the entries being very similar in nature but each car having a USP of its own. The Sylphy has excellent rear legroom, especially for its class. The Civic is good to drive, quite enjoyable in fact, as is the Accord and the Axela. The Accord is pretty (in my book) while the Axela looks a bit sporty. The Carina will be cheap to buy.

Sticking to your criteria, these cars are generally low-maintenance, but that is also if you take good care of them. A vehicle can only handle so much abuse. The Civic is not very common, so getting an expert mech to manage it might not be easy, but hey, Honda has a showroom now. I am sure they will be of help.

Ease of disposal? Sell the Carina to a taxi operator; they will be glad to take it off your hands, but expect some aggressive haggling seeing how they are in it for profit. Palm the Axela off to a Mazda enthusiast.

They are few and far between (for now) but they do exist. If they cannot be found easily, start a Facebook group for a Mazda Owners Club and see who joins. Then try to sell them the car. You can sell either of the Hondas to me, I am a sucker for VTECs, but there is no guarantee that I will buy it. The Sylphy? Reputation hurts it. People believe Nissans are useless cars, but this is not necessarily true. Only the Wingroad and the B15 fit this bill. So the Sylphy might be the trickiest to fob off on someone else.

Dear Baraza,

I wish to comment on an article from one of your readers who described our Kenyan-trained engineers as being useless.

It should be noted that engineering is a universal science and it does not matter where you learn it. Our greatest weakness as a country has been misuse of facilities. We overload our roads and neglect basic maintenance.

We are a city with a population of just over three million, thus we do not qualify to be called congestion. One of the greatest failings of our development policy has been a concentration of everything in Nairobi. So while the total vehicle population in Kenya is slightly over a million, most of those operate around Nairobi. We need to create a metropolis connected with an efficient transport system and instil discipline on our drivers.

M. Oremo,

Kitale.

Interesting. I always thought if we had world-class engineers, we would have at least invented something. Or started our own car company like the Italians.

Trains have always helped reduce congestion irrespective of country. I believe the discussion I had with that reader involved simple trains, not the high-speed versions. The subway idea will also not work, at least not as easily as it sounds.

That is why I was suggesting having four or five huge above-ground train stations. Trains will also help minimise the deterioration of our roads by eliminating  the long-distance juggernauts that plague the main  A109/A104 corridor.

These juggernauts are also the prime suspect in the “overloading of our roads” as you called it, aren’t they?

We can have good roads if we elect sensible leaders of good moral fibre. Then again, politics and economics lie outside the scope of my contract with Nation Media Group, so I will leave it at that.

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