Dear Baraza,
I am an ardent reader of your informative column and I thank you for the great work and research.
I am planning to buy my first car and I plan to use it to travel approximately 140km to Nairobi every Saturday and Monday.
I am a fan of sports cars, so when I came across Mazda RX-8 with a 1.3-litre engine, and fell madly in love with it.
However, I realised that the car uses a rotary engine which makes its fuel consumption very high. I would like a car that is economical with fuel and has a high resale value. Kindly advise me on the following,
1. Whether it is possible to replace the RX8 rotary engine with another one that is not as thirsty.
2. How does the RX-8 compare with Toyota Celica GT? Kindly advise me on any other better sport car models.
3. Finally, since I would like to import the car, is the import duty for sport cars higher than that of ordinary boxes?
Duncan Muthoni
The Mazda RX-8 is a sweet little car, but the rotary engine technology was doomed from the start, which was way back in the late 1960s, because it was not really a workable one.
Mazda just insisted on exploring that option as a way to look “unique” from other manufacturers, but even they had to eventually accept the circumstances and adapt accordingly. The RX-8 was the last car ever to use a rotary engine and it is no more.
Anyway, the high fuel consumption comes from the fact that there are three power strokes per every revolution of the crankshaft for a single rotor — the Wankel equivalent of a reciprocating engine piston — as compared to “half” for the piston — one power stroke per two revolutions of the crankshaft. The power stroke is the phase when fuel is burnt to produce power.
Other complications connected to a rotary engine are high oil consumption, lack of torque, which necessitates a high-revving engine, which in turns leads to even higher fuel consumption (the RX-8 revs to 9,500 rpm) and is expensive to maintain since the rotor tips, made from carbon, get cooked very fast and are always in need of replacement.
Anyway, to your question:
1. Yes, it is possible to replace the rotary engine with a reciprocating one. However, the work and money involved are off-putting, especially in fabrication and computer work.
At the end of it all, you may have even forgotten that the original intention was to save money. You might be better off sticking it out with your rotary and replacing it with another rotary once it goes bang. With good care, this might not necessarily happen.
2. The Mazda RX-8 is “sportier”. It has more horsepower (230hp vs the Celica’s 190hp), it is revvier (9,500 rpm is not a joke), it looks more snazzy, handles better, and is generally quicker. Other options would be a Nissan 350Z, a Honda S2000, Mercedes-Benz SLK, Chrysler Crossfire (stay away from this one), and BMW Z3 or Z4.
3. This I am not sure of, but I hardly think so. A friend just imported a crazy-fast sports car (R35 Nissan GTR) and initial calculations based on KRA’s universal customs duty criteria closely matched what the actual payment made was. So I do not think there is a “special” sports car importation tax.
Dear Baraza,
I have have been seeing buses with engines mounted at the rear and I am curious to know the following:
1. How does this setting compare with engines mounted at the front in terms of transmission, efficacy and maintenance.
2. Assuming two buses with the same engine specificiations (with one having the engine in front and the other at the rear) are going uphill, how would they compare? I am assuming one engine is pulling the load and the other is pushing.
3. Do the rear engine buses have a drive shaft since the engine is on top of the driving wheels?
Chris M M
I have had this debate between rear-engine and front-engine buses before. We had some interesting points, but these are the ones that stood out regarding your question:
1. Transmission: Front-engine buses have some advantage here because a rear-engine bus requires remote controls from the driver area to the back, where the engine is. These remote controls include the accelerator and clutch (for buses with a manual transmission). Also, the placement of the transaxle (gearbox, engine, and diff is all in one unit) means repairs and maintenance is a lot more complicated than in a front-engine bus.
However, rear-engine buses have been found to be much quieter than their front-engine counterparts because there is noise isolation. The rear-engine setup also means the engine and the driven wheels are at the same end of the vehicle, eliminating the need for long prop-shafts travelling along the centre line of the bus from the front to the back axle.
This absence of a lengthy prop-shaft means that the bus body can be fabricated with a much lower floor, thus maximising the available space from that chassis and hence optimising efficiency.
2. The difference would be hardly noticeable. Buses rarely suffer from loss of traction, and I know this particular question concerns that. In both cases, the engine would be pushing the bus because either way, drive is going to the the rear axle. Placing the weight over the rear axle will not really make much of a difference.
The difference between pushing and pulling usually comes from the driven axle and not engine position. A front-wheel drive car pulls, while a rear-wheel drive car pushes, irrespective of engine placement.
3. Yes, they have to have a drive-shaft. There is no other way in which power from the engine can reach the wheels for a traction engine without drive-shafts. (Note: traction engines are the sort where the engine power directly powers the wheels.
The other type is a reaction engine where the vehicle motion comes from Newton’s most famous law. A good example is a jet engine, where the momentum of the exhaust gases pushes the entire vehicle)
Hi Baraza,
I have noticed that Scania F330 buses are quite adept at scaling steep sections, and that Isuzus, on the other hand, are more of jacks of all trades but not good for speed and power on either flat or steep surfaces. Nissan Diesels, I have also learnt, are quite underpowered when going uphill but become beasts on flat surfaces and even outsprint the Scanias and Isuzus. Could you kindly demystify this phenomenon and also drop in a word or two on efficiency and durability of the three.
Victor Dola.
From your description, I would guess either you are referring to obsolete models of these buses or maybe the respective drivers had different ideas on how to approach bus driving. The F330, for starters, is no longer on sale. It has since been replaced by the F310, which is just as quick but more fuel-efficient due to having a smaller engine, a 9,000cc five-cylinder unit compared to the F330’s 11,000cc six-cylinder.
When you say the Isuzu is “not good for speed and power in either flat or hilly surfaces”, I am tempted to think that you are referring to the old Isuzu MV118, which has been out of production for, what, 13 years now? It was replaced by the Isuzu MV 123, which is turbocharged and intercooled up to 270hp and 980Nm of torque, with a six-speed gearbox, and, from experience it is not exactly slow.
It might not have the sheer go of the Scania pair (which have 330hp and 310 hp respectively), but is works just fine on hilly and flat surfaces. Unless you were referring to the smaller FRR, in which case that is a lorry dressed as a bus, so forgive its lethargy on mountains.
The Nissan Diesel UD is another one. The CB31 SXN is a weak noisy thing which eventually found its calling in life — ferrying prisoners between courtrooms and jail. The updated version, the CB46 Turbo Intercooler, is a lot better: It is quieter, quite fast, and hugely reliable. Again, it is no match for the Swedes in making molehills out of mountains, but then again it is not THAT bad now, is it? Have you ever been in a CB31? Now, that one was POOR on the hills.
Anyway, the phenomenon of different performance capabilities… The Scanias use close-ratio gearboxes and taller final drives in the diffs (mechanical devices that transmit torques and rotation). This gives them almost unbelievable acceleration and hill-climbing power, but trims down their top speeds somewhat.
Not forgetting the advanced turbocharging AND turbo-compound technology that yields massive outputs from the relatively small engines — the F310, like I said, has a 9,000cc engine but it also develops the most torque: 1550Nm. The Nissan Diesel UD CB46 Turbo InterCooler does 290hp and 1,079Nm of torque, but from a 11,670cc engine. The Isuzu MV123 Turbo Intercooler also has a small unit; 9,800cc, giving 270hp and 980Nm.
Though the UD and the Isuzu are also turbocharged and intercooled, theirs are much simpler setups and are combined with taller, widely spaced ratios in the gearboxes and much smaller diffs to give high top speeds, but the acceleration and climbing power are slightly compromised. I hope this helps.
In terms of efficiency, the Scanias rule. Both of them. The Isuzu is not so bad, but sadly for the UD, it comes last. Durability sees the list almost being reversed. UDs do not die; they get sold and continue working on other routes.
They are harder to kill than a cockroach on steroids. Isuzus (MV 123) are ephemeral by comparison and are prone to turbo failure, especially when driven by people who did not take the time to listen when care for turbo engines was being explained to them. The Scanias fall somewhere in between.
Dear Baraza,
I am a die-hard enthusiast of the Peugeot pedigree and happy that for the first time in many months you critiqued the ‘Simba’ but dwelt on an old model. Anyway, to my problem. I have owned the Peugeot 405GL for six years and cannot complain except for a rear right suspension, which was eventually fixed.
However, due to two factors — my retirement and and the high cost of fuel— I approached my mechanic who suggested that we change its double carburettor to one fixed on a 305. It was fine until I noticed an increase temperature.
He replaced the cooling fan but now my three-month-old Chloride Exide battery is unable to crank the engine if the car stays static for a day. What is the problem? Would a 305 carburrator compromise power?Any known/tried benefit and/or damage?
Ossome.
I believe you installed the wrong carburettor in your Peugeot 405 GL. It is a, what, 1.8-litre? 2.0-litre? The smallest I would give it is 1.6 litres. The Peugeot 305, on the other hand, was most commonly found in 1.3-litre guise.
By installing a carburettor meant for a smaller engine into a bigger one, you are starving the bigger engine of fuel. The result is that it burns air and fuel in incorrect ratios. The ideal or stoichiometric air-fuel ratio is around 14.7:1. If it goes any lower, say 10:1, then the car is running rich — burning more fuel than it should for the air coming into the engine. If it goes any higher, say 17:1, then the car is running lean, i.e it is burning a lot less fuel for the air getting into the engine.
I believe the smaller carburettors have led you to the second circumstance: You are running lean. The symptoms are typical: a lean-running engine also runs very hot and it is hard to start because a lot of fuel is used in the cranking process and yet here you are, starving the engine even further with your small carburettor jets. And once it is running, yes, power will be severely compromised.
The only remedy is to revert to the original carburettors.
Dear Baraza,
First, you are doing great work. Your column is witty, informed, and clever. Keep it up.
Now, I like to keep my car very clean, so I hose down the engine, wax the body and tyres, and spray the undercarriage.
1. Does hosing the engine have any effect on new V-Tech engines?
2. Is it true that a buildup of dirt and oil affects the engine’s ability to cool down?
3. Does waxing and polishing affect the paint work?
4. What is dust-proof car paint?
5. Why does local paint work seem inferior to the original?
Lastly, I have come up with a fuel dispensing pump concept after getting conned by my driver. Who can I pitch this concept to?
Mathers Davies.
High praise indeed, Davis. I am flattered. Now, to your questions:
1. Hosing down the engine is never advisable. That powerful jet of water could easily make its way into nooks and crannies where it is not needed i.e into an electrical system, then you will find yourself in undesirable circumstances where your car will not start, or will not run properly, or the Check Engine Light is on and the diagnostics are not isolating the problem.
The best thing would be to wipe the engine with a wet/damp rag using water where the dirt is easy to get out and the relevant cleaning agents (degreaser and such) where necessary. Yes, it is more taxing physically, but it is the way to go.
2. Yes, that build-up causes cooling issues. While it may not interfere directly with your cooling system components, the grime and dirt around the engine forms an overcoat or a sweater. Part of the heat loss form an engine is through radiation. The heat build-up may sometimes exceed the cooling capabilities of the equipment available.
3. Only if you are using bad quality wax or polish. If anything, waxing and polishing your car is supposed to IMPROVE the appearance, not deteriorate it.
4. Some paints/waxes/polishes can get sticky in very hot sun, and then attract dust which then embeds itself in the goo. I think (I am not 100 per cent sure) dust-proof licks are those that stay crisp even when baked to within an inch of their lives, thus whatever dust falls on them can still be wiped off without any risk of damage to the paintwork.
5. I would say poor business practices. Profiteering. The need to make a quick buck without having to invest too many resources in a venture.
This device of yours: There are two ways you can sell it. The first is if you can mass-produce it yourself after approaching owners/proprietors of various petrol stations and convincing them that not only does the device actually work, but that they also need it, and need it now.
The second is to approach the multinationals that own the oil companies. You could sell you intellectual property rights to them or enjoy royalties for the rest of your life but that will only happen if they believe that it benefits them.
