Q1: My ride is a BMW E36, 325i, 1994 automatic model, with nearly 197,000km mileage. The car was fine until two weeks ago when it went into limp mode, and the ABS light and gear oil light on the instrument cluster lit up. There was a tremendous loss of power. It could not even climb the ramp in a basement. After driving it slowly for 25km, there was a strong burning oil smell in the cabin, and in the boot. Does it need a top overhaul or is there an engine and transmission problem?
Gerald Hu
Malacca
Based on your description, what we can conclude is that either the engine or gearbox has a fault.
If the two major components are found to be damaged, both require expertise to repair and the cost may be high. On the other hand, it could also be related to the electronic control system of your car since your car entered limp mode or back-up mode.
As we are not there to inspect your car, it is very difficult for us to pinpoint the exact problem. Therefore, we would recommend you consult the nearest service centre specialising in your car brand for more accurate and detailed diagnosis and proper corrective measures.
Q2: I have always come across the horsepower and torque figures on car brochures. I am quite confused about these figures as some of my friends say horsepower is more important for performance while others say it’s torque that matters. How are horsepower and torque related?
Clueless
Setapak, KL
This is an age-old question that surfaces every now and then.
The torque represents the amount of rotational force the engine generates. In other words, torque is the twisting effort of a rotational object. It is measured in Newton-metre (Nm).
The engine power output is the power that is produced within a given time. Although kW is the international unit, the units of HP and PS are also used. The power output is the result of the engine speed multiplied by torque. Because the axial torque decreases due to decrease in the intake efficiency that occurs at high speeds, the power output peaks at a certain level. This peak is called the maximum power output.
At low revs (engine or vehicle speed), the torque is high but power is low. At high revs, it's the reverse.
Furthermore, horsepower and torque do not necessarily peak at the same rpm.
Now when we're talking about automobiles, the amount of horsepower or torque generated at the flywheel is not very useful when determining acceleration. What is useful, however, is horsepower and torque "at the wheels".
The problem here is that drivetrains cannot be perfectly efficient and pass 100% of the power of the engine through its components to the wheels. Some of the power is lost for several reasons.
Generally 15-25% of engine power never make it to the wheels. There are different types of drivetrains, which are the components linking the engine and the driving wheels. Generally, drivetrains with more weight and those with more components will be less efficient.
Whether torque or horsepower is more important depends on the vehicle's application.
If you are driving on roads with long, steep inclines or hauling heavy things, then higher torque is more important than high horsepower.
But horsepower rules the roost if you are the type who do a lot of quick acceleration driving.
Q3: I am pumping RON95 petrol for my 1997 Proton Wira 1.5 automatic with carburettor but feel that I can get better mileage with RON97. Is there a big difference between RON95 and RON97 when it comes to getting maximum mileage assuming that the driving pattern is the same?
Chan
Ipoh
Before we can talk about whether RON95 or RON97 is better, we need to talk about octane rating to gain a better understanding.
The octane number is one of the measures to indicate the characteristics of petrol and represent the fuel's anti- knock ability. A substance is added to the fuel to reduce or eliminate the explosive force or detonation resulting from too rapid a combustion.
Petrol with higher octane ratings are less likely to cause engine knocking than those with lower ratings.
To increase the octane number, some petrol contain lead, while others are unleaded. Because some engines are designed to use leaded petrol, while others need not, the proper type of petrol must be used.
The octane rating refers to petrol fuel. The higher the octane rating, the better is its ability to resist detonation or knocking
Knocking is created by an abnormal combustion of petrol in the cylinder. This sound is generated by the repetitive hammering of the cylinder wall, which reduces the power output of the engine and could cause serious engine damage if the problem is not quickly resolved.
Because of this characteristic of petrol, it is better to use the higher octane rating compared to the lower rating.
The price is a bit different of course but you will get better mileage and performance from the petrol of higher RON. The other benefit is using such fuel will protect your engine as a whole because knocking is prevented.