Entries from March 2008 ↓

Preamble
I’m often asked what’d be the estimated life of a car engine, say an M800 or for that matter even a Honda City. Needless to say I find myself at a loss for words when pitted against such ones. Sample the following QnA that had with a fairly knowledgeable guy…

Question
What’s the funda for an ICE’s life i.e. how much should I expect a used Honda 1.3 DX engine to last - given that it shows 42 Kkm on the odo as of now. I have heard that 1-Grand Mark is the near end of a Car engine and time for an overhaul. Would that mean I only have another 58 Kkm or so to see before I have to visit the garage for an expensive overhaul? Or does it also depend on the way one drives and maintains the engine??

Answer
A question like this is difficult to answer with reasonable accuracy. It’s some what like asking why some Guys croak at 30 and some > 75, when the average life expectancy in India is 50!

For example, I have seen any # of M800s in DLH with engines killed by 70 kkm whereas I had a ‘91 std with a Retrofit AC, driven by atleast 6-members of the family over a period of 10 yrs/144 Kkm, with engine still in full pep/nil oil consumption – to the extent none could figure out that the odo had once turned over!

For starters, consider the following extract from my Article ‘Funda’s of Automobile Engg.’

Q: What is Engine Life Factor (ELF)? How can it be calculated?

A: It’s a ‘Factor’ given by the Formula ‘ELF = 100,000/Max RPM x Compression Ratio’ of an ICE. Since it’s a ‘number’ only, it’s devised to ‘compare’ the Life and Reliability amongst comparable ICEs.

Now where does that leave one - gasping for breath or waiting to exhale!?

On the other hand, it’s been my experience, based on funda’s of A-E, that the life of a Car Engine largely depends on the following - perhaps in that order:

1) Its basic design/materials, ‘workmanship’, and OEM-QC standards.
2) How well mated it’s to the Car by way of ‘Power to Weight Ratio’ - anything below 70 is an ‘edge’ design.
3) The proverbial ‘nut behind the wheel’.
4) How well it’s been ‘run-in’ and subsequently driven/serviced/oil-changed.
5) How often and for how long it’s been driven at >75% of its max rating - rpm/bhp. Cars in India lose out on this front compared to their western counterparts that log most of their mileage in 5th gear a/a ours in 3rd - typically translating to 1.66:1 ELF wise!

It’s my reckoning that OE Engines of most present day cars with PWRs > 70 can easily do 200 Kkm+ if ‘well looked after’. However, when it comes to assessing the ‘residual life’ of a used car engine, one can go about it scientifically as follows:

A typical expression found in various W/S Manuals in respect of the ‘health’ of a 9:1 Compression Ratio (87 Octane) Petrol Engine states:

i) Max ‘dry’ CR - 13.5 kg/cm @ 400 rpm/normal Starter cranking speed.
ii) Permissible Inter-cyl variation - (+/-) 1.0 kg/cm.
iii) Wear-down/service limit - 10.0 kg/cm.

Therefore, by implication, one can predict the remaining useful life of an engine by comparing its present CR with its values under (i) and (iii) above, vis a vis its ‘true’ Odo reading at the time of such a Test.

However, this will tell you about the state of its pistons/rings and valves only and not about its various other wear prone parts, such as journals/bearings etc. Only a ‘trained’ ear can tell the latter to some extent, by listening to its ‘noise spectrum’ at various loads/speeds.

A guide to all it does, and how it does it. The more we know about engine oils, the more wisely we can choose the best oil for our cars and MUV/SUVs.

Engine oils do more than you think. It’s easy to name the main function of engine oil: to lubricate every moving part of your engine with a protective film that reduces friction. But engine oil has at least four other duties, and failure to perform them all can seriously reduce the performance and life of your engine.

First, your engine oil cleans your engine. Gasoline and diesel engines can produce soot, ash, acids, and moisture that eventually form sludge, varnish, and resins. If they collect on critical engine parts, it means serious trouble. A quality engine oil keeps them suspended until filtered out or drained away when you change your oil.

Next, oil seals microscopic hills and valleys on piston rings and cylinder walls. Without proper sealing action, you’ll lose power and waste fuel.

Further, engine oil also protects your engine against rust and corrosion.

And finally, oil cools vital parts such as camshaft, rods, and pistons that the engine coolant in your radiator cannot reach. As much as 40% of the cooling job in your engine is performed by the oil in your crankcase.

Some facts about viscosity index

The Viscosity Index or ‘VI’ measures the change of an oil’s viscosity over a wide range of temperatures. The higher the VI of an oil, the less it will thicken when cold, and the less it will thin out when hot. A high VI oil will be more effective when lubricating your engine over a wide temperature range. Changes in viscosity and VI result in different viscosity grades, so you can pick the best grade for your vehicle.

Here’s a description of the five most common ‘SAE’ multi-grade oils:

0W-30: Premium winter grade oil. Provides year-round protection and fuel economy. Can be used where SAE 5W-30 is recommended.

5W-30: Premium multi-grade oil for easier cold-weather starts, maximum protection, excellent fuel economy and added engine life. The preferred grade for most cars built after 1989.

10W-30: The most commonly recommended multi-grade oil by OEMs in India. Delivers excellent all-round performance for the average driver.

10W-40: A premium multi-grade oil for hotter-than-normal running conditions, say where ambient temperatures exceed 40°C. It’s capable of providing extended engine life under such high temperature conditions.

20W-50: Thicker premium multi-grade oil for added protection against metal-to-metal contact; specially formulated to meet the needs of high performance Engines.

Making a change for the better

Today’s engines are efficient and sophisticated machines, often using multiple camshafts, turbo-chargers and other features. They also run faster and hotter, placing tremendous demands on engine oil performance.
That’s why it is essential to follow a strict oil-and-filter change schedule for your car. Changing the oil and filter remove harmful contaminants that may build up in your oil.

A fresh supply of engine oil with its specially selected additives will restore the protection your engine needs against corrosion, gum deposits, excessive wear, and other problems.

The oil and filter should be changed at the interval recommended in your owner’s manual. Every 5000 -10,000 km or 6-12 months is a common recommendation in India, especially for the BS-III Engines.

Speaking of performance additives

Most oils look, feel, and smell the same but their performance can be vastly different, thanks in part to their ‘in-built’ additives. Additives suspend dirt, inhibit foam, improve cold-weather flow, prevent corrosion, reduce friction, and add other qualities.

Many specialty additives or oil treatments are sold separately as brand names and promise longer life or extra performance for your engine. Remember that modern oils are recipes with measured portions of ingredients. Upsetting the recipe balance could lead to problems.

An oil formula may include a little anti-wear additive the same way a cake includes a pinch of salt to bring out flavour. If a little salt works, should you add more? Probably not, and the same goes for oil additives.

Believe in choosing the best quality oil you can afford and change it according to your Owners’ Manual is wiser in the long run.

Preamble
Prior to the ‘3-part series on F1 machines‘, we had a look at the philosophies behind F1 and Stock Cars’ tyres. So it occurred to me that a peep into the world of ‘Aircraft Tyres’ could be as interesting. I thus spoke at length with my ‘Tyre Guru’ – Mr. Sudershan S Gusain – and this is what transpired…

Today’s Aircrafts are a culmination of the state of art engineering know how of all disciplines – be it mechanical, structural, electrical or electronics. They more than ably fulfill mankind’s eternal desire to fly – literally around the world and in much less than 80-hours!

Present day commercial Jets have some unique features when it comes to their Tyres. For without their required ‘functionality’ AND ‘reliability’, they may perish at the drop of a hat – not to mention carrying hundreds of lives alongwith. Therefore, these two requirements take precedence over aesthetics.

Tread design of ACTs is ‘plain/rib’ type, since such patterns result in great ‘straight-line’ stability, smooth rolling, lower noise levels, less prone to irregular wear, along with very good ability in channeling out water on wet runways to eliminate loss of control while landing/take-off due to ‘aqua-planing’.

You may recall that this is similar to ‘wet’ F1 tyres. Besides, since Aircrafts do not zigzag or are called upon to traverse through soft ground, they don’t need to have Stock Car like tread patterns.

Tread rubbers of ACTs (as well as F1) tyres have to have great braking efficiency and high temperature withstand abilities. As a result, unlike Stock Cars, durability takes a back seat here. Besides, ACTs have also to face extreme operating conditions, such as:

1. They have to withstand very wide range of temperatures and that too within a short span of time. For example, at a cruising altitude of 10,000 meters, their ‘hold’ temperature can be low as (-) 45°C. Within half an hour or so upon ‘approach’ to landing, it changes from this to near ambient at ground level. And soon after ‘touch down’, their tread surface can rise to (+) 250°C or more! And nearly the same is true in reverse after a take off!
2. Load on an ACT is around 25-30 tons ‘per tyre’, as against a typical SUV @ ~800 kg per tyre and a typical truck @ ~ 4-6 tons per tyre.
3. Consequently, ‘inflation pressure’ in an ACT is very high. For commercial jets, it’s around 220 psi, as against 30~35 Psi of a stock car. For such reasons, ACTs (and F1’s) are filled with pure nitrogen out of necessity and this philosophy is trickling down to demanding stock car users as well.
4. The takeoff speed of an Aircraft depends on many parameters such as its ‘laden-weight’, the ambient air temp/density, wind direction/velocity etc. The take off speed of common jetliners these days is around 300 km/h and landing around 240 km/h.

Apart from the above/extreme operating conditions that ACTs have to withstand, their manufacturers have to keep their weight to minimum possible so as to minimize the aircraft’s fuel consumption. This is far from easy and one of the reasons why so few Companies around the world successfully produce ACTs to today’s demands. Because of such extreme requirements and limited tread depths, ACT tread wear’s are much faster and surprising as it may seem, it’s viable to ‘re-tread’ them today, as opposed to ‘Not Recommended’ for Stock Cars.

Accordingly, ACTs are sent for retreading after around 350 landings for Radial and 200 landings for Bias Ply tyres. On an average, a Radial ACT can be retreaded upto 3 times (350×3=1050 landings) and a Bias type upto 6 times (6×200=1200 landings). Quite like Stock Cars, Radial ACTs are preferred due to better rolling resistance, traction and the fact that they offer almost 150% higher number of landings between retreads.

However, unlike conventional retreading techniques, retreading an ACT is a highly evolved task. For example, after a retread, their balance and uniformity in all the domains has to be checked such that it conforms to the ‘original’ spec again. It’s for such reasons that leading ACT mfrs have plants dedicated just to retreads.

To conclude for present, it may interest you to know that the worlds most advanced commercial jetliner as on date, the ‘Airbus-A380’ has 20 nos tyres of size 1400×530R23/40PR in its rear under carriages and 2 nos 1270×455R22/32PR for the nose. Bridgestone Japan is the chosen vendor for these, producing them at their Plant in Kurume, Japan.
And, for a change, I’ll ask readers a question this time. Most of you may have read of ACTs bursting at take off, also. WHY? If you know the answer, e-mail it to expert@indiaautomobile.com ALONGWITH your full name and address. The correct ones received by Sunday the 16th March ’08 will be published in these columns next week i.e. Friday the 21st March ’08.

Preamble:
Last and the week before that, we had a look at some facts and figures behind F1 Cars/Races. As promised, here are some more – tho’ finishing the present 3-part series - but definitely not the end of the topic as such…

Fuel used in F1 Cars
No specials fuels are used – only Unleaded/‘Green’ Petrol - similar to that available at our roadside filling stations. It has to comply with the strictest EEC standards concerning pollution. At one time, the fuel used in F1’s consisted of a mixture of hydrocarbons and was a very special fuel, which bore little resemblance to commercial petrol. The FIA thus introduced regulations with the dual aim of not only steering the oil companies’ research in the right direction so that it would benefit the ordinary motorcar but also significantly reducing motor exhaust emissions.

Tyre Changes per Race
The present FIA Regulations stipulate that each driver may use a maximum of 32 dry-weather tyres (40 in 1998) and 28 wet-weather tyres throughout the duration of an event. Each driver may use a maximum of two ‘rubber specifications’ for his dry-weather tyres during free practice, but he must designate the rubber specification he wishes to use for the rest of the event before the start of qualifying practice.

Thus, the maximum number of tyres he may use for qualifying practice, the warm-up and the race is 28 (14 front and 14 rear), chosen from amongst the 32. The Scrutineers, who are also responsible for checking that no driver exceeds the maximum number of tyres allowed, identify all of these tyres by means of an FIA-supplied bar-code system.

Refuelling during a Race
It is allowed but not obligatory. It must be carried out with the refuelling equipment specified by the FIA. The system is based on aviation equipment and complies with all the other safety requirements laid down by the FIA.

Speed Limits
Strange though it may seem, yes, but only in the pit lane, where the speed limit is either 80 or 120 kph (50 or 75 mph), depending on the circuit and the configuration of the pit lane. There are electronic devices checking the speed of the cars along the whole of the pit lane. If a competitor exceeds the limit during a Race, he is usually penalised with a time penalty whereas if he exceeds it during a practice session, he is usually fined ($ x km).

However, as in everyday life, the severity of punishment is proportional to the seriousness of offence, and also takes repeat offences into account. To avoid this, most Constructors equip their cars with a speed limiter, which the driver has to activate (usually by pressing a button on the steering wheel) as soon as he enters the pit lane. However, sometimes drivers forget and thus end-up paying a penalty!

Weighing of F1 Cars
The Scrutineers may weigh the cars any time, to make sure they never weigh less than 600 kg, including driver. Electronic weighing devices are located at the entrance to the pit lane to enable these checks. During qualifying practice, an electronic programme selects at random the cars which are to be checked. When a car is chosen by the computer, a red light comes on and the driver returning to his pit must proceed to the weighing area. If the weight of the car is insufficient, the driver could be excluded from the event, but he has the right to request that the car be weighed a second time.

To avoid cheating, any car that breaks down on the circuit is made to pass in front of the computer, which decides whether it must be weighed in the same condition. At the finish of a Race, all the cars are directed to the ‘parc de fermé where they are weighed. The drivers are also weighed separately before proceeding to the podium or to their motor-homes. If a Car+Driver weight does not comply with the 600 kg limit at the finish, it maybe excluded from the classification. This has happened in the past.