Probably the most maligned, misunderstood and wrongly condemned item under the bonnet, is the Turbocharger. You must have heard of turbochargers "Blowing"? Well only in exceptional circumstances, and then only when pushed past the limit will a turbo "blow". Modern turbo's are very reliable, have few moving parts (They do move pretty fast!) and if correctly sized and sensibly driven and serviced, will last several hundred thousand kilometers.

Likewise the modern engine, petrol or diesel is designed to give hundreds of thousands of trouble free kilometers, despite the relatively high operating speeds. Modern designs incorporating the latest materials and manufacturing technology will outlast the early designs by a considerable margin.

SOME BASIC INFORMATION

South African conditions are considerably different to most other countries where enforced speed limits, high traffic density and shorter distances do not allow the continuous high speeds possible here. We also suffer from lower quality diesel fuel with relatively high sulfur content and lower lubrication levels. These conditions have led to higher maintenance costs, poor performance and increased turbo and engine failure. Regular maintenance, sensible driving and the use of the best quality fuels and oils will benefit engine, turbo and drive train life. Some of the more common failures and their causes are listed below :-

Engine failure

	Cracked or holed pistons - Diesel engines, Faulty injection, high combustion temperatures, due to over fuelling. Petrol engines - over advanced ignition timing, lean fuel mixture, turbo boost pressure too high.
	Bearing failure - Diesel engines, over fuelling or irregular servicing leading to oil sludging and subsequent low oil pressure. Petrol engines, oil temperature too high, irregular servicing.
	Cracked cylinder head - overheating, injection fault, cooling system failure - water pump/ cooling fan drive failure, blocked radiator, thermostat failure, engine overloaded when cold, turbo boost pressure too high, over fuelling leading to high combustion temperatures.

Turbocharger failure

	Hot shut down, particularly after driving hard or for long distances - this causes the oil to be carbonized in the turbocharger causing a dry start when next started and premature bearing and seal failure. Please note that hot shut down will ultimately cause deterioration of plastic and rubber components under the bonnet.
	Infrequent oil, oil filter and air filter changes.
	Foreign matter and /or obstructions in turbocharger air or oil systems.
	Blocked oil feed pipe - on petrol vehicles in particular, the oil feed pipe to the turbo passes quite close to the exhaust manifold, and this combined with hot shut down can cause carbonization of the oil in that pipe eventually leading to the pipe becoming restricted and finally blocked.
	Failure of the waste gate actuator allowing the turbocharger to over speed with resultant shaft breakage, thrust bearing damage, or bearing failure.

Please note that turbochargers can usually be rebuilt to manufacturers specification at approximately half the cost of a new turbocharger. There is no preventative maintenance for turbochargers as once the turbocharger is opened it will require new bearings and seals at the least. Easily identified symptoms of the need to overhaul your turbocharger are :-

	Blue oil smoke from the exhaust when the engine has been idled for a few minutes.
	Blue oil smoke after the vehicle has been run against compression, say down hill and accelerated again at the bottom of the hill.
	The turbo seems to boost later and later.
	Boost pressure too high - this can only be tested whilst pulling hard up a hill using a boost gauge in the vehicle or on a chassis dynamometer.
	Increased turbo "lag" ie. A delay between putting your foot down and the power increasing.

FREQUENTLY ASKED QUESTIONS.

1) Will the turbocharger shorten the life of my engine?

The turbocharger unit itself will not influence engine life as it is nothing more than an air pump, pumping air into the engine. It does however allow for an increase in fuel into the cylinder for increased power. This increases the combustion temperature and if this is not limited to reliable levels it can cause premature engine failure. It is very important that fuel and boost levels do not exceed the manufacturers specification.

2) Will an intercooler have an influence on engine life?

An intercooler cools the charge air before it enters the engine and this is certainly favourable for engine life as this drop in temperature is carried right through - reduced combustion, exhaust and turbo temperatures. As mentioned above, if the fuel settings are increased too much, in an effort to make unreasonable power gains, the positive affect is lost and in extreme case could cause engine failure.

3) Must I idle the engine for a time before switching off after driving a turbocharged
    vehicle?

This will depend on a number of factors. Turbochargers such as the Mitsubishi with 360 degree water cooling on the bearing housing can be driven as you would a normally aspirated engine around town, as can those fitted with Turbo Savers. However if the vehicle has been driven hard or for long periods at high speed or when towing, the manifold and turbocharger will be at red heat and it would be wise to drive the last few kilometers at reduced speed or idle the engine for a couple of minutes before switching off to prevent damage to plastic and rubber components under the bonnet.

4) If I fit an intercooler, can I switch off a turbo engine immediately?

Cooler temperatures will certainly help, but the answer to item 3 above still applies.

5) Should I be servicing the turbocharger regularly?

There is no set turbocharger service schedule. Many turbochargers will do in excess of 300000 km without requiring any maintenance. It is important to remember that the turbocharger uses the same oil as the engine and therefore regular oil and filter changes will enhance turbo life as will the procedures listed in 3 above. Only have the turbo removed and attended to when the symptoms described elsewhere are apparent, and the cause has been isolated to the turbocharger by someone competent to do so. The occasional dynamometer test to check that all settings are correct can be worthwhile.

6) Is it true that the diesel in this country is of such poor quality that it can lead to
    engine problems?

Both Sasol and Total offer diesel with lower sulfur content, specifically aimed at the turbo diesel owner. Whilst this is without doubt an improvement on the standard fuel it is not yet as good as that available in Europe, where diesels and turbo diesels are very popular, and give outstanding service and reliability. Generally speaking our fuel has more sulfur and lower lubricating qualities than it's European equivalent, this causes higher combustion temperatures, and injection system problems. It is therefore essential to have your injectors serviced, and change oil and filters even more regularly than the manufacturer specifies. Fuel and fuel system problems are responsible for some 80% of all diesel failures. Care should be taken to ensure you fill up at reputable filling stations. Fitment of Fuel Conditioners such as Algae-X will control the Bacteria formation in your fuel system.

7) Will an intercooler benefit a normally aspirated diesel engine?

Unless your air is being picked up from a hot spot under the bonnet the intercooler will have no benefit. Most vehicles pick up air at or near ambient temperature, and an intercooler which is cooled by ambient air cannot reduce the temperature below ambient. A turbocharged engine is compressing the air in the turbo which increases the temperature well above ambient, hot air is less dense than cool air and this means that there is less oxygen available to support the combustion process. Turbo charging is not about boost pressure, but about density ratio - ie an increased density means increased oxygen, allowing more fuel to be burnt properly and increasing power.

8) My turbo whines or whistles, is this normal?

Turbochargers run at very high rpm - as high as 150000rpm in some cases and even the slightest damage to either the compressor wheel or the exhaust turbine can effect balance and cause a noise. Exhaust and inlet manifold leaks are often confused with turbo noise, so consult an expert before replacing or repairing a turbo unnecessarily.

For more information please email us at info@alpinedevelopments.co.za