Tech Stuff

Tech Stuff

The "Idling Rule" with Turbo-Charged Cars


Small displacement turbocharged engines are getting increasingly popular on our roads. With tougher emission norms & fuel-economy concerns worldwide, the trend is only expected to grow. Nearly every diesel car in the market is turbocharged now. Turbo-petrols will also be commonplace soon.

Team-BHP lists some fundamental steps toward caring for your turbocharger. This is important as we keep hearing about premature turbo failures these days. Turbo's aren't cheap to repair or replace either; the bill can run anywhere between Rs. 50,000 - 2,00,000!

While engines usually have an rpm limit of 5,000 - 7,000 rpm, turbos spin at up to 150,000 rpm! In turbo-charged cars without intercoolers, temperatures can shoot over 150 degrees C. Did you know that inertia keeps the turbo spinning even after you switch the engine off? A hot shutdown is one of the top reasons behind turbocharger failure. All the mass-market cars have oil-cooled turbos where the oil dissipates heat and prevents damage to the bearings inside. There's also the issue of heat soak from exhaust gas. The worst thing you can do to your turbo is switch the engine off immediately after a hard run.

HKS - a top Japanese manufacturer of turbochargers - has this to say:

"The number one cause of turbo failure is oil "coking". Oil "coking" occurs when a turbocharger is not properly cooled down and the oil that normally lubricates the center cartridge heats up and forms solidified oil deposits."

That burnt oil eventually goes on to block passages.

Some folk insist that modern water-cooled turbos don't require a cool down period after a drive. While they are partially correct, remember that the national engines of India (Fiat's 1.3L MJD & Renault-Nissan's 1.5L DCi) are NOT water-cooled. Yes, nearly all of the mass market cars have conventional oil-cooled turbochargers. It's only some premium cars (not all) costing over Rs. 15 lakh that employ water-cooled blowers. Even then, it doesn't hurt to let that Mercedes turbo cool off for a minute after a hard drive. Further, not all turbos are built equal. If your turbo is fragile because of cost-cutting or design defects, it's all the more vulnerable to premature wear. At the end of the day, it's only a matter of 30 seconds. While there are a lot of valid arguments supporting the cause of idling, even the naysayers will agree you've got nothing to lose by practicing the idling rule.

Abusing your turbocharger can affect its longevity. With time, the turbo will become less effective. Take care of your turbo so that it gives your engine adequate boost and thus, an enjoyable driving experience for years to come.

Redlining the Indian Automotive Scene