10-4 Magazine - For Today's Trucker

August 2007 - Performance Zone
PISTONS DON'T BURN!
By Performance Specialist Bruce C. Mallinson

Uninformed service managers, salesmen and mechanics should keep their ignorant thoughts to themselves when giving you advice on your truck’s diesel engine. If they have never driven a semi truck for a living, they are not qualified to tell you what to do. And when they say, “If you turn it up, you’ll burn it up,” don’t believe them. It’s just not true.

First off, all of the electronic engines have steel top pistons and they can’t burn (you also cannot burn a hole through them). I have contacted several shop owners that I do business with on a daily basis and have asked them if they have ever seen a two-piece steel top piston burn and the answer is always, “No!” However, the piston skirt is aluminum and it can break, and when that happens the piston head, which is the steel portion that doesn’t burn, goes sideways or flops over and breaks the liner. This situation is not called “burning a piston” – it’s losing a piston skirt. Yes, serious damage has occurred and now your engine needs a cylinder kit and a head, but your piston is not burned. In all our years, we have only seen one broken piston skirt in our shop.

In my opinion, lugging your engine is the main culprit of a broken piston skirt. The harmonics in an engine being lugged are far greater than in an engine that is allowed to run free. When running in the hills and mountains, use a lower gear and keep your engine at its “sweet spot” (such as 1500 or higher on the tach). You drive your truck every day and you should know the sweet spot. Your turbo boost gauge, pyrometer, amount of throttle and the feeling you get through your seat will help you to determine the sweet spot of your engine. Keep your engine at or near its sweet spot, and you’ll minimize the chances of lugging and breaking a piston skirt. By the way, it’s your engine and you should be able to do with it as you please – after all, you are the one paying for it.

Back in the early 1990’s, several low horsepower engines were built with aluminum pistons. These aluminum pistons can get a hole burnt through them (actually they crack and then the flame from the burning of the fuel burns a hole through them). This does not happen to steel top pistons. In fact, a steel top piston is so strong that if a valve breaks off, the piston will beat the broken valve into the cast iron of the head and there will be very few marks on the piston. Detroit Diesel was the first engine company to use a two-piece steel top piston. Today, all of the Detroit, Caterpillar and Cummins pistons are made by the same company called Mahle, which I think is based out of Detroit, Michigan. So we all have something to thank the Detroit Diesel engineers for – the invention of the two-piece steel top piston.

All of the older mechanical Cummins and Caterpillar engines have aluminum pistons and that is why we coat them with ceramic and Teflon. The ceramic on the top of the piston reflects heat and keeps it in the combustion chamber to better burn the fuel and the Teflon on the skirt allows the piston to move more freely in the cylinder liner. We also coat the newer steel top pistons and aluminum skirts with the same coating. It is a two-week process to coat the pistons, but we will soon begin stocking coated pistons for all of the popular Caterpillar, Detroit and Cummins engines. This will take place when we move into our new facility in Saxonburg, Pennsylvania (about 35 miles north of Pittsburgh) in the very near future.

So the next time a service manager or mechanic tells you you’re going to burn it down or burn a piston in your electronic engine if you turn it up, just ask him if he has ever seen a burned steel top piston. If he says yes, ask to see it (and then please send it to me because I would love to see it, too). If he says yes, you pretty much know that he is lying, so should you trust anything else he has to say? Why is it that so many mechanics have to be negative to owner-operators? I think they are jealous. Here you are, all nice and clean, looking good, touring the country in a beautiful rig, and they are stuck in a dark, dirty garage in the same town where they were born and raised. True high performance mechanics feel differently – they are happy to see you, always have positive things to say and love to help you in your quest to improve your truck. That is the kind of mechanic I love to deal with (and the kind you should look for)!

We are very close to having a Pittsburgh Power Computer ready for owner-operators who run either an ISX Cummins or EGR Detroit DD5 with 515 horsepower. In fact, we are in the process of building 50 ISX computers right now. These computers will make your truck fun to drive. For all of you who have a C-12 Cat under the hood, the Pittsburgh Power Computer will make it possible for you to run with your friends with the 550 Cats. We also now offer a larger turbo for the C-12, which is a great engine, it just needs a little more fuel and some more oxygen to run with its big brother (the C-15). The price of the turbocharger is $995 and, since it’s a new turbo, you get to keep your old one as a spare.

Don’t forget, please have your mechanics send me those burned steel top pistons that they always talk about – I’ll even pay the freight, because I just gotta see them! When dealing with high performance products for your engine, trust your instincts and your gut feelings – not someone who has never driven a truck for a living. If you have any comments or questions about efficiency and/or performance, please contact me at (724) 274-4080 or send me an e-mail to bruce@pittsburghpower.com today. I eat, sleep and breathe high performance, and I won’t steer you wrong!