Tech Tips: Differences in DD15 Pistons And When You May Need An Overhaul

Ever wonder why there are many different types of pistons in your diesel engine? And why certain pistons are included in your engine rebuild kits?

Overhauling your engine is a big and costly undertaking and we know that choosing the right kit for your engine can sometimes be difficult. Different engines can use different components, even within the same model. You might notice that with the pistons In the DD15 kit.

In this video we're talking about the different piston types, and why they've changed over time. Here at Highway and Heavy Parts our team of experts can help you find the right rebuild kit for your engine, so you're not wasting time and money on the wrong parts.

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What Symptoms Indicate It's Time To Overhaul Your DD15?

You might be wondering what symptoms can indicate that it's time to overhaul your DD15. Some things you should keep an eye out for include:

  • Excessive blow-by

  • Poor performance

  • Poor fuel mileage

  • Rough running

  • High oil consumption

Blow-by is one of the biggest indicators that it's time for an engine overhaul. Blow-by is the amount of gases that pass the pistons and piston rings. Excessive blow-by where more gases are allowed to escape because of piston and piston ring wear can cause a higher rate of oil consumption. Other causes of blow-by might be turbo issues, worn valve guides, or problems with your cylinder head.

The main job of the compression ring is to seal the gas above the piston and the lower ring is the oil control ring. The rings are attached to the piston and slide up and down in the cylinder. The crosshatches of machining marks on the cylinder allow the piston rings to seal. This is what makes the finish on the liner so important.

The piston ring and liner seam themselves together and work together to create a seal. Every time the piston comes up and compresses the air we rely on the piston rings to seal the air above the piston. When fuel is injected into the cylinder and causes an explosion and forces a piston back down. But we're asking the piston ring to seal the compression and to seal the oil. That's why a re-ring kit will reuse the pistons if they're in good shape, but we won't reuse a liner or ring set. Those are nearly always going to be worn out.

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What Does Excessive Blow-By Mean in My Engine?

When you start to get excessive blow-by it likely means that the ring can no longer hold the compression above the piston. That's when you'll really start to see problems. Pistons have had to change through the years to meet the different demands and changing engines, both cast and forged pistons have been around for quite a while. When we started to get into the EGR engines we started to see that the one-piece forged steel piston was out.

Prior to that, we saw a lot of aluminum pistons, but then manufacturers realized the pistons needed to be stronger to keep up with the demands of the engine. So then they move to a steel crown and aluminum skirt, those pistons evolved into the one-piece forged steel pistons, which we typically see in the EGR engines. These engines include the 14L Detroit Diesels, C15 Acerts, C13 Acerts, Cummins ISX, and the DD15.

Changes In Detroit Diesel Pistons

Detroit Diesel Piston and RingsMore recently the piston material has changed again to friction welded steel. That's because of the emissions requirements, we're seeing higher pressures and temperatures in the engines which require stronger pistons. The EGR system is used to cool the temperatures, but in the end, the engine is trying to burn exhaust gas under higher pressures and temperatures to come out cleaner.

Everybody had to increase the compression ratio to change the piston to squeeze it tighter to get it to fire cleanly. So when pistons couldn't handle it the first move was from a one-piece aluminum to a two-piece, then to a one-piece forged steel piston, and then finally to the friction welded one-piece piston.

Why Buy From HHP?

If you're looking for an overhaul kit for your DD15, Highway and Heavy Parts can help make sure you're getting exactly what you need. The type of piston you need is dictated by your engine's manufacturing date so it's important to ensure that you're getting the right one when you order a rebuild kit. That's why we sell the same pistons in our kits as the OEM does.

With some aftermarket companies you don't know what you're getting out of the box. We use the same technology as the OEM, so you know you're going to be getting a piston that works on your engine. There are only a handful of piston manufacturers out there so in most cases, we're actually getting our pistons from the same supplier as the OEM. We only source from the most reputable manufacturers.

You don't have to worry about whether the piston is the right material for your engine, we're sticking with what the OEM is using. When you call for a DD15 overhaul kit from Highway and Heavy Parts, not only will we be talking to our team of experts who can help make sure you're getting the kit with the right components for your engine, you'll also have access to our huge inventory of parts.

You won't have to wait as long to get your parts, meaning you can get back and running sooner. Many of our kits and components we can get to you in two days or less in most cases. Don't sacrifice quality to get the best price possible, we have it all right here, the best value, and high-quality replacement parts backed by an industry-leading warranty.

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