Automakers can tap into further weight loss by ditching rubber hoses

Replacing heavy rubber hoses with thermoplastic tubing presents a small yet significant gain for automakers looking to reduce weight and assembly complexity, learns Freddie Holmes

Be it through ambition or necessity, automakers have placed a greater focus on curbing vehicle emissions in recent years, leading many to pursue vehicle lightweighting. A relatively straightforward way to do so is to change the materials that are used for a given part or system, and not only in major structural elements of the vehicle. Many discrete components have seen less technological advances over the years, and present new opportunities for further weight savings.

Rubber hoses, for example, may not seem the most significant target for a diet, but vehicles can quickly and easily drop a few pounds by swapping from thick, heavy rubber, to a slender thermoplastic solution. One area in particular that has been highlighted by engineered plastics and fluid management firm dlhBOWLES is the tubing used in the positive crankcase ventilation (PCV) system, an emissions control that recycles crankcase gases into the engine intake.

PCVs have been in mainstream use since the 1960s, and are present on virtually all internal combustion engines (ICEs) today. As the engine heats up, a mixture of oil vapour and moisture tries to escape, and the PCV essentially recycles that gas, which contains harmful hydrocarbons. “Early internal combustion engines allowed this gas in the crankcase to escape into the atmosphere,” explained David O’Neal, Engineering Director at dlhBOWLES. “Instead of letting that gas just escape, it is put through the cylinder one more time for the chance to burn off whatever is capable of burning.”

Both the PCV and evaporative emissions system are mandatory for anything that has an ICE, such as hybrids and plug-in hybrids… The tighter you can package tubing and systems that cannot be eliminated from the ICE, the better

A PCV system controls the way this gas is conveyed between the crankcase and the intake, and requires some form of hose or tubing system. While PCVs have become a staple technology on passenger car engines, many still rely on heavy and difficult to install rubber hosing, and simply swapping these hoses to a thermoplastic tubing solution could bring significant benefits both to the finished product and on the manufacturing line. The weight of the overall system could be halved, and overall installation complexity for the PCV system can be significantly reduced.

“There are still many heavy rubber and metal components used in the PCV system, and we have proven in various applications that these can be replaced by lighter thermoplastic assemblies,” said Daniel Konrad, Vice President of Engineering at dlhBOWLES. “We’ve seen examples of hose systems on the market where weight can be reduced by as much as 70% by switching to a thermoplastic system. This is an overall contribution to vehicle weight saving, and thus CO2 emissions reduction.”

The butterfly effect

Targeting larger single structures to make the biggest weight savings in one go is often seen as a more attractive, straightforward approach to lightweighting. However, this comes at a high cost. By comparison, targeting more discrete components and systems can lead to useful weight savings, but also a host of other benefits downstream such as reduced design and integration complexity.

Swapping from a rubber hose to thermoplastic tubing, for example, brings various benefits and often at a reduced overall cost. “It is one of the most cost effective ways of taking weight out,” explained O’Neal. “Every gram that you save in the vehicle comes with a benefit, and this is one of the areas that automakers have tapped.”

It is not just the hose to consider, but also the parts that hold it in place to ensure it does not wear or become loose over time. The collection of these fasteners, heat shields, and tubing creates a ‘system’, and it is the optimisation of this system that falls into dlhBOWLES’ expertise. Indeed, a complete thermoplastic tubing solution is significantly lighter than a rubber equivalent, and in some applications, can save around half a kilo over the original system. For example, a thermoplastic PCV tubing system used on one pick-up truck engine today weighs just 423 grams (0.93lbs) compared to 927 grams for the original rubber hose system. In addition, total mass is reduced by 54% for this particular application.

There are still a lot of heavy rubber and metal components used in the PCV system, and we have proven in applications that a lot of these can be replaced by lighter thermoplastic assemblies

However, when considering the significant weight savings that can be made through body-in-white (BIW) lightweighting, it would seem reasonable to assume that rubber hosing falls fairly low on the list of priorities. On the contrary, a growing number of automakers are looking at thermoplastics “with great interest,” continues O’Neal, and not only for the PCV, but also for vacuum and engine coolant systems. “These are all application areas where you can get significant weight savings without driving up costs,” he advised.

For example, power brake systems use vacuum energy to assist with braking force, and a vacuum brake hose – or tube – transports this energy from the engine intake or vacuum pump to the brake booster cylinder. Thermoplastic tube systems can be up to 70% lighter than a more conventionally designed system utilizing rubber hoses, and ‘quick connectors’ can be used instead of metal pinch clamps on the vehicle assembly line. There are also benefits in terms of packaging; given the thinner walls of these tubes, space is freed up in the engine bay.

Looking ahead, this may prove useful for automakers seeking to electrify already tightly packed ICEs. Indeed, packaging requirements are expected to continue constricting going forward; the addition of a battery and electric motor brings extra mass that negatively impacts electric driving range and ICE emissions. Anything automakers can do to offset that mass becomes increasingly valuable, suggests Konrad.

“Both the PCV and evaporative emissions system are mandatory for anything that has an ICE, such as hybrids and plug-in hybrids,” he said. “You have to bring in emission control systems, but the engine has to be packaged in a reduced space because of all the electric components in there. The tighter you can package tubing and systems that cannot be eliminated from the ICE, the better it is for the overall application. We’re well positioned to support this worthwhile trend.”

This article appeared in the Q4 2018 issue of M:bility | Magazine. Follow this link to download the full issue