Cooling System Evolution
Published Date: 10/19/2015
BY CHRISTIAN P. KOOP -- From what I have observed looking back over the years, it appears to me that most commercial medium- and heavy-duty truck manufacturers, including for fire apparatus, have always seemed to lag behind the automotive industry in certain areas of technological development. The same still seems to hold true when it comes to the engine's cooling system.
There is an important advancement when it comes to cooling systems that has yet to be embraced by manufacturers that will not only improve the cooling system's efficiency but will also create extra room for technicians to perform repairs and maintenance in the engine compartment. In June 2014, I wrote about the importance of properly maintaining your rig's engine cooling system. I mentioned how the engine cooling system sometimes takes a back seat to other preventive maintenance areas such as lubrication, oil filtration, and air filtration-even though a failure in the cooling system could cause an expensive breakdown. Catastrophic engine failure because of a serious overheat can be one of the most expensive items to hit the maintenance budget. I am sure most will agree this is not a good thing with today's shrinking maintenance budgets, particularly if it could be prevented-not to mention what could happen from a life safety perpsective at a fire scene if the engine fails because of a cooling system failure.
Although it appears most of today's commercial truck and fire apparatus appear to be making use of the latest technological developments and innovations available, I still think the cooling system is taking a back seat to the other major engine systems in terms of innovation. A case in point is when automobiles went from the traditional rear-wheel-drive platform to a front-wheel-drive transverse mounted engine. In this case, engineers were forced to abandon the radiator cooling fan that had traditionally been mechanically belt-driven off the water pump drive pulley and use electric fans mounted right on the radiator housing. By doing so, they inadvertently created an energy efficiency advantage and improved system redundancy by going from a single fan to two electrical fans.
Diesel Cooling System History Up until about 13 years ago, diesel engine cooling systems in most commercial heavy-duty trucks, including fire trucks, remained virtually unchanged. This changed when the Environmental Protection Agency (EPA) enacted stricter emission regulations for the 2002 model year. These regulations were created to reduce nitric oxide and nitrogen dioxide (NOX) and diesel particulate matter (PM) emissions. These regulations would gradually become stricter for model years 2007 and 2010, forcing diesel engine manufacturers to make major changes to their engines to meet regulations. One of these was introducing exhaust gas recirculation (EGR). In 2002, EGR technology had already been in use in gasoline automobile engines for more than 30 years. The introduction of EGR technology created several issues for the truck manufacturers. Heat rejection was a major issue, and many heavy-duty rigs had component system failures related to elevated under-hood temperatures. This was linked to the EGR system generating more heat for the cooling system and taking up some valuable real estate in the engine compartment.
Most full size fire apparatus diesel engines are in the 400- to 500-horsepower (hp) range. These engines will require anywhere from 40 to 50 hp to turn a mechanical cooling system fan under full load. That equates to approximately 10 percent of the engine's hp just to run the cooling system fan. Converting from this mechanically driven fan to electric fans to cool the radiator will equate to an improvement in efficiency, which will translate into savings in fuel. Advanced Cooling System Engineered Machined Products (EMP) is a company based in Michigan that has recognized this important factor and has been building an advanced electronic engine cooling system since 2006. It has been installing this system as a retrofit in older buses and in new transit buses very successfully across the United States and Canada and has logged more than one billion in-service miles. The company named the product the Mini-Hybrid for transit buses because of the fuel savings of up to 18 percent that can be realized. However, looking at it from a technician and maintenance standpoint, I think fire apparatus would benefit greatly by incorporating this system. I have seen it personally, and it frees up considerable space (real estate) in an otherwise already tightly cramped engine compartment.
Several years ago, Broward County, South Florida, not only retrofitted its in-service transit buses but started specifying the system in new fleet additions and was able to realize substantial dollar savings because of reduced diesel fuel expenditures. To provide a better perspective of the system, it incorporates multiple electric fans depending on the size of the engine, with the fans mounting directly onto the radiator very similar to the way they are mounted on a front-wheel-drive/transverse-engine automobile. The system is totally computer-controlled using the Society of Automotive Engineers (SAE) J1939 Controller Area Network (CAN) protocol, which is linked to the engine and transmission. The system reads vehicle speed, engine speed, coolant temperature, intake manifold temperature, and transmission temperature and interfaces with a diagnostic service tool, which provides the technician with diagnostic status via J1939. The fan control strategy is very energy-efficient in that individual fans come on gradually and consume energy only if needed and, because of the variable speed, will only run at the speed required to maintain correct engine temperature.
The basic goal of the cooling system strategy is to keep the engine as warm as possible with fan motor constraints, such as only turning on after the engine thermostat opens; to turn on at full speed just below the maximum allowable engine temperature; and to avoid diagnostic faults. There are also a number of software features available. However, one that I think would be useful for apparatus is the one that allows the driver to reverse the fans as a timed event at full speed to blow off dirt and debris from the radiator cooling fins. The duration of this timed event is also configurable. Other features include battery charge protection (another one vital for fire apparatus), curbside noise abatement, thermal soak, fail-safe mode, independent fan control, diagnostic detection, fault tolerance, temperature regulation set points, temperature regulation source (via J1939 engine OEM temperature sensors and EMP sensors), engine compartment circulation, historical data, J1939 address, and a heartbeat at the control modules. System Diagnostics System diagnosis basically involves loading service tool software from EMP on a PC or laptop. The interface between the vehicle and the computer can be accomplished using adapters manufactured by Nexiq, Noregon, or Vansco with firmware updates that can be downloaded directly from the vendors' Web sites. These interface adapters, as most technicians already know, work with other service tools such as the Detroit Diesel Diagnostic Link, Caterpillar Electronic Technician, Cummins Insite, and Allison DOC. Those techs already familiar with the software used to diagnose engine and transmission issues will feel comfortable navigating and using EMP's dashboard that has bidirectional control and a diagnostic page that provides a fault code list and status.
Yet another important factor with the EMP cooling system is improved safety. Most transit buses use a hydraulic system to drive the engines' mechanical cooling fans. This is because many engines are mounted in the rear with a side-mounted radiator. Hydraulic fan drive systems are also used on some fire apparatus I am familiar with that have been plagued with poor reliability because of leaks. Hydraulic system failures can spray oil on hot exhaust engine manifolds and ignite. Electric fans not only will eliminate this potential source for a fire, but they also will add significant cooling system redundancy because there are multiple fans (eight or more depending on radiator size), and if one or two fail, the remaining fans will still have sufficient capacity to maintain safe engine operating temperatures. Compare this to what is most common on fire apparatus today-a belt-driven single fan coupled to a pneumatic clutch arrangement-and the multiple electrical fans are easily more reliable because failure of the clutch or the plastic fan blades may cause an overheat condition and can even destroy the radiator if either of these components suffers catastrophic failure, which I have seen happen.
As I have stated in past articles, I am a firm believer that having good access equates to less downtime, which also saves dollars in the long haul. Most fire departments keep their emergency response vehicles longer than 10 years, and many end up keeping them 15 years to longer than 20 years in some cases. I really think fire truck OEMs and potential end users should do their homework and at least take a hard look at this system. I think it will benefit fire apparatus in much the same way it has in the transit market-not only in fuel savings but also in system reliability, built-in redundancy, and an improved safety factor. Cooling system reliability in an emergency response vehicle is even more important in my book than fuel savings. The traditional clutch-driven system has only one fan and one clutch. If either fails, the system will cause the engine to overheat. If the engine is not shut down in time, this can lead to complete engine failure.
Think about this the next time your rig is at a large fire scene and has to pump for an extended time period.
CHRISTIAN P. KOOP is the fleet manager for the Miami-Dade (FL) Fire Department. He has been involved in the repair and maintenance of autos, heavy equipment, and emergency response vehicles for the past 35 years. He has an associate degree from Central Texas College and a bachelor's degree in public administration from Barry University and has taken course work in basic and digital electronics. He is an ASE-certified master auto/heavy truck technician and master EVT apparatus and ambulance technician. He is a member of the board of directors of EVTCC and FAEVT and a technical committee member for NFPA 1071, Standard for Emergency Vehicle Technician Professional Qualifications.