Friday, June 14, 2013

Advantages of evaporative cooling in cash-transit vans

Brazilian armored cash-transit van, based in a local derivative of the Mercedes-Benz Vario, with 2 roof-mounted evaporative coolers
Evaporative cooling, altough having its effectiveness more restricted when the air natural humidity goes higher, still has some advantages that makes it figure as a good way to improve thermal comfort in vehicles when a regular air-conditioner is either expensive or hard to set properly. Currently, in Brazil, it's even more popular for some special applications such as cash-transit vans than a conventional air-conditioner, mostly because of the fuel savings it can provide.
The roof-mounted conventional air-conditioner in this cash-transit van (Volkswagen frame with AutoLife body) takes more space than a set of 2 evaporative coolers, requires an amount of engine power to operate and is also heavier.
Taking this operational scenario for a case study, we might remember the effects of extreme temperatures in the health of the operators: during the summer, the internal temperature of a cash-transit van can easily reach 50°C/122F, and the poor air renewal inside the cabin ends up leading to phisycal and mental fatigue, blood pressure alterations, skin allergies, eyes dryness and respiratory distress. Meanwhile a regular air-conditioner requires the engine on to activate the compressor, evaporative coolers (also referred to as "swamp-coolers") can operate as stand-alone units in electric power only, and some are programmable to pre-set a comfortable working environment for the crew.
Even the Spanish-based Prosegur, one of the world-leading cash-transit companies, runs evaporative cooling on its Brazilian fleet, also extending the benefits of this setup to some of its other South-American branches, most notably in Peru and Uruguay
The maintenance of an automotive evaporative cooling device is also easier to perform, requiring basically the water fill-ups (more frequent than recharging the refrigerant gas of an A/C, but still an easier and safer procedure), periodic replacement of the humidifier filters (usually at each 3 months) and eventually the replacement of the fan electric motor or its brushes. But since the roof-mounted evaporative coolers are more self-contained, access to the components for the preventive maintenance is quicker, leading to a reduced time to be spent with these procedures, while an A/C requires sealing tests for leaks with an UV reagent for visual contrast, compressor driving belt and electromechanical clutch pack replacements, and in extreme situations may even require the dashboard to be disassembled.
Comparing to a regular air-conditioner, the effect of an evaporative cooling setup over the fuel consumption is more negligible, not just due to its ligther weight increasement but also due to the lower mechanical load, since it doesn't require an engine-driven compressor. Instead of using a synthetic gas, it uses only water as the cooling fluid, which also reflects as an environmental benefit since the most usual refrigerant gas commercially available is HFC-134, also known as R-134a, ranked among the so-called greenhouse gases and with a lifespan longer than carbon dioxide when released in the atmosphere. And meanwhile R-134a requires an energy expense to be manufactured, evaporative coolers can use rainwater.
The Brink's Company uses rainwater collectors in all its Brazilian branches

Saturday, June 01, 2013

4-cylinder Diesel engines: the best response to the claim for better fuel-efficiency in trucks

We all know Americans love trucks, and they also have their loyal enthusiasts in export markets. A good example is the Cadillac Escalade EXT, which offers a good balance of luxury and heavy-duty capabilities. There is, however, a significative downside regarding those vehicles: the fuel-efficiency is compromised by their size and weight..
Usually, massive V8 gassers, or eventually flexfuel, are the most usual engine option for an American full-size truck, altough other options could also provide a fair performance with improvements to the fuel savings. I can't deny my favorite choice are Diesel engines, due to their higher thermal efficiency, adaptability to alternative fuels, and also because they're cool too. With the right gear ratio selection, even some 4-cylinder turbodiesels, with a displacement considerably below the 6.2L of the currently-offered V8, can be a good match to an Escalade while not feeling underpowered at all.

Many commercial trucks with a GVWR that often doubles the Escalade, such as the Isuzu NPR, are available with engines ranging from 3.0L to 5.2L, and still leave a good safety margin for towing in case of engine swap...
It's worth to remember the technical evolution regarding Diesel emissions aftertreatment, which can lead to an end to the misconceptions pointing these engines as "filthy". At the long run, they're even cleaner than a comparable gasoline-electric hybrid driveline, not just due to the lower energy spent to manufacture a Diesel engine but also the lower amount of raw materials in opposition to a complete hybrid setup with the electric motor, additional electronic controllers and the traction battery pack.

Mercedes-Benz 240D: features one of the most dependable engines ever made, but had its limitations regarding performance and acoustic comfort
Another feature that evolved significantly in the 4-cylinder Diesels is the acoustic comfort. A good example is Mercedes-Benz: its earlier Diesels still used to clatter a little even tough the indirect injection makes it less noisy, and also used to feel quite underpowered comparing to a gasser in spite of the increased fuel-efficiency. But nowadays, with turbocharging and advanced electronic engine management, even the flagship S-Class is available with a 2.1L 4-banger Diesel. The common-rail injection, due to the multiple jets for every injection cycle, improves the sound deadening and also makes the engine run smoothier.

Often, the unavailability of Diesel versions for some SUVs, like the Chevrolet Suburban, is pointed as a prejudice to increase their global presence, altough some enthusiasts claim that only a huge V8 can lead to the genuine American "soul" into them. That perception of the amount of cylinders as a premium feature is quite dumb, since it also increases the internal frictions inside the engine, decreasing its efficiency...

GMC 6-100/6-150: Brazilian equivalent of the 3500HD
However, even when there is a Diesel engine available for an American truck, it's usually bigger than it's really necessary for many operators. Okay, it can be cool to have a massive Diesel V8, but often a 4-cylinder can already get the job done. For example, the GMT400 trucks had the IDI boat-anchor 6.5L V8 turbodiesel available in North America, meanwhile its Brazilian counterparts were available with a 4.0L 4-cylinder Maxion S4T and a 6-cylinder MWM Sprint 6.07 TCA, both featuring direct injection. Not every truck buyer requires a torque amount greater than what a gasser V8 is able to provide, but the RPM bands of a Diesel are desirable even if it's a 4-cylinder, like in a walk-thru van.

Nowadays, it's no surprise that 4-cylinder turbodiesels are getting an increased popularity even among the hot-rodding folks, most notably the Cummins 4BT, which can develop over 200hp for relatively cheap but, altough these power figures can sound unimpressive, the high torque and the lower fuel consumption than a comparable gasser are a premium.

In many markets, 4-cylinder turbodiesels nearly eliminated 6-cylinder and V8 gasser trucks. One of the most notable cases is the Land Rover Defender. It was available with the Rover 3.9L V8 gasser until '97, and after the demise of this engine there were versions fitted with the BMW M52 2.8L straight-6 catering to the South African market until 2000. Since then, however, there is no gasser Defender and, after the demise of the 2.5L Td5 (5-cylinder turbodiesel) in 2007 due to emissions regulations, the only engines available for the Defender were 4-cylinder turbodiesels shared with the Ford Transit van, being a 2.4L until 2012 when a 2.2L replaced it also for emissions-related reasons.

In Brazil, for example, in '97 the Ford F-1000, local equivalent to the F-250, was available with a 2.5L Maxion HSD in a 2WD version, altough it was phased out for the following year. The (4.9L) straight-6 was available for the 2WD F-1000, but wasn't so popular. In the 4WD F-1000, the 4.3L MWM X10 was the only option, mostly favored for its ruggedness in harsh environments.

In a worldwide base, 4-cylinder Diesel engines have been regarded as an effective balance between capability and fuel-efficiency. Even in special applications, such as ambulances.
Mercedes-Benz 710, Brazilian latest equivalent to the European Vario: its latest version was fitted with a 4.0L OM-364LA 4-cylinder turbodiesel, which torque rating is insignificantly lower than a Vortec 5300
After all, there's no need to be afraid of a 4-banger Diesel, it won't make a full-size cutaway van less reliable or an Escalade less luxurious.