Thursday, October 20, 2016

Why do I prefer a van over an SUV with a similar powertrain?

When it comes to car bodystyles, the SUV is among the most controversial ones. The acronym stands for sport-utility vehicle, but it's definitely arguable how sporty and utilitarian those pigs rigs are in a direct comparison to a van with a similar powertrain. For example, how could we justify a Toyota Hilux Surf/SW4/4Runner justify as a better option instead of a HiAce? Well, even though 4WD was not available for the HiAce through official importers in most markets, the success of those JDM versions with this feature as second-hand Japan exports in some Latin American and African countries may be a clear indication that I'm not the only one who would rather choose the van bodystyle. Be it for commercial purposes, extended family trips or leisure, there are many reasons leading this to become a more reasonable option.
Sure there are a few compromises, the most notable one being the cockpit and rear passenger door positions that would eventually not be in accordance to the export destination of a Tokyo-takeaway. Right-hand drive vehicles suitable to the left-hand traffic direction in Japan often have to go through a mandatory left-hand drive conversion in order to be allowed registry in countries such as Paraguay and Bolivia for example, even though the rear sliding door that was meant to be used in the curb side in a left-hand traffic such as Japan remains unchanged, thus becoming off-side for right-hand traffic which is prevalent in most of the Americas. At least in the continental mass, the only countries with traffic on the left side of the road are Suriname and the former British Guyana. Apart from those, only some island countries in the Caribbean such as Jamaica and Trinidad and Tobago keep the "English hand" traffic ordinance.
Another matter of concern regards to vehicle dimensions and off-road capability. It's quite predictable that a forward-control van is going to feature a longer front overhang, imposing some limitation to the approach angle, but it also offers some advantages such as a shorter wheelbase which keeps the turning diameter smaller and thus improves the maneuverability in tighter spaces ranging from rural unimproved mountain roads to urban parking spots that are often not so friendly to larger vehicles. Ground clearance and suspension travel might also be matters of concern for those who take off-road capabilities more seriously, even though some degree of components interchangeability makes it not so difficult to apply some upgrades originally meant for an SUV. However, since those Japanese vans that belong to the same class of the Toyota HiAce have an extremely utilitarian design still more focused on city and road operations, their wheel wells may be not so suitable to the oversized wheels and tyres frequently seen on SUVs like a Toyota Land Cruiser Prado. Actually, since a smaller tyre is usually more easily affordable, that would not really bother me.
SUVs being fancier than vans usually lead them to have a bigger footprint when we take in account their external lenght and width, but that doesn't reflect accurately in an improvement to interior space as it could be eventually supposed. A full-lenght bonnet/hood already takes too much of the platform lenght that could eventually serve to enhance the cargo and passenger capacity. Since midsize and full-size SUVs still rely more frequently on the traditional body-on-frame layout claimed to enhance the off-road capacities, with higher frame rails that would be supposed to be essential to overcome clearance issues for drivetrain and suspension components by setting the cabin floor to a higher position, internal height also becomes smaller and so goes the interior volume when a given external height limit is applied to both an SUV and a van. Even if we went to look some previous versions of the Toyota Hiace Regius/Grandia/Solemio that featured a semi-bonneted layout with the cockpit set a little further, the shorter cowl still leads to a greater use of space for passengers and to accomodate their luggage or even find some way to carry bulkier items or to fit a few more comfort features.

Another feature mostly neglected by able-bodied people is the usually wider door opening, as can be seen in the classic Volkswagen Kombi. Leading to either an easier loading and unloading of cargo or a more comfortable boarding and unboarding of passengers, it becomes particularly appreciable while dealing with disableds and the elderly. It's one of those features that some people accept to trade-off when they choose either a traditional SUV or a car-based "crossover" in order to not have a vehicle that looks like a cheap workhorse. It seems even crazier when, apart from the crossover SUV trend that led to a dismissal of vans and minivans as the people-mover of choice in many households, we remember all the urban cowboys who spend considerable amounts of money to get a pick-up truck with lots of fake chrome just to show off but would never even haul a sack of oats...

Friday, October 07, 2016

Why are ethanol and LPG not so suitable for the current generation of hybrid cars?

One question that has been raised for quite a long time is the suitability of hybrid cars such as the Toyota Prius to alternative fuels. Even though the average Joe might already regard the lower gasoline consumption as a step forward in the efficiency field and other aspects such as reducing the dependency on petroleum from war-torn and other politically-unstable zones or some environmental concerns, the capability to run on other fuels either perceived as "cleaner" or more affordable due to regional availability is becoming more relevant. Ethanol and liquid petroleum gas (LPG, also labeled Autogas in some countries) are well-proven as automotive fuels in a worldwide basis, but the current generation of gasoline-electric hybrid cars has some specific operating conditions that impose difficulties to use those fuels.
There had been some talks about a gasoline/ethanol flexfuel Prius since its official introduction to the Brazilian market in 2012 while it was still in the 3rd generation, but it never turned into a production model. Because of the ethanol fuel specifications in Brazil, with a 96% concentration on volume and about 4% residual water content, vaporizing is not so easy during cold starts and thus some cold starting aid is required when the fuel is used in a conventional port-injection engine such as the 2ZR-FXE fitted to the Prius. Older dedicated-ethanol and earlier flexfuel cars in Brazil required an auxiliary gasoline tank for the cold starts, nowadays mostly replaced by a thermostatically-controlled electric heating system for the fuel injection rail. Due to the intermittent operation of the internal-combustion engine in a hybrid vehicle on heavy urban traffic conditions, ethanol ends up not being so practical for all-year round operation. Unlike vehicles with a conventional non-hybrid driveline, which have benefitted from the downsizing trend that brought direct injection and turbocharging into the mainstream car market, the majority of hybrid cars keep the naturally-aspirated port-injection layout even though it's not due to cost concerns as often perceived. Since the prevalent sales argument for hybrids is a direct comparison with Diesel in the field of overall energy efficiency and emissions, resorting to this setup allows a lower intake flow temperature which leads to a lower nitrogen oxides (NOx) emission. Due to a small portion of the air/fuel mixture always returning to the intake manifold during the compression stroke because of an intentional delay in the intake valve phasing to emulate the Atkinson effect that turns the power stroke longer than the effective compression stroke, more latent vaporizing heat is absorbed from the subsequent intake charges, allowing the engine to run leaner while mitigating the risk of detonation/pre-ignition and not increasing the NOx emissions.
Therefore, a lower heat rejection can be expected from a hybrid car's engine. Eventually, such residual heat could be recovered and applied to vaporize the fuel through a heat-exchanger like it's usually done in a car converted to run on LPG, however it doesn't eliminate the need to use gasoline during cold starts until the engine temperature stabilizes. However, an intentional production of residual heat meant to help vaporizing some alternative fuel might not justify from an overall efficiency standpoint, while a short run before the idle shut-off might not lead the engine to a temperature suitable for neither ethanol nor LPG without having to resort once again to gasoline for a smooth restart. An upgrade from port-injection to direct injection could overcome this issue, but the air intake temperature and the compression heating would become higher enough to reflect into an undesirable increase of NOx emissions that would cut one of the most important competitive advantages held by the gasoline-electric hybrids against Diesel in times like these post-Dieselgate days.
Hybrid car owners looking for some gasoline replacement are actually not totally deprived of options. Despite of relying on a heavier and bulkier fuel system that leads to some compromise of the loading ability, compressed natural gas (CNG) is suitable to the intermittent operation of the engine and, since it's already stored in vapour phase at basically every ambient temperature, cold start won't be an issue. For those who seek renewability when choosing an alternative fuel, biomethane is the way to go. Since the chemical properties are identical to fossil natural gas, a transition to biomethane is easy as most of the pipeline and refuelling infrastructure won't require major changes.