Saturday, June 18, 2011

Turbo: from the discrediting to the hope

Turbo has been known by diesel motorheads and credited for the revolution in those formerly regarded essentially as an agricultural tool and currently dominate some of the main automotive markets such as Germany. But still divides opinions about its application in engines powered by other fuels, usually operating in the Otto cycle.

Worshiped by motorsport enthusiasts, despised by automotive industry experts for decades, nowadays depicted as the salvation in these times of downsizing, the turbocharger (often just called “turbo”) is having as a prestige feature even in segments where it was seen as a mere improvisation or 
workaround. Taking the kinetic energy expelled alongside the exhaust gases to push more air into the intake ends up pointed a way to have a more complete and efficient combustion process, leading to better performance and lower emissions of carbon monoxide, a lethal gas (also used as a poison by the Nazis) and more polluting than carbon dioxide. Gone are the days when an executive sedan, for example, would need at least a 2.0L engine to be considered a "respectable car", while after all the development of an "environmental consciousness" a 1.4L engine turbo often getting a wider market share in this segment. It's still a bit away from the Brazilian reality, where only the Fiat Linea has such an option (and still offered as “sporty”, quite far from being taken seriously in a more formal market - lacks the Dualogic automated transmission optional for the non-turbo 1.8L), but in more developed markets finds space in larger models such as the Opel Insignia (which shares the platform with the Chevrolet Malibu) are equipped with this kind of powerplant. It is worth noting that, for example, the Insignia in the Portuguese market is not being offered with naturally-aspirated engines for the wagon (Sports Tourer) versions.

Some consumers, however, still associate the turbo to the street races underground illegal culture, as well as a slow at low revs, a phenomenon known as turbo-lag that was harder to get around in the days when the carburetor was 
majesty. Today, however, with various electronic management systems for injection and ignition, turbo-lag effects can be reduced at the engine start-up, to get the turbo "full" sooner. Yet it must be remembered that a proportionally-dimensioned for the engine’s displacement and speed range makes the turbo lag less sensible, especially now when there are variable geometry turbochargers, in which the position of the blades is changed according to engine speed and pressure of the exhaust gas flowing inside the hot turbo housing to "fill up" faster.

Perhaps the average Brazilian customer concerns with the turbo because of the way the local market was limited both due to the circumstances of an economy more closed during the military regime and by the poor quality of the locally available gasoline leaded the engines to have lower compression ratios 
to avoid "knocks", making it impossible, for example, the use of more compact powerplants in some domestic cars of the 70s and 80s. A case in point is "Dodginho" 1800/Polara, based on the British Hillman Avenger.While in the land of afternoon tea used 1.2L and 1.5L engines, this one ended with the 1.8L. And with the advent of alcohol another myth gained strenght: that such fuel was the only one that properly supports the use of turbo, so that even today is not difficult to find mechanics who fiercely defend it because of the greater ease to tune a turbo engine due to the higher octane in the sugarcane-based fuel making it less prone to knocks when it reaches its optimal operating temperature, and that "culture" makes many good professionals to be considered "amateurish" and "relaxed" due to their work with turbos. It is worth noting that in Argentina the "Dodginho" even used the 1.5 engine, actually with a compression ratio different from similar European but not as low as the Brazilian counterpart.

Another case that can be analyzed under this perspective is the Ford Sierra, similar to the Maverick in sine and that in some markets such as Argentina came to use the 2.3L OHC so-called Georgia engine manufactured in Taubaté, shared with the Maverick and that was even 
exported to the United States in turbo version with Holley fuel injection, which use was not allowed in the Brazilian market due to the Informatic Technology Law, reserving the market for locally manufactured products - such option could have given a good survival for the Galaxie-based Landau on the market, for example. But the engines range for the Sierra in other markets included even some engines that here would be restricted to models like the Escort and the Renault-based Corcel, such as the 1.3L that for years was benefited from a more favorable taxation in Sweden, leading to the local Stockmann dealership to offer a plug-and-play turbo kit, so the 1.3L reached a performance comparable to the aspirated 2.0L offered in higher-end versions. Interestingly, some Brazilian companies such as Larus manufactured turbo kits for Argentinian cars like the Sierra, the Renault Fuego and classic Peugeot 504 and 505.

A similar situation occurred between 2001 and 2004 in Brazil when Volkswagen was selling the Gol and Parati spotting a 16-valve 1.0L turbo engine rated at a similar power to the 8-valve non-turbo 2.0 (albeit with slightly less torque), which ended up leading the gasoline-powered 1.6L going out of offer for a brief moment. 
And Ford itself came to use the supercharger (popularly known as "blower") in the RoCam 1.0L Zetec engine for the Brazilian, Venezuelan and Colombian versions of the Fiesta and EcoSport (this one had the supercharged 1.0L only in Brazil due to a favorable tax class, using in Colombia and Venezuela an argument attributing a "sporty" character to the mechanically-driven compressor, even when the aspirated 1.6 engine had a slightly better performance (and the use of the turbo could bring more benefits to 1.0 to take advantage of an energy wasted instead of taking engine’s own power to be driven as the blower does).

And now the turbo again is having a very favorable moment like never before. 
With all the impact of issues relating to ecology, has been appointed as the easiest solution in the short term to reduce pollutant emissions in cars with Otto cycle engine, powered either by gasoline, alcohol or gaseous fuels like CNG widely used in Brazil (although there are myths about its use in turbocharged engines, mainly due to an even greater penetration of the so-called "faucet kit" in the Brazilian market for conversion to CNG) or liquefied petroleum gas that is forbidden to automotive purposes in Brazil, but widely used in countries such as Japan (where the turbo engines range goes from the Kei-Jidosha with their 660cc engines sometimes with a better performance than an average Brazilian non-turbo 1.0L to prestige supercars like the Nissan GT-R), Hong Kong, Italy, Australia and even the United States. Not only for more efficient combustion, as well as the possibility of a smaller engine to perform the same service that often would require an engine nearly twice bigger. A case that seems particularly interesting to analyze is the traditional American pickup Chevrolet Silverado / GMC Sierra, which has the basic versions fitted with a 4.3L V6 engine rated at 195hp/4600RPM and 260lb.ft/2800rpm, while Chevrolet even offered on some models as the HHR and Cobalt a 2.0L 4-cylinder engine with turbo, direct injection, 260hp/5300RPM and the same 260lb.ft already at low 2000rpm - is that there comes a certain aspect of "culture" of Uncle Sam's land, home to large motor enthusiasts, and the agency responsible for establishing emission limits for vehicles, EPA is infested with bureaucrats who are not so committed to environmental protection. What interests me in this case is that the Chevrolet engine plant in São José dos Campos currently produces 2.0 turbo engines for export, and this would fit like a glove in the Blazer, still widely used by police forces, where the V6 engine is still worshiped by the enviable performance and that after being removed from the Blazer Brazilian versions got without a suitable replacement. But despite initial resistance from some consumers to use a significantly smaller engine, the arch-rival Ford is having some success up with the EcoBoost turbo engines range, then could provide a pretext for giant GM counter-attack. It is worth noting that GM has considerable experience with the turbo, from the time they controlled the automotive division of Saab and also the use of the system in models from Opel and Isuzu, now a partner in the design of medium-sized pickups, and that in some markets use the sales and technical assistance network from the traditional American company to sell trucks.

Although some mistrust still surround the turbo, it’s appearing as a very suitable solution to meet a broad and diverse consumer market worldwide, contributing to a reduction in operating cost of the car manufacturers, enabling the 
development of a more compact design to some vehicles (creating a lower barrier to air resistance and further improving the performance and consumption) that could have been fitted with smaller engines and still provides a gain in production scale, turning possible with different stages of tune the same engine become adequate to meet the consumers in various vehicles’ classes, from a pocket-rocket or a midsize executive-class sedan, through a sport-utility vehicle or a work truck.

Saturday, June 11, 2011

Hub-motors: how a hybrid can make sense.

Electric drive is often reported as better because, despite the use of heavy batteries, can be applied as a weight-saving feature eliminating the components associated to a mechanical transmission when hub-motors are used, and also allowing a smaller (then lighter) internal-combustion engine to provide all the kinetic energy needed to move a generator to provide electric power to the drivelines, like the Audi A1 e-tron that uses a 250cc 20HP Wankel engine to move the generator and 4 hub-motors delivering 61hp to the wheels like a 1.0L average Otto engine would do, but the 145Nm torque range is closer to a 1.6L.
Another benefit is the flexibility to the floorpan arrangement due to the absence of a gearbox (this is due to their reversibility, not requiring a reverse gear) and a driveshaft tunnel in the middle of the vehicle, allowing a lower boarding platform, extremely useful when handling heavy loads or there is an elder or a wheelchair user getting inside the vehicle. These advantages are well-known by the hybrid/electric vehicles enthusiasts but we don't see it so widespread as it's supposed to be. For example, would be the best setup for a serial-hybrid such as the Chevrolet Volt. Even the acclaimed parallel-hybrid Toyota Prius, cult-followed by a lot of tree-huggers just for being the first mass-produced hybrid car, could have some benefits from a quite simple change in its current driveline, replacing the electric motor bolted to the front transaxle for a pair of hub-motors in the rear wheels. We must also consider that usually a parallel-hybrid relies on the electric drive only in low speed, such as city traffic, while in highway the electric driveline means just a dead weight. The hub-motors setup, by the other side, while providing traction would even allow the internal combustion engine to have a lighter work, then needing less fuel.
When a front-wheel drive vehicle accelerates, there is always a weight transference to the rear axle due to gravitational acceleration, then, plus the advantage of the friction losses reduction, the rear electric drive would compensate for the weight distribution unfavorable to the traction, improving the drag and then reducing the energy amount needed for the vehicle to start moving. Driving uphill the traction enhancement from this system is far more sensible. Also, with all-wheel drive the stability in higher speeds is enhanced...

In partnership with Protean Electric, GM Europe is developing a hybrid version of the Opel/Vauxhall Vivaro van, a major developer of the hub-motors technology.

While the current non-hybrid versions are fitted with an average FWD driveline, some of the prototypes when fitted with a parallel-hybrid setup have hub-motors added to the rear axle. This system can even be retrofitted into existing vehicles. Considering again the benefits of the auxiliary rear-wheel drive, would also be helpful either in snow days or unpaved roads.

Friday, June 03, 2011

Corvette and the downsizing: time for a change?

This post is dedicated to some of the Truck Mod Central guys.

Well-known worldwide as an American institution, the Corvette is portrayed as a legend, comparable to famous European high-end sports cars such as some Ferrari and Porsche models, among others.
It's also known to spot another America's #1, the Chevrolet small-block V8, currently in its 4th generation but still relying on a traditional OHV layout while its opponents from Europe and Japan usually have DOHC cylinder heads. However, some hoaxes about a possible engine downsizing are getting some space in the media and already generating some discussion. OK, it's a possibility in these days of EPA and CAFE witch-hunting, but would it be really a change so enormous in the Corvette's basic concept? Maybe not...

Currently powered by either a 6.2L (430HP @ 5900RPM/424lb.ft. @ 4600RPM - also available with a supercharger for 638HP @ 6500RPM/604lb.ft. @ 3800RPM in the ZR-1 version that is "cheaper", has a close performance and is not so gas-guzzler as a Ferrari 599 GTB Fiorano with its hi-revving normally-aspirated DOHC 6.0L V12) or a 7.0L V8 engine (505HP @ 6300RPM/470lb.ft. @ 4800RPM). But, instead of its European counterparts with specially developed engines, the Corvette relies essentially in the same engines used by the large pickups and body-on-frame SUV's from Chevrolet and GMC, with a smoothier throttle response, preferred by a lot of American customers.

Rumors about a smaller engine have gained force since the GT2-class C6-R Corvette appeared with a 5.5L version of the V8, with 500HP. For a street-legal version, reported to be released in a 440HP rating, a feature that would be expected is direct injection, already found on some of its opponents such as Ferrari 458 Italia. But either hi-revving or a DOHC head still find some resistance from the most traditional Corvette customers and enthusiasts. Then forced induction comes as a reasonable option to manage the lower displacement issue without sacrifice the power but, again, different concepts have been shown as the way to go: turbo or supercharger?

While some people are still worried about the turbo-lag, and then considering the engine-driven supercharger as the most cost-effective option, there are those who would prefer to enjoy the kinetic energy thrown away by the exhaust pipes to drive a turbo. Nowadays, with the advances on engine management achieved with the electronics, a turbo setup seems to be the most reasonable. Advancing the ignition point at the engine startup has been reported to "wake up" the turbo earlier, for example, and also more modern turbo designs such as VGT have become helpful to manage this issue. And obviously, a properly-sized turbo is essential to have the most suitable boost ratio according to the engine revving.

As far as a lower displacement goes, considering FIA's current standards considering each liter in a forced-induction (most notably turbocharged) engine equal to 1.7L in a normally-aspirated, I wouldn't expect anything above 3.6L to replace the 6.2L in the entry-level Corvettes, retaining its current power/torque ratio or improving it. Maybe now that Ford, GM's archi-rival, is having some success with its Ecoboost range even in the F150 pickup, could be an incentive for a downsizing attempt. And it's perfectly viable for GM, since a 3.6L DOHC V6 engine is already available in its range and some aftermarket turbo setups have been successful, specially in Australia. However, a loyal Corvette enthusiast would still desire the V8 layout. Then, even the DOHC Northstar engine in its supercharged 4.4L version, rated at 469HP @ 6400RPM/439lb.ft. @ 3900RPM from the STS-V is often pointed as a reasonable option for an entry-level model to meet both EPA newer regulations and the enthusiasts.

Anyway, one thing is certain: even with some changes, the Corvette must retain its essentially American soul, and this is a hard challenge for the engineering team...