Monday, November 30, 2009

Escoria��es - 10� parte

Leia tamb�m a 1� parte, 2� parte, 3� parte, 4� parte, 5� parte, 6� parte, 7� parte, 8� parte e 9� parte.

7 � Pe�as mal ajustadas

A � Folga insuficiente entre pist�o e cilindros


Este tipo de anomalia pode causar engripamento e escoria��es em um motor pelo rompimento do filme de �leo quando o pist�o se dilata.

Constata-s essa condi��o geralmente por uma �rea brilhante e polida, acima ou abaixo dos furos do pino (nos pist�es de saia interi�a) e escoria��es nas faces de contato.

B � Muita interfer�ncia no pino do pist�o

Um ajuste apertado no pino do pist�o impede que o pist�o se expanda e contraia normalmente, da� resultando folgas insuficientes.

Por isso, quando um pino for instalado sem folga suficiente no furo do pist�o ou na bucha da biela, normalmente dever�o ser encontradas riscos ou escoria��es unicamente nos lados do pist�o onde est�o os furos dos pinos devendo encontrar-se escoria��es e rebarbas nos furos dos pinos.


Escoria��es causadas por um pino instalado muito apertado

C - An�is com folga insuficiente entre pontas.

Os pist�es e os an�is se dilatam � medida em que se aquecem atingindo a temperatura de opera��o do motor.

Por isso, conforme j� mencionado anteriormente em �Troca de an�is�, � importante que todos os an�is tenham pelo menos o limite m�nimo especificado de folga entre pontas, pois, em caso contr�rio, as extremidades dos an�is podem encostar-se e causar escoria��o, quebra dos an�is ou engripamento do motor.

Uma folga entre pontas inferior ao m�nimo especificado pode, por exemplo, ser devida ao fato de estar o cilindro com 0,025 mm (0.001�) menor que a medida prevista, ou pelo fato de usar-se u jogo de an�is incorreto para este motor.

D � Ajuste inadequado das camisas de cilindro

Muitos fabricantes de motores para servi�os pesados, fabricam os motores com camisas substitu�veis em lugar de cilindros fundidos com o bloco, exibindo dois tipos de camisas: secas e molhadas, como j� foi mencionado anteriormente.

O ajuste de camisas secas em um cilindro retificado tem grande influencia na durabilidade e no desempenho dos pist�es e an�is de segmento e considerando este fato, os fabricantes despenderam anos e anos, provando e desenvolvendo o ajuste certo das camisas para determinado motor.

Assim sendo, � de estrema import�ncia que o ajuste dessas camisas no bloco seja o mais perfeito poss�vel pois, caso contrario, fatalmente ocorrer�o escoria��es e engripamento.

Existem tr�s maneiras de ajustar uma camisa incorretamente:

1 � Ajuste muito folgado.
2 � Ajuste muito apertado.
3 � Ajuste em cilindro deformado.

Um ajuste muito folgado da camisa reduz a transfer�ncia de calor desta para o bloco, deixando-a superaquecida pelo calor que recebe dos an�is e dos pr�prios gases da combust�o.

Uma combina��o dessa situa��o com a realiza��o de servi�os pesados, pode provocar a ruptura do filme de �leo lubrificante e causar escoria��es no motor.

Por outro lado, quando se instala uma camisa com muita interfer�ncia, al�m de o pr�prio bloco poder ficar deformado, o que pode ocorrer � que, como o calor gerado pelo funcionamento do motor faz com que a camisa se dilate, e n�o existindo condi��es para que ela se dilate para fora devido � excessiva interfer�ncia com o bloco, a camisa acaba se dilatando para dentro, diminuindo de di�metro.

Com isso, a folga entre camisa e pist�o chega a reduzir-se a zero, rompendo o filme de �leo e provocando escoria��es e engripamento.

Al�m disso, dependendo do caso, essa diminui��o do di�metro interno da camisa pode tornar-se permanente.

Quando o motor estiver frio, em determinados pontos, ficar� um vazio entre a camisa e o bloco, onde v�o se acumular carv�o e resina, que ir�o prejudicar a transfer�ncia de calor no local e tornar-se novos pontos de superaquecimento e escoria��es.

Quanto � instala��o de camisas em cilindros deformados, o que poder� ocorrer � que: ou a camisa se moldar� � deforma��o do cilindro, ficando tamb�m deformada e dificultando o assentamento dos an�is, ou n�o se deformar�, formando, no entanto, um contato irregular com as paredes do cilindro, deixando v�os onde se acumular�o carv�o e resina, causando os problemas descritos anteriormente.

Grandes dep�sitos de carv�o ou resina na parte externa das camisas, sinais de escoria��es ou engripamento nos an�is e/ou nas camisas o pontos brilhantes e polidos, evidenciam a deforma��o ou o esmagamento da camisa devido a irregularidade no cilindro.

E � Desalinhamento de Bielas

Quando as bielas est�o desalinhadas, os an�is n�o tem uma superf�cie de contato adequada com a parede do cilindro, os pist�es se desgastam de forma desigual, o consumo de �leo � anormal e o motor tem maior tend�ncia para engripamento e escoria��es.

Identifica-se uma biela desalinhada pelo desgaste irregular do pist�o, no sentido diagonal, em pontos opostos, conforme mostra a figura abaixo.


Pist�es com desgaste em diagonal

O contato com a parede do cilindro aparece na parte inferior da saia, � esquerda e, na �rea dos an�is, � direita. Verifica-se, tamb�m, um sinal de desgaste, come�ando � direita na parte superior, descendo em forma diagonal e prolongando-se transversalmente para a esquerda e na parte de baixo da saia.

Portanto, verifique sempre o alinhamento das bielas antes de substituir os an�is, a fim de evitar os problemas acima.

F � Perda da trava do pino

Embora de natureza diferente da escoria��o e engripamento como descrito at� o momento este � um problema relativamente comum e que e que tamb�m provoca riscos e quebras dos an�is, pist�es e cilindros.

A avaria do pist�o do tipo ilustrado na figura abaixo � devida ao afrouxamento da trava do pino, � quebra da extremidade da trava do pino, ou a um peda�o de metal solto, deixado no interior do pino.


A avaria neste pist�o foi causada pela perda da trava do pino.

Em casos desse tipo, devido � in�rcia, o objeto solto martela o pist�o e o cilindro na �rea do cubo do pino, danificando o pist�o enquanto procura sua sa�da do motor.

Al�m disso, esses objetes soltos podem passar atrav�s do oco do pino, danificando o pist�o e a parede do cilindro no lado opostos.

As travas dos pinos podem soltar-se devido a:

1 � Desalinhamento das bielas.
2 � Excessivo jogo axial do virabrequim.
3 � Pinos do pist�o muito longos.
4 � Conicidade dos colos do virabrequim.
5 � Cilindro retificado fora de alinhamento.
6 � Peda�os de metal deixando dentro do pino do pist�o.
7 � Travas de pinos frouxas.
8 � Uso de trava de pino incorreta.
9 � Travas de pino instalados incorretamente.

Friday, November 27, 2009

Novo CrossFox por R$ 45.550

Isto mesmo R$ 45.550, � o valor no novo CrossFox, por�m ele n�o traz ar-condicionado. Este item � opcional caso queira instalar este o valor salta para 49.390 reais.

Ele vem de s�rie com dire��o hidr�ulica sistema i-System, computador de bordo, dire��o com regulagem de altura e profundidade al�m dos vidros e travas el�tricas.

Thursday, November 26, 2009

Mercedes-Benz W212 E-Class launched in Malaysia


It's finally here, the all-new E-Class (W212) being launched by Mercedes-Benz Malaysia (MBM) at a glitzy evening function at the Palace of Golden Horses. To begin with only the E300 V6 will be available for sale immediately, priced at RM458,888.

The mass-market E200 CGI (estimated to retail about RM370k) will only be available sometime April 2010, along with the E250 CGI (circa RM410k) at about the same time. Both variants will have the same 1.8L lump in different state of tune and turbo-boost - along with direct injection - churning out 184hp/270Nm and 204hp/310Nm respectively. In contrast the E300 is powered by a naturally-aspirated 3.0L V6 pumping out a combo of 231hp/300Nm. Both the 4-cylinders E-Class only make do with 5 A/T 'box while the V6 will sport Merc's 7G-Tronic.







Novo CrossFox 2010

As revistas Quatro Rodas, Auto Esporte e Carro novamente n�o seguraram a ansiedade e mostraram a cara do novo CrossFox.

O Novo CrossFox 2010 chega as concession�rias a partir de dezembro. A carinha � a mesma do novo Fox, com os far�is que lembram o Polo europeu.

As modifica��es no visual tiraram um pouco do fora de estrada deixando-o com um visual mais limpo. Ele n�o tem o quebra mato dianteiro e o suporte do estepe fica mais escondido. A abertura do porta-malas � autom�tica que � feita ap�s a abertura completa do suporte.

Ele traz de s�rie dire��o hidr�ulica, ar-condicionado, vidros e travas el�tricas, setas de dire��o integradas nos retrovisores externos al�m da regulagem de altura e profundidade do volante. As rodas s�o de 15 polegadas feitas em a�o os rodas de liga s�o opcionais.

Clique nas fotos para ampliar


Fonte

Wednesday, November 25, 2009

Revelada Strada Sporting 2010

As primeiras imagens oficiais da nova vers�o Strada Sporting, foram divulgadas pela Fiat na segunda feira (23).

Ela vem com rodas de liga 16 polegadas, spoilers e farol com mascara negra. No interior traz volante de couro com costuras em vermelho, cintos vermelhos e protetores esportivos nos pedais.

Vem com motor 1.8 Flex de 113 cv abastecido com gasolina e 115 cv quando abastecido com �lcool.




Estas s�o as duas fotos disponibilizadas e a Fiat n�o divulgou ainda valores.

Wednesday, November 18, 2009

2010 Hyundai Sonata 2.4 to have 201ps/250Nm GDI engine




To help meet its goals of environmental leadership, Hyundai Motor Company unveiled the 2.4 Theta II GDI, its first Gasoline Direct Injection engine before an audience of engineers attending the Ninth Annual Hyundai-Kia International Powertrain Conference.

Representing the biggest advancement in fuel injection, an �80s technology that replaced the carburetor, GDI puts Hyundai at the cutting edge of engine design and management by achieving three seemly incompatible goals: GDI lowers emissions while raising power output and improving fuel economy. Prior to GDI, a gain in one area came at the expense of the other two.

With a compression ratio of 11.3:1, the 2.4 Theta II GDI delivers 201ps at 6300rpm and 250 Nm of torque at 4250 rpm in its Korean domestic market specification.

�The Theta II GDI convincingly demonstrates Hyundai�s advanced powertrain engineering capabilities,� said Dr. Lee Hyun-Soon, Vice Chairman and Chief Technology Officer.

One serious limitation of conventional fuel injection is that as engine revolutions increase, the valve opening and closing times get progressively shorter, thus reducing the time available to inject fuel. GDI avoids this problem altogether by positioning the fuel injector in the most optimal location, directly inside the combustion chamber to offer unparalleled precision. With this shorter and more direct path, far greater control is attained over the combustion process: A high pressure fuel pump injects the fuel at pressures of up to 150 bar, in precise amounts and intervals.


The injection is split into two phases to achieve optimum combustion: in the first phase, the pilot injection and ignition trigger the piston's downward power stroke. Then, in the main injection phase, during the piston's descent, more fuel is injected and is ignited. This split-injection technique reduces loading on the catalytic converter and helps lower emissions. This is particularly beneficial during cold starts when emissions are highest because the catalyst has not reached its optimal operating temperature. Split-injection enables the catalytic converter to reach the optimal operating temperature faster thus reducing emissions by 25 percent during cold starts and meet�s California Air Resources Board�s ULEV-2 and PZEV standards.

GDI�s other benefits include improved dynamic performance and better mileage. Compared to a conventional engine of the same displacement, GDI delivers 7 percent more torque at low revolutions and 12 percent more torque at the high-end for better take-off and overtaking performance. Perhaps best of all, a vehicle equipped with a GDI engine will get about 10 percent better mileage than a vehicle equipped with a conventional multi-point fuel injected engine. Precise mileage figures will be announced when retail sales begin.



GDI has been applied to the second generation of Theta: Theta II features numerous design enhancements over its predecessor starting with the application of a three-stage variable induction system (VIS) which improves engine "breathing," automatically adjusting the volume of the air sucked into the combustion chamber to create the optimal air-to-fuel mix under different engine load conditions.


Further performance gains were made possible by incorporating Dual Continuously Variable Valve Timing (DCVVT) which improves engine breathing on the intake and exhaust sides for better fuel economy and lower emissions. Depending on engine load and speed, DCVVT can extend or shorten the duration of the valve opening and closing for more power and lower emissions. And the DCVVT system is governed by a new steel chain with an innovative roller and tooth designed for silent operation and durability.


While DCVVT and VIS improve power output, engineers have also come up with several important weight saving innovations. Special attention was focused on the bulkhead, the area of the aluminium cylinder block accumulating the highest stresses: Reinforcement yielded a stiffer block without incurring a weight penalty. A redesign of the crankshaft (semi-eight-balance type) led to an equally important weight reduction. The catalytic converter is also lighter thanks to a new canning process which allows for the use of thinner gauge stainless steel and requiring far less welding.


Another major engineering challenge was to reduce internal friction to attain better fuel economy. Friction reduction measures include a revision of the piston pin from a fixed-type to a full-floating design which cuts down on friction between the piston and cylinder wall. And under the piston crown, engineers have added a cooling jet which sprays oil over the piston walls reducing friction and contributing to an improvement in fuel economy.


Thursday, November 12, 2009

Andropause Rx: A Porsche to restore low testosterone?


Scientists have conducted a rather interesting study, according to an article posted at Zeintec (Zei-News) online newsletter.


A group of men were first given ownership (for a full hour) of a �75,000 Porsche 911 Carrera Cabriolet, followed by ownership (for a full hour) of a sixteen year old Toyota Camry, which definitely fell into the �beaten-up-family-car� category.

Before the drive began in the Porsche, tests were conducted on saliva samples from each man and a testosterone level was noted. After the men took a drive through the country side, alone in the car with no witnesses, there was a significant increase in these levels! To take it a step further, the levels increased even MORE when the man drove through a town or city where there were plenty of female onlookers to fluff their tail feathers for.



BUT when the man took an hour drive in the Toyota, there was no increase in their testosterone levels and sadly, some men even showed a slight decrease!

For a man, owning a Porsche would be the equivalent of having the brightest feathers amongst your peacock rivals! It is common knowledge that a low testosterone level in a man can lead to a decrease in health; bad moods, sleep difficulty, putting on weight and a low sex drive...So the conclusion we come to: driving a Porsche is great for your health!




Recall do Nissan Sentra 2008

A Nissan anunciou nesta quinta-feira, 12 de novembro, a convoca��o de um recall para verifica��o e eventual substitui��o do cilindro mestre dos freios dos modelos Sentra fabricados em 2008.

De acordo com a montadora, o equipamento pode apresentar vazamento de flu�do, que � informado ao condutor por meio de uma luz no painel. Caso o ve�culo continue sendo utilizado nestas condi��es, haver� um aumento no curso do pedal de freio e, consequente, a perda progressiva da capacidade de frenagem.

A inspe��o leva aproximadamente uma hora e pode ser agendada em qualquer uma das revendas da marca. Caso a substitui��o da pe�a seja necess�ria, o reparo leva cerca de duas horas e n�o tem custo para o cliente.

Para maiores informa��es, a Nissan disponibiliza o telefone 0800 011 1090 ou o site oficial da empresa.

Confira os n�meros dos chassis envolvidos no reparo:

Nissan Sentra (fabricados entre 23 de fevereiro e 18 de abril de 2008)
3N1AB61D28L703250 a 3N1AB61D68L705261
3N1AB61E99L600000 a 3N1AB61D09L602144

Perodua Viva Elite


Today I shall get down-to-earth, back-to-basics with this car review. No other car epitomize this better than Perodua Viva Elite. It is by no means bargain-basement cheap, considering that Perodua is considered a national car maker and is afforded tariff exemption, special tax incentives et al.






Not paying much attention to this Perodua model initially, I was surprised at how decent this rebadged Daihatsu Charade (of previous generation) can be. Things that matter like ABS, twin SRS airbags are there. Even the wing mirrors are electrically foldfable. Hear this UMW Toyota: (well, they are of the same core business group anyway), where's the electric folding mirror action for the RM175k Toyota Prius?

Then there's also adjustable seatbelt anchorage points on the B-Pillars. Similar items in Toyota Avanza and even Nissan Grand Livina? No.

Though the seats are not the last word in comfort - its flanks support and backrest are a little thin/stingy but the thigh supports are surprisingly adequate (at least for my short stature) i.e. ant-posterior length-wise up to the mark. Once again, even the ever popular (D-segment!) Toyota Camry is a little shortchanged here. Serious.

Drive wise, there is nothing much to complain about. It's sprightly enough, light footed and willing on the move. There's even 4 -speed auto now, versus the Kancil 850 EZ which my better half owned 8 years ago. Idling vibrations is still noticeable, even though idling engine speed is pretty high at 1000rpm. The instruments panel are simple, clean and easily legible. something that the other 'major' national carmaker needs to learn for its Neo model or even its new Evora...er, I meant Exora.

The chassis gets a tad floaty as you breach our national highway speed limit but I guess flogging it to, say 130 km/h is much akin to wearing your Croc sandals to do snorkeling.

Funnily, the alloy wheels managed to look like wheel caps, which is something rather 'bizarre' considering that some good wheel caps can mimic otherwise these days!
In contention for a NST-Maybank COTY award 2009, whether the Viva Elite will present better value than the Hyundai i10 remains with the end-user. While the little Hyundai does handle better and has a better interior, the Viva's trump cards are its features.

At the end of the day, most motorists at this entry-level budget segment will likely emphasise on Viva's resale value in the future as a key consideration factor in their purchase.
Or perhaps another choice may be the newly relaunched, facelifted and renamed Naza (Kia) Picanto?







Wednesday, November 11, 2009

BMW Motorrad Concept 6

A BMW criou a moto conceito com motor de seis cilindros em linha denominado BMW Motorrad Concept 6. Ela tem o estilo de competi��o Caf�, da linha S�rie K.

Ela tem o motor 1.6, por�m a BMW n�o divulgou a pot�ncia. Outra consequ�ncia do alinhamento dos cilindros est� na largura da moto, 10 cm menor que a tradicional.

Ela tem a suspens�o em liga-leve que reduz seu consumo a deixando com consumo equivalente ao das vers�es 4 cilindros.

Clique nas fotos para ampliar:


Fotos do Bugatti Galibier

A Bugatti divulgou imagens do 16C Galibier Concept o superesportivo foi apresentado em setembro durante as comemora��es do centen�rio da marca.

O carro conceito ainda n�o tem previs�o de ser produzido. Ele � feito de forma artesanal em fibra de carbono e alum�nio que s�o cromados.

O 16C foi inspirado no Type 57, fabricado entre os anos de 1934 e 1940. O motor � um motor 8.0 W16, o mesmo do Veyron, por�m roda com Etanol.

O conceito ser� mostrado nos dias 4 e 13 de dezembro nos Estados Unidos.






Fonte

2010 Porsche Boxster Spyder


Porsche AG is at it again. This time around the boys at Zuffenhausen sprinkle their special edition magic on their facelifted (2nd generation 987 series) Boxster S, creating another Spyder variant: aptly named the Porsche Boxster Spyder.

Powered by the similar state-of-tune 3.4L naturally-aspirated Boxer-6 found in the Cayman S, the Boxster Spyder has a peak output of 320hp instead 310hp in the standard Boxster S. The Spyder will zip from standstill to 100km/h in 4.8 seconds when specified with Porsche Doppel Kupplungsgetriebe (PDK) twin-clutch gearbox, along with the (extra cost option) Sports Chrono Package. Terminal velocity is a lofty 267 km/h. In comparison, the standard Boxster S does the same century sprint in 5.0 seconds. Just how well the lightened and simplified pull-over canvas roof takes to this Vmax is anybody's guess. Yes, the regular electric folding top has gone the way of weight saving.




The most noticeable differences on the Spyder are the new 'double-bubble' rear deck, reprofiled front bumper, a set of newly designed alloy wheels and a large fixed rear spoiler.


Also obliterated in the interest of excess fab shedding are the standard Boxster's daytime running lights and fog lamps. The cabin has been stripped out of any "excessive" equipments like audio system and air conditioning. Both these items however, can be refitted as cost options! The interior also gets a pair of seat-belt like strips as door pulls instead of the regular metal door opening handles. In addition, there is also a pair of sport bucket seats of lightweight carbon-fibre construction.

After all these 'dieting' measures, this special edition Boxster manage to shed 80 kg off a regular Boxster S. To be exact, the Spyder tips the weighing scale at 1,275 kg.




Reliving a legacy harking back to the days of the iconic Porsche 550 Spyder from the 1950s, the 2010 Boxster Spyder essentially replaces the standard Boxster's electrically retractable soft-top with a simple and lightweight pull-over contraption that hooks up onto the windshield frame. It also sports rear double-humps just distal to the roll-over hoops, with a sloping contour reminiscent of the Carrera GT.






The new Boxster Spyder is slated for worldwide launch sometime February 2010. Base price starts at �53,100 (US$78,400) in Europe. Would the price be hovering near a standard Cayman S with PDK (RM665,000) if this is at all made available in Malaysia next year?




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