原帖由 cyberstudio 於 2008-6-4 01:09 發表
This is a complex question with no simple answer. But in my humble opinion, the biggest difference is in "smoothness". The more cylinders you have, generally the smoother will be your torque curve, me ...
For a typical 4 cylinder engine, torque is weak at low rpm. A 5 cylinder engine is significantly smoother than 4. A 6 cylinder shows additional improvement, but not as much an increase as you go from 4 to 5.
Mr. CyberStudio,
You are mostly correct in your post here, but the bolded line I quoted here is wrong. 5-cylinder engines are inherently rough-running because of the odd number of cylinders thumping up and down the engine block. In fact, 5-cylinder engines are often considered to be an inferior design because they lack the smoothness and power of a 6-cylinder engine, and the fuel economy of a 4-banger. This is why they are not that common in production cars. Generally speaking, inline 6 engines are the smoothest. V6 and I4 can be made to run quite smoothly as well.
Also, the old Mazda MX-3 Precedia had the the smallest production V6 rated at 1.8L. It was certainly a rare gem.
We need to ask the owner what cars he/she likes, budget/how deep s the pocket.
No point to go all over the map and dont know his preference.
Some only want cars from Fatherland, and some appy with Rice rockets.
If u know what to buy even a used car can be good, let the frst owner to pay for the initial depreciation.
Some even say u can need to own the car for several yrs longer inorder to justfy a hybrid.
The truth is buying any new car will cause a lot of environmental damages, u need mining, raw materials, energy to make steel. But if everybody stop buying new things our economy will be at a stand still. US account of 30-50% of world market, will see how bad will t affect us if they really catch a bad cold.
Some co design efficient bigger engines, IE Honda's variable 6.
Also depends yoru application, if u need to carry lots of people all the time then a bigger engine is advisable. I learn one organisation use Nissan Altima 2.5 and Camry 4 cyl to shuttle full pass load, the drivers find Camry lacks power as compare the Altima.
So u'll be screwed if u had made the wong choice of engne.
This is a complex question with no simple answer. But in my humble opinion, the biggest difference is in "smoothness". The more cylinders you have, generally the smoother will be your torque curve, meaning that you get more or less the same torque regardless of rpm.
For a typical 4 cylinder engine, torque is weak at low rpm. A 5 cylinder engine is significantly smoother than 4. A 6 cylinder shows additional improvement, but not as much an increase as you go from 4 to 5.
There are several configurations for 6 cyclinder, for example, inline or "straight". A straight 6 is a very long engine, and it can no longer be placed in the traverse orientation in the engine compartment. You will find such cars with a relatively long engine compartment, with the front wheels very close to the front bumper, and with some room between the front wheels and the firewall (e.g. Lexus IS250, BMW, Mercedes). This configuration is not good for front wheel drive - you will find almost all straight 6 to be rear wheel drive cars (or all wheel drive).
Volvo is one of the mainstream manufacturers with 5 cyclinder engines. The engine is now just short enough to be placed in the traverse orientation and therefore you find Volvos to be front-wheel drive cars (or all wheel drive). Having an odd number of cylinders, the engine is not naturally balanced and requires certain designs in the crankshaft, flywheel, engine mounts, etc. to compensate.
There are a lot of other configurations, such as H4, V6, H6, etc. Technology has been improving and if you drive for example a 4 cyclinder late model Camry you may notice that while it still drives like a 4-cylinder its smoothness has improved significantly.
V6, being shorter than straight 6, can be placed in the traverse orientation and suitable for front wheel drive. V6 is a lot more popular than straight 6 because front wheel drive is more popular than rear wheel drive.
Horsepower = torque x rpm. It is very common to find high horsepower 4-cylinder cars which revs up to 8,000rpm. Such cars are usually not smooth to drive. Depending on your style you may prefer a car with more cylinders than 4.
發表於 2008-5-30 18:35
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