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    Im confused..

    What exactly is the main difference as far as driving the actual car is concerned between a petrol car and a diesel car?

    And whats the difference between a car thats got power steering and a car that hasnt.. How different are they to drive etc..?

    Sorry if i sound dumb!
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    First Question:

    Diesel: Summarizing, it has a shorter rev range and shorter bursts of power, as much of it is developed using torque rather than bhp. They are normally slower, although catching up nowadays, and still sound like a tank although that is also being silenced as we speak. The power is the most obvious thing, with mid range lovely, whilst a sprint would be boring. Due to the short rev range, the thrill of red lining it is all over quicker than you think.

    Petrol: Completely the opposite to the above! But uses unleaded (which is cheaper) and uses cheaper parts. And is better :p:

    Second question:

    Power steering comes in different varieties -
    The Fiat Punto for example has a button called 'City'. When depressed, the steering wheel is so light, you'd be worried about doing 70mph in it. When taken off, the steering is still extremely light, but more feedback is given allowing for more confidence on a motorway.

    Vauxhall uses EPS (Electronic power steering) which is electric. Hey ho.

    Heavier versions of power steering can also be obtained (which I prefer due to the feedback). I don't wnat soemthing that has no powers steering, as reverse park, or any types of parking can become a struggle.

    A car with heavier steering is better for those who really want to drive a car (like rally in it), and the City feature offered by Fiat is great for City driving.
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    A petrol car is a very different car to a diesel car in the way the engine works. On a technical side, instead of igniting fuel, in a diesel engine, the air/fuel mixture is highly compressed and auto ignites under that high compression. This leads to a higher typical torque for a given BHP output. Nearly all new diesels are turbocharged, that is, the exhaust gases are used to turn a turbine which "sucks" in air and forces the additional air into the engine. A normal engine has to do the sucking itself unlike the forced action of the turbocharger. This leads to a higher output of BHP and torque from a non-turbo engine.

    But from your question you're not after that sort of answer. Typically the differences for driving are that a petrol car is more responsive and will provide its power over a longer period of rpm. A diesel has more torque and will allow you to pull away with fewer RPM and in a higher gear from a lower speed without stalling/damaging the clutch. Typically a diesel will be at 30% (or more) lower RPM for a given speed (i.e. modern Megane Dci is at 1600rpm at 60mph, you can compare that to your own car).

    THe main real difference is that most modern diesels are turbocharged (TD, Dci, Dti, CDTi, JTD, MJTD etc.), this means you get a lot of extra power and most significantly torque which makes driving easier due to fewer gear changes. A traditional TD has a very odd style in that you get very little power, the turbo will kick in around 2k RPM and bam, power for 1k RPM and then you change up. A more modern TD has a more progressive turbo (e.g. variable vain) hence you get less of a turbo kick and more acceleration from idle RPM. A diesel runs out of puff earlier than a petrol and a typical change of gear will be a lot lower in a diesel than a petrol in terms of RPM. Comparing diesel and petrol is a bit of an odd one, most people say "X BHP out of a turbocharged engine is rubbish, because it's diesel, if it was a petrol it would be Y BHP". However, that ignores the fact that economy is still excellent etc. etc. When you have a mainstream manufacturer like Renault offering a 175bhp 2.0 diesel, BMW et al offering similar, it puts petrols in their place a little - especially when it can do 48 MPG, has low CO output etc. etc.

    For smaller cars, the slight (it used to be a lot more) mass difference between the engines means that a diesel car might not be as nimble on the road.


    There are two main types of PAS (power assisted steering) - hydraulic and electric. More and more modern cars have got electric system which is basically motor assisted where as the older system had a hydraulic pump system. It makes the steering lighter and typically can make the lock to lock (number of turns of a steering wheel) fewer as less effort is needed to turn the wheel. The consequence of PAS on a small car is small (unless it is a heavy engine in which case it is fairly necessary for a pleasant town drive). However, you wouldn't want a larger car with PAS, especially if you're small built (male or female). Some people say that they miss some of the feedback they get from the road when they have PAS. Advantages of the electric system is that the PAS tends to be very progressive. What I mean by this is that at low speeds the PAS can offer more assistance and at higher speeds it can be turned off. The Fiat range for example has the "CITY BUTTON" (or girlie button) which allowed manual changing of this. Additionally to this, electric PAS only turns on when needed on most cars, thus saving power over hydraulic systems.

    In terms of diesel and petrol cars, it depends on your driving style, personally I prefer the diesel style but have owned 3 petrol cars...! I enjoy the MPG you get even when pushed from a diesel and like the ability to drive lazily (few gear changes) when I can't be bothered but enjoy being able to push the car when I want. A petrol - to get the most of out - requires high RPM constantly. This is especially true with VVTi (or VVT etc.) cars which is variable valve timing. This means that at higher RPM, the engine responds very differently but to get this change, you need high RPM!

    I apologise for the lack of organisation, it is late and the issue is very broad! I suggest you type "diesel vs. petrol" into google.
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    (Original post by walshie)
    The Fiat Punto for example has a button called 'City'. When depressed, the steering wheel is so light, you'd be worried about doing 70mph in it. When taken off, the steering is still extremely light, but more feedback is given allowing for more confidence on a motorway.
    It turns off at a designated speed, which is either 20, 25 or 35 mph, I forget which and I have a feeling the Punto is 25 mph and the stilo 35 mph but I might be wrong.
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    I did think that myself!! My brother had a crappy punto as his first car, and I did notice the steering get slightly heavier. I just assumed that was due tot he speed of the car. Oohps.
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    No, although not many people know it's the case! I am not sure if it even states it in the owner's manual.

    There are some arguments about whether keeping it on always kills your PAS motor but there's little evidence and since it only actually works when you turn it makes very little difference. I assume it was a safety decision by Fiat to have it switch off at a pre-designated speed.

    It must be a good system - I haven't heard of one case that I can remember of the Fiat electric steering going faulty. There was a stilo 1.8/2.4 recall for the steering rack but not PAS related.
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    When I drive my dad's Multipla I miss the feedback so much, but, I dred manuovers in the Punto lol

    The latest system Fiat have developed makes sense, normal light power steering, then, under 10 MPH City Mode hardcore "Is the steering wheel attached to anything" power steering
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    Good post by pghstochaj, to some it up, diesels rev less, have a shorter power band, are harder to stall and have more torque. They also sound like dirty transit vans and are generally slower, but this is getting better these days.
 
 
 
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