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Is turbo petrol better than na petrol for driving? eg. evo v bmw 530i. Ignoring reliability etc
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I suspect the answer to that depends on the actual engine. The VAG TFSI engine has lots of torque and I would have had it in my Octavia vRS, and been happy with it, if I did a lower mileage. I don't think there is much difference in perfornance, throughout the rev range, between the TFSI (197 bhp) and the TDI (170 bhp but more torque). The new 1.4 TFSI has a lot of good things said about it, but I can't remember if good torque is one of its virtues, and I've yet to drive one.
The petrol makes a nicer noise, although in fairmess the CR diesel in mine is a lot quieter than its PD predecessor.
I believe the BMW 3.0 petrol and diesel are another well-matched pair: you could search for a fairly recent thread on this - I think about 530i versus 530d or was it the 3-series?
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Torque of course for lolloping rapidly and economically round town, the other thing for those high-heartrate episodes on the road...
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I don't wish to sound like a boy racer because I am actually a mimser but I do love the souind a petrol makes when you rev it. Sometimes I have to rev my little 1.2 16v to make progress and its a lovely sound.
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Torque is needed for carrying load. Rev is for power and thus higher top speed. You can increase torque via gear box. For trucks and buses torque is important. For cars, I prefer revs. :-)
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I love the sound and feel of my 2.3 V6 supercharged Mazda- rev's to red line effortlessly but given choice a big basic grunty V8 would do me fine. - with auto of course.
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Sometimes I have to rev my little 1.2 16v to make progress
All the time, I'd have thought, Rattle!! ;-)
GB summed it up for me, horses for courses, long trips over Europe give me a decent TDi any day, racing round a circuit it would have to be a big American V8 with built in lovely soundtrack!
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Having spent the past week trying to wrestle a 1.1 petrol clio up the steep roads & mountain passes of Madiera, give me torque every single time.
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Ah Madeira m'dear.
Did you try the old road to the Nuns Valley AE - Thats one for the scary mountain passes thread ..
At one point its 1000 ft drop straight down...
Best not to try it after a few slugs of Poncha...
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Yes, turbo petrol engines tend to be pretty good torque-wise: the 122PS 1.4 TSI/TFSI is rated at 148 lb ft (200 Nm) at 1500 rpm upwards.
Small turbo'd petrol engines like that are going to become more popular: the new Astra will have them and Ford are phasing in their EcoBoost range of turbo-petrol engines.
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Imagine an engine in a box, the only bit apparent to the oudside world is the power output shaft. We attach the shaft to a brake and we measure 100 bhp at 5000 rpm. The ngine inside the box could be produceing 100 bhp at 5000 rpm or it could be a smaller engine produceing 100 bhp at 10000 rpm with a 2 to 1 reduction gear. It could even be a 15000 rpm screamer with a 3 to 1 reduction gear. The engines which rev higher to produce the power will produce the power with less torque, remember power=torquexrpm. After the appropriate reduction gear all the engines look the same at the shaft whichcomes out of the box, at least in the 100bhp 5000 rpm condition.
What I presume peopel really mean when they talk about torque in this situation is a flat torque curve. The sort of engine which will let you lift off in a highish gear and can cruise at 70 or so useing 2500 revs. A big lazy V8 or a turbocharged diesel. All that means is that you have an engine optimised to produce the power that you want at low rpm. As you want the power at low rpm it needs to be fairly big or use forced induction. Howver, the fact that this engine does not give us a kick in the backside as the rpm rises just means that it is strangled at high speeds.
Come on, Number Cruncher, you will explain it better.
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Let me explain it for you in real world terms.
Driving up a very very very steep hill in madiera. you come across a stray dog that wanders into the middle of the road. YOu stop, kick the mangy cur out the way with the toe of your boot and you climb back in the car.
Handbrake on, 4000 revs, slip clutch let handbrake off and revs die and car stalls.
Handbrake on, 5000 revs, slip clutch, much smell from clutch, wheels spin on loose gravel, car starts to move, and you make progress having taken 10000 miles ouf the clutch and reduced the tyres to slicks.
Thats lack of flat useable torque across the rev range, something diesels provide in spades.
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>Handbrake on, 4000 revs, slip clutch let handbrake off and revs die and car stalls.
Handbrake on, 5000 revs, slip clutch, much smell from clutch, wheels spin on loose gravel, car starts to move, and you make progress having taken 10000 miles ouf the clutch and reduced the tyres to slicks.<
Are you the same AE who said buying an ex-rental car is a good idea? ;-)
To return to the subject, I'll have revs anytime thank you - Last time I drove a biggish turbo-diesel it had six gears, hence stump-pulling torque for about 3000rpm but kept running out of steam and had to be rowed up and down the gearbox all the time. What's the point?
I think the best answer is a 12-cylinder engine that revs like a turbine and always has a piston on the power stroke somewhere, hence can't be stalled. But then I would say that, wouldn't I?
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The very best I could do would be to recommend the articles;
S.S. Tresilian (Rolls Royce) "The Piston Engine", parts 1 to 7b, Automotive Design Engineering, 1965, (4)2 - (4)10
which are summarised in a chapter on comparative engine deign in chapter one of the 1986 book "Gasoline Engine Analysis" edited by J Fenton.
The chapter on comparative design takes the idea discussed by lotuxexige of similar engines, and takes it a bit further.
There's not much I can add to the question/answer, mainly because the concept of "better" is rather dependent upon personal taste and the proposed usage of the vehicle.
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Number Cruncher, your last paragraph says it all.
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The conditions described by AE are very rare in the tarmac surfaced world so it is no surprise the Clio would not deal with the hill start well.
Having drive a whole range of cars, my favourite has to be the LPT (in for example the Forester XT). The sheer wave of torque combined with a 7,000rpm redline means that instantaneous accelleration is available at relatively low rves, but without the need to change up too quickly. It is addictive if you havn't driven one in a while. It makes my Outback feel tame.
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Oh no darling, £1500 isn't that much for the first service .....
tinyurl.com/turbooooo
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The engines which rev higher to produce the power will produce the power with less torque remember power=torquexrpm.
Here are some good real world examples of three very different ways to achieve about the same power output.
Kawasaki ZX-10R
998cc in line four petrol
Max power: 188PS @ 12,500 RPM
Max torque: 113NM @ 8,700 RPM
MG ZT 190
2497cc V6 petrol
Max power: 190Ps @ 6500rpm
Max torque 245Nm @ 4000rpm
Audi A4 2.7 TDI
2698 cc V6 turbodiesel
Max power : 190 PS @ 4000 RPM
Max torque : 401 Nm from 1,450-3,250 RPM
Despite the same outputs, the bike engine would be painfully hard work in either car. The Audi engine would be pretty much unusable on the bike, and the MG's engine would probably be close to working well in any of them (gearing and packaging issues aside on the bike) ! :-)
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The area under the torque curve, is the best way of comparing. Unfortunately, I know of no-one who uses this.
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Weslake used to say that the total power under the curve was what mterred, not peak power. Sounds as though it make sense in the torque measurement as well.
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Which is better, i'm not sure i can answer that.... i prefer revs. I had a supercharged petrol that revved to 8k RPM. It was highly highly addictive but on the downside did 20mpg.
My daily needs require less running costs so i plumped for a pretty gutsy diesel producing just shy of 500nm chipped or 400nm or torque as standard.
For my daily drive i will go diesel everytime, a 123d being extremely satisfying to drive with a twin turbo setup.
However, if my miles went i would not hesitate to buy a new model ford focus RS.
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My Corsa coped just fine down Snowdonia with 4 people in the back. I drove up the road to Portmadog without any problems yes it was not fast but it was not slow either you just have to be very creative with the gear changes but that makes it fun but if you do it a lot it would soon become tiring. I enjoyed it because it was a one off I admit if I was doing it all the time I would have liked more power.
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Ford are phasing in their EcoBoost range of turbo-petrol engines.
Apologies if mentioned previously but more info in an HJ news item:
www.honestjohn.co.uk/news/item.htm?id=10187
I like the way Europe get engines from <1.4 up to 2.0, while USA already have a 3.5 V6 with 370PS. How about sticking one of those in an 'eco' Mondeo? :-)
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