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The arrival of the DMF has changed the way people drive Diesels, at one time it was all about letting it lug, most knowledgeable advice seems to suggest that doing so will lead to failure of that and the possibility of other problems.
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Good points both (Although I am a diesel fan so it pains me to hear the 'pathetic farmyard contraptions' being treated so harshly!
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I'm sorry but you can fiddle about with diesels all you want but the fact is a diesel engine makes the vehicle sound like it should be carrying a horse.
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I'm sorry but you can fiddle about with diesels all you want but the fact is a diesel engine makes the vehicle sound like it should be carrying a horse.
Yeah...and? In a world where Lady Gaga and Skrillex can get their noise pollution called 'music', is it too much to believe some might like the sound of diesels? ;-)
Edited by mss1tw on 14/10/2012 at 19:07
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I'm sorry but you can fiddle about with diesels all you want but the fact is a diesel engine makes the vehicle sound like it should be carrying a horse.
Utter nonsense. Would not want a modern petrol. No torque, costs a fortune in petrol. Our 1.6 diesel pulls like a traina nd does 50+ mpg average. Rattles a bit when cold but once on the move you don't hear it, quiet as some petrol once warm.
If you cannot make a sensible statement don't make one.
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I agree, I wouldnt want a 1.6 modern petrol either ;)
My petrol does 37mpg average and has no turbo, DMF or DPF to worry about, so less chance of a breakdown and mechanical failure
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Recent experience of driving two rental cars, both regular petrol engines mated to slushbox automatics leads me to the conclusion that modern petrol engines have less torque than they used to, that modern cars are heavier and economy has not improved.
Despite the rattle outside the car, I will have my slushbox turbo diesel all the time thank you. Petrol automatics need to be attached to engines of at least 3 litres to be any use.
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Petrol automatics need to be attached to engines of at least 3 litres to be any use.
Mine is. So there.
:P
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Petrol automatics need to be attached to engines of at least 3 litres to be any use.
Don't be silly, the modern small capacity petrol turbos would be perfect for automatic transmissions, the torque converter would disguise the lack of grunt off idle. But of course proper autos make CO2 figures worse in government tests so they are becoming rarer as time passes.
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I've noticed the revving tendency too. It's only really noticeable as a pedestrian around junctions.
I think there it might be a combination of the lack of torque below 1500RPM and gear ratios 1,2, 3 being badly matched to the real world. some bright spark at the EUSSR thought it would be a great idea to prescribe gear selections for the different parts of the drive cycle. Result: manufacturers put long legs on the first 3 gears. Consequence: drivers just hang onto lower gears for longer.
Diesels engines need fairly closely matched low gears because of the short rev range, but can tolerate a deep overdrive up high. I drove a Clio 1.5dci for a while and at 30mph it just wasn't happy in 4th, but 3rd felt too low. Very frustrating to drive.
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manufacturers put long legs on the first 3 gears.
Got to disagree there. Most modern cars have a first gear that is all but useless because they have to be able to tow up a certain gradient at a certain altitude to be given a max towing weight. Our Mondeo was embarasing, pull away in first, 15mph you would be snatching second as it hit the governor and the 1.0 petrol left you for dead as the engine was off boost when you got 2nd. My BMW diesel has great gear ratios but it is an exception. The wifes petrol Puma and Mini Cooper S had great ratios but neither were approved for towing.
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Well I've found that both the Renault Clio and the Golf V diesel (5 sp) had tall lower gears with noticeable 'gaps' between the ratios.
Our Mondeo was embarasing, pull away in first, 15mph you would be snatching second as it hit the governo
I don't know why you'd want to accelerate in first anyway, it's a clutch saver, not an accelerating gear. Most of the fuel goes into accelerating the engine, rather than the car.
I never go past 2000RPM in first otherwise the acceleration suffers.
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I've never calculated the mph / 1,000rpm in first in the V60, but in the other gears it's as follows:
2nd: 12mph / 1,000rpm
3rd: 17.5 / 1,000
4th: 25 / 1,000
5th: 32 / 1,000
6th: 39 / 1,000
IMO 3rd is perfectly matched to the torque curve & delivery, giving great overtaking punch past slower vehicles in the 30-50+mph speed range. The gap to 4th is just a smidge too wide for my taste, and I don't slot 6th unless doing 60+ on a motorway.
I was a little spoilt by the 6-speed box on my old Passat PD130, in which 3rd / 4th / 5th were quite closely stacked, with a nice short-throw action. Made 'making progress' a little like riding a 2-stroke bike, keeping it in the optimum rev band.
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I don't know why you'd want to accelerate in first anyway, it's a clutch saver, not an accelerating gear. Most of the fuel goes into accelerating the engine, rather than the car.
What a stupid comment. I accelerate in 1st gear because when pulling out of junctions it avoids being rammed by another car or worse still a 38 tonner. Pulling away in 2nd is not an option, you are probably doing 20mph before the turbo really starts pulling.
Suppose you slip the clutch and then complain the clutch is knackered.
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No, I advocate alwazys 1st to start, but short shifting into second. No clutch slipping required.
Depending on the gearing of the car and the engine characteristics, you can often accelerate quicker by short shifting into second than you can screaming away in first-even though there is less power available.
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I don't know why you'd want to accelerate in first anyway, it's a clutch saver, not an accelerating gear. Most of the fuel goes into accelerating the engine, rather than the car.
Rubbish, Over the years I've spent thousands of hours down the drag strip in/on a multitude of vehicles both two and four wheeled from standard, heavily modified to bespoke - maximising the use of first gear is generally the best way in terms of acceleration unless the vehicle has far too much power for the gearing.
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Utter nonsense. Would not want a modern petrol. No torque, costs a fortune in petrol. Our 1.6 diesel pulls like a traina nd does 50+ mpg average. Rattles a bit when cold but once on the move you don't hear it, quiet as some petrol once warm.
If you cannot make a sensible statement don't make one.
Remove the turbo from the equation and see how drivable your diesel is, modern small capacity turbo petrols share similar "wall of torque" driving characteristics to a turbo diesel without the smell, noise and limited rev range. Of course a petrol engine can still be a cracker without a turbo - unlike a diesel. Yes diesels are more economical whoopee do!
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Remove the turbo from the equation and see how drivable your diesel is,
Why would you do that? Unlike petrol engines, turboing a diesel is a no-brainer.
The characteristics of petrols do not lend themselves to turbocharging because:
1.) they are more free revving than diesels so turbo spool up time is more noticeable.
2.) the throttling of the intake air means that boost must be dumped on lift off-not so with a diesel
3.) detonation is a real issue with a turbo petrol (especially at low revs)-not with a diesel. Sure you can use fuel enrichment or spark retard-expensive waste of fuel. Diesels cool with excess air-which is free.
4.) turbocharging a diesel improves part 'throttle' efficiency-it certainly does not do this with a petrol.
modern small capacity turbo petrols share similar "wall of torque" driving characteristics to a turbo diesel without the smell, noise and limited rev range
Rot! The downside of a turbo is that the flow range is limited and hence the rev range of any engine they are fitted to is limited. Turbo petrols don't really have a much wider rev range than diesels. If the turbo is spooled by 1500RPM, it'll choke at ~4500RPM. You can rev beyond this-but you won't make any more power.
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Drive an ecoboost 1 litre ford petrol and tell me turboing a petrol is a bad idea! Limited range? What do you think variable vane turbos are for? And why do many diesels require sequential turbocharging? Don't talk daft, of course petrols have a wider rev range than diesels - you're the one talking rot. Every driven a petrol BMW 330? Grunt from tickover to the 6,500rpm redline - where it's still pulling like a train until it hits the limiter.
Perhaps diesel are more suited to turbo charging, that doesn't make petrols unsuited, but diesels without a turbo are hopeless.
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What do you think variable vane turbos are for?
Diesels. Only porsche uses variable vane turbos on gasoline engines, but then they have a proud history of persevering with bad ideas (3 litre 4 pot and air cooled boxer spring to mind).
. Every driven a petrol BMW 330? Grunt from tickover to the 6,500rpm redline
Yes, that's n/a! Put a turbo on it and the rev range becomes limited by the flow range of the compressor-which is the same as for a diesel.
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Being that we are discussing turbos I obviously meant the turbocharged BMW straight six perhaps it's the 335 not the 330, I have borrowed one - it's turbo-charged, it's petrol powered and it's a screamer - yet it pulls like a train from tickover - there's no fall off of power at the top end. It has sequential turbo charging much like many diesels to make boost low down and up top. The rev range of diesels is limited by the burn rate of diesel fuel - it physics captain - you can't argue with it. The equivalent BMW diesel does not have anything like the rev range trying to ague otherwise just makes you look daft.
The lack of variable vane turbos in the petrol world is to reduce costs, they are not common because manufacturers are bringing out adequately powerful engines without them, petrol engines don't require them to achieve a half decent rev range. Variable vane turbos work brilliantly with turbo petrol engines, after-market turboed Suzuki Hayabusas putting out 500 plus bhp are testament to that - and they still produce boost just off idle. As you see the capacity of petrol engines reduced in size to reduce emissions - expect to see more petrol powered cars with variable vane turbos.
I know you can't be wrong about anything engine related and you'll argue any point to death – but you are wrong. Live with it.
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it's petrol powered and it's a screamer - yet it pulls like a train from tickover - there's no fall off of power at the top end. It has sequential turbo charging
No it doesn't; the N54 uses parallel turbos. The replacement N55 engine reverted to a single turbo. A 3.0l engine in a small car is hardly a tough test for a turbo since there's plenty of naturally aspirated grunt for the weight if the car.
The lack of variable vane turbos in the petrol world is to reduce costs,
No it isn't. Chrysler used a variable geometry turbo on their 2.2 I4 back in 1989. They are not used because exhaust enthalpy is higher in petrols and they do not noticeably benefit from variable nozzle designs.
The problem remains that the compressor (NOT the turbine) has a limited flow range from surge to choke. Variable geometry turbines does not alter this fact, it merely allows one to use more of the available compressor map.
As far as sequential turbocharging goes, diesels can use them too!
As you see the capacity of petrol engines reduced in size to reduce emissions
Well obviously! But the 3.0 I6 BMW diesel uses less fuel than the 2.0 I4 BMW petrol. The 6 pot is a more powerful, more refined, and fuel efficient engine. The petrol engine is the entry level engine for those that can't afford the 3.0 diesel.
I don't see the obsession with high revving engines. My 49cc chainsaw can hit 11000 RPM. It doesn't make it a good engine. It's probably the most efficient device ever made for turning fuel into noise.
Edited by unthrottled on 17/10/2012 at 20:37
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I don't see the obsession with high revving engines. My 49cc chainsaw can hit 11000 RPM. It doesn't make it a good engine. It's probably the most efficient device ever made for turning fuel into noise.
Take a ride on Harley-Davidson some time.
At least the chainsaw has a valid purpose...
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So it's parallel charged - it still pulls from tickover to the redline (7K just looked it up) try that with a diesel.
This wasn't an argument about economy - it was about the relative merits of the engines, and petrols do have much wide power bands and are more refined.
The obsession with revs is revs make power - simple.
Petrol engines being the "entry level" engines tell you all you need to know bout diesels - in order to extract petrol-like levels of power and refinement from a diesel - much money needs to be spent and complexity added, so the asking price goes up accordingly.
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The obsession with revs is revs make power - simple.
HP = constant*torque*RPM.
So you can either use more revs or more torque to achieve your power goal. Petrols tend to use the former, diesels the latter. Doesn't really matter which except fot the fact that high revs always leads to a high parasitic loss-you can't tune that out of the equation.
much money needs to be spent and complexity added, so the asking price goes up accordingly.
Can't disagree with that. In a perfect world, I'd be running a carburettor fed OHV V8-refinement, power, low end grunt, fantastic accoustics all contained within a surprisingly small and cheap package.
But at £1.40/litre, fuel economy is of some concern to most motorists (although it is often overstated). Personally I think a decent size diesel is a better compromise than a petrol any day. And as far as complexity goes, hybrids are fsar more complex than diesels-and the battery system is totally useless in cold weather.
I'd rather walk than drive a pious.
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In fairness the Prius' key market is places like California. It's hugely popular in Los Angeles and even though the lifetime eco-credentials are questionable, it fits well with LAs aim to deal with it's smog problem.
Your love of diesel doesn't seem to be shared worldwide. It still hasn't really caught on in America and certain Governments own policies all but ban it entirely.
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It's because the Government's unhealthy addiction to fuel duty revenue has led reasonable, petrol driving people to get into diesels after many years and they don't know how to drive the pathetic farmyard contraptions.
It may have escaped your eagle eye Jamie but these "pathetic farmyard contraptions" have emerged victorious in the past seven Le Mans 24 hours-even when strangled with turbo intake restrictor plates and having to use DPF's - against the best-engineered petrol units available in the racing world today.
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It may have escaped your eagle eye Jamie but these "pathetic farmyard contraptions" have emerged victorious in the past seven Le Mans 24 hours-even when strangled with turbo intake restrictor plates and having to use DPF's - against the best-engineered petrol units available in the racing world today.
Because the regulations favour diesels for political reasons. In an open format of racing nobody in their right mind would use a diesel engine unless the rules are twisted enough to give them an unfair advantage - which is precisely the case in your example. Petrols are strangled too - but more so.
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