RE: Diesel myths debunked
Discussion
daemon said:
StottyZr said:
ADM06 said:
Indeed it did achieve the manufacturers figure, but it's not one of these new fangled quick diesels
Possibly heirin lies the issue, the fangled fast diesels have the ability to burn copious amounts of diesel. This is required to make lots of power, theres no way around it unfortunately. Although if you drive the new fangle diesels very gently and never use the power, they are extremely frugal. ADM06 said:
But the petrol one will get nearly 40mpg when driven gently and they have 450bhp conversions...
I think the mpg claims of petrol cars on PH is another myth. Fwiw my Boxster S, 3.2 litre, only 262 bhp, not a big car, would never see anything like 40mpg. It gets into the thirties on a cruise, but it's average is 28, as indeed was my old MX5 come to that.
heebeegeetee said:
I think the mpg claims of petrol cars on PH is another myth.
Fwiw my Boxster S, 3.2 litre, only 262 bhp, not a big car, would never see anything like 40mpg. It gets into the thirties on a cruise, but it's average is 28, as indeed was my old MX5 come to that.
Your Boxster isn't direct injection though whereas the x35i is.Fwiw my Boxster S, 3.2 litre, only 262 bhp, not a big car, would never see anything like 40mpg. It gets into the thirties on a cruise, but it's average is 28, as indeed was my old MX5 come to that.
Vladimir said:
The reason I use that example is because the 335i and 335d are so similar in output, size and both have a pair of blowers. The 335i is quicker to 60 and 100 yet it's not completely clear cut and demonstrates that torque IS important even though so called hardcore PHers try and spout a load of tosh about gearing to attempt to "prove" that it's irrelevant. Well clearly it isn't.
This exactly the kind of argument I would expect from someone who clearly doesn't understand the first thing about power and torque. Very obviously torque itself is important, your car wouldn't move at all without it. However peak engine torque is completely irrelevant. What IS important is the area under the usable torque range. An engine that develops a high peak torque over a very small vehicle speed range will typically not be as useful as one developing a lower torque over a much wider speed range given the limitations of of current transmissions (i.e. ones with discrete gear ratios). CVT boxes will be a game changer, if they can devlop ones capable of taking the required power reliably without horrendous losses.ADM06 said:
XitUp said:
ADM06 said:
Yes but not by myself. Try driving in 5th at 20mph, bet it'll stall after shaking you to a minor concussion.
What kind of 
drives in 5th@20? changes down if they don't have to? If you want to run a correctrol engined car then drive it economically when the circumstances negate having fun, ie 20/30 limit stretches. (diesel drivers not included, as they have no choice in the matter)
that does this is the kind who doesn't like labouring their engine too much and likes to have some engine braking.I dislike diesel cars. I dislike people who talk rubbish more.
Fox- said:
Your Boxster isn't direct injection though whereas the x35i is.
Ok, but I've been reading of large capacity engines doing 40mpg for quite a while on PH now, certainly long before current generations of engines.Yet even so, whenever I read a group of 'Our Cars' road tests in the back pages of a car mag, I can almost always tell which cars are petrol and which are diesel from the mpg figures alone. This 'blurring of the lines' between petrol and diesel mpgs doesn't seem to exist anywhere outside PH in my experience.
For instance an issue of EVO 2-3 months ago had a Fiat 500 petrol and Jag XF diesel on similar mpgs.
heebeegeetee said:
Ok, but I've been reading of large capacity engines doing 40mpg for quite a while on PH now, certainly long before current generations of engines.
The BMW sixes are pretty decent though. I can count on high 30's from Motorway trips in mine. This is easily enough for me to feel like I'm not pouring money into a hole in the ground and gives me a 500+ mile tank range.Fair enough it takes cruise at 70 to manage it but to be fair 70 is the speed limit on the Motorway anyway.
Mr2Mike said:
This exactly the kind of argument I would expect from someone who clearly doesn't understand the first thing about power and torque. Very obviously torque itself is important, your car wouldn't move at all without it. However peak engine torque is completely irrelevant. What IS important is the area under the usable torque range. An engine that develops a high peak torque over a very small vehicle speed range will typically not be as useful as one developing a lower torque over a much wider speed range given the limitations of of current transmissions (i.e. ones with discrete gear ratios). CVT boxes will be a game changer, if they can devlop ones capable of taking the required power reliably without horrendous losses.
Well the 35d unit produces a very flat torque curve so clearly it's you that doesn't understand.
And you can waffle on as much as you like but the 335d is quicker around Bruntingthorpe than the 335i despite an auto box, less power, more weight and slower raw acceleration figures. I wonder why?
Edited by Vladimir on Sunday 29th April 10:56
doogz said:
Your definition of the word "flat" is clearly different to everyone elses. 
yeah I was thinking that, although that's a big area of high figures under that curve.Someone on this thread has made the statement "Diesels don't pull under 2krpm", but what is that curve showing? Nigh on 300 torques at 1200 rpm?
heebeegeetee said:
yeah I was thinking that, although that's a big area of high figures under that curve.
Someone on this thread has made the statement "Diesels don't pull under 2krpm", but what is that curve showing? Nigh on 300 torques at 1200 rpm?
It's a twin turbo with sequential turbocharging designed specifically to address the 'diesels dont pull under 2krpm' problem, so that'll pull just fine under 2krpm.Someone on this thread has made the statement "Diesels don't pull under 2krpm", but what is that curve showing? Nigh on 300 torques at 1200 rpm?
The 2.0 4 cylinder, on the other hand, won't. Until it gets to 2krpm you can actually hold your foot flat to the floor without any real disceranable effect on acceleration. Once you hit 2krpm the performance is actually pretty strong, but it's lifeless under that point which can be quite frustrating pulling away etc.
Vladimir said:
Well the 35d unit produces a very flat torque curve so clearly it's you that doesn't understand.
And you can waffle on as much as you like but the 335d is quicker around Bruntingthorpe than the 335i despite an auto box, less power, more weight and slower raw acceleration figures. I wonder why?
How the hell is that flat?And you can waffle on as much as you like but the 335d is quicker around Bruntingthorpe than the 335i despite an auto box, less power, more weight and slower raw acceleration figures. I wonder why?
Edited by Vladimir on Sunday 29th April 10:56
Fox- said:
It's a twin turbo with sequential turbocharging designed specifically to address the 'diesels dont pull under 2krpm' problem, so that'll pull just fine under 2krpm.
The 2.0 4 cylinder, on the other hand, won't. Until it gets to 2krpm you can actually hold your foot flat to the floor without any real disceranable effect on acceleration. Once you hit 2krpm the performance is actually pretty strong, but it's lifeless under that point which can be quite frustrating pulling away etc.
But aren't we all agreed that four pots diesels are a bit cr4p anyway?The 2.0 4 cylinder, on the other hand, won't. Until it gets to 2krpm you can actually hold your foot flat to the floor without any real disceranable effect on acceleration. Once you hit 2krpm the performance is actually pretty strong, but it's lifeless under that point which can be quite frustrating pulling away etc.
My Astra, with what's considered a half decent 150bhp unit had a power band between 2501 and 2504 rpm. And that was it. It sounded dire too. The van's is better with two turbos but the noise still offends my ears (luckily it has loads of sound insulation and double glazing on most windows).
Fox- said:
The thing is I doubt anyone is referring to a 335d when they whinge about diesels. 90% of diesels do not have an engine like that found in the 335d.
And 90% of patrols don't have the petrol engine found in the 330. Engines are different, from the crap, to the sublime, in every category, using different fuels. The sooner people realize this, the less chance we will have yet more of these diesel vs petrol threads. Fox- said:
The 2.0 4 cylinder, on the other hand, won't. Until it gets to 2krpm you can actually hold your foot flat to the floor without any real disceranable effect on acceleration. Once you hit 2krpm the performance is actually pretty strong, but it's lifeless under that point which can be quite frustrating pulling away etc.
Are you referring specifically to the BMW 2.0, 'cos this emphatically is not our experience with our VAG 2.0 with dsg, which can spend much of it's life below 2k and still keep ahead of the traffic. doogz said:
That's also true, but then, there's a lot of comparisons between 4 pot petrols and 6 pot twin turbo diesels, which isn't exactly a fair comparison either.
No, but so very often it is owners of dull four pot petrols deriding BMW diesels. Vladimir said:
Mr2Mike said:
However peak engine torque is completely irrelevant. What IS important is the area under the usable torque range.
Well the 35d unit produces a very flat torque curve so clearly it's you that doesn't understand.A high flat torque graph is better than a low flat torque graph, but an engine with a low flat torque graph will be more drivable than one with high peaks and low troughs.
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