chocolate_o_brian

iTrader: (22)

Ahhh, zhis is true. Ze German build quality hass me hooked, ya?

Zhis von is ze Berlin-Mashup Wagen. See vhat I did there?

ScoobyJawa

Stick my F31 xDrive 330d in sport mode and sport shift on way to the office down some great roads and plenty of overtaking and hooning, only drops to 34-35mpg for the trip rather than the 42-45 just normally. Plus will get 55mpg on a run! Think that's pretty good really!

ditchmyster

iTrader: (7)

No, no, no, you've all got it wrong.

What cost £4k does 0-60 in 4.8, returns 28mpg day to day does 36mpg on a run, has AWD, can get a washing machine in the back and is trouble free.

Recent browsing of Autotrader indicates it's also depreciation free over 3yrs.

RS Grant

My 123d with DPF-removal and map made 275bhp and 380lbft... it was comically quick through the gears, I sometimes think I should have kept it and invested in a Quaife LSD actually.


Cheers,
Grant

Carnut

How has technology moved on with diesels, the engine used to be made out of cast iron and weigh a ton, there is going to be a limit to how much fuel can be saved, after all, you can't run a combustion engine on thin air and weight saving is going to be a new focus IMO.

ScoobyJawa

*cough*

http://www.dailymail.co.uk/sciencete...id-117mpg.html

Evolution Stu

iTrader: (2)

The main improvement in modern years has been the ability to inject more fuel and extend rev range cleanly.
For many years we were limited to how much we could inject due to the inherent burn speed limitations of derv so as revs climbed and each cylinder cycle got faster, the amount we could burn in the required time got less and less, which is why they traditionally had such a narrow power band with a big peak, or as Clarkson once put it while driving a jag round the nurburgring... LOL.

Now we are injecting multiple events at 18000psi which allows us to inject the slow burning fuel in a much shorter time frame than previously allowed and in a derv engine... fuel = power.

The multiple injection event technology means we no longer have to listen to the clatter that injecting 30+mg per stroke used to cause, and that is why diesels are getting quieter.

Carnut

I had a feeling that someone would come back to me saying that, although its not a combustion engine, its a separate hydraulic motor.

But what about the BMW i8 and i3, I think the i8 gets about 135mpg.

I wonder if these cars will see the end of diesels leaving a few petrol performance cars for enthusiasts, either way, there's a new era of car on the way.

jaygsi

iTrader: (46)

Not the best reasons


Pro's for petrol

1/ Diesels give out sut which is dangerous to your health

2/ Your car sounds like a tractor ,

3/ Most have less power than petrol versions

4/ Price of desiel is more than petrol

5/ They cost more to buy new

6/ They pour smoke out when you put your foot down

Carnut

I think Stu might be along soon to make you eat your words.

hodgy0_2

thanks very interesting - and presumably explains why modern diesel fuel pumps are such big ticket items

Evolution Stu

iTrader: (2)

Yes, even older Beemers like mine run 16000psi and with a remap will happily inject at 17000psi all day long with no problem. Its a hyperdermic pressure and pretty damn dangerous system to work on.

The burn time problem has always been a big one and it was compounded by Euro emissions requiring us to reduce Nox and install DPF's as both these requirements need the same thing... retarded SOI (Or EOI as some call it). Retarding SOI means we now have even less window to inject fuel efficiently so the only way we could get the same fuel into the cylinder in a smaller timeframe was to inject it in at a higher pressure.

Multi injection events have helped too as we now start the process with up to 4 small pilot injections and follow it with a main. This helps timeframe and also reduces knock as we start the process with a "smaller bang" so to speak. All only possible due to massive injection pressure.

hodgy0_2

I have been told that the pressures are so high and the particles so small it would push the diesel through your hand if you had it in front of the nozzle

Matteeboy

I'm a bit sick of hearing yet more diesel clatter everywhere; I smile when I hear even a lowly petrol engine.

I think they've had their heyday with BMWs sixes (and Audis too); development seems to be slowing, petrols and hybrids are where it's at.

DPFs, DMFs, EGR valves; all artificially extracting pollutants at the expense of reliability.

I will always be fond of the grunty BM and Audi units but I don't plan to get another diesel car.

john banks

Me neither, would swap for a massive petrol engine in the same car but they are much more expensive.

ditchmyster

iTrader: (7)

Interesting you guys that have had them and were / are singing their praises not so long ago wouldn't buy them again.

Petrol ftw.

banny sti

iTrader: (68)

The torque novelty wears off pretty quickly let me tell you Ditchy, so glad I should have my type r back this week!

jameswrx

iTrader: (4)

Indeed.

I worked for 7 months buying cars in the motor trade and drove dozens of modern diesels. Always saw myself in a nice 530d or similar but after driving diesels a lot, the novelty does wear off. What I find with them is they feel fast when you least expect it, ie when you're pottering along and squirt it when you'd be labouring a petrol. But when you're wanting to drive fast they suddenly feel slow.

thenewgalaxy

Bit of diesel hate going on above, I'm surprised. I went straight from a V6 petrol to a four cylinder diesel.

I miss the sound and the top end poke but for me the diesel is the superior cruiser on the motorway and a better daily driver.

25mpg vs 55mpg also makes a huge difference...

CharlySkunkWeed

iTrader: (7)

Same here. Though I do very few miles . Only thing I miss is the sound , hate diesel noise as it is , but cant beat the sound of a scooby. I was paying for Super Unleaded anyway so diesel is nearly the same price.

jameswrx

iTrader: (4)

I actually thought my mate's 525d sounded pretty good, he has had dpf & cat delete and a remap though.

Evolution Stu

iTrader: (2)

Totally agree, and my other car is a V8 M5... never use it anymore, it just doesn't offer anything better than the Derv and costs comedy money to fuel.
In 98% of situations its substantially bloody slower too sadly!

stevebt

iTrader: (8)

My Impreza has more torque than my BMW yet I never get bored of that

Matteeboy

People get rather confused with torque; my 335d had more than the old AM vanquish but certainly wasn't as quick. It's all about gearing with bhp still being the most important factor.

A quick diesel IS a fast car; my 335d embarrassed several much "faster" cars both off the line and on the move but they won't do anything magical like some people seem to think.

Since getting a turbo petrol which happens to hit peak torque at a mere 1300rpm then making a lot of lovely noises (mine even has a form of dump valve!) up to over 7k rpm with great throttle response (a huge weakness of diesels), while being astonishingly low on emissions and a higher EU rating (6) than any diesel AND getting mid 30s mpg on a long run, diesel feels a bit pointless.

Our van is diesel; works fine, pulls okay (180bhp) but makes me want to scratch my own ear drums out and the emissions stuff will eventually throw a hissy fit.

john banks

Mid 30s on a long run for that weight of car though just plays to the strength of a diesel as unless you are doing 90mph it isn't very good compared to recent diesels even of similar output. There are EU 6 diesels now, Adblue injection in the exhaust typically, I bought the last of the 3.0 TDI that didn't have it and is EU 5.

I'm not a fanboy, but it isn't all one way or the other. For me, the noise was much better than expected, as was the cruise economy, the twisties economy is worse, but no less enjoyable than equivalent petrol.

banny sti

iTrader: (68)

Long run fuel economy is the strength of a diesel, my golf managed a 400 mile round trip at an average of 63mpg.

Evolution Stu

iTrader: (2)

The problem is, from EU4 through 5 and 6 the fuel economy tends to get poorer and the throttle response worse. The manufacturers really are fighting a losing battle with economy and throttle response Vs emissions to get the things through type approval which is why Adblue is quite likely to become the norm for road cars instead of just HGV's as its a bit more effective than mechanical emissions control and looks better to the consumer as it can bring back economy gains.



That huge trough there (the two darkest shades of blue), is the injection timing retard purely to get a 2008 Turbodiesel through type approval.

Pretty huge gains are possible in fuel economy and responce if you spend some time remapping the euro 5 and 6 systems to swing the compromise back into your own favour.

dpb

From what I can see on the road diesels ( excepting trucks ) will sooner or later sit in the same category as petrol sports cars , just too costly all round for the average consumer

john banks

Presumably the cyan area of advanced injection timing at high load at idle is never hit, lots of petrol ECUs have funny values up there. The rest of the dark blue trough looks like an extension downwards of the engine speed related timing differences with a minor influence from load, but clearly that isn't what the engine likes for torque and economy from your findings. Are you rising the low water mark on the whole saggy part of the map then?

Do you think you could design a good injection timing map with a 2x2 table with interpolation just having the four corners? From the physics I understand of diesel injection, apart from any VE humps which the load measurement should account for I'd think so with the main influence being RPM.

This is good marketing for an ECU remap vs a tuning box too

Evolution Stu

iTrader: (2)

Indeed, maybe under heavy laboring at WOT in a manual gearbox and wrong gear but generally yes, its an un-accessed area.

Pretty much yes. If you compare the cal tables of pre Euro4 vehicles with the same engine you can see the downward trend with the start of pre and main injection. Once NOx became the big issue for Euro4 and above the only way to reduce that is to retard the injection timing and make the burn less efficient as NOx production is greatest at peak combustion temperature and is not so dependant on the amount burnt, but more the temperature at which its burnt (Specifically, its produced as we exceed 2000kelvin). and of course increase the injection of Exhaust gas (EGR) but the latter causes other problems such as excess particulate matter with load since it also is lowering combustion temperatures and creating more particulate emission.

Of course EGR also lowers power output per stroke by reducing the available oxygen in the cylinder which is why generally its disabled under heavy load conditions.



Workable, yes. Good, no. There are just too many variants for us to go back to what would almost be a mechanical injection timing pump. High power TD engines now inject upwards of 90Mg per stroke and idle at only 7mg so we have a huge variation in time to ignition. If you take a modern BMW SOI map, it looks like this:



And if you look at it carefully you will actually be able to see the EuroCrats retard area where the car will be cruising at 50, 60, 70mph.
Look for areas between 1000 and 2500rpm and under 40mg/ps (average brisk overtake inj qty on this car).
Then look at the advance step when the engines outside its type approval speeds (3000rpm)

There are 12 of those SOI maps to control main injection and the same again for Pre and post injection along with all the other variables contained in the EDC16, some 120'000 switch points and calibration tables. We only really need to look at around 80 of them for better performance / economy though thankfully.