Diesel economy vs petrol in the twisties
#32
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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!
#34
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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
Cheers,
Grant
#35
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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.
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#37
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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...
"nothing, nothing, nothing, 204bhp, change gear"
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.
Last edited by Evolution Stu; 12 August 2014 at 03:14 PM.
#38
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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.
#39
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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
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
#40
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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
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
#41
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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.
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.
#42
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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.
#43
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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
Last edited by hodgy0_2; 12 August 2014 at 06:04 PM.
#44
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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.
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.
#45
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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.
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.
#48
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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.
#49
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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...
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...
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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...
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...
In 98% of situations its substantially bloody slower too sadly!
#54
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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.
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.
#55
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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.
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.
Last edited by john banks; 14 August 2014 at 10:37 AM.
#57
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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.
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.
Last edited by Evolution Stu; 14 August 2014 at 12:45 PM.
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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
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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.
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.
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
Last edited by john banks; 14 August 2014 at 11:52 AM.
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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?
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.
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.
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.
Last edited by Evolution Stu; 14 August 2014 at 12:49 PM.