Diesel - Update, Interesting......

[GJD]

Thought I would have a nice leisurely drive into work this morning.....

Normal route, 20% A/B roads, 80% motorway

Never let revs wherever possible get above about 2000-2200rpm

No rocket acceleration or coasting down hills, put cruise on on motorway

Used 6th Gear at 70mph on motorway

Result?

46.6MPG compared to normal 36 - 37mpg on exactly the same route and traffic conditions

Didn't really take any longer, quite enjoyed the drive to be honest and it was not too much work involved in getting the gear changes right. Surprised myself at the 6th gear, no problem at 70mph

Maybe the car is just starting to bed in - just over 9,000 miles now from new

So, for once, I am extremely happy! Going to try this approach each drive now, would be cracking to get a tank average above 40mpg........

[Matus]

great!

[Scarlet Pimpernell]

Mine used to do this too....did 500 miles this week, just as you have....I'm a gentle driver...result = 39.7mpg! It's 2 months away from the big one (20k service), and feels very lethargic again.

Jusr pure and simple strange!

My "orange ring" is set to 2300rpm, and I drive to try and change gear at just over 2000rpm...

The 6th at 70 = thrumming again - the mirror becomes useless and unless it's down hill, I have to shift into 5th....not good again, and not too happy either!

I have never known such an inconsistently performing car - ever!

[VrmmVrmm]

I've been preaching this for ages, careful driving adjusting to the demands of the machine...however this is NOT an "I told you so" reply.

What I want to say is this, I had my worst mpg in a year last week. It was the week I coincidently had to have the car seviced for 30,000 klms...just oil and filters etc. The car is back in the groove once more...EXCELLENT...mpg.

So what am I saying?

Well I now believe that the air filter is a BIG player in the return of economy in the 220D. My mechanic who is ex Lexus dealership said the engine is so refined that he would always change the main air filter at every service. Thus ensuring the very best performance and mpg return every time you take the car on the road.

Happy Christmas and safe driving to all LOC members during the holiday.

[Lex Bhoy]

I've been preaching this for ages, careful driving adjusting to the demands of the machine...however this is NOT an "I told you so" reply.

What I want to say is this, I had my worst mpg in a year last week. It was the week I coincidently had to have the car seviced for 30,000 klms...just oil and filters etc. The car is back in the groove once more...EXCELLENT...mpg.

So what am I saying?

Well I now believe that the air filter is a BIG player in the return of economy in the 220D. My mechanic who is ex Lexus dealership said the engine is so refined that he would always change the main air filter at every service. Thus ensuring the very best performance and mpg return every time you take the car on the road.

Happy Christmas and safe driving to all LOC members during the holiday.

Going by the above quote then, would this mean that an induction kit could be the answer, as this will increase the amount of clean air entering the engine....

Not sure how this may effect the warranty, but could be a solution once out of warranty...

[GJD]

well, just back from a 200 mile trip, 90% motorway rest A roads (but in heavy stop / start traffic)

Stuck by what I said at outset of this post - never above about 2200rpm, 6th gear at just above 70mph cruising on motorway - very little if any vibrations on mine now at this speed, even up some pretty steep hills.

Got 43.8mpg over the 200 miles which is way better than I have ever got before. Filled up just over half way and tank average is now sitting at a never before seen 44.7mpg with estimated tank mileage of 500+ (ever before above 460)

Yes, you do have to concentrate to get the quick gear changes in, especially 1-2-3 and it is SO hard not to want to use all that power but its there in reserve just in case and the results are astounding!

[Matus]

Stuck by what I said at outset of this post - never above about 2200rpm, 6th gear at just above 70mph cruising on motorway - very little if any vibrations on mine now at this speed, even up some pretty steep hills.

that is interesting. I dont go under 75mph on 6th and even at this speed I don't think my engine likes it... But the consumption is OK...

[VrmmVrmm]

Stuck by what I said at outset of this post - never above about 2200rpm, 6th gear at just above 70mph cruising on motorway - very little if any vibrations on mine now at this speed, even up some pretty steep hills.

that is interesting. I dont go under 75mph on 6th and even at this speed I don't think my engine likes it... But the consumption is OK...

Hi Matus...If I'm in traffic which is constantly moving along at 50+ mph (80klms) I can use 6th no problem at all the engine pulls fine and only 1200 revs.

However if I need to speed up even only by an extra 5 mph I would have to change down immediatley.

As I drive to work each morning I go out on to a road where the traffic is nicely spaced (long line of vehicles, no overtaking) and doing 50+mph for about 12 miles. This I think is a contributory factor in how I am getting the fabulous economy. In my experience 6th can be used but not in circumstances where you'd be accelerating and stopping and starting etc. I always change to 6th for any downhill 50+mph driving the engine takes it as you would expect...no problem. Revs drop...fuel consumption drops...same speed even though slowish can be maintained. This car as you know can be tweaked by the driver to get the best out of it...I've always been of the opinion that that is what driving is. Even in Formula 1 the same principle applies ...here's a machine ...drive it...BUT optimally...or else you lose. I also believe that an auto diesel would be nice, however the driver would lose all the tweaks and fuel consumption would be higher more than likely. I like you and others believe in this car...its a challenge and thats part of the enjoyment for me.

[Scarlet Pimpernell]

It's a strange old machine....my views are very mixed.

Vrrmvrrm - that is why you can get good economy. Driven at 50mph the IS220d will hit and exceed 50mpg.

Some of the competition will exceed 60mpg under exactly those conditions...but that's not the point.

The main point here is that you can get what is regarded as reasonable economy (i.e. mid to high 40's), but at the expense of using any of those 177horses or 295lb's!

And I dare say that many petrol VVTi's will also give you 40's mpg under those conditions, and some of the newer ones will exceed 50mpg too. Bottom line is that there is very little point in going for this diesel for economy. It ain't gonna deliver! Especially when derv is now 5% more expensive than petrol to start with - so I agree that it's OK, but it really isn't anything to write home about.

I've been driving around in Vx and Pug desels for work, and I can tell you that "cained" they average 42-45mpg over all. That includes the 407 HDi's, all variants - they consistently better 40mpg no matter how hard you drive them.

The Lexus does struggle...and weight may be a part of this. Just stick the consumption into "Histogram" mode, drive at 70mph, in 6th, and leave it. Watch the bar tumble at even the slightest incline. Do the same in 5th, and it still isn't that good. Do the same at 50 in 5th however, and see how it hardly moves except for steep hills. The car is heavy, and for that it will never be economical.

It's all fine and dandy having all the extra's, but they do add KG's, and the extra safety in the car will also add weight!

PS - flip side - if it is weight, then why is the 250Auto so good?

[Matus]

Stuck by what I said at outset of this post - never above about 2200rpm, 6th gear at just above 70mph cruising on motorway - very little if any vibrations on mine now at this speed, even up some pretty steep hills.

that is interesting. I dont go under 75mph on 6th and even at this speed I don't think my engine likes it... But the consumption is OK...

Hi Matus...If I'm in traffic which is constantly moving along at 50+ mph (80klms) I can use 6th no problem at all the engine pulls fine and only 1200 revs.

However if I need to speed up even only by an extra 5 mph I would have to change down immediatley.

I tried today and no...

OK, the engine is able to go on 1200rpm od 6th but it "rumbles" - very deep sound, like hell. I almost could feel all the screws to unloose. I don't think it does good to the engine. Even the owners manual says that 6th can be used over 120kph, I think. I really don't want to save 0,5l of diesel per 100km and have the engine trashed at 50.000kms - I am not saying that this is happening to your engine, but I am sure I can not drive at 1200rpm on 6th.

Such a low revs I use only on 1-2-3 and 4th from 1500rpm, 5th from 1600rpm and 6th from 1700rpm.

[FinLex]

I tried today and no...

OK, the engine is able to go on 1200rpm od 6th but it "rumbles" - very deep sound, like hell. I almost could feel all the screws to unloose. I don't think it does good to the engine. Even the owners manual says that 6th can be used over 120kph, I think. I really don't want to save 0,5l of diesel per 100km and have the engine trashed at 50.000kms - I am not saying that this is happening to your engine, but I am sure I can not drive at 1200rpm on 6th.

Such a low revs I use only on 1-2-3 and 4th from 1500rpm, 5th from 1600rpm and 6th from 1700rpm.

These are the rev limits for me, too. Well, the Sport is okay on 4th from about 1400 and fifth will work from 1500. This is due to the shorter overall gearing. The funny thing is that on 6th gear my Sport requires at least 1700 RPM, so no difference there between normal and Sport.

[markoose]

I've been reading all of the posts about idling speeds and fuel economy and have some comments. In my opinion reduced fuel economy compared to some

competitors' slightly older diesel engines is because of the emissions reducing features of the Toyota 2.2 diesel engine.

In a diesel engine we burn the fuel (hydrocarbon) with air (nitrogen and oxygen) and ideally this would produce only nitrogen, carbon dioxide and water.

However, the engine designers have to perform a complicated balancing act in order to keep harmful emissions caused by less than ideal combustion in check.

These harmful emissions are carbon monoxide, carbon (soot) and NOx (oxides of nitrogen). Funnily enough CO2 is a product of perfect combustion yet is still

undesirable due to its possible contribution to global warming. Although diesels produce less CO2 than petrols I believe that you get a comparable amount of

CO2 produced from a tank of diesel as you do from a tank of petrol, however the diesel goes further on a tank and hence releases less per kilometre.

When the combustion process occurs at a high temperature the fuel and air are able to react together more efficiently and this means that we move closer to

out ideal of complete combustion. Because the fuel is more completely burnt it means we have released more of the available chemical energy in the fuel and

hence reduced the amount of unburnt fuel emitted in the exhaust gas. We also reduce the amount of soot and carbon monoxide that are produced when incomplete

combustion occurs i.e. if there is not enough air (and hence oxygen) to react with the carbon part of the hydrocarbon we get just carbon © and carbon

monoxide (CO) rather than CO2. So the engine designers need to keep the combustion temperature up.

A problem is that diesels have a lean air-fuel ratio by nature and so this means there is a surplus of air (oxygen and nitrogen) with no fuel (hydrogen or

carbon) to bond to and at high temperatures the nitrogen and oxygen bonds in complex ways to form NOx gases, these react with sunlight to form low-level

ozone (photochemical smog) and cause allergic reactions and lung damage. So we actually need to make sure that the combustion process is not too low OR too

high. One way of managing NOx production is to allow the ECU to introduce an inert gas to the mix, which will therefore reduce the amount of air in the

mixture (so there is less oxygen to react with the nitrogen). This also happens to lower the maximum temperature that the mixture can naturally reach during

combustion and increase the specific heat capacity of the mixture (so it takes a greater amount of heat energy to raise the temperature of the mix by a given

amount). This inert gas can be the exhaust gas and the system is called exhaust gas recirculation. However, diesel engines still produce lots of NOx

compared to a petrol engine and so Toyota uses a fifth fuel injector to mix a small amount of diesel as a reductant with the NOx-rich exhaust gas. The

oxygen in the NOx is more strongly attracted to the hydrogen and carbon in the diesel and so forms water, nitrogen and carbon dioxide.

So the engine is using extra fuel to reduce the NOx into less harmful gases, perhaps contributing to the relatively poor fuel economy when compared to older

more polluting diesels. Also it's possible that in order to maintain a temperature sufficient to prevent excessive incomplete combustion the ECU is naively

programmed to automatically crank the idle point up if the engine temperature is low and the climate control is switched on - but does not check to see if

the compressor is running or not.

The engine also has a particulate filter, which cannot "self-clean" or "regenerate" unless it is at a high enough temperature. If you are in stop-start

conditions and/or are driving below about 40mph the ECU will eventually intervene and try to raise the exhaust temperature by changing the fuel injection

parameters. I'd speculate that this might require more fuel to be used and in turn may generate more NOx and therefore require more fuel to be used as a

reductant by the fifth injector.

So in conclusion you've got a very clean car but the trade-off is slightly worse fuel economy.

[Scarlet Pimpernell]

....phew....

just finished a bag of crisps and a mug of tea whilst reading that lot. It's excellent...and I could just about follow it (shows the light is on and someones at home!!).

Any way, all of this seems to mean that if you want simple, economical transport, get a decent modern petrol engine, or is the situation worse for, say, a BMW320i 170bhp, which can take you reasonably quickly over 50 miles on one gallon????

Are these diesels cleaner than a modern petrol engine of euivalent performance and size (e.g. BMW320i/170)??

PS - I use the new 170bhp 2.0l BMW engine as a cracking example of how a manufacturer has made a very decent engine...if anyone hasn't driven one - go try it. It loves to be driven, and may not have the torque in the midrange, but in auto form it is I reckon the perfect engine! Just a shame it a rich mans Mondeo!

[Tango]

PS - I use the new 170bhp 2.0l BMW engine as a cracking example of how a manufacturer has made a very decent engine...if anyone hasn't driven one - go try it. It loves to be driven, and may not have the torque in the midrange, but in auto form it is I reckon the perfect engine! Just a shame it a rich mans Mondeo!

I had one such BMW auto estate from Hertz for a week in Northern Italy just before Christmas. It went well enough once I worked out the rather tiresome start up procedure, but no comparison to my IS250 Se-L on any front, apart from maybe mpg.

[Matus]

Are these diesels cleaner than a modern petrol engine of euivalent performance and size (e.g. BMW320i/170)??

no.

And I believe, that once when they will be, the consumption will be equal.

[Roonaldo]

Have the people with poor fuel economy checked tyre pressures? Just a thought, but this makes a significant difference.

I have averaged 40.5mpg over the last 21000 miles, and the quoted combined cycle for the Sport is 37.6mpg I think. I always make sure the tyres are at 35psi front and 38psi rears (this is for 18" wheels), I use cruise control wherever possible on motorways aswell. Mines an 06 car that hasn't had 5th injector replaced or ECU upgrades etc, but I have excellent fuel economy.

After the 20000 mile service, the fuel economy dropped to 36/37mpg roughly, but after checking the tyres I discovered that the pressures were 5psi below what they should be, maybe the dealer adjusted them incorrectly. After putting them back up to normal, the economy went back up to normal.

[javadude]

but after checking the tyres I discovered that the pressures were 5psi below what they should be, maybe the dealer adjusted them incorrectly.

The pressure in the tyres will drop when the weather gets colder too.

[Pagnobito]

My computer says 35.4mpg average overall...

Had 30K service yesterday, and they updated the ECU again (it was done at 20K too). I didn't ask for it, nor do I have any reason to believe that the car needed it, but they did it anyway. Didn't need to add any oil between services. It feels slightly smoother after the service, can't say there is any power difference.

I can get the MPG higher on the tank setting - 40+ but I like acceleration and that is not good for mpg!

[Matus]

I did some measuring* on the highway and:

1. at 130km/h (81mph) is the consumption 7l (40,35mpg)

2. going between 160 and 180 (100-112mph) - unfortunately due to the traffic it is not possible to keep constant speed, is the consuption 8,5l (33,23mpg)

So it looks like that the ratio of increasing consumption is lower than the ratio of increasing speed, which is interesting, because normally it is opposite. I think this causes the gearing. It is clear that the 6th is for high speed driving.

If it was legal here, I would be travelling at 180kmh all the time on the highway...

*measured with half tank, 4 people in the car, 205/55/16 winter tires

[Scarlet Pimpernell]

Similar to what I have found in the past too, but that assumes a flattish road. The moment you get any sort of gradient in 6th gear, the consumption really drops. That's when it hurts.

Mine currently is averaging very badly - 22mpg in town. I haven't been a long run for 3 weeks in it, but will be tomorrow, so that'll give me a better idea, and I'll know whether to book it in earlier than the 20k service....

[GJD]

Update a few weeks on.......

I have been religiously recording my MPG for the last couple of months now and driving as I now believe the car is intended to be driven. Yes, when needed I will use the power available but generally I now drive sensibily and on motorways stick to about 78 with cruise on in 6th (although Garmin Satnav indicates I'm actually doing 72mph!). I have now been driving in the 'new' style for so long I don't even have to think about it.

Anyway, end result is that I am now getting 40+mpg each and every tank of fuel - only 1 blip and this was when I was stuck on the M5 for 2 hours in very slow traffic (<10mph)

When I started my recording process, the running MPG was 36.38 - now it is 39.06 and continues to rise each and every tank.

My driving is 70% motorway, 30% A / B roads and I'm finding now that even on the A/B roads, I'm getting high 30's mpg. Car has now done 15,000 and is 5 months old.

So, in short, I'm getting there and am now far more happy with the car.

Only other thing to report is was cleaning it last weekend and noticed bubbles on 2 of the alloys - will try and get them swapped out under warranty at next service.