C30 Engine : Specific Fuel Consumption curves

[Mark Hygate]

First post having joined the forum after becoming a double Volvo owner!

Found the forums after searching for anything about Fuel Consumption/Figures since picking up my new C30 2.0D 6-speed a couple of weeks ago; and have reviewed back several months on related threads – but what I was after didn’t seem to be there.

I know several of you have been curious/disappointed over the apparent fuel consumption from the 2.0D engine (any of the models indeed), but I wondered if any of you have seen, or have access to, the Specific Fuel Consumption curves for the car(s)? If not, then I will be trying Volvo themselves (unless of course a happy Volvo design engineer happens to pass by themselves and is willing to post!)

Way back when I was doing both the first and second degrees in Mechanical Engineering and Vehicle Technology we did all those nice experiments with simple engines. Normally aspirated petrol engines with those simple technologies we could all understand were mated to basic 4-speed boxes. We measured fuel flow at various engine speeds and learned all about compression ratios, valve timing, air mixes and even early turbo-chargers alongside the ever popular super-chargers!

My point, however, is that we worked out that nearly all engines (at that time) were geared so that the fuel consumption was minimised in 4th gear at about 56mph (~90kmh)– which, as the older amongst us will recall, was the constant speed at which all cars had their fuel consumption quoted. This isn’t done now and we have the Urban and Motorway figures simply averaged to a Combined. I note that many of you comment that you don’t seem to see those figures being achieved.

What I’m after therefore is an understanding of the ways in which we might drive if we wanted to minimise fuel usage. The Specific Fuel Consumption figures at different engine speeds would allow the drawing of the relevant curves so we could make our own choices; as indeed would recommended gears for various speeds (say 30/40/50/60/70 mph); or even ranges of engine speeds within which we should drive (say 1500-2000); to achieve the same result.

Engine technology has changed a lot over the years: it’s a diesel unit and the power delivery is different to those I experimented with; turbo-chargers are almost standard; EURO IV compliance puts a lot of additional filtering in the exhaust increasing back pressure; and we’re mated to a closer range 6-speed box in order to increase performance (which, of course, is not good for fuel consumption).

The 2.0D is, however, a very widely used unit I understand, originally from Mazda I believe. I’m sure its characteristics have been well mapped out. Does anyone know, therefore, if we have access to the relevant figures to enable this analysis?

I originally rather fancied the 1.6D, but had decided against the car as I couldn’t get it with a 6-speed box and a base-SE spec. Got seduced into the C30 2.0D/M R-Design Sport SE in Titanium Grey(!) by a nice salesman the other day purely by chance and now truly have a mid-life crisis, but sensible, car. It’s very good indeed, but I would like to save fuel occasionally – I just want to find out how…..

[Flanaia1]

Hi

I think we followed very similar academic paths, I did my degree in Mechanical Engineering but then went on to specialise in Process adn Chemical Engineering. I am sure you are aware of the EC Fuel consumption test and how they arrive at the data for the combined figure but I have posted it below for anyone else interested.

I work part time as a race driver / advanced driver instructor and work quite closely with some manufacturers so am able to access data on their marques.


FUEL CONSUMPTION TEST (Directive 80/1268/EEC as amended by 2004/3/EC)

The new test has been agreed internationally and provides results that are more representative of actual average on-road fuel consumption than previous tests. There are two parts: an urban and an extra-urban cycle. The test cycle is the same as that used to determine the official exhaust emission classification for the model of vehicle in question.

The cars tested have to be run-in and must have been driven for at least 1,800 miles (3,000 kilometres) before testing.

Urban cycle
The urban test cycle is carried out in a laboratory at an ambient temperature of 20°C to 30°C on a rolling road from a cold start, i.e. the engine has not run for several hours. The cycle consists of a series of accelerations, steady speeds, decelerations and idling. Maximum speed is 31 mph (50 km/h), average speed 12 mph (19 km/h) and the distance covered is 2.5 miles (4 km).

Extra-urban cycle
This cycle is conducted immediately following the urban cycle and consists of roughly half steady-speed driving and the remainder accelerations, decelerations, and some idling. Maximum speed is 75 mph (120 km/h), average speed is 39 mph (63 km/h) and the distance covered is 4.3 miles (7 km).

Combined Fuel Consumption Figure
The combined figure presented is for the urban and the extra-urban cycle together. It is therefore an average of the two parts of the test, weighted by the distances covered in each part.

Whilst i have no specific fuel consumption curves for the Volvo, I still think the design philosophy is to optimise the fuel consumption at 56 mph (average motorway speed) in the highest gear possible be that 5th or 6th depending on the box.

Will talk to my contacts at Ford and see if I can get some data for you also some of the tuners I deal with may already have the standard maps, in any case if you have bought the car it would be easy enough to read the fuelling maps and download them for analysis. The 2.0d works well with remapping as the temperature profiles on the map are so wide you can get better power and economy by optimising these and the fuelling, some tuners are better than others so if you go this route please beware. That said I have just got the 1.6d Drive V50 and that has an encrypted ECU so you can't remap. (or at least that is what they told me not physically checked it yet though)

Think I have an article on a c30 remap will try and find it and post it for you.

[Flanaia1]

Have a look at this link if you have not seen it might answer some of your questions

http://www.c30world.com/forums/showthread.php?p=67195

[Harvey1512]

At some point, when you have the figures put together, can we have the results published in English? My understanding of this, I translated this thread via Google Translate, is that Mark is trying to find out when is the most economical time/speed to change through each gear. The how's and where's are beyond me, degree in politics not Mech Eng, but the end results would be interesting.

Please do the engineering speak for those who understand it but for those who live at only a Noddy level please also do a really basic version. Thanks.

[Mark Hygate]

Thank you all for some interesting and speedy replies.

Flania,

The EU Directive is a useful summary thank you. Curiously the original Directive still used Constant 90kmh and 120kmh as figures. And a whole extra forum to peruse as well!

Harvey,

You're quite right. I opened in a technical vein quite deliberately to make sure I put down everything. However, in the end the whole question will boil down to a very simple answer in one respect.

At what speed (in 6th gear presumerably) should I drive at to achieve maximum fuel economy with this car?

This time last year, unsurprisingly as fuel prices shot up, I started to take things a little more seriously in my 1.9D V40 (last of the old style). My distance driving is mostly dual-carriageway/motorway and I found that dropping from ~66mph to about 59mph (staying in front of the trucks and still great for A-roads too) made a significant difference. Then increasing the tyre pressures to the equivalent of what the C30 now lists as 'ECO' made an extra 4mpg (equally significant) possible. Those days I almost got upset if the fuel usage started to drop back towards 50mpg - 56 was much nicer!

The new car (old one now more lonely on driveway as second car) is very different and likely to be much more fun. I'm not sure I'd be after the extra power resulting from the re-maps, but if that reduction in fuel usage is correct it may have to lot to recommend it!

[Harvey1512]

Mark, I don't begrudge any of the technical speak. You need to do all of the clever stuff to get to the answer. It also made me smile that the conversation between you and Flanaia1 was absolute, complete and utter gibberish to me. I look forward to keep checking this thread to see how you get on.

[bryand]

Originally Posted by Flanaia1

Have a look at this link if you have not seen it might answer some of your questions

http://www.c30world.com/forums/showthread.php?p=67195

Fame at last (that's my car)!
The engine is a Peugeot design; mine I think was manufactured in Dagenham and it has a Siemens ECU. I'm used to Bosch ECUs which are easier to talk to: I have yet to find a reliable diagnostic lead for data logging purposes (so any tips would be welcome).
To optimise fuel consumption I drive with the instantaneous MPG meter displayed, and bear in mind the time lag in producing useful data. The remap certainly showed up a dip in output ('flat spot') from 2000 - 3000 rpm which the new map filled in, with excellent results because this is a frequently-used rev range. The existence of the flat spot was also found by another C30 driver with the same remap, so maybe it's endemic to the 2.0D.
The attachment unpacks to a spreadsheet of one of the only logs I ever got off the C30. Make of it what you will.

[Mark Hygate]

Fame indeed bryand!

Yes, the engine certainly seems to be the 1,998cc diesel engine that resulted from the Phase 2 element of the Ford, Peugeot/Citroen & Mazda partnership - which is one of the reasons I'm sure this data should be available as it's a very widely used engine; especially in this every so slightly greener world of ours - Jeremy Clarkson's views notwithstanding

I'm genuinely curious about your point about the 2000-3000 rev range being frequently used, however. Bearing in mind that I'm thinking of fuel economy, if this was a petrol unit then I might agree with you, but diesel car engines normally operate at least 500 revs lower.

Certainly when warm, and unless accelerating quickly, I would probably argue that one could drive (assuming this is how the engine 'thinks' we should do so to preserve fuel) almost always keeing the revs between 1400-2000 (50-70mph in 6th).

What we do have under our bonnets is an engine well optimised for overtaking-acceleration given that the maxium torque is delivered at 2000 revs - but this design for diesel performance doesn't help our fuel economy!

[7050man]

Interesting thread guys. Particularly with the specific technical stuff from a design perpective.

My view is that 6th gear is not always the best to be in anyway especially on the motorway and driving with econmy in mind.

Best speed that I use on motorway with no uphill gradient is 50mph. As soon as start slight uphill run then 5th may be better under certain conditions (headwind, load carried, weight of fuel). Engine not being loaded and before turbo is really being used is at about this speed I find.

The instantaneous display will confirm, along with a sensitive ear, when you either need to change down.

All of the above is in my experience only relevant with the conditions I've decribed.In reality roads in the UK at least aren't flat and straight for that long, so other speeds and gears come in to play.

Bottom line is, be sensitive to throttle position, listen to how the engine loaded note changes, watch the fuel instant display and learn how this displayed figure varies under different road, throttle, load and engine sound conditions.

Other thing is, that if you really want to maintain a good low average, don't cruise around much over 60mph and stick to the speed limit.

[Flanaia1]

Originally Posted by bryand

Fame at last (that's my car)!
The engine is a Peugeot design; mine I think was manufactured in Dagenham and it has a Siemens ECU. I'm used to Bosch ECUs which are easier to talk to: I have yet to find a reliable diagnostic lead for data logging purposes (so any tips would be welcome).
To optimise fuel consumption I drive with the instantaneous MPG meter displayed, and bear in mind the time lag in producing useful data. The remap certainly showed up a dip in output ('flat spot') from 2000 - 3000 rpm which the new map filled in, with excellent results because this is a frequently-used rev range. The existence of the flat spot was also found by another C30 driver with the same remap, so maybe it's endemic to the 2.0D.
The attachment unpacks to a spreadsheet of one of the only logs I ever got off the C30. Make of it what you will.

Nice car and nice work with the remap will have a look at the spreadsheet later, thanks. Are you finding the siemens ecu easier to work with than the bosch in terms of mapping? I agree comms is more difficult to siemens units

best regards and thanks for posting