[Phil №❶]

The mechanical speedo needle moves by having a magnet spinning at the same speed as the cable. These many rotations allow the magnet to grab the needle and rotate it as it passes but not strong enough to cause a 1:1 rotation. It is effectively a short magnetic pulse. Before the needle drops back to zero the magnet has rotated full circle & grabs the needle again & the process repeats continuously.  The faster the speed, the more pulses & further the needle rotates. There are dampers built in to smooth the pulses & in so doing, errors in the readings are also introduced. It was the best mechanical solution to speed measurement available in older cars. Very much outdated by modern electronic systems.

The only sure way to know which system is accurate is to use distance / time calculations.

Remember that most GPS systems use windows CE & quite slow processors internally. 

[neoto]

Let me correct you a little, 847563 - rotating magnet causes the eddy currents in the metal bell that surrounds the magnet. These currents interact with the magnet and cause a torque on the needle. However, there is an additional clock spring to counteract this torque which makes the needle reflection proportional to magnet rotational speed and hence car speed.

[Phil №❶]

I think that was what I was clumsily trying to say, thanks & glad to be corrected. My point was that with all that mechanical stuff with counteracting springs etc. The speedo is prone to errors either across the entire range or during a certain range of speed. I remember a motor magazine including speedo accuracy in their data for tested cars. Some were really close & others were a joke, usually at the higher speeds. 

[Ultralights]

Finally returned to Sydney, last 800km run back down the coast,   calculated fuel use was 4.5L/100km.   pretty happy,  especially when i got 5.1 on the trip up with no traffic at night and sitting on the posted limit all the way.
the main difference was the traffic, rolling along at 80 kph average, 100 in 110 zones, and 90 in 100 zones etc,  so didnt use cruise control, and everyone putting along at 80 when behind a caravan on the single sections, 

so best economy i have found is in light traffic rolling along at 80kph in top gear. 

[Dazzler]

Excellent 

[mjt57]

Speaking of diesel economy, in another thread they were discussing the various functions of the trip computer, what happens when you reset the data and so on.

The other night, on the way home from work I remembered the comments and decided to reset ave spd, DTE and fuel eco readings.

The trip home, a 10 km one with a mixture of 60, 80 and 100 limits, saw the reading go from about 5.8 to 6.1 or something like that. It varied a bit during the drive home.

The original figure was averaging since I bought the car and through 3 fills, over about 2,100 km.

Tonight, coming into work I checked it. It's currently reading 7.1l/100 km.

I was reading the brochure today (it's handy to refer back to). The manufacturer claims around 4.5l/100 km, which I've never come anywhere near achieving (best was about 5.7).

I'm putting this down to me perhaps driving it a bit hard and that the engine is still a bit tight.

As for driving it "hard" I tend to rev it out to around 4k before changing up when entering main roads, so I can get up to traffic speeds quicker and safer. But around town it's lucky to get over 2-3k rpm. And I tend to keep engine revs between 1,500-2000 rpm when not accelerating.

eg: at 60 kays I'll be in 4th, 80kays change to 5th and 6th anything above 100 km/h.

How does this sound to you guys? Remember, this is my first turbo diesel. Previous vehicles were 5.7l V8 SS Commodores (6 sp manuals) and a 3.0l V6 Mazda Tribute auto.

[Dazzler]

Don't take too much notice of your average over such a short distance .. but it does sound to me like you are driving/revving a bit harder than the average CRDi owner on this site (Understandable when you see what you were driving before)

[Phil №❶]

I'm new to diesels too. Our cars are autos and red line at about 4700 rpm on the tacho. Some people will disagree with me here, but apart from an emergency, there is no need to spin your engine up to 85% of its capacity. That works well with 5.7 V8's (sounds good too), but the power and torque happens at lower revs in a diesel and therefore requires a change in driving style. As your car is a manual, you have the ultimate say in when you change gears, for better economy, I wouldn't go past 3 - 3.5 k. The turbo kicks in @ 1750 RPM @ that is the beginning of a nice little rev range of power & economy.

As far as resetting the trip data, I always reset all info at the servo. I set the display to avg consumption & leave it there. After a few k's & the figures settle down to something meaningful, I get rapid info on my driving style for about the next 50 k's. Then the display begins to stabilize as the averaging becomes based on increased km's. Current tank is 5.5 after 100 k's, in an auto. 

[Asterix]

MJT

Do you really rev it up to 4000 rpm..?
Than I understand why you don't get a better fuel economy.

Try to shift gear at 2600-2800 rpm, or even lower, then I promise you, you will get better economy.

I normally shift at about 2200-2500 rpm, depending on how fast I need to accelerate to keep up with the traffic. It even works with 4 people in the car without any struggle.

My average is 5,5 LPH when I drive to work with 4 persons in the car, 2x25 km every day. When i put in some longer trips, I can get 5,2 LPH 

[mjt57]

MJT

Do you really rev it up to 4000 rpm..?

As I wrote above, this is usually when I enter main roads such as where the limit's about 70-80km/h.

Around town which is what most of my driving is, I tend to keep it below 3,000rpm.

Thing is, even on long trips with the car steady at 100-110 km/h in 6th I'm still getting around high fives on the economy.

Going to Melbourne tomorrow. When I fill up I'll reset everything and see how it goes.

[Lakes]

hard to say, but my trip pc is on 5.1 L / 100k i have 16,500k up i filled up tonight after doing 1,120k since last fill up i put 57L in so it's close to what trip PC average says. that was a mixture coastal roads mountains & sydney commuting i just drive normal not trying to get economy realy. but am used to driving diesels, but this is only the second diesel i've owned personally in my life. i love this 6 speed much smoother Torque than my first one. but they are not a performance car still i enjoy driving it.

[mjt57]

Just filled the car (4th fill). Put 44.26l into it (shortly after the fuel light came on). Filled it, as per usual, to the first click. However, did it at a different servo to all the other times. In the first 3 fills it was filled to the first click and took nigh on 43l exactly.

Anyway, used 44l in around 650km for 6.4l/100km.

This included one 350km round trip to Melbourne which also included Melbourne metro driving and local driving.

I'm doing my best to drive it conservatively to see if I can hit the (seemingly) mythical sub 5l/100km economy. But to no avail, it seems.

According to Acar, my Android phone car app, I'm pretty well averaging 6.2-6.4l/100 km.

Now, either I'm flogging it compared to you guys, which then I have to assume that you all drive your cars like pussies given how I'm driving mine, or perhaps someone is exaggerating their vehicles' economy or that I have something wrong with mine.

But I am stumped if I can figure out how to get it down to 4.5l/100km which is Hyundai's advertised fuel consumption figure.

The difference between advertised and attained, for me is about $20 a tank based on diesel being $1.45 a litre.

Or around 255km a tank.

There's a scheduled service at 7,500km. It's not a "compulsory" service by Hyundai, but I might get it done, depending on what they do and what it costs. I'll get them to check the economy. Dunno what I can do about it, as it's one performance factor that's highly variable if they say "sorry, your problem...."

[Ultralights]

If you haven't done the 7500km service yet, the engine still hasn't been run in, it's only after about 10,000 to 15,000 km you will see the economy improve.  Together the 4.5 on the highway, I do the limit exactly or just sit being a car or truck that's close to the speed I'm comfortable at, no rush in a 800km trip.   I have an Ultraguage fitted so try to keep the boost below about 5psi, this seams to help a lot, but I also drive to keep the revs low,  in traffic change into second as soon as I can, at about 1800 rpm, and change around 2000rpm if in no hurry, but even doing this, I'm still keeping with the traffic flow. And get it into 6th or top gear from about 60kph, and let the torque do the work.  Also leave it in gear when coasting to lights, it turns off the fuel flow while coasting.

On long highway runs, on hilly roads, use gravity going down hills to accelerate to say about 110, and when you get to a hill, keep the throttle steady and let the car slow to say 80 when you get to the top, and repeat as you go up and down.   I did notice the cruise control resulted in worse economy, but the return trip I did had a lot more traffic, hence I used 5.1 going up with no traffic and on cruise, and 4.5 returning in highway traffic and no cruise control.   Oh and not carrying around tonnes of crap in your car helps as well.  After 6 months ownership, I still only have a few keys, coins and the iPod in the car,   And a bit of dirt dust etc,  weight =fuel burn.

[Dazzler]

MTJ as Ultralights says it should improve with a bit of mileage ..

I would just get you local mechanic to throw some good oil like Mobil one or Shell Helix Ultra Extra in at around 7500kms and a new genuine oil filter.. and see if that makes a difference too. That is about all the dealer will do but if you use a local mechanic that you trust and supply your own filter and oil you will probably save $100 

[constipated]

Just filled the car (4th fill). Put 44.26l into it (shortly after the fuel light came on). Filled it, as per usual, to the first click. However, did it at a different servo to all the other times. In the first 3 fills it was filled to the first click and took nigh on 43l exactly.

Anyway, used 44l in around 650km for 6.4l/100km.

This included one 350km round trip to Melbourne which also included Melbourne metro driving and local driving.

I'm doing my best to drive it conservatively to see if I can hit the (seemingly) mythical sub 5l/100km economy. But to no avail, it seems.

According to Acar, my Android phone car app, I'm pretty well averaging 6.2-6.4l/100 km.

Now, either I'm flogging it compared to you guys, which then I have to assume that you all drive your cars like pussies given how I'm driving mine, or perhaps someone is exaggerating their vehicles' economy or that I have something wrong with mine.

But I am stumped if I can figure out how to get it down to 4.5l/100km which is Hyundai's advertised fuel consumption figure.

The difference between advertised and attained, for me is about $20 a tank based on diesel being $1.45 a litre.

Or around 255km a tank.

There's a scheduled service at 7,500km. It's not a "compulsory" service by Hyundai, but I might get it done, depending on what they do and what it costs. I'll get them to check the economy. Dunno what I can do about it, as it's one performance factor that's highly variable if they say "sorry, your problem...."

A few recommendations, have you thought of filing to the brim instead of 1st click. I can get around at least 10 more litres this way. With all the foaming, I'm sure 1st click is not very accurate. May affect your calculations.

Secondly, does your car have trip computer to give you average speed. I use this on a tank by tank basis. I know with my driving that 37km/h equals about 5.9 L/100km. If I do 40km/hr average it drops to around 5.5-5.6.

I think it'd be great if we started a spreadsheet of average speed per tank and calculated consumption.

[mjt57]

A few recommendations, have you thought of filing to the brim instead of 1st click.

Yeah, I've thought about it. However, wouldn't there be MORE foaming as you continue to force feed it?

Not sure how it can affect my calculations, as I'm entering in actual amount filled and distance travelled. And as my Acar data tells me, each fill is around the 43l mark shortly after the low level light comes on and I'm putting in about the same amount each time.

If I fill it to the brim, then that means that for that fill at least, the consumption calcs will be innaccurate as it will have seen that fill period as being heavy consumption. Subsequent ones will be fine, though.

And given that the fuel gauge shows FULL when I stop at the first click, how will DTE calcs be affected if there's an extra, say, 10l going in that it can't compensate for?

Secondly, does your car have trip computer to give you average speed. I use this on a tank by tank basis.

Yes. I have the SLX. And of this fill I'm resetting all fields each time. Acar doesn't have the ability for me to record that info at the time of refuelling, but I may just jot it down on a note (the phone has a memo pad app).

[ElleB]

Forget the technology for now...

 The only way to know an accurate figure is fill to the lip of the filler neck.. Sure it takes a bit of time and you need to allow the foam to settle  etc, but with that full and the  trip reset or the  mileage noted in a log book.... you cant go wrong.

 Make sure that you use the right conversion figures if your changing from Km to MPG etc.... For us "oldies" MPG means a whole lot more, especially when you drive a 1935 Dodge that weighs about 32 CWT  ( remember them)? 

 Just be sure to fill it to the same place next time and you will be right.... you should be able to see the fuel lapping at the neck of the filler tube...

We use the same pump at the same garage ( BP) when ever possible. This is because a lot of semi's pass through and refuel there on the trip over the mountains ( and have a coffee while they wait.... ).
 So the fuel is fresh in the tanks and that cant be a bad thing.

Give it a go.... you might be surprised...and ...note that the motor is still tight and so it will improve...

Cheers

  Elle B

[Phil №❶]

To be truly accurate it is necessary to fill to the brim, however, the manual says not to because of problems with fuel expansion in hot weather possibly from a cold underground tank. If you don't fill to the brim, then the calculation will be affected by any variation in the fill quantity. The fuel pump click off at the 1st sign of foaming reaching the nozzle, which is a physical event which can be affected by other variables eg.

1. The rate that the fuel is pouring into the vehicle.
2. The slope of the car.

So, filling the tank at a slow rate will reduce foaming and therefore admit more fuel to the tank before foaming eventuates. This will take longer and tends to upset everyone else at the servo.
If the slope of the car leans towards you, then less fuel will be admitted to the tank before a false indication of foaming will eventuate. Conversely, sloping away from you would admit more fuel. To demonstrate this point, get a juice container, put a line at half way on 1 side only.  Tilt the container in each direction and fill to the line. repeat tilting the other way.

The variations are not great, but will affect your calculations because THIS fuel quantity is used for calculating fuel consumption using the PREVIOUS distance. This only works correctly if the fuel quantity loaded, represents how much fuel was required to replace the fuel to the SAME level in the tank prior to driving. this does not reliably happen due to the above variances. The fuel filler pipe to the tank is quite long and IMO could hold about 4 litres of fuel too. 

[constipated]

Yeah, I've thought about it. However, wouldn't there be MORE foaming as you continue to force feed it?

Not sure how it can affect my calculations, as I'm entering in actual amount filled and distance travelled. And as my Acar data tells me, each fill is around the 43l mark shortly after the low level light comes on and I'm putting in about the same amount each time.

If I fill it to the brim, then that means that for that fill at least, the consumption calcs will be innaccurate as it will have seen that fill period as being heavy consumption. Subsequent ones will be fine, though.

And given that the fuel gauge shows FULL when I stop at the first click, how will DTE calcs be affected if there's an extra, say, 10l going in that it can't compensate for?

Foaming is like filling up a glass with soft drink or beer. The foam is what triggers off your initial 1st click. If you look carefully down the filler neck you will see it rapidly recede.

There is a thread somewhere when I asked about how to fill to the brim.

Once you get 1st click you have to wait maybe 15 seconds, then lift out the nozzle till you have a clear view down the filler neck, then fill up slower with the nozzle aimed so it runs down the side of the filler neck.

Eventually it foams again but you can see it again. You pause, then do again until eventually the foam settles and you can see the level of diesel in the filler neck.

It probably does affect DTE calculations. I ignore what they say until the tank is half full anyway.

By the way what do others think of the idea of a thread with fuel consumption figures and average speed readings. This would hopefully help indicate individual driving conditions.

Maybe we'd see that the people quoting figures in the 4s or low 5s are averaging more like 70-80km/hr.

[Phil №❶]

Yes constipated, good remarks.

The DTE is most effective & accurate as the tank approaches empty & a planned fill is required.

Good idea IMO about fuel consumption / average speeds, can't do any harm.

Regarding filling, I usually strike the right fill rate to be able to see the foam and keep filling rather than stopping and starting each time. You have to be careful though because eventually the foam is replaced with clear fuel so you have to take it easy at that point. I've never had a spill or any other event. 

[bryanj86]

When filling i just fill it. I always use the premium diesels with the anti foaming stuff in it..seems to help!

[mjt57]

When filling i just fill it. I always use the premium diesels

Premium diesel? Who sells that? None of the BPs or Caltexes that I've used here in Victoria have it.

The only different bowser was a Shell one which had a "high flow" sign on the nozzle, which I'm told is for trucks to use.

[FatBoy]

Caltex have Vortex Diesel at many outlets, lots in Melbourne and rural Victoria too.

[rustynutz]

Martin, Caltex Vortex Diesel is apparently available at the Safeway Caltex outlet, corner Seymour St & Princes Hwy in Traralgon and at 37 Kirk St,  Moe.... 
That's about the extent of it in your area.

You can download a list in CSV format from HERE

They are non existent in my area... 

[mjt57]

Thanks Rusty. I didn't see it there. I will have a look next time I need to fill up.

Just briefly, other than anti-foaming, what benefits does it offer?

[Dazzler]

It's supposed to have more injector cleaners and stuff in it and some reckon it gives the CRDi a bit more go or that they run a bit smoother and quiter (that is right isn't it Russ?) We only got it down here after I traded ours .. 

[rustynutz]

It's supposed to have more injector cleaners and stuff in it and some reckon it gives the CRDi a bit more go or that they run a bit smoother and quiter (that is right isn't it Russ?) We only got it down here after I traded ours .. 

I have no experience of it, Daz....You might be thinking of John (Lakes)?

[Dazzler]

Oh sorry, yeah probably (I didn't realise you hadn't used it at all)

Strange how Tassie has it now and Gippsland doesn't 

This explains it a bit...

http://www.caltex.com.au/productsandservices/pages/vortexpremiumfuels.aspx

[rustynutz]

Oh sorry, yeah probably (I didn't realise you hadn't used it at all)

Strange how Tassie has it now and Gippsland doesn't 

This explains it a bit...

http://www.caltex.com.au/productsandservices/pages/vortexpremiumfuels.aspx

Thanks mate, yeah, I'd like to use it but the nearest servo is around 45 minutes away.... 

[bryanj86]

BP has premium diesel...Diesel Ultimate. But you need to look for the BPs with teh advertising regarding it.....