Sr180 - Poor Mpg? Check This!

[romulon]

As the attached pic shows, that's 51.0 MPG Average consumption. Not bad eh, for a 2.2D-Cat Auris SR180 that's "chipped" and likely capable of over 200BHP! (in theory its 210BHP, but who cares :P ).

Fitted diesel tuning box is latest (adjustable) type as supplied by Parts King (aka Kingo), running on BP Ultimate diesel for the last fill-up (~43 litres went in), Morrisons diesel for all fill-ups before that.

Bear in mind this is NOT achieved by doing a frikin' long journey (at a fairly constant speed in 6th gear), like some of the clever peeps in this forum do, or by painfully slow, boring driving either. That's not representative of typical usage.

And I'd be the first to point out you won't get this MPG by caning it everywhere - if you use that power all the time, MPG will fall through the floor - this applies to ALL cars!

This Average MPG figure is the result of my 'normal' usage, as follows...

Mileage consists of two 18 mile journeys each day Mondays to Fridays (work - 8 hours/day) which is mixed town & country and includes motorway (M42 jn 1 to 3, and 3 -> 1 return journey), plus one 2 mile each-way trip on Saturday, plus a 23 mile each-way mainly country roads trip on Sundays. With the occasional exception to this, the above is a typical week. The Average MPG value was 'reset' last about 3K miles ago.

Standard Dunflop sport tyres, car has totalled about 14K miles so far, so it's arguably barely 'run-in'.

Try beating that under similar usage conditions...

Forgot to mention that although I keep one eye on the instantaneous MPG readout, I don't go slow... I definitely keep up with the (o/s lane) traffic .

Air-con has been ON whenever I've wanted it on (most of the afternoon journeys lately, especially the return from work).

As a parting note, I would like to point out that this car is now seriously quick when push comes to shove, (that tuning box made a big difference) though I have to admit I only indulge that level of power very occasionally.

But on those rare occasions... the grin it produces says it all. :D

[Daveyonthemove]

I look forward to seeing the average MPG when the tank is at the last bar.

I have found that i can usually get 47-49 mpg from mine on its first run after a fill up, but once i do a journey across town the MPG drops and stays low. 43mpg is average for me on most fill ups, so if you can get 50mpg consistently over several tank full's then you are doing very well.

[acetip]

Have you checked the fuel consumption by brimming the tank and checking what it taked to repeat this or used FUELLY.the read out on your dash are rarely accurate and mostly optomistic.

I have read the some tuning boxes effect the dash read out accuracy.but as having never had one cant say one way or the other.

[Daveyonthemove]

Have you checked the fuel consumption by brimming the tank and checking what it taked to repeat this or used FUELLY.the read out on your dash are rarely accurate and mostly optomistic.

I have read the some tuning boxes effect the dash read out accuracy.but as having never had one cant say one way or the other.

Fair comments, the only REAL way to prove MPG is to brim the tank and work out the litres used against the miles covered.

That said, I have found my Auris MPG readout to be accurate to with in 0.5 MPG on most occasions, and spot on now and then so the tuning box on mine isn't confusing the ECU, but like you, I have seen it happen on other cars.

[acetip]

Have you checked the fuel consumption by brimming the tank and checking what it taked to repeat this or used FUELLY.the read out on your dash are rarely accurate and mostly optomistic.

I have read the some tuning boxes effect the dash read out accuracy.but as having never had one cant say one way or the other.

Fair comments, the only REAL way to prove MPG is to brim the tank and work out the litres used against the miles covered.

That said, I have found my Auris MPG readout to be accurate to with in 0.5 MPG on most occasions, and spot on now and then so the tuning box on mine isn't confusing the ECU, but like you, I have seen it happen on other cars.

Hi Davey.

yes the do vary,even toyota ones.my mondeo 2 ltr 130 bhp tdci was on aerage was returning on my local country roads 49 mpg.but showed on dash as 57 mpg.then my st 2.2 155 bhp tdci i was getting about 48 mpg but the dash reading was only showing 47 mpg.not far out.

you would think there would be better quality electronics these days.

[Daveyonthemove]

My ST was very optimistic. I have seen 55mpg on the dash, and only got 42mpg when brimming the tank.

Like you say, you would expect better these days.

The most frustrating thing for me where Toyota is concerned, is the estimated miles left in the tank. It ALWAYS reads 390 miles available when the tank is full, and I can usually get 300 miles from the first half a tank, but the Miles left will never give an accurate estimation on the second half, or the next full tank.

I can't understand why it can't predict 450-500 miles from a full tank and adjust as the MPG increases or decreases. I'm baffled.

[acetip]

My ST was very optimistic. I have seen 55mpg on the dash, and only got 42mpg when brimming the tank.

Like you say, you would expect better these days.

The most frustrating thing for me where Toyota is concerned, is the estimated miles left in the tank. It ALWAYS reads 390 miles available when the tank is full, and I can usually get 300 miles from the first half a tank, but the Miles left will never give an accurate estimation on the second half, or the next full tank.

I can't understand why it can't predict 450-500 miles from a full tank and adjust as the MPG increases or decreases. I'm baffled.

To be honest,ive never realy checked the miles left read out on my car.must give it a ckeck when i next fill up.normaly get about 410 miles when last bar starts flashing.My auris is a 1.6 petrol.

[OldSkoO1]

I managed 52.6mpg over a decent journey in mine and saw high 40's plenty of times but that was after restting the avg. mpg calculation. As said, with cold starts and town thrown in, it soon dropped to low 40's.

Still not bad and on par with VAG 170 and BMW 123d's. Perhaps slightly worse overall due to the agressive EGR re-circulation. They could do with some swirl flaps in the inlet manifold.

[Parts-King]

I have just had a customer with a RAV who had issues with his MPG, he put one of our chip kits on his car and has just emailed in to say the following

Thanks very much for organising the chip. I had it fitted on Fri and am delighted that the car has gone from 35mpg to 44mpg! That's doing my normal motorway journey to work but if I drive carefully around town it even goes up to 47!!! It also accelerates like a rocket and seems very smooth. I ................ am finally delighted with the car.

Kingo

[davethefish]

The most frustrating thing for me where Toyota is concerned, is the estimated miles left in the tank.

Tell me about it. Yet again I left my wallet at work, only realising when I pulled up at the fuel pump at my nearest Shell garage. :censor:

Not normally a problem but I had been on low fuel since work (Manchester, about 19 miles) and was now on the last fuel block on the dash, still 7 miles from home. Needing to get home and back to the garage (14 miles), I checked the miles left, '0 Miles'. :ffs:

I was faced with a conundrum! I thought, do I fill up and say "Oh no, i've not got my wallet!", no, done it once before at that place...

I thought, I'll get back no probs, but will I make it back to the garage?

Well, long story cut short, I did but was bricking it. On fill up though the car took 49.71L, aren't they a 55L tank? I could have had another 35+ miles out of it?

So the moral of the story is 14 miles on 'O miles' left in tank is possible and STOP LEAVING YOUR WALLET AT WORK. :D

[acetip]

The most frustrating thing for me where Toyota is concerned, is the estimated miles left in the tank.

Tell me about it. Yet again I left my wallet at work, only realising when I pulled up at the fuel pump at my nearest Shell garage. :censor:

Not normally a problem but I had been on low fuel since work (Manchester, about 19 miles) and was now on the last fuel block on the dash, still 7 miles from home. Needing to get home and back to the garage (14 miles), I checked the miles left, '0 Miles'. :ffs:

I was faced with a conundrum! I thought, do I fill up and say "Oh no, i've not got my wallet!", no, done it once before at that place...

I thought, I'll get back no probs, but will I make it back to the garage?

Well, long story cut short, I did but was bricking it. On fill up though the car took 49.71L, aren't they a 55L tank? I could have had another 35+ miles out of it?

So the moral of the story is 14 miles on 'O miles' left in tank is possible and STOP LEAVING YOUR WALLET AT WORK. :D

Did the same thing a while ago,no wallet no card.So left wife there while i drove home which was a couple of miles.

On the way way home i got to thinking that was not a bad deal,the wife foe a tank of diesel.but my conscious got the better of me.but then after having her a while maybe they would have brought her back and not charged me for the fuel cos they would have been glad to be shot of her.wishful thinking.there again she is not that bad.

[davethefish]

Did the same thing a while ago,no wallet no card.So left wife there while i drove home which was a couple of miles.

On the way way home i got to thinking that was not a bad deal,the wife foe a tank of diesel.but my conscious got the better of me.but then after having her a while maybe they would have brought her back and not charged me for the fuel cos they would have been glad to be shot of her.wishful thinking.there again she is not that bad.

:lol2:

I'm sure she's very nice and will probably never see your above post.

[Daveyonthemove]

I have only left my wallet at home once when i filled up, and i was very lucky as it was the day before my birthday, so i had a few cards in the car. I tore them all open and found I had enough cash to buy the fuel and had change for a Twix. Very lucky!

[acetip]

Did the same thing a while ago,no wallet no card.So left wife there while i drove home which was a couple of miles.

On the way way home i got to thinking that was not a bad deal,the wife foe a tank of diesel.but my conscious got the better of me.but then after having her a while maybe they would have brought her back and not charged me for the fuel cos they would have been glad to be shot of her.wishful thinking.there again she is not that bad.

:lol2:

I'm sure she's very nice and will probably never see your above post.

your correct on both counts.

[romulon]

Ok, part 2 of the saga continues here.

(Should have posted this last week but I had 'feeling lazy moment' that lasted a over a week!)

As the attached pic shows, the same tank of fuel taken to the point where the 'LOW FUEL' warning started.

(Looks like I took the snapshot while the remaining single fuel indicator segment was flashing in the 'OFF' state, hence no fuel level is visible! - sorry about that).

Anyway, the intention was to note the ACTUAL fuel consumption using the old fashioned way - fill up at the same pump, note the amount pumped in and the mileage done.

That would allow me to compare against the trip computer's calculated Av. MPG figure, which appears rather 'optimistic'.

Here's the result;-

On Sunday 28/08/2011 I re-filled (with BP Ultimate Diesel) at the same pump (and facing same way).

Displayed Average MPG was 51.2 MPG.

Fill-up quantity was 45.8 litres, total logged journey was 471.1 miles.

This calculates to be approx. 46.7 MPG.

Assuming the fill-up figures are correct;-

Trip Computer Error = (100 * ((51.2 - 46.7) / 46.7)) %

= + 100 * ( 4.5 / 46.7 ) %

= + 9.6 %

So those of you who suspected the original reported MPG figure was 'optimistically high' were absoultely right !

And I have a "theory" as to why this is so...

Correct me if I am wrong, but... (nerd alert! Health warning applies to techno tripe below...!)

I believe the Auris 2.2 D4D calculates full usage by summing all the individual injected shots of diesel per unit time (for example, fuel usage might calculated in "Litres per hour").

It can do this because it knows the common rail fuel pressure, and it knows how long it opened the injectors for each injection cycle to meet the driver's demand.

It's calibrated at the factory, so the calculated rate of fuel usage is reasonably accurate. So far, so good...

However...

I have added a diesel performance box, which "cons" the engine controller module (ECM) into thinking the common rail fuel pressure is lower than it actually is (note that the amount by which the pressure value is 'lowered' varies - it is not a constant factor - or so I'm told).

Anyway, the ECM "compensates" for what it sees as the apparently low fuel pressure, by increasing the injector opening time. This results in the power boost that's due to the performance chip, because the REAL fuel pressure is higher than it thinks it is, and so more diesel is injected than it knows about.

Unfortunately... as a side-effect of this, it causes the ECM to mis-calculate the rate of fuel usage (Litres/hour), because it is using the 'lowered' fuel pressure value instead of the 'real' pressure value.

The calculated fuel usage will therefore be lower than than the real fuel usage, which means the calculated MPG figure will be similarly higher than the real MPG.

In my case, I would venture a guess that on the above trip it has under-estimated average fuel usage by around ... 9.6% !

If anybody followed any part of what I just wrote , do you think my 'theory' for the 'optimistic' Av. MPG figures is plausible?

Basically I'm thinking that the calculation error above is mostly due to the tuning box.

On a seperate point though I would also have to say...

The real, measured figure of 46.7MPG is a lot better than I remember getting BEFORE fitting the box (around 38 mpg is nearer what I was previously getting).

And even with the +10% optimism removed, it isn't so bad for a SR180 under the described driving conditions... ^_^

So although its dissapointing (51 MPG would have been very nice), 46.7 MPG and over 200BHP on tap I think I can live with :P

[acetip]

Ok, part 2 of the saga continues here.

(Should have posted this last week but I had 'feeling lazy moment' that lasted a over a week!)

As the attached pic shows, the same tank of fuel taken to the point where the 'LOW FUEL' warning started.

(Looks like I took the snapshot while the remaining single fuel indicator segment was flashing in the 'OFF' state, hence no fuel level is visible! - sorry about that).

Anyway, the intention was to note the ACTUAL fuel consumption using the old fashioned way - fill up at the same pump, note the amount pumped in and the mileage done.

That would allow me to compare against the trip computer's calculated Av. MPG figure, which appears rather 'optimistic'.

Here's the result;-

On Sunday 28/08/2011 I re-filled (with BP Ultimate Diesel) at the same pump (and facing same way).

Displayed Average MPG was 51.2 MPG.

Fill-up quantity was 45.8 litres, total logged journey was 471.1 miles.

This calculates to be approx. 46.7 MPG.

Assuming the fill-up figures are correct;-

Trip Computer Error = (100 * ((51.2 - 46.7) / 46.7)) %

= + 100 * ( 4.5 / 46.7 ) %

= + 9.6 %

So those of you who suspected the original reported MPG figure was 'optimistically high' were absoultely right !

And I have a "theory" as to why this is so...

Correct me if I am wrong, but... (nerd alert! Health warning applies to techno tripe below...!)

I believe the Auris 2.2 D4D calculates full usage by summing all the individual injected shots of diesel per unit time (for example, fuel usage might calculated in "Litres per hour").

It can do this because it knows the common rail fuel pressure, and it knows how long it opened the injectors for each injection cycle to meet the driver's demand.

It's calibrated at the factory, so the calculated rate of fuel usage is reasonably accurate. So far, so good...

However...

I have added a diesel performance box, which "cons" the engine controller module (ECM) into thinking the common rail fuel pressure is lower than it actually is (note that the amount by which the pressure value is 'lowered' varies - it is not a constant factor - or so I'm told).

Anyway, the ECM "compensates" for what it sees as the apparently low fuel pressure, by increasing the injector opening time. This results in the power boost that's due to the performance chip, because the REAL fuel pressure is higher than it thinks it is, and so more diesel is injected than it knows about.

Unfortunately... as a side-effect of this, it causes the ECM to mis-calculate the rate of fuel usage (Litres/hour), because it is using the 'lowered' fuel pressure value instead of the 'real' pressure value.

The calculated fuel usage will therefore be lower than than the real fuel usage, which means the calculated MPG figure will be similarly higher than the real MPG.

In my case, I would venture a guess that on the above trip it has under-estimated average fuel usage by around ... 9.6% !

If anybody followed any part of what I just wrote , do you think my 'theory' for the 'optimistic' Av. MPG figures is plausible?

Basically I'm thinking that the calculation error above is mostly due to the tuning box.

On a seperate point though I would also have to say...

The real, measured figure of 46.7MPG is a lot better than I remember getting BEFORE fitting the box (around 38 mpg is nearer what I was previously getting).

And even with the +10% optimism removed, it isn't so bad for a SR180 under the described driving conditions... ^_^

So although its dissapointing (51 MPG would have been very nice), 46.7 MPG and over 200BHP on tap I think I can live with :P

I think your assumption and your consumption are correct.

Read somewhere about chipping etc does give optomistic readouts.even when you know your not getting the consumption shown,its pleasing to see it creep up a bit and you (or i do) drive a bit steadier to see if will show even better average displayed

[davethefish]

Assuming the fill-up figures are correct;-

Trip Computer Error = (100 * ((51.2 - 46.7) / 46.7)) %

= + 100 * ( 4.5 / 46.7 ) %

= + 9.6 %

Cracking post, the whole thing (I just didn't want to quote the whole page again)