General 100hp mpg drop?

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General 100hp mpg drop?

Any fuel injected car slowing down in gear with the throttle pedal untouched will not use any fuel until the engine reaches tick-over revs. Coast along with the 'box in neutral - the engine revs will drop to idle speed and begin to use fuel.
 
Any fuel injected car slowing down in gear with the throttle pedal untouched will not use any fuel until the engine reaches tick-over revs. Coast along with the 'box in neutral - the engine revs will drop to idle speed and begin to use fuel.



So this means when coasting in gear my immediate consumption should show zero? Why wouldn’t it then? Could this problem be related to coils or plugs? Faulty sensor?
 
Hi Guys

late to the chat but.

our 2005 1.2petrol can get really silly MPG(showing my age there) ive been into the 80's and 90's when i'm not on a time constraint. it does need the throttle body clean soon as it occasionally has the wobbly idle, not surprised as its 15 years old and with 90k plus on the clock

our 2013 1.2 petrol doesn't really get over 60MPG doing the same journey. although it does drive better now i've put Iridium plugs in it. 50k

I find driving in wet weather can reduce the mpg by about 15 % not only running wipers/heater but the drag of the water. it has been wet for quite a long time recently

last thing to ask JustApanda do you really trust the VW UP economy readout on the dashboard say Zero Emissions!.

Tim
 
Hi Guys



late to the chat but.



our 2005 1.2petrol can get really silly MPG(showing my age there) ive been into the 80's and 90's when i'm not on a time constraint. it does need the throttle body clean soon as it occasionally has the wobbly idle, not surprised as its 15 years old and with 90k plus on the clock



our 2013 1.2 petrol doesn't really get over 60MPG doing the same journey. although it does drive better now i've put Iridium plugs in it. 50k



I find driving in wet weather can reduce the mpg by about 15 % not only running wipers/heater but the drag of the water. it has been wet for quite a long time recently



last thing to ask JustApanda do you really trust the VW UP economy readout on the dashboard say Zero Emissions!.



Tim



Yes i do trust it to be accurate. As I usually calculated fuel usage after the fact based on fuel volume used. And my results were always similar, not exact obvs but no significant difference to say it was inaccurate. Its also not the only car I’ve seen to say zero when coasting in gear. My 09 polo tdi did the same. So I know theres a problem with my panda, I just need to be pointed in the direction of what it could be.
 
So this means when coasting in gear my immediate consumption should show zero? Why wouldn’t it then? Could this problem be related to coils or plugs? Faulty sensor?

Depends what you actually mean by coasting in gear.

Coasting is when there is no connection between engine and wheels, either gearbox is in neutral, or clutch is down. If clutch is down, gear selection is irrelevant.
Do you mean on the overrun, so accelerator off, and momentum of car pushing the engine?

Coasting is bad practice, it destabilises the car, reduces the effect of the steering, and surprisingly increases braking distances, but not due to lack of engine braking. (There's a lot of physics going on there)
Find a safe, quiet, straight road with good visibility. With no other traffic, position yourself in the centre of the road, at around 25-30mph. Gently sway the steering left-right a few times. Important, gently sway, not abrupt swerves. If anyone does not understand the difference, don't do this. Your risk. Feel how the car behaves.
Now repeat with the clutch down. It'll feel loose.

When coasting, the engine has to remain ready for use, so the computer will fuel it at tickover, so will show a fuel consumption, may be mpg (l/100km) or g/hr (l/hr).

On the overrun, no fuel is fed into the engine until it drops near to tickover, when fuel is gently fed in to prevent a stall. If well above tickover, on the overrun, clutch and gear engaged so engine being pushed by momentum, fuel use should be zero. This may show as 99mpg, or just no display.
If display shows fuel being used, it is possible that the accelerator pedal is not telling the ECU that it is fully off. Look for restricted movement, or connect to MES or a suitable diagnostic program that will show accelerator pedal position.

Or change the display to a different reading and stop worrying.
 
Depends what you actually mean by coasting in gear.



Coasting is when there is no connection between engine and wheels, either gearbox is in neutral, or clutch is down. If clutch is down, gear selection is irrelevant.

Do you mean on the overrun, so accelerator off, and momentum of car pushing the engine?



Coasting is bad practice, it destabilises the car, reduces the effect of the steering, and surprisingly increases braking distances, but not due to lack of engine braking. (There's a lot of physics going on there)

Find a safe, quiet, straight road with good visibility. With no other traffic, position yourself in the centre of the road, at around 25-30mph. Gently sway the steering left-right a few times. Important, gently sway, not abrupt swerves. If anyone does not understand the difference, don't do this. Your risk. Feel how the car behaves.

Now repeat with the clutch down. It'll feel loose.



When coasting, the engine has to remain ready for use, so the computer will fuel it at tickover, so will show a fuel consumption, may be mpg (l/100km) or g/hr (l/hr).



On the overrun, no fuel is fed into the engine until it drops near to tickover, when fuel is gently fed in to prevent a stall. If well above tickover, on the overrun, clutch and gear engaged so engine being pushed by momentum, fuel use should be zero. This may show as 99mpg, or just no display.

If display shows fuel being used, it is possible that the accelerator pedal is not telling the ECU that it is fully off. Look for restricted movement, or connect to MES or a suitable diagnostic program that will show accelerator pedal position.



Or change the display to a different reading and stop worrying.



Ok, it seems I’ve used the wrong terminology. Thanks for clearing that up. I meant overrun then. Car in gear, foot off accelerator and clutch and rolling forward. I get no display when I’m idling but in overrun it’ll only display 2L/100km which is strange and worrying.

I did manage to change the thermostat today as I had the issue of the heat gauge dropping while driving. Now its sits in the middle and on a short drive I’m finally getting 6.9l/100km average. Which should drop on my commute to work tomorrow. I do suspect I may need to change the stick coils at some point... would a fuel additive help with improving ignition or waste of time?
 
It could be that the software is simply unable to show less than 2l/100Km. Idling on the driveway, consumption is infinite (since you cover no distance), but I think it can't show more than 99l/100Km.
So don't overreact.

gr J
 
Hi All

Our max economy with engine engaged slowing down in gear is as follows

2005 panda 141.2mpg
2013 panda 99.9mpg(not enough digits to show any more)

Ive not come across a fiat yet with a readout of litres per 100km on the dash.

to give a number for economy that can get higher with gentle driving and money saving works on my mindset,
I wouldn't be able to make great effort for the number of litres used per 100km to reduce as it doesnt feel so beneficial if you get what i mean.

Tim
 
Hi All



Our max economy with engine engaged slowing down in gear is as follows



2005 panda 141.2mpg

2013 panda 99.9mpg(not enough digits to show any more)



Ive not come across a fiat yet with a readout of litres per 100km on the dash.



to give a number for economy that can get higher with gentle driving and money saving works on my mindset,

I wouldn't be able to make great effort for the number of litres used per 100km to reduce as it doesnt feel so beneficial if you get what i mean.



Tim



Im in South Africa so our units used will be different. I think its programmable through the obd. Anyway 141 mpg is 1.6l/100km so also not zero. My question about what my car displays is because I’m unfamiliar with fiats and thought something was wrong based on previous experience with other manufacturers based on the same conditions...
 
The low consumption (high mpg) figure displayed on closed throttle is not technically correct but the actual value checked on distancei travelled per fuel added usually agrees quite well with the trip figures.
 
This thread makes me wonder if the 100hp I ran for 6 mo rhs in 2011 had a poorly coil as I never get over 43mpg and sometimes got under 40 mpg despite being a steady enough driver ( 68mpg in diesel Panda)
 
Mine recently had a set of coils because one failed and another seemed questionable. On long fast(sh) runs it was giving about 44mpg.


I've just fitted a cheap exhaust which has the correct mid box but seems to have a 1200 type back box. Guess what the mpg has really dropped. The weather will have an effect but I'm probably seeing just 37mpg on the same runs.

So it's likely an old exhaust that's clogged in some way or just plain wrong (like mine) could be the culprit.
 
Just thought I would update on those coils..........
....... one failed tonight.

Fortunately I kept the original fiat ones so wasn't a major issue. All running again now.

It lasted nearly 8 months, but still not great. Trying a warranty claim as it states a 1 year warranty on the ebay add. Worth a try I guess.
 
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