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Fa51wan

Lupo tdi mpg

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I had an average of just under 10mpg on my way to work this morning and was doing 40mph most the way driving sensible. Any ideas why it's so bad? Had it carbon cleaned last week and it's not remapped yet also got egr blank. Help please 

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Green temp.

Under ten must be really really really smokey

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2 hours ago, Fa51wan said:

I had an average of just under 10mpg on my way to work this morning and was doing 40mph most the way driving sensible. Any ideas why it's so bad? Had it carbon cleaned last week and it's not remapped yet also got egr blank. Help please 

How did you measure this? 

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I thought that.

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Check your oil level to see if it is rising or high. As said, there would be clouds of very obvious black smoke if it was trying to burn it. How are you measuring it?

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If it chucks more fuel in, it'll simply go faster. There's no throttle valve on a diesel (ok, so there's a spring loaded EGR choke flap), so air restrictions are minimal. If the EGR valve failed, then that could cause low power (obvious fault that'd be easy to notice), and the car would be difficult to drive. Can't think of anything that'd cause high MPG other than brakes dragging. Blocked oxidising cat?

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6 hours ago, Rich said:

Green temp.

Under ten must be really really really smokey

Doesn't smoke when driving just a little puff on start up, forgot to mention it's got a cat back on as well so would notice smoke

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5 hours ago, Skezza said:

How did you measure this? 

Measured it with my obd reader, not sure how accurate it is but I've only been getting 260 odd miles to a tank so even then it's not great for a tdi

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3 hours ago, Sausage said:

Check your oil level to see if it is rising or high. As said, there would be clouds of very obvious black smoke if it was trying to burn it. How are you measuring it?

Will do.

With an obd

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I did manage an average of 11 on my way back from work which is an improvement. Also changed my air filter which was overdue.

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approx 7.5 gal tank, but 260 / 7.5 = about 35mpg.

Mine does about 360 on short journeys = 48mpg. (60+mpg when i do long runs). 

Duff temp sensor means it runs a cold richer map and apart from clogged air filter, binding brakes, soggy tyres, fuel leaks, injector seal leak (rising oil level) is the most likely suspect.

Edited by Sausage
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1 hour ago, Sausage said:

approx 7.5 gal tank, but 260 / 7.5 = about 35mpg.

Mine does about 360 on short journeys = 48mpg. (60+mpg when i do long runs). 

Duff temp sensor means it runs a cold richer map and apart from clogged air filter, binding brakes, soggy tyres, fuel leaks, injector seal leak (rising oil level) is the most likely suspect.

that equates to my average, more or less depending on the run type. 70mpg is a fantasy unless you are prepared to do Motorway runs at a steady 55, but 10mpg is equally ridiculous, either a leak or theft

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4 hours ago, Sausage said:

approx 7.5 gal tank, but 260 / 7.5 = about 35mpg.

Mine does about 360 on short journeys = 48mpg. (60+mpg when i do long runs). 

Duff temp sensor means it runs a cold richer map and apart from clogged air filter, binding brakes, soggy tyres, fuel leaks, injector seal leak (rising oil level) is the most likely suspect.

Will look into it later thanks mate

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17 hours ago, Fa51wan said:

Measured it with my obd reader, not sure how accurate it is but I've only been getting 260 odd miles to a tank so even then it's not great for a tdi

About as accurate as pissing in the wing to try and measure wind speed mate.

The way to do it properly is to accurately calculate your distance travelled using some kind of GPS odometer setup and do it by several brims of the tank (up to the click). I'm speaking from plenty of experience in this particular game.

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Google mpg calculator and out the info in.

I got 524 miles from £51 (42 litres) and I'm getting an okay mpg.

Simply done by running to empty, tanking it, resetting the trip and keeping the receipt on the passenger seat for next time.

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1 hour ago, Rich said:

Google mpg calculator and out the info in.

I got 524 miles from £51 (42 litres) and I'm getting an okay mpg.

Simply done by running to empty, tanking it, resetting the trip and keeping the receipt on the passenger seat for next time.

Yep this is the way......

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9 hours ago, Sausage said:

Duff temp sensor means it runs a cold richer map and apart from clogged air filter, binding brakes, soggy tyres, fuel leaks, injector seal leak (rising oil level) is the most likely suspect.

Petrol engines this is true.

In diesels, the only thing coolant temp affects is injection timing. It advances the injection point if it thinks it's colder and retards it if hotter. The ECU also measures air temp and fuel temp. It wouldn't make much difference to efficiency- maybe only about 2-3%. The air and fuel temps affect timing the most. 

I can't think of any reason that would give that poor milage. Especially if there's no black smoke. Very odd.

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Forgot about dirty MAF above.

Puffs of white smoke and lumpy on cold start up could well be an injector out of whack (or glow plug out if cold enough for them)

Also: https://www.myturbodiesel.com/wiki/camshaft-timing-torsion-value-adjustment-on-vw-and-audi-pd-tdi-engines/ 

 

 

Edited by Sausage

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I'd probably go with the theory above but possibly caused by the loom inside the cylinder head, they are prone to breaking down.

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I still await accurate MPG figures.

OBD2 MPG readers are almost always BS and the good ones (Scangauge for example) still rely on manually inputting tank details and simply trim the figures based on injection cut off.

Trust me on this..... I spent bloody years trying to calculate uber accurate MPG figures. Not 30 seconds one day to work :) 

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