Mk2 1.9TDI 105hp - what does your trip say when doing 120kph?

[RubyCubes]

Recently purchased a 2009 Mk2 Elegance model Superb with a 1.9TDI 105hp engine to replace a 2004 B5.5 Highline model Passat with a 1.9TDI 130hp engine. The Superb has the 18" Skoda Themisto alloys and the Passat had 17" OEM alloys. The Superb has 160k miles on it and my Passat had 167k miles - bought the Superb as a nice person drove into my Passat and wrote it off. The Superb has a fully stamped service history and I read through to check and it was serviced bang on every service time. She was serviced and the timing belt and water pump changed by a garage (stamped) 6k miles ago - this Superb is in (100k+ miles) mint condition and everything indicates she was very well looked after.

 

The Superb is new (to me) so haven't gotten to do a proper full tank/distance mpg check and am currently working from the trip so understand it won't be 100% accurate but I'm finding differences between the two cars that I'm a little wary about. I'm working from UK mpg and found the Passat's trip to be generally accurate when compared to full tank MPG test.

 

Based on a consistent journey I do driving 50mph for 90% of the journey, I used to easily get 60 mpg in the Passat with aircon on (albiet in eco mode) and driving without consideration for improving MPG, while now I'm getting 53 mpg in the Superb at absolute best with everything turned off. That 53mpg was achieved changing my normal driving style to change gears a little sooner than I normally would and accelerate much less than I did with the Passat - I've followed all the standard mpg saving tips (tyre pressures correct, nothing in the car bar the spare tyre etc) and the breaks aren't sticking.

 

I'm also noticing that when doing bang on 120kph on a motorway using cruise control for a 30 minute drive I've done for years the Superb's trip reads as averaging 35mpg give or take a few, while on the Passat also using cruise control doing the same journey and speed I was getting 48-52mpg. Again, I know the trips can be off but that's a 27% decrease in mpg doing the same journey with very similar engines in similar enough cars and both using cruise control - plus it's summer time and the weather here is nice and warm so mpg should be at it's highest.

 

I understand the Superb is a little heavier and the 25 less horses under the hood mean I don't have the same punch the Passat had, but I'm thinking something must be up.

 

Am I over concerned here or should I get it scanned to see if there are any faults showing up?

 

 

 

 

[RubyCubes]

I'm in Ireland and just realised I have miles and kilometers in my post above as my Passat was a UK import with miles and the Superb is an Irish car with Kms - I forgot to stay consistent with one unit. If it helps to ask a single question:

 

> When traveling at 120kph or 75mph, what does your trip computer say your lp100k or mpg is?

> My old 2004 1.9tdi 130hp Highline Passat would have shown 5.9 lp100k, or 48mpg

> My 'new' 2009 1.9tdi 105hp Elegance Superb is showing 8.0 lp100k, or 35mpg

 

I'm wondering is this off and suggestive of an issue.

[chimaera]

The Superb is about 150-200 kg heavier than the Passat which is going to make a hole in economy. I'm not that familiar with the 1.9's performance in the Superb, but my DSG CR170 will manage about 6 l/100 km at a 120 km/h cruise (that's with the MFD calibrated to read true). The MFD tends to read optimistic normally by about 15 %, meaning the indicated economy is better than actual.

 

Have you done a brim-to-brim measurement of economy yet? Until you do that you're really only guessing about it.

 

Any idea what kind of driving it had before you bought it? If it was a lot of city driving, the internals could be a bit coked up and this would definitely reduce the economy a bit.

[RubyCubes]

Cheers for info chimaera.

 

It's the discrepancy between the MFDs that is concerning me as I figured they're probably similarly inaccurate, though my Passat's was pretty accurate based on a brim-to-brim test so the fact the Superb's is so much lower on the MFD I'm thinking the lpk could be even worse than displayed. I haven't gotten to do a brim-to-brim yet with the Superb though.

 

The service intervals and mileage on it would suggest she was driven distances and records show it was never a taxi. The lad I bought it from had it 1.5 years and had a 150km daily commute with 90% motorway and I had to go with him from his work to his gaf to buy it and he was doing 120kph, so I think she got well driven.

 

I have noticed a whooshing noise (like a dump valve) when changing lower gears (1st through 3rd) and have read this can be a sign of a boost pipe leak which can impact mpg/lpk. Maybe I need to check all the pipes to see if something is amiss...

 

Just to add also, the manual says the 1.9 105hp Superb should get:

• 7.5 l/100km for Urban
• 4.8 l/100km for Non-Urban
• 5.7 l/100km for Combination

 

The Passat manual says the 1.9 130hp should get:

• 7.5 l/100km for Urban
• 4.5 l/100km for Non-Urban
• 5.6 l/100km for Combination

 

Given both are virtually identical and I'm driving the same routes I'm thinking something has to be up.

Edited 2 August, 2019 by RubyCubes
Added manual l/100km figures

[J.R.]

Same engine in a Octavia never gives less than 60mpg at 130KPH.

 

The weight of the vehicle will not make any measurable difference at a steady speed.

 

The MFD was 13% optimistic and the above figure is after recalibration by VCDS and subsequent verification on many brim to brim tank fillings.

 

I recently had a boost pipe leak, clipped joint prung apart under boost pressure and it made a big difference to fuel consumption off boost around town it drove OK but used a lot more fuel.

 

Failing that a cam belt replacement might have been incorrectly timed.

Edited 2 August, 2019 by J.R.

[chimaera]

11 minutes ago, J.R. said:

Same engine in a Octavia never gives less than 60mpg at 130KPH.

 

The weight of the vehicle will not make any measurable difference at a steady speed.

 

The MFD was 13% optimistic and the above figure is after recalibration by VCDS and subsequent verification on many brim to brim tank fillings.

 

I recently had a boost pipe leak, clipped joint prung apart under boost pressure and it made a big difference to fuel consumption off boost around town it drove OK but used a lot more fuel.

 

Failing that a cam belt replacement might have been incorrectly timed.

Weight makes a difference at any speed, steady or otherwise, because roads are rarely flat and straight.

[TheRobinK]

I'd expect the 18 alloys to have a consumption penalty over the 17's on the Passat but it wouldn't cover what you are seeing.

 

Like chimaera, I haven't used your engine in a Superb but I am using its replacement ( the 1.6d common rail in a Superb Elegance also giving 105hp and the same torque). So, our cars are similiar spec (Elegance), same hp and torque and a similiar weight (if you have a saloon then mine will actually be heavier). I'm on 17' Laurel alloys.

 

At 120kph cruise (Ennis to Dublin on the M7 - into the city and then back again, aircon on) the MFD gave me 5.2 l/100km.  I know from experience that a brim to brim paper calculation after the run would give me a (true) 5.5 l/100km.

 

I get about 4.6 to 4.7 l/100km (62 mpg) if I am doing your 90% driving at 50 mph (this would be my drives from Ennis to Sligo...!)

 

So - even though the common rail engine would give few mpg better, I think your consumption is too high and you are right to investigate. That whoosh/boost issue is a great place to start.

 

 

[RubyCubes]

Cheers again for all the info and advice.

 

I checked the pipes from the top as best I could before I start looking from below and noticed the pipe connection in the red circle below wasn't fully in place - in the second picture you can see a silver ring that is sticking out, I undid the clip and when I pushed the pipe further into the connection it 'clicked' and you can't see the silver ring anymore so I think it's now properly connected. I wish I'd recorded the whoosh noise to compare as I can't tell if it's reduced or not, but I think it's reduced but is still there somewhat.

 

I took it for a quick spin on a nearby motorway (M3) and it read 5.5 l/100km average over a 7km run just on the motorway, but the stretch I was on I think is mostly slightly downhill. I'll try a longer drive and see.

 

I've read that a whistling tends to indicate a pipe leak after the turbo, whereas a whoosh indicates a pipe leak before the turbo - but I've also read that a whooshing can be normal and is just a recirculation valve unloading extra boost when gears are changed but the YouTube videos I've found of the recirc noise don't sound like the dump valve type noise I'm hearing. Just to help me identify things in case I need to go looking for other possible leaks, am I correct with the below (based on the first photo):

• The green circle is the MAF
• The green arrows show the pipes for the air INTAKE
• The red arrows show the pipes coming from the turbo / EGR

I have noticed some oil at the connection where the blue circle is and am wondering if there is a possible break in the pipe there. Given this position is after the turbo/EGR would I be right in thinking oil here would indicate a leak?

 

 

 

 

 

 

 

 

 

 

Edited 3 August, 2019 by RubyCubes

[bigjohn]

On 01/08/2019 at 23:14, RubyCubes said:

Recently purchased a 2009 Mk2 Elegance model Superb with a 1.9TDI 105hp engine to replace a 2004 B5.5 Highline model Passat with a 1.9TDI 130hp engine. The Superb has the 18" Skoda Themisto alloys and the Passat had 17" OEM alloys. The Superb has 160k miles on it and my Passat had 167k miles - bought the Superb as a nice person drove into my Passat and wrote it off. The Superb has a fully stamped service history and I read through to check and it was serviced bang on every service time. She was serviced and the timing belt and water pump changed by a garage (stamped) 6k miles ago - this Superb is in (100k+ miles) mint condition and everything indicates she was very well looked after.

 

The Superb is new (to me) so haven't gotten to do a proper full tank/distance mpg check and am currently working from the trip so understand it won't be 100% accurate but I'm finding differences between the two cars that I'm a little wary about. I'm working from UK mpg and found the Passat's trip to be generally accurate when compared to full tank MPG test.

 

Based on a consistent journey I do driving 50mph for 90% of the journey, I used to easily get 60 mpg in the Passat with aircon on (albiet in eco mode) and driving without consideration for improving MPG, while now I'm getting 53 mpg in the Superb at absolute best with everything turned off. That 53mpg was achieved changing my normal driving style to change gears a little sooner than I normally would and accelerate much less than I did with the Passat - I've followed all the standard mpg saving tips (tyre pressures correct, nothing in the car bar the spare tyre etc) and the breaks aren't sticking.

 

I'm also noticing that when doing bang on 120kph on a motorway using cruise control for a 30 minute drive I've done for years the Superb's trip reads as averaging 35mpg give or take a few, while on the Passat also using cruise control doing the same journey and speed I was getting 48-52mpg. Again, I know the trips can be off but that's a 27% decrease in mpg doing the same journey with very similar engines in similar enough cars and both using cruise control - plus it's summer time and the weather here is nice and warm so mpg should be at it's highest.

 

I understand the Superb is a little heavier and the 25 less horses under the hood mean I don't have the same punch the Passat had, but I'm thinking something must be up.

 

Am I over concerned here or should I get it scanned to see if there are any faults showing up?

 

 

 

 

 

You really need to measure tank to tank over a few fill ups - It is difficult to judge by one small journey as even a simple fact of going up or down hill gives a huge variation in mpg. Also trip computers can vary somewhat compared to reality.

 

I had a 2003 Superb mk I with the 1.9 100pd engine (similar to the 105) and with real life tank to tank calcs on a run did about 53mpg - overall average (inc urban) was about 50mpg. It did this from 18months old/18,000 miles  until I sold it 10 years later with over 160,000 miles on the clock. The trip computer was actually 4mpg pessimistic!!

 

I have also driven a Passat of that age (130ps I think) and the real life consumption was nowhere near 60mpg - and the trip computer was very optimistic

 

The trip computer on my MKII 1.4tsi is surprisingly accurate. Note some versions of the Superb II 1.9pd came with a DPF - usually the Greenline verison.

 

 

Edited 3 August, 2019 by bigjohn

[J.R.]

That red connection is the one that I inadvertently did not reconnect properly, for some reason the internal O ring had jumped outside of the joint preventing the clip from engaging.

 

 Any degree of leak there will dramatically affect your performance and fuel economy, if it was worked on by someone else then I recommend that you remove the pipe spigot and make sure that the O ring is present and undamaged, check any others too that may have been disturbed.

 

99% certain that you have found your problem.

 

PS, I believe that some of your arrows are facing the wrong direction.

Edited 4 August, 2019 by J.R.

[J.R.]

On 02/08/2019 at 17:41, chimaera said:

Weight makes a difference at any speed, steady or otherwise, because roads are rarely flat and straight.

 

Yes but most if not all of the extra fuel burned raising the extra weight is regained on the downhill stretch assuming a constant velocity, if you are constantly accelerating and decellerating then weight will come into play.

 

At steady speeds an increase in mass has a inconsequential effect on fuel consumption.

 

Other then the time it takes you to get to Vmax is your car measurably slower when carrying one or more passengers?

Edited 4 August, 2019 by J.R.

[chimaera]

1 hour ago, J.R. said:

 

Yes but most if not all of the extra fuel burned raising the extra weight is regained on the downhill stretch assuming a constant velocity, if you are constantly accelerating and decellerating then weight will come into play.

 

At steady speeds an increase in mass has a inconsequential effect on fuel consumption.

 

Other then the time it takes you to get to Vmax is your car measurably slower when carrying one or more passengers?

No, you burn about twice as much fuel on the climb as you save on the descent.

[J.R.]

I will bow to your superior knowledge.

[chimaera]

14 minutes ago, J.R. said:

I will bow to your superior knowledge.

To be fair, you're not completely wrong.

 

When you go up a hill, you add potential energy to the car equal to mgh (car mass times acceleration due to gravity times height change). You get back most of this on the way down (the 2nd law of thermodynamics will have its due). So some of that potential energy is lost, in proportion to the car's mass.

 

The bit people tend not to consider is that only about 40 % of the fuel's thermal energy is available at the wheels. Flipping that over, you use 2.5 times as much thermal energy as you gain in potential energy on the way up, and recover maybe 0.9 times as much of that potential energy on the descent. The other 1.6 times worth is lost, and that scales with the car's mass.

[SuperbTWM]

Its worth checking the timing with VCDS, a bit of fine adjustment might eek a bit more fuel economy out of her.

 

Also, there is no re-circulation valve on a diesel due to there being no throttle butterfly so there shouldn't being any pronounced whooshing noises other than the normal noise of the turbo spooling up and down

[J.R.]

So I was 100% right then..........................................

 

to bow to your superior knowledge

 

I knew all about the potential energy and second law of thermodynamics, I had not considered the thermal efficiency though.

 

I still reckon that compared to the differences of drag coefficent and frontal area between the Octavia and the Superb the increase in mass will have a de minimus effect on steady speed motorway economy.

 

Cant prove it though.

[chimaera]

To put it more simply, only 36 % of the extra fuel burned during a climb (90 % of 40 %) is recovered on the descent, and the amount of fuel used goes up with the vehicle's mass.

 

A 1.7 tonne Superb is going to consume 13 % more fuel on climbs than a 1.5 tonne B5 Passat. The Superb also has worse aerodynamics than the Passat (Cd of 0.29 vs 0.27), so it's going to burn more fuel at a constant speed too.

[RubyCubes]

Thanks again all for the info and advice. Some interesting points I wasn't aware of around the aero and consumption.

 

I think that pipe might have sorted it as a 25 minute run on the motorway gave an average of 5.5 l/100km going one direction and the 25 minute run back gave 6.5 l/100km going the other direction, though if that's optimistic like most MFDs I'm thinking there might still be something impacting. The tyres are 95% new but their rating is E for fuel efficiency - they were on it when I bought it - so they are probably playing a part too.

 

I don't have access to VCDS so I was going to get one of the OBD2 Bluetooth readers such as the one attached to check the timing advance. However, I've read posts here and reviews on Amazon saying they don't fit well into the Mk2 Octavia's port and am wondering if the Mk2 Superb will have the same problem. Has anyone successfully plugged one of these into their Mk2 Superb's OBD port? In relation to the timing advance, there are a few (very long posts) that seem to eventually converge on suggesting PD TDI engines should have a torsion at idle of 0.0, so am hoping to see something near enough to that.

 

Nice video of the process here, though not sure I'll undertake the adjustment myself if it's off.

 

 

[kindalen]

I have used an OBD11 bluetooth reader on a 1.9tdi Superb for years with no problem.

[RubyCubes]

12 hours ago, kindalen said:

I have used an OBD11 bluetooth reader on a 1.9tdi Superb for years with no problem.

 

Is it a Mk2 Superb you've been using it in?

[kindalen]

Yes Mk2.

[ruffday]

I think the main reason for lower fuel consumption here could be the lower power in the heavier car.

You will use more fuel in the lower powered car on similar runs

[3T51704x4]

Mind you that noise would be top of my list, IF you do have a boost leak from a split pipe/damaged O ring, split intercooler or failing turbo, you have found the source of the discrepancy.

[RubyCubes]

I'm still getting the whoosh noise but it has reduced a lot - I wonder if there is a leak elsewhere and will be using a pit in a week to get a good look underneath as I can't find any more from the top.

 

Although the noise is still there somewhat, the lpk/mpg seems to now be matching the Passat's - at least as far as the trip is saying - I'm off at the minute so haven't been doing my normal commute to do a brim to brim check yet.

 

While the trip isn't necessarily accurate at least I'm comparing the same trip against itself with the below figures so those improvements are at least accurate.

 

Prior to reconnecting that pipe:

> 70km journey doing 80kph for 90% of the journey = 5.3 l/100km (with a passenger)

> 50km journey doing 120kph for 90% of the journey = 8.0 l/100km (just me in the car)

 

Since reconnecting the pipe:

> 70km journey doing 80kph for 90% of the journey = 4.7 l/100km (with the same passenger)

> 50km journey doing 120kph for 90% of the journey = 6.0 l/100km (just me in the car)

 

I'm getting one of those scanners so will report back on anything else i find so anyone else who may have similar issues can try out what led to lpk gains.

 

[PD_Paul]

I have a similar problem with my car which has done 150,000 miles and is used as a taxi.  Fuel consumption is poor even on a long run and this is based on owning an Octavia with the same engine previously.

 

I have checked all the usual things such as tyre pressures, wheel alignment, binding brakes and all filters have been recently changed.  I visited fellow forum member Martin (Gizmo) last weekend and have some readings below from VCDS.

 

Car starts and drives ok, but I would appreciate it if you can see anything obvious which might explain the poor fuel consumption and how I can rectify it.

 

Group 4

Engine speed   819/min

Injection start   0.0

Injection duration   8.7KW

Torsion value   0.0KW (adjusted from -1.5)

 

Group 13

Injection quantity

Cyl 1      Cyl 2      Cyl 3      Cyl 4

-1.32      0.09       0.47       0.71

 

Group 15

Engine torque   56.1N/M

Fuel consumption   1.0l/hr

Torque request   0.0N/M