Author Topic: Poor economy in 7th gear DCT  (Read 797 times)

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  • dk Denmark
Poor economy in 7th gear DCT
« January 28, 2018, 06:11:15 »
Hi all. This is my first time on the forum, so iím sorry if this topic has been brought up before.

A couple of months ago i bought a brand new i30 1.6 110 Diesel DCT. And iím generally pleased with my first 10k km.

However, iíve noticed that my fuel consumption is poor whenever iím in the 7th gear. And i donít understand why.

Cruising with 110km:
7th gear - 16km/l (~2,200 rev)
6th gear - 18 - 20km/l (~2,500 rev)

Same thing happens at 130km, just with slightly lower km/l numbers for both gears.

Has anyone tried the same, or even heard of the 7th gear performing bad in terms of fuel consumption? Could it be a software problem? Or do i perhaps need to run another 10k km to break in the car?


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Re: Poor economy in 7th gear DCT
« Reply #1 : January 28, 2018, 06:21:12 »
Hi all. This is my first time on the forum, so iím sorry if this topic has been brought up before.

A couple of months ago i bought a brand new i30 1.6 110 Diesel DCT. And iím generally pleased with my first 10k km.

However, iíve noticed that my fuel consumption is poor whenever iím in the 7th gear. And i donít understand why.

Cruising with 110km:
7th gear - 16km/l (~2,200 rev)
6th gear - 18 - 20km/l (~2,500 rev)

Same thing happens at 130km, just with slightly lower km/l numbers for both gears.

Has anyone tried the same, or even heard of the 7th gear performing bad in terms of fuel consumption? Could it be a software problem? Or do i perhaps need to run another 10k km to break in the car?
Having  no experience with this model I'll ask a few questions.

So are these instantaneous fuel readings you are quoting?

If so, does it have cruise control, what readings does that produce?

have you done any actual consumption tests as in fill the car up to the brim and going for a long drive then filling to the brim and doing manual calculations?

Could it be that it's labouring a little in 7th when accelerating and forcing that fuel rate up?

I'd be tempted to do my own calculations and seeing what it is averaging.

  • 2008 i30 SLX CRDi Auto, 2010 i30CW SLX CRDi Auto. 2008 i30 CRDi SX manual, Welly

Re: Poor economy in 7th gear DCT
« Reply #2 : January 28, 2018, 06:28:34 »
Hi all. This is my first time on the forum, so iím sorry if this topic has been brought up before.

A couple of months ago i bought a brand new i30 1.6 110 Diesel DCT. And iím generally pleased with my first 10k km.

However, iíve noticed that my fuel consumption is poor whenever iím in the 7th gear. And i donít understand why.

Cruising with 110km:
7th gear - 16km/l (~2,200 rev)
6th gear - 18 - 20km/l (~2,500 rev)

Same thing happens at 130km, just with slightly lower km/l numbers for both gears.

Has anyone tried the same, or even heard of the 7th gear performing bad in terms of fuel consumption? Could it be a software problem? Or do i perhaps need to run another 10k km to break in the car?
Having  no experience with this model I'll ask a few questions.

So are these instantaneous fuel readings you are quoting?

If so, does it have cruise control, what readings does that produce?

have you done any actual consumption tests as in fill the car up to the brim and going for a long drive then filling to the brim and doing manual calculations?

Could it be that it's labouring a little in 7th when accelerating and forcing that fuel rate up?

I'd be tempted to do my own calculations and seeing what it is averaging.

Hi. Yes these are instant readouts, done over the same 10km course on my daily commute in identical weather and conditions.

Cruise control is engaged for these readouts - i forgot to mention that.

I havent tried the manual consumption test, but i might give it a try in this week.

Honestly i dont feel it laboring (or assume it would) at 110km/h with +2,000 revs.

Its weird. Because the numbers are replicatable for me at almost any speed. 110, 130, 150km/h. 6th gear is always giving me 1-2km/l extra...

  • 2017 Trend 5 Door Hatch, Diesel 1.6, Auto, Stargazing Blue

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Re: Poor economy in 7th gear DCT
« Reply #3 : January 28, 2018, 06:53:07 »
Hi all. This is my first time on the forum, so iím sorry if this topic has been brought up before.

A couple of months ago i bought a brand new i30 1.6 110 Diesel DCT. And iím generally pleased with my first 10k km.

However, iíve noticed that my fuel consumption is poor whenever iím in the 7th gear. And i donít understand why.

Cruising with 110km:
7th gear - 16km/l (~2,200 rev)
6th gear - 18 - 20km/l (~2,500 rev)

Same thing happens at 130km, just with slightly lower km/l numbers for both gears.

Has anyone tried the same, or even heard of the 7th gear performing bad in terms of fuel consumption? Could it be a software problem? Or do i perhaps need to run another 10k km to break in the car?
Having  no experience with this model I'll ask a few questions.

So are these instantaneous fuel readings you are quoting?

If so, does it have cruise control, what readings does that produce?

have you done any actual consumption tests as in fill the car up to the brim and going for a long drive then filling to the brim and doing manual calculations?

Could it be that it's labouring a little in 7th when accelerating and forcing that fuel rate up?

I'd be tempted to do my own calculations and seeing what it is averaging.

Hi. Yes these are instant readouts, done over the same 10km course on my daily commute in identical weather and conditions.

Cruise control is engaged for these readouts - i forgot to mention that.

I havent tried the manual consumption test, but i might give it a try in this week.

Honestly i dont feel it laboring (or assume it would) at 110km/h with +2,000 revs.

Its weird. Because the numbers are replicatable for me at almost any speed. 110, 130, 150km/h. 6th gear is always giving me 1-2km/l extra...
I think you're right though anything above 2grand on the Hwy and it's generally in a sweet spot or at least the old FD is. Maybe this is a good question to throw at Hyundai.

  • 2008 i30 SLX CRDi Auto, 2010 i30CW SLX CRDi Auto. 2008 i30 CRDi SX manual, Welly

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  • dk Denmark
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Re: Poor economy in 7th gear DCT
« Reply #4 : January 28, 2018, 06:59:39 »
Hi Tazh

 :wttc:

This is strange considering the max torque is from 1750 revs and @ 10000 km it should be run in. I think I get better economi in my old 2008 5 speed @ 110km/h than you report for 7th gear..  :confused:
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Re: Poor economy in 7th gear DCT
« Reply #5 : January 28, 2018, 07:05:38 »
Hi Tazh

 :wttc:

This is strange considering the max torque is from 1750 revs and @ 10000 km it should be run in. I think I get better economi in my old 2008 5 speed @ 110km/h than you report for 7th gear..  :confused:
I wonder what the mass is? 2200 is very close to what I sit in auto (4) and manual (5) but I think my manual is closer to 2100 for my FD
  • 2008 i30 SLX CRDi Auto, 2010 i30CW SLX CRDi Auto. 2008 i30 CRDi SX manual, Welly

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  • dk Denmark
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Re: Poor economy in 7th gear DCT
« Reply #6 : January 28, 2018, 07:20:25 »


I wonder what the mass is? 2200 is very close to what I sit in auto (4) and manual (5) but I think my manual is closer to 2100 for my FD

The mass..? 

I get ca 19 km/L doing 110 km/h in fifth, don't remember the revs. I know it's 2100 @ 90km/h
  • i40 CRDi 100 kW 2013

Re: Poor economy in 7th gear DCT
« Reply #7 : January 28, 2018, 07:58:34 »
Guess it's time to pay my dealer a visit then. Crossing my fingers, and hoping it's some kind of software update i need.
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Re: Poor economy in 7th gear DCT
« Reply #8 : January 28, 2018, 08:48:56 »
 :welcome: Tazh,

I would do some brim to brim calculations and see what your overall economy is. That is what matters. The instentanious readout might be wrong. Trip computers can only do so much.

The 7 speed  DCT in my current model 1.6 Turbo petrol seems very efficient although I haven taken any notice of the instant readout while in 7th gear. I'm averaging 7.5 l/100 kms for my first 15,000 with the airconditioning running perhaps 50% of the time and a good mix of city and highway driving. This is lineball with the official combined figure.  :cool:
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Re: Poor economy in 7th gear DCT
« Reply #9 : January 28, 2018, 16:36:01 »
I pay little regard to instant fuel economy figures, across numerous makes and models I have found them to be a wank. The actual fuel economy figure is what I watch.

Also is the 10k course the only driving you are doing? If do I suspect it is the vehicle trying to do a DPF regen upon reaching temp. If your commute is only 10k it will not have enough time to do it so will continue to attempt it each time until it is done.

It is important that if your vehicle has a DPF you take it for a nice long drive every now and again to allow the DPF to burn off all the stuff it collects (yep getting technical here).
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Re: Poor economy in 7th gear DCT
« Reply #10 : January 29, 2018, 02:50:27 »
I pay little regard to instant fuel economy figures, across numerous makes and models I have found them to be a wank. The actual fuel economy figure is what I watch.

Also is the 10k course the only driving you are doing? If do I suspect it is the vehicle trying to do a DPF regen upon reaching temp. If your commute is only 10k it will not have enough time to do it so will continue to attempt it each time until it is done.

It is important that if your vehicle has a DPF you take it for a nice long drive every now and again to allow the DPF to burn off all the stuff it collects (yep getting technical here).

Thanks for the concern, i realize now i haven't been totally clear in my words. The 10km course i mentioned is only a piece of highway i tested the instant readings (Drove 10km, took an exit, drove back, and tested the same 10km again). My daily commute is 2 x 120km of highway :)
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Re: Poor economy in 7th gear DCT
« Reply #11 : January 31, 2018, 10:05:57 »
UPDATE:

I had the car at my local Hyundai retailer, and they haven't heard of such issue before, and had no software upgrade either to fix it.
They agreed on doing an in-depth look at my car, when i drive it to it's first 30.000km/service. I will update this thread, if i learn something else in the meantime.
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Re: Poor economy in 7th gear DCT
« Reply #12 : January 31, 2018, 16:51:57 »
Thanks for the  update. I still doubt it is an issue. Please try our suggestions of measuring fuel useage against distance covered using manual calculations. It will probably work out at a point or two worse than the trip computer figures, but still surprisingly close to the advertised milage for your style of useage.  :cool:
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Re: Poor economy in 7th gear DCT
« Reply #13 : January 31, 2018, 20:49:55 »
I always wondered how the car works out fuel consumption until i askedan engineer in the trade who told  me fuel used was based on injector opening times and volume going through.  On another make of car i checked the calculated consumption against a 600km trip and the actual consumption using    fill to fill method about 10%  less...just for info
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Re: Poor economy in 7th gear DCT
« Reply #14 : February 02, 2018, 04:23:32 »
I'll try that next week. For this week i'm stationed in Zurich, visiting some family.

But worth noticing is this video, where you can see me transition between 6th and 7th gear. And as you can see, the fuel consumption doesn't change much. (I know this wasn't what you asked -- But at least you can see the challenge i face, and why i wonder)
:link: 20180130_181414.mp4 - Google Drive

My main concern is, that my old Audi A3 was listed for 22,7km/l and on average i got 25km/l on the highway. Compared to my Hyundai which is listed for 24,4km/l, and i get ~15-16km/l on highway, which at least cost me 75pounds more a month to drive. Which is not ideal for me, with my daily 240km on the highway.
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