TDI vs FSI: fuel consumption

[docjames]

2.0FSI golf - in the driving you suggest, we do 10-12L/100km, but down to 6's on highway.

usual urban mix (80% stop-start/20% fwy/80kph highway) we're getting around 8-9L/100km. And we've done low kms too (13000km total in three years!)

[THR]

^ Thanks!

I drove home just before and the roads were quiet and the trip was around 6.2, which was good. So the stop/start makes a huge difference.

[orsegtsport]

I have a few workmates with both GTI's and TDI's. Driving into the BNE CBD their fuel consumption is about the same, much to the disgust of the TDI owners......

A TDI is only really efficient at cruising speed on the highway where you're not using the turbo. The moment the turbo starts spooling up say goodbye to fuel efficiency. You get punished for having fun in any turbo car, be it petrol or diesel.

TDI's can run very efficiently at the low suburban speeds too, in fact I actually get better get economy around town if the roads are quiet, than I do on the highway. Even when the traffic is reasonably heavy, I still get great economy, as long as it's not bumper to bumper the whole way home.

Went to the rugby in Subi last night (Go you good thing! ),which was mixture of very heavy traffic around the city, and very quiet roads out in the suburbs), and I still averaged 5.1L/100 km. So in anything other than total gridlock, the TDI will still have a significant advantage over the GTI.

[Mischa]

at risk of sounding incredibly repetitive: if a tdi is driven hard it will use exponentially less fuel than a gti or tsi driven hard. this is due to a few factors which i cbb to write down right now

[BarneyBoy]

Lets do some calculations. First some assumptions:

If fuel is $1.75/L
If diesel will give better fuel consumption by 5L/100 KM

So for every 100km you save 5L of fuel.
5 x $1.75 = $8.75 / 100km

At $2,500 more:
2,500/8.75 = 285.714 lots of 100km
= 28,571.4km before you break even.

Now consider if Diesel only gave 3L/100 km difference, that works out to be 47,619km before you break even.

The higher the fuel cost the quicker you will recoup the difference, the higher the difference in fuel consumption, the quicker you will recoup the difference.


Look at it this way though, the ufront capital cost is a once off, the recurrent hit's you ever week. If you can pony up a little more upfront you WILL save a few bucks each week.

If your only doing 10,000km per year, it will be three years before you break even on your upfront, but then whats resale of the diesel vs a petrol? There are lots of factors. I still stand by if you can afford it upfront, why not get better consumption figures.

And when you sell it (say after 3 years), you will get back 66% of that extra $2500 (the retained value). So the extra cost at time of sale is only 800 odd dollars. It's called Whole of Life Value. Whatever the car costs up front minus what you get back at the time of sale = its ACTUAL cost.

With all due respect, your calculations are the same incomplete calculations that many of our esteemed motoring journos are making. It's no different to making comparisons without running costs, or without repair/spare parts cost. To be fair you must look at the cars cost over its lifetime. And that includes its sale.

[greygolf8]

My TDI DSG has done 7k and gets about 5.7 in the country at around 110 with cruise control. In the city (no cruise) its about 7 using S mode. Will have to try D mode & drive like grandma to see if its a big diff. Start / stop uses lots fuel and the traffic lights in Syd are amazingly unco-ordinated on main roads.

[THR]

Yes, ... Sydney's traffic lights are amazingly unco-ordinated, as you say.

[GTom]

Yes, ... Sydney's traffic lights are amazingly unco-ordinated, as you say.

I wouldn't go that far..... The beuty of the traffic signal system is that it can revert to other systems used in America and elsewhere. The system used in Sydney (The SCAT System is actually developed in Sydney by the DMR (Now the RTA) and exported world wide to Japan part of the US and Europe) It is one of the best systems in the world. There was a study done I think mid last year when they actually put a section of lights to a timed system (New York/London Europe kind of style) and that just nearly stuffed alot of people around, least to say complaints just sky rocketed for that area!

The problem is it is very hard to give priority to more then one stream of traffic..... Min. Green time in Syd, is 30 Sec. and Max green time is 3 minutes.

My rant over..... Basically what i just said.... The traffic lights aren't as uncoordinated as they may seem it can be a hell of a lot worst!

[craigy]

TDI's can run very efficiently at the low suburban speeds too, in fact I actually get better get economy around town if the roads are quiet, than I do on the highway. Even when the traffic is reasonably heavy, I still get great economy, as long as it's not bumper to bumper the whole way home.

Went to the rugby in Subi last night (Go you good thing! ),which was mixture of very heavy traffic around the city, and very quiet roads out in the suburbs), and I still averaged 5.1L/100 km. So in anything other than total gridlock, the TDI will still have a significant advantage over the GTI.

I have to agree about the urban economy.
If the traffic is light I'm achieving better than 6l/100 on my drive to work (school holidays) but on the freeway at 115 I'm getting high 6's-7s. One very suprising thing I have noticed is that at 40km/h in school zones the MFD shows better than 5l/100, my BMW 330CI was around 12-13l/100 at 40km/h.
My long term average is 7.5l/100 over 3000km.
If the traffic is very heavy I'm getting mid 8s.

[Mischa]

its not magic, diesels are more efficient under load whereas petrols are more efficient while cruising (mainly due to the weight of components in the diesel engine)

[THR]

The system used in Sydney (The SCAT System is actually developed in Sydney by the DMR (Now the RTA) and exported world wide to Japan part of the US and Europe) It is one of the best systems in the world.

I don't know what cities you've visited but the signalling system here is extremely poor. It doesn't adjust for the time of day, nor does it sense when vehicles are present (i.e. pressure sensors under the road). Thus you can have a series of light sequences without receiving a green arrow or, vice versa, a series of green arrows when there is no traffic that requires it.

In addition, due to lack of sensors and proper time based sequencing, you have extended periods of green at night time for no good reason. Or you can sit on a red light for totally ridiculous periods of time.

So many times you get a green light only for the next set to turn red. And then the next set. And the next set. So you're constantly crawling. Rather than having proper sequencing so that you get green, then the next go green, etc.

Frankly, the signalling system in Sydney is terrible and sub-standard compared to most other cities.

[GTom]

I don't know what cities you've visited but the signalling system here is extremely poor. It doesn't adjust for the time of day, nor does it sense when vehicles are present (i.e. pressure sensors under the road). Thus you can have a series of light sequences without receiving a green arrow or, vice versa, a series of green arrows when there is no traffic that requires it.

In addition, due to lack of sensors and proper time based sequencing, you have extended periods of green at night time for no good reason. Or you can sit on a red light for totally ridiculous periods of time.

So many times you get a green light only for the next set to turn red. And then the next set. And the next set. So you're constantly crawling. Rather than having proper sequencing so that you get green, then the next go green, etc.

Frankly, the signalling system in Sydney is terrible and sub-standard compared to most other cities.

Intersections do use sensors, but not pressure sensors, they use induction loops basically the same way a speed camera senses a car go over it and calculate the speed etc. Vehicle detection I think was trialled but came back as not accurate enough...... It has a 90% success rate, the induction loops are 95+ if not higher.

Can't go into specifics but lets say the system is "smart" enough to sense trouble, if vehicles move slower then normal through any intersection it then sends an alert to the person who is responsible for any given section within the road network.

From these induction loops it basically counts the amount of cars going through and also what speeds the vehicles are doing. However not every intersection has this sensor, but almost every one has it.

The system is also integrated to CCTV at specific locations most are able to be controlled, so instead of sending out a crew they can basically link to what ever intersection (if a camera is present) and control a situation (i.e send out Police or a TEPS crew)

In regards to the constant red lights, you'll often find that the road you are traveling on is not the priority of the sequence.

Again it's impossible to give more then 1 stream of traffic priority.

You'll also find that it is possible to set parameters for any time of day normally i think it's off peak and peak sequences...

[Greg Roles]

I find the lights up here in Brisbane very co-ordinated, especially AT peak hour, so much so that I usually speed up / slow down to get into a "groove". At 5pm out of the city, the major arterials seem to be quite timed and if you can get it timed right can have a virtual green run home. At least that's what I'm finding?

I think if you want to find a problem, especially in heavy traffic, well there's plenty to find!

[blutopless2]

we get the following figures out of our cars...
Polo GTI (std 110kW 5spm) 7L/100k's
03 New Beetle cabrio (std 2L 85kW 5spm) 6.5L/100k's
Jetta TSI (std 2L 147kW 6sp dsg) 8L/100k's

[ABCD]

Probably too late for this thread but here goes
6sp manual 2.0L TDi
Bit over 2 years old with 35000km
Mixture of city stop/start and motorway driving
5.6L/100km on trip computer long term average