43 real world mpg MK2 Golf 8v GTI...No? 51.7mpg 21/04/12 439miles a tank.

Discussion in 'Mk2' started by Toyotec, Jan 7, 2012.

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  1. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Background

    Fuel is becoming increasingly expensive these days and long term owners of older VW vehicles do feel the pinch and may consider alternatives which includes purchasing a newer vehicle.
    A similar discussion in a recent thread here
    Thing is can you achieve over 40mpg from a old Golf Mk2 made over 20 years ago?
    Well I decided to find out and no better car to attempt this exercise than my recently purchased 8v MK2 GTI called "J0RAN".

    [​IMG]

    The objectives

    • Establish real world FE from a MK2 Golf GTi 8v in good working order
    • Correlate real world FE to the MFA display.

    The car

    At over 168K miles this car has had a good life and was routinely serviced by either VW dealer or a independently trained specialist.
    My subjective thoughts about the car were:
    • The car feels very healthy to drive and previous glances of the MFA display has shown 36-38mpg. Can this be trusted?
    • The performance of this vehicle is no better than a new 2010 Focus 1.6 TiVCT, which I also drive extensively with the Golf MK2 having significantly worse NVH by todays standards and less "creature comforts".
    • As a side note a modern Focus 1.6 TiVCT would also achieve up to 40 mpg.

    Testing procedure

    So let's get the testing started.

    First we should note:
    • The car was running a good state of tune from the last garage that looked after it IMO.
    • The, AUG gearbox, airbox and dizzy settings are std.
    • The wheels and tyres are BBS RA 6.5x15 with 195-50-15 rubber from my old 8v 2.0.
    • The tyre pressure, was ~ 29-31 psi all around. No attempt was made to equalised or increase the nominal pressure.
    • Drive route for the exercise began from warmed up conditions when the gastank was refuelled.
    • Drive cycle included motorway, A and B roads in the city.
    • H/L and the blower were used which would have put extra load on the alternator as you would when driving in colder ambient and the dark.
    • Vehicle was cold started on most journeys and drive commenced ~ 10secs later except for initial refuel @18.26 litres where the vehicle was fully warmed up.

    Now that information about the car has been established, a prep drive was done to observe the MFA as well as the vehicle performance during sensible driving. All was well and I carried on monitoring the drive until the tank was running very low then the car was refuelled.

    This is where the fuel gauge was at the start of the test, before refuelling at the petrol station.

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    18.26 litres in fuel was put into the tank

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    I had 28 miles to go and the fuel gauge then settled as seen below.

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    The MFA and odometer was reset and the test began.

    Each journey was noted for start mileage, end mileage, cold starting and final MFA reading. The distance and time was was double checked with the Sat Nav.

    Here is the readings just before leaving the car overnight.

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    The following morning I set off for work.

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    During this drive on the motorway, 50.5mpg was achieved as displayed by the MFA. I managed to drive sensibly at this level of fuel consumption until the journey was complete some 61 miles later.

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    Later that day after work, the car was used to commute to Garage Streamline which is in Central London on very slow city B roads. In this trip my worst mpg was achieved.

    [​IMG]

    Hours later the car was cold started again and I went home with the final journey achieving as seen below.

    [​IMG]

    The following day the car made it to the same petrol station it was fuelled at 2 days before and some 174.5 miles later.
    My fuel gauge looked this when I arrived or about the same as the initial fuel stop ~ 175 miles ago.

    [​IMG]

    Please note the final mpg for this trip was less than displayed as I left the car idling a bit while the pictures were taken.

    I then filled it up with approximately the same amount of fuel as in the start of the test.

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    I deliberately put 18.27 litres to differentiate from the last time.
    The fuel gauge settled at...

    [​IMG]

    Unless there is serious lag or delta in the gauge itself it can be safely assumed ~ 18.26 litres of fuel were consumed in this exercise.

    My Findings

    The above journeys are summarised in the table below.

    Actual FE

    Pence/litre Amount spent Total UK gallons from litres Distance travelled in miles mpg UK l/100km mpg US
    136.9 25 4.017 174.7 43.49 6.49 36.22

    Using MFA readings to work out FE for 174.7 miles.

    Journey discription and miles MFA indicated mpg end of trip Accessories Comments
    28.7 miles petrol refill to home 42.9 H/L, Blower M/A/B
    61 miles home to work 50.5 H/L, Blower B/A/M/Fast A
    36.4 miles work to intermediate stop 37.3 H/L, Blower Fast A/B city
    20.1 miles intermediate stop to home 39.9 H/L, Blower B city/A
    28.5 miles home to petrol refill 44.6 H/L, Blower B/A/M
    Average MFA FE (UK) for 174.7miles 42.9 (under read by 1.3% from actual)

    M- Motorway
    A- A road
    B- B road
    Fast - A road with 70 limit
    City - possibly stop start traffic


    The MFA, despite its mechanical inputs for load and speed, seem very accurate under reading at just 1% less than actual for this exercise. This maybe due to test noise or delta in actual fuel level.
    The speedmeter seems to over read by an offset but this does not affect the odometer which tallied with the sat nav for each journey.
    City start stop driving had a detrimental effect on FE but not as drastic as if the car was fitted with a big engine such as a VR6 (more parasitic loss).

    Potential FE improvements

    This car, even though well serviced, could benefit from tuning to improve some areas for part load response.
    Tyres pressures should be equalised pumped to around 35 psi and the wheel alignment checked.


    Answering the objectives

    So can you achieve more than 40 mpg from a MK2 Golf GTi w/digifant 2 in a reasonable state of tune? Based on this experiment yes even up to 50mpg
    Is the MFA accurate? Based on this exercise surprisingly yes.
     
    Last edited by a moderator: Dec 11, 2013
  2. turbotommy Forum Member

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    Very interesting thread (my tdi averages about the same day to day driving like a granny) would be very interested how you could improve its MPG without going to silly measures.
     
  3. jamesa Forum Junkie

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    Thank you ... :thumbup:
     
  4. danster Forum Addict

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    Breaking News Just In....

    Reuters report Toyotec in dangerous law breaking criminal activity. :o

    No, not driving an 8v vehicle. But using a mobile phone at the petrol pump. tut tut. :lol:
     
  5. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Sorry to break the bad news...It was my Panasonic TZ8 ;)
     
  6. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Just simply tune up the car as has been done do with the rest of the fleet, pump up the tires to be equal and send it to align. Do not expect a massive improvement like 60mpg etc but should see less variation between urban and extra urban driving.
    If I get time we will see.

    No problem
     
  7. Gaddmeister Forum Member

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    :lol::lol::lol:
     
  8. danster Forum Addict

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    A quick google search suggests said camera has a flash. Now that could be deemed as a potential fire hazard or ignition source.

    And if it was an old fashioned camera with film. This would needed either developed, or the use of a negative scanner to get the pics to up loadable std. This would require gadgetry, and unless that gadgetry was powered by a carbon neutral source, it will have to be added to the overall carbon footprint and emissions of the car and this study. [:-B]
     
  9. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Neine Herr Danster-San

    Flash would have fecked up pictures so camera feature for "Night Scenery" used [:D]

    The camera is like 16v direct injection device with user programable fuel injection :lol: Developing of flim is going back to side valve and carb days :o

    I digress...nighty night everyone...
     
  10. Blue MK2 Forum Member

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    Great write up. This is why I dont want to do an engine conversion.

    I do need to get mine tuned up though. Can you book me in Toyotec?
     
  11. DC75

    DC75 Forum Member

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    i love these experiments and will conduct the same with my cars. couple of things though:-136.9 for normal unleaded! save yourself 7p per litre at tesco near toomeys, any idea how big a fuel tank is on a mk2 gti? as i will be doing this from full tank to zero(keeping a couple of litres in the boot when tank gets low and starts to cough)over a 2 week working period, i will also do this in the summer when the use of lights and heater will be used less, do you think there will be much difference? at the moment im getting about 350-380 miles per tank compared to the usual 400-420 in the summer.
     
  12. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    The experiment is was all about consistency. That petrol station would have been outside my drive cycle and offset the cost due to the extra distance.
    Gastank capacity for a 90 spec is stated as 55 litres in the Instruction Manual.
    I ran the car until it ran out of petrol recently and the fuel gauge read very similar to where it was on the test. As my driving involved the motorway, I did not want to chance breaking down, hence my method to determine the amount consumed and replenished was the same.
    The fuel in the winter needs to be more volatile, to allow the vehicle to start at say -25C and in warmer times, like the summer the RVP has to be reduced to prevent vapour lock in fuel lines and in the dispenser itself. I not in the know if the additives placed in summer fuel cause and a slight increase in octane which would have resulted in your increased FE. However in the summer your cold starts and warm up times are less severe and you are likely to use less accessories.
    Assuming a nominal 50 litres is refilled and that 50 litres = 10.9 gallons then you achieve
    32.1-34.8 UK mpg in the winter
    36.7-38.5 UK mpg summer.
     
  13. garfayliu Forum Member

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    Hey Eddie, nice write up..

    Can you qualify what
    means please?

    I still struggle to be sensible, but imagine it is be light on the throttle, say half way down, change up before 3K, and use gears to slow down rather than putting into neutral and braking, aim for consistent 70mph speed (though not sure if this is about 3.5K in 5th on 02A in ABF).

    Cheers.
     
  14. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Good question and I can attempt to expand.

    Driving sensibly:

    1. Anticipating what will happen in to the traffic flow and adjusting approach speed to avoid sudden braking or acceleration.
    2. Keeping engine speeds under max torque peak/VE which in this engine would be under ~3200rpm - to evaluated on G meter and on dyno soon.
    3. Gentle pullaways in start stop traffic @ 1000-1200 rpm or avoiding deep throttle excursions or high load. Used with anticipation to avoid excessive idling.
    4. Cold starting and pulling away ~10 secs after.
    5. Hot starting and pulling away ~5 secs after.
    6. Obeying the speed limt at all times if not keeping just under it.

    I may have forgot something but hope you get the picture :thumbup:
     
  15. Matt48 Forum Member

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    Well done Toyotec good to see someone else get 44mpg.

    It surprised me too that the MFA was quite accurate on mine. I think you should be filling up for 129.9 to 131.9 so that was over priced.

    I've got to say that over 11 years of driving the same car I dont feel the mpg has got worse in that time. 97k to 235k now. However as an old git I'm no boy racer.
     
  16. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    South Mimms Motorway services suck!!

    All for research though...
     
  17. m1keh Forum Member

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    Just another fuel economy gaining tip here. Along the lines of the anticipate what will happen point, even during driving with no traffic try and release the throttle far enough before a junction so you will not have to use the brakes at all and engine braking will do all the work. Same goes for corners etc.
     
  18. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Agree:thumbup:
    Also during backouts your injectors should shut until a threshold rpm or load is meet.
    Good for going down hills.
     
  19. muppet9966 Forum Member

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    That's a great write up.
    I wonder what looks you got at the petrol station with your camera in hand - you must have looked like a tourist - lol.

    As the MFA seems accurate enough, I need to get mine sorted in my CL.
    I wonder what MPG the MFA will display when I get it working, I mainly do 50miles motorway driving a day and I think I achieve 35MPG.
    This seems low to me but may be right for a 1.6.
     
  20. beaniegti

    beaniegti Forum Member

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    Nice to see a bit of thought put in to this topic rather than relying solely on the mfa, although it seems yours is working well :thumbup:

    Just to add to the topic: I've just completed a very long drive through france in my 16v. The car has had a bit of a hard time of late, feeling a bit down on power and a shade out of sorts so getting back was of more importance than breaking any land speed records. This seemed like the perfect opportunity to get an idea of its 'real' mpg even if it didn't feel 100%.

    So tank brimmed and off i went.

    After hundreds of miles at a steady 60-65mph (yaaaawwwnn!) i eventually re-brimmed the tank and worked out my mpg. The result...just under 42mpg.

    Not bad, but not brilliant given the type of driving done-i'd hoped for more despite it being winter. However, upon finally resting the car in england i found one rear caliper was slightly sticky (i'd known about this) and so was one of the fronts (the giveaway, aside from the whining, was one completely black alloy and one rather clean/normal one!) so i'd hope that with properly working brakes i'd have got a slightly better result. The car has also had the head 'done' and the WUR adjusted and has never been quite as frugal since that.

    Interestingly the MFA reckoned i had managed just 36mpg so it was a nice surprise to have bettered that!
     
    Last edited: Jan 8, 2012

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