Economy / Power Question

Discussion in 'General Discussion' started by Swiss Toni, Sep 28, 2008.

  1. Swiss Toni

    Swiss Toni Hardcore MB Enthusiast

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    I am looking for the "compromise".

    The combination of power and economy that suits me best.

    To make the comparison, we have to use the official "combined" figure for economy and the bhp figure for the same car.

    So...

    Is the a site on t'internet where I can enter, say, bhp and get the model with the highest combined economy figure with that power output or greater?

    eg some varients of the 1.9 VAG 130BHP unit quote a combined econmy of 48mpg.

    At 130bhp, 140, 150 (and more) - what are the most economical cars available?

    Cheers

    :eek:
     
  2. st4

    st4 Banned

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    You'll be looking for something diesel and relatively lightweight. BHP/MPG a BMW 118/20/23d series with efficient dynamics will make an excellent bet + RWD but Turbo failure isn't unknown.

    A VW Golf 2.0TDi/Audi A3/Skoda octavia with the same engine will be good.

    If you want pure economy they do a bue motion polo or a gutless Seat Ibiza of a similar tech.

    Getting a match for economy/power is one thing, but what is the type of car you're after, a saloon, a hatch etc.
     
  3. Dieselman

    Dieselman Banned

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    Just use the measured CO2 figures. They are a direct indication of economy.
     
  4. st13phil

    st13phil MB Club Veteran

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    Do you happen to know the constant that's used to calculate the CO2 figure from fuel consumption for both petrol and diesel engines? Or a link? TIA...
     
  5. st13phil

    st13phil MB Club Veteran

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    I've never owned a car with the VAG 2.0 engine, but my direct experience of the VAG 1.9 PD engines is that he 150 uses approx 5% to 6% more fuel in like-for-like real world driving that the 130 in essentially the same car. That was over approx 80,000 miles in each car (MkIV Bora/Golf). One thing to be aware of is that the 130 in the Passat with 5-speed box is downrated on torque compared to the 130 when mated to the 6-speed box.

    My other comment is that although the 150 is marginally quicker in a drag race, you won't notice the performance difference vs the 130 (6-speed) for 99.9% of the time so if fuel economy is important then I'd go for the 130 - which is also more plentiful and cheaper.
     
  6. Dieselman

    Dieselman Banned

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    From memory:
    (CO2 content of fuel/mpg)*620

    For diesel the Co2 per gallon is 12.2 kg
    For petrol the Co2 per gallon is 10.6 kg

    Example:
    Diesel
    12.2/36*620 = 210g/km
    Petrol
    10.6/25*620 = 262g/km

    Conversely using a bit of simple algebra one can work out the mpg from the Co2 figures.
    (Co2-Gallon/Co2 rating)*620 = mpg
     
  7. Dieselman

    Dieselman Banned

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    Can you get a 130Bhp with a five speed box.?
    I thought the 6 speed was developed due to the requirement of the additional torque over the 115Bhp engine.
     
    Last edited: Sep 29, 2008
  8. Will

    Will MB Club Veteran

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    Yep, we've got a couple of 130PS Passats at work with 5-speed manual boxes.

    After my trouble with the whole gearbox/clutch etc on my old Audi, I don't rate the 5-speed manuals at all.

    Will
     
  9. Dieselman

    Dieselman Banned

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    Thanks. I've never seen a 5 speed 130.
    Interesting you say about the clutch. A collegue had an A3 where the master cylinder went South after 2 years.
     
  10. Corrado

    Corrado Hardcore MB Enthusiast

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    Guess these are at a given speed, so if most miles were done at significantly different mph the effects of vehicles' Cds could alter the league table ranking.
     
  11. Will

    Will MB Club Veteran

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    These are the previous model Passat, late 2005 from memory.

    I'm pretty sure they're the 130 models as I remember speccing them at the time.

    The Audi was a bit of a lemon, they had to replace the selector, then the master cylinder, then they changed the slave cylinder, flywheel, release bearing and the clutch - all under 2000 miles from new :crazy:

    It was much better after that, but still never perfect IMHO - sometimes you'd have to pump the clutch to get it to go into gear.

    Originally it would crunch going into gears with the cluch fully depressed. Sometimes you'd be 'making progress' and when downshifting you'd be left unable to select a gear at speed, and worst of all the clutch pedal would sometimes jam when pressed down, so you'd have to hook it back up again...

    Not what you should expect from a brand new car costing circa £28k at the time.

    Will
     
  12. Dieselman

    Dieselman Banned

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    Exactly the same issues.
     
  13. Seamster15

    Seamster15 Hardcore MB Enthusiast

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    Bluemotion is way too slow. It will do you head in.
    I would go for the older PD units. The 130bhp is the one to go for, power and economy.

    We have the 140 TDi in on of our cars and it not a really nice engine tbh. Plus 39mpg yesterday on the motorway is not inpressive....

    Simon
     
  14. Dieselman

    Dieselman Banned

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    No. They are the rated Co2 outputs as defined by the test cycle.

    Obviously a more economical driver will achieve a better mpg so a lower Co2 output.

    Someone once posted the MPG of their BMW 540, which worked out to an average Co2 output of....

    Go on, guess....




    Yep...540g/km.
     
  15. Will

    Will MB Club Veteran

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    It's got my blood boiling just thinking about it again now...

    My 20 year old self-maintained 190Es are more reliable, better to drive and give me less stress than this old A4 was!

    That's one car I'm certainly glad to have seen the back of.

    Will
     
  16. Mactech

    Mactech Hardcore MB Enthusiast

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    I have always been interested in the power/economy compromise.
    During practical testing of all the cars I have driven if you add the average mpg to the average mph you yet the 'fuel number'
    For a reasonable size car giving long distance comfort, my winner so far is the 1.9 CDTI Vectra!:eek: (shown)
    But I did get almost 75 mpg from a 1.4TDI Polo on holiday recently but that only had 90bhp compared tp 150 of the repmobile.
     
    Last edited: Jun 23, 2009
  17. Benzowner

    Benzowner Hardcore MB Enthusiast

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    If that is true, and I bow to your greater knowledge, why is Co2 constant, but mpg different for the speed, urban, extra urban etc. Should not the weight of the right foot also be factored in:D :D
     
  18. Dieselman

    Dieselman Banned

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    May I refer you back to Post #14.

    The standard Co2 figures are calculated on the standard test cycle, which equates to a set mpg for that vehicle on that test cycle.

    If the average mpg is known then the average Co2 can be calculated.

    Take mactech's case of his Vectra at 71mpg.
    (12.2/71) *620
    =104 g/km.

    pretty good and well below the published figure.

    Maybe we need to set mactech a new target. 100g/km.. :D
     
    Last edited: Sep 29, 2008
  19. st4

    st4 Banned

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    Well there is one 540i that I can think of that won't be releasing any CO2 anytime soon....
     
  20. wemorgan

    wemorgan MB Club Veteran

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    I've found this government site quite useful in the past.
     

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