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Thread: RPM how high

  1. #1
    Guest The Big Yin's Avatar
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    RPM how high

    So for the past 2 weeks I have bee driving my Mum's car. Because i cold not ge my car out of the street.
    It is a 58 plate Mazda 5 1800cc

    And What I noticed is that when sitting at 80mph the rpm is up at 4000rpm. That is crazy. In my 9-5 aero at the same speed I am more like 2000rpm. is it gearing or the difference in engine size?

    No wonder it is bad on petrol.

  2. #2
    Guest TrIcK^'s Avatar
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    Tis not an Aero. Sit between 65 to 70.

  3. #3
    Guest Si's Avatar
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    IT's the gearing for the engine. No point in having a car with 5th gear that runs you at 2k at 80mph if it's not generating enough power to even overcome the wind resistance.

  4. #4
    Guest fullmetalgasket's Avatar
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    Yup, purely gearing for the reasons Si gives (and probably one or two extra)
    Sounds like my 190E, top gear put it at about 4k @80mph - the E class I got next had an overdrive (Plus an extra litre ) and would be doing just under 3,000 rpm at those speeds (geared for a 145mph top speed - in an early 90's estate )
    My G/F's old Jimny can beat your mums car though, that would be screaming along at nearly 5000rpm by 80 if you could get it that fast

  5. #5
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    Surely you are used to a 4AGE buzzing away at about 12k rpm at 20mph in 5th, aren't you?

  6. #6
    Guest The Big Yin's Avatar
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    Quote Originally Posted by Aitch View Post
    Surely you are used to a 4AGE buzzing away at about 12k rpm at 20mph in 5th, aren't you?
    Yeah thats different though
    it's 26 years old it get's away with stuff like that lol

  7. #7
    Guest Egon's Avatar
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    My parents have a shitreon picasso that i had to borrow for getting things that dont fit into bmw 3 series (read as "quite a lot") once and in 5th, it was doing 4000rpm at 70mph.
    It was hideous. Noisy and so unrelaxed.

  8. #8
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    4000 @ 80 is 20 mph/1000rpm, which sounds a bit short for a 1.8 petrol - are you sure there isn't a 6th gear?

    Normally, top gear on a sensible sized car is about 23-25 mph/krpm for petrol, although much taller (30+) for a diesel.

    Small-engined cars (like my EG4 Civic and my other half's 1.0 Yaris) are usually closer to 20 - like Si says, it's about actually having enough power to maintain cruising speed (and also some in reserve so you don't have to change down every time you come to a gentle slope).

  9. #9
    Guest Si's Avatar
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    My other half specialises in buying cars that are particularly crap at high speed cruising, and make it even worse by being stupidly noisy. Her DC2 is pretty silly for it, her Eunos R LTD was even worse - 5.2k at 90

  10. #10
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    thats how you get decent CO2 figures, whack in a spastic set of ratios so it works well on the dyno, convinces simpletons they're saving the world but is actually crap in real life

  11. #11
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    Try driving something like a Spitfire or an Austin 1100 at 80 on the Mway for any length of time and then compare.

    Even in the late 70s having a 5th gear was rare and the only sensible option for motorway cruising was aftermarket overdrive kits.

  12. #12
    Guest fullmetalgasket's Avatar
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    Yeah, my Westy was interesting on the motorway - I used to take her upto 90* as the resonence resulted in a quieter drive at higher revs than the ~4000rpm in 4th at 70/75

    *Indicated only officer - which was waaayyy off actual

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