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MPH and Gear Ratios - Audi
Bit nerdy this- but I have what is probably the best car I have ever had- An Audi 1.9 Diesel. However what absolutely ruins it is the gear ratio in top. I spend allot of time on the motorway doing Ahhh 70MPH and I keep wanting to change up- It would be loads quieter, more relaxed and get me lots more MPG. The engine is plenty torque'y enough at low revs.
Why did Audi do it that way? - and Is there a way the gear ratios can be changed easily?
Why did Audi do it that way? - and Is there a way the gear ratios can be changed easily?
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Comments
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What revs is it doing at 60 in top ? 5,6, or 7 speed boxYou scullion! You rampallian! You fustilarian! I’ll tickle your catastrophe (Henry IV part 2)0
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I used to find my old N reg A4 1.8T was better on fuel at 80mph than at 70mph...0
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A3, A4 or......?? What year?"You were only supposed to blow the bl**dy doors off!!"0
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Bit nerdy this- but I have what is probably the best car I have ever had- An Audi 1.9 Diesel. However what absolutely ruins it is the gear ratio in top. I spend allot of time on the motorway doing Ahhh 70MPH and I keep wanting to change up- It would be loads quieter, more relaxed and get me lots more MPG. The engine is plenty torque'y enough at low revs.
Why did Audi do it that way? - and Is there a way the gear ratios can be changed easily?
Incorrect. It is ENGINE LOAD that determines MPG, not the speed the engine is doing or the gear ratio. It is MORE economical to drive around town in 3rd gear doing higher revs than in 4th gear for example.
Whilst it would be undoubtedly quieter, it won't necessarily be more economical. I have a 6 speed car. A lot of the time on the UK motorway network, 5th gear is more economical, especially where its hilly or if its windy.0 -
Same here 6th gear is 70+, In theory 85mph is more economical than 70. Not that i would travel that speed
of course, But it really is.Censorship Reigns Supreme in Troll City...0 -
Incorrect.
Whilst it would be undoubtedly quieter, it won't necessarily be more economical. I have a 6 speed car. A lot of the time on the UK motorway network, 5th gear is more economical, especially where its hilly or if its windy.
Remind me is that diesel or petrol I can't remember."If you act like an illiterate man, your learning will never stop... Being uneducated, you have no fear of the future.".....
"big business is parasitic, like a mosquito, whereas I prefer the lighter touch, like that of a butterfly. "A butterfly can suck honey from the flower without damaging it," "Arunachalam Muruganantham0 -
Has someone changed the wheels, ie 16" down to 15" this will alter the gear ratio0
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grizzly1911 wrote: »Remind me is that diesel or petrol I can't remember.
Diesel. It would make no difference if it were petrol as its still all about engine load, not engine speed.0 -
Has someone changed the wheels, ie 16" down to 15" this will alter the gear ratio
It would, if they had not done what one usually does and compensated by putting higher profile tyres on to keep the overall wheel + tyre diameter the same.
I'm not sure how legal it would be to significantly alter the overall diameter like that, but I don't think it would be the cause of the OP's concerns anyway.
I get the impression the OP is unhappy with how high the engine revs are when the speedo indicates 70. If someone had put smaller wheels on and not compensated with higher profile tyres, the speedo wouldn't know that. The new, smaller diameter wheels would not change the relationship between engine revs and speedo indication. The only change would be that at an indicated 70, the car would actually be travelling somewhat slower than 70. i.e., even if someone had changed the OP's wheels, if the OP went back to the correct size of wheel and tyre, the problem - unhappy with how high the engine revs are at an indicated 70mph - would remain.
If the OP wants to be able to travel at an actual road speed of 70, with the speedo indicating 70 (within the normal tolerance of a speedo) and with the engine revs lower than they currently are, the answer is a different gearbox. That may or may not be possible. I doubt it's easy.0 -
Diesel. It would make no difference if it were petrol as its still all about engine load, not engine speed.
To expand a bit ….all engines have a “sweet spot” (or more realistically a fairly narrow range) of maximum efficiency.
There are some seriously hard sums involving about pumping losses, tuned inlet & exhaust pressure pulses, flame fronts, BMEP etc etc but generally the maximum efficiency point coincides with maximum torque production.
Upshot is that for best mpg at a given speed you need to be running the engine at the “sweet spot” speed and be in whatever gear you need to get the required road speed0
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