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I am a little confused about performance and engine numbers. I have two cars.

The oldest is a Škoda Fabia Combi 1,2 TSI and the other is a Nissan Micra 1,2 5D. MAN.

According to the specs, the Fabia engine power is set to 63kW / ~86HP and it weighs 1591kg The Micra engine power is 59kW / ~80HP and it weighs 1425kg

As far as I understand, the Fabia has a turbo, the Micra does not. However, I would have said that the Fabia performs similarly to my old Opel Corsa which had 70kW / ~95HP which had a 1.3 Diesel engine.

The Micra has always been slow to accelerate, but is there some other factor I am missing in my comparison?

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    If your Škoda Fabia Combi 1,2 TSI has a turbocharger, it may be a baby sized one for a 1.2L engine. Turbochargers add power depending on factory tuning and is generally described as a performance boost in power at certain rpm. Owner's manual should describe when boost in power occurs at whatever rpm was determined. Turbocharged engines tend to add a performance boost over non turbo engines of similar size and vehicle weight.
    – F Dryer
    Commented Dec 8, 2023 at 6:12
  • @FDryer so you are saying that the HP is on paper - based on the engine, and the actual boost i should be able to look up in the manual?
    – JoSSte
    Commented Dec 8, 2023 at 7:30
  • The HP is the maximum power, it is different for all RPM, same for torque, both are indicators
    – pdem
    Commented Dec 8, 2023 at 13:11
  • I'm guessing the Micra is the one whose torque/power curves are shown here, but it doesn't look like I found the correct Fabia here. Maybe you could find the correct vehicles and edit your question to add links to the correct data? Commented Dec 8, 2023 at 16:48
  • @JoSSte, hp and torque are measured for acceptable standards of power output plotted against rpm. While many equate hp as talking points, torque is the power behind acceleration times. Factory specs are published but be aware that power may be at the shaft before power robbing losses thu the xmission and differential. Wheel hp is rarely mentioned but SAE power is shaft output. Expect around 4-15% power loss from accessories like drive belt, water pump, alternator, power steering pump, xmission and diff.
    – F Dryer
    Commented Dec 8, 2023 at 18:11

2 Answers 2

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I think there are two factors which you are not taking into account in your analysis.

First, final drive ratios make a big difference in how a vehicle behaves performance wise. I wouldn't know exactly what the difference is between the two vehicles in question, but if the final drive ratio is lower (higher numerically), it will feel as though it has better acceleration. If the final drive ratio is higher (lower numerically), it will feel more sluggish.

Secondly, what you are testing by is seat of the pants. There's no way to know exactly how a car performs unless you test them, which could be by putting them on the dyno or taking them on a known distance sprint (ie: 1/4 mile drag strip or a 0-60 test). Unless you have empirical data it's all subjective. This could be part of what you're feeling and how you are thinking the vehicle is behaving.

While horsepower and torque are always good indications, they aren't the end-all-do-all to get you final results of how a vehicle behaves. They are just one factor in the big scheme of things.

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  • Do ECUs learn how the driver usually uses the vehicle and adjust the performance accordingly over time? So, if the Micra was driven more enthusiastically for a few weeks, might it increase the amount of fuel used to increase acceleration? And conversely, a driver who likes a more sedate progression along the carriageway would gain fuel frugality? (Lol look at me using big words.) Commented Dec 8, 2023 at 16:55
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    @AndrewMorton - According to how the ECU is programmed (fuel map, timing maps, etc), it will continue to attempt to produce the best it can towards those maps regardless of the driving style of the person behind the wheel ... so basically no. It won't. What does happen is, fuel mileage goes down when someone is harder on the vehicle (ie: spirited driving) because the vehicle is being commanded by the driver to produce more torque more often. It just takes more fuel to drive this way. Conversely it takes less fuel to drive sedately. Commented Dec 8, 2023 at 18:30
  • @AndrewMorton I think (but not sure) that the DSG auto gearboxes from VAG adjust the gearing program according to the way you drive. Commented Dec 8, 2023 at 19:26
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I think I got the answer after a while. The specs of the engine I was looking at did not take a lot of details into consideration. Apparently things like Carburetor and fuel injection, turbo and other elements have an impact on the perceived performance.
I found this curve comparison where I could look up the two engines:

https://www.automobile-catalog.com/curve/2008/2199320/nissan_micra_1_2_80.html#gsc.tab=0 https://www.automobile-catalog.com/curve/2011/3140810/skoda_fabia_combi_1_2_tsi_86.html#gsc.tab=0

curve comparison

It might be only 6 HP in difference - but the actual performance is much more.

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    Those curves are about what I'd expect - the torque curves are what tell the story of why the two drive very differently. For real-world driving you're going to be doing a lot of your acceleration in that 1500-3750rpm bracket where the turbo is giving the Fabia a significant torque advantage over the Micra. Commented Jan 3 at 13:52

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