Eli5: 2 cars have the same Horsepower but different engine in terms of displacement (2.0L TDI vs 3.0L TDI) but what difference does it make and which one is better?
In: 87
It depends on what you want to do with the car. If you want to go fast on a track, low weight is good and low end torque is not as important as horsepower.
If you want to haul heavy loads, a higher torque engine will move better as its usable power is in lower rpms.
Turbochargers allow you to reach higher horsepower output but require a higher rpm than a big normally aspirated engine.
And gearing in your transmission also matters. A lot of sports cars try to stay in the most usable power band of the torque curve so that is why they have more gears.
generally speaking, the smaller engine with same output will be working harder relative to it’s size. from a performance standpoint the smaller engine would usually be lighter and therefore the car might be faster. but an engine that’s not working as hard means it may last longer under normal usage.
so the real answer is, “it depends”
generally speaking, the smaller engine with same output will be working harder relative to it’s size. from a performance standpoint the smaller engine would usually be lighter and therefore the car might be faster. but an engine that’s not working as hard means it may last longer under normal usage.
so the real answer is, “it depends”
It all depends on when the engines make their power. While both may have the same peak horsepower (this is how hp is measured) they may have completely different toeque curves, which matters more for drivability.
Now since you mentioned Diesel, the differences are much less important than gasoline. This is because Diesel engines tolerate much higher compression ratios than gasoline. Diesal engines also perform MUCH better under force induction than natural aspiration.
So to keep it ELI5 the simplest explanation is for diesal the engine displacement does not matter. As long as they are rated at the same they ought to consume the same amount of fuel and drive similar.
All things being equal if everyone drove at wide open throttle everywhere the engines would consume the same amount of fuel and produce the same amount of power.
All things arent equal and i dont know about you but as a professional uber driver i dont drive everywhere at wide open throttle. There are two schools of thought and I personally do not have a strong feeling either way. There are those who believe a big engine working not very hard will consume less fuel. I dont personally put much stock in that because most people speed and drive faster than engine speeds are designed for optimal fuel usage.
The other school would say more displacement more fuel consumption. This is because you can drive a small engine at low load its a smaller engine by design it requires less fuel to turn over. Less internal mass, less weight etc. In my personal experience the smaller the engine the less fuel it consumes !!!assuming part throttle driving!!! So in terms of fuel consumption either you believe that an engine with less load consumes less fuel or an engine thats smaller requires less fuel. I have not seen compelling evidence either way, but I HAVE NOT LOOKED IT UP. This is just based on my own mechanical knowledge.
If fuel consumptions not an issue for you there is no practicle difference. Some people – people who speed & drive on 2 lane highways a lot – will more appreciate the bigger engine because they “tend” to have more torque and do not have to rev as hard. Less relevant for Diesal because of the way it works. If I have a choice I will always go with a smaller engine because thats what i prefer.
Small engines being more efficent is also not the defacto case. My Imprezza had a 2l but it was so highly tuned and geared that on the highway it drank gas faster than my brothers 5.7l truck.
Imo gearing is more important than engine size. If you are interested for actual car selection drive both and do a lot of different types of driving. Not the little 4 turn fiasco dealers will take you on. Go on the freeway drive around town etc.
So which is better? For my money it is up to personal opinion. Smaller engines tend to be less popular with “normal” people because they value feel over fuel consumption. Speaking for North Americans anyway since fuel traditionally has been mega cheap. I do not like being shackled to something that costs me $100 twice a week to keep running, but i am a bit of a miser also i drive like 50,000km a year.
It all depends on when the engines make their power. While both may have the same peak horsepower (this is how hp is measured) they may have completely different toeque curves, which matters more for drivability.
Now since you mentioned Diesel, the differences are much less important than gasoline. This is because Diesel engines tolerate much higher compression ratios than gasoline. Diesal engines also perform MUCH better under force induction than natural aspiration.
So to keep it ELI5 the simplest explanation is for diesal the engine displacement does not matter. As long as they are rated at the same they ought to consume the same amount of fuel and drive similar.
All things being equal if everyone drove at wide open throttle everywhere the engines would consume the same amount of fuel and produce the same amount of power.
All things arent equal and i dont know about you but as a professional uber driver i dont drive everywhere at wide open throttle. There are two schools of thought and I personally do not have a strong feeling either way. There are those who believe a big engine working not very hard will consume less fuel. I dont personally put much stock in that because most people speed and drive faster than engine speeds are designed for optimal fuel usage.
The other school would say more displacement more fuel consumption. This is because you can drive a small engine at low load its a smaller engine by design it requires less fuel to turn over. Less internal mass, less weight etc. In my personal experience the smaller the engine the less fuel it consumes !!!assuming part throttle driving!!! So in terms of fuel consumption either you believe that an engine with less load consumes less fuel or an engine thats smaller requires less fuel. I have not seen compelling evidence either way, but I HAVE NOT LOOKED IT UP. This is just based on my own mechanical knowledge.
If fuel consumptions not an issue for you there is no practicle difference. Some people – people who speed & drive on 2 lane highways a lot – will more appreciate the bigger engine because they “tend” to have more torque and do not have to rev as hard. Less relevant for Diesal because of the way it works. If I have a choice I will always go with a smaller engine because thats what i prefer.
Small engines being more efficent is also not the defacto case. My Imprezza had a 2l but it was so highly tuned and geared that on the highway it drank gas faster than my brothers 5.7l truck.
Imo gearing is more important than engine size. If you are interested for actual car selection drive both and do a lot of different types of driving. Not the little 4 turn fiasco dealers will take you on. Go on the freeway drive around town etc.
So which is better? For my money it is up to personal opinion. Smaller engines tend to be less popular with “normal” people because they value feel over fuel consumption. Speaking for North Americans anyway since fuel traditionally has been mega cheap. I do not like being shackled to something that costs me $100 twice a week to keep running, but i am a bit of a miser also i drive like 50,000km a year.
You’re getting into torque vs power territory. All things being equal, consider 1000 rabbits vs 4 horses pulling something. We can imagine that 1000 rabbits can pull the same thing about as fast as 4 horses (yea, I’m making up numbers), so they’re capable of the same peak horsepower (work per second). But can 1000 rabbits pull an RV out of the mud? That’s the torque part of the equation. What can produce the strongest rotational movement to the wheels?
Some applications really need to optimize on torque vs just total power…such as pulling and towing.
You’re getting into torque vs power territory. All things being equal, consider 1000 rabbits vs 4 horses pulling something. We can imagine that 1000 rabbits can pull the same thing about as fast as 4 horses (yea, I’m making up numbers), so they’re capable of the same peak horsepower (work per second). But can 1000 rabbits pull an RV out of the mud? That’s the torque part of the equation. What can produce the strongest rotational movement to the wheels?
Some applications really need to optimize on torque vs just total power…such as pulling and towing.
Generally speaking, a larger engine makes more power at a lower rpm and more torque.
A lot of it is tune. My Sprinter has the same engine as a Metris but makes 50hp less. The only difference is the tune.
Generally speaking, a larger engine makes more power at a lower rpm and more torque.
A lot of it is tune. My Sprinter has the same engine as a Metris but makes 50hp less. The only difference is the tune.
Grandpa always said no replacement for displacement.
The 3.0L has more overall potential than the 2.0L, even if they were stock the same horsepower the overall engine likely has more room for modifications to further improve performance.
For instance both of the above motors are turbo diesels, the 3.0L can hold more overall air and hence theoretically can hold more charged air.
A 1 PSI improvement to either motor will mean the 3.0L will have more overall power as a result.
That said, for every 10lbs of weight lost you effectively gain 1 HP (in terms of performance).
Generally speaking the smaller motors also have higher redlines than larger motors too, higher RPM = higher average power.
HP figures on motors are peak power, that value doesn’t mean much… average power does and even moreso average wheel horsepower.
If an NA motor reaches 400HP at 7200 RPM and the turbocharged vehicle reaches 400HP at 2800 RPM, the turbocharged vehicle is going to be considerably quicker because it has higher average power.
Latest Answers