Feeling of acceleration
#1
Feeling of acceleration
hello to all, a question remains a mystery to me to this day and no answer seemed to be relevant.
let me explain, if acceleration is linked to torque at the wheel, the vehicle that has more power and torque for an equivalent weight accelerates stronger, but I've always wondered why our turbo vehicles "feel" so fast and gives you that punch in the back that I haven't found on na much more powerful cars with more torque.
Where does this feeling of acceleration come from? is it the shape of the torque curve or the power delivered suddenly by the pressure that makes the turbo so "violent".
let me explain, if acceleration is linked to torque at the wheel, the vehicle that has more power and torque for an equivalent weight accelerates stronger, but I've always wondered why our turbo vehicles "feel" so fast and gives you that punch in the back that I haven't found on na much more powerful cars with more torque.
Where does this feeling of acceleration come from? is it the shape of the torque curve or the power delivered suddenly by the pressure that makes the turbo so "violent".
#2
Humans perceive "jerk" more than we do acceleration. That is, the rate of change of the acceleration, or the 3rd derivative of position (position => velocity => acceleration => jerk).
Cars with big V8s or big turbos let you go from low levels of torque to high levels very quickly just by putting your foot down, and that feels fast.
Cars with smaller, high-revving NA motors don't have that same rush as the torque climbs (at least, not unless have a very fast transmission and downshift), so they feel slower even if they're turning the same times.
--Ian
Cars with big V8s or big turbos let you go from low levels of torque to high levels very quickly just by putting your foot down, and that feels fast.
Cars with smaller, high-revving NA motors don't have that same rush as the torque climbs (at least, not unless have a very fast transmission and downshift), so they feel slower even if they're turning the same times.
--Ian
#3
however it would seem that even cars with big v8s don't feel as brutal as less powerful turbo cars, I've seen quite a few people somewhat disappointed in the acceleration part of some full torque v8s that haven't been experienced, in comparison of their turbo cars. for example according to an owner a zo6 c5 will not provide as much punch as a less powerful Impreza sti etc many examples are possible and go in the direction where even the big v8 does not feel as fast as the turbo (but more than high rpm engines though) does this come from the progressive delivery feature na?
#4
on the v8s that I have experienced with a fairly large displacement, they say. at the go-around in the right part of the regime it seemed to react instantaneously and very briefly then continues and continues linearly so that the acceleration is finally "little felt". turbo look like I'm accelerating: a little, a little a little more, well, a lot, and boom all the power comes at once.
#5
Tweaking Enginerd
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All the tq all the time is faster than all the tq half the time... period. Tq is acceleration. 250lbft at 2500RPM for a given gear is the same as 250lbft at 6000 RPM in the same gear, even though the hp numbers are vastly different.
#6
Humans perceive "jerk" more than we do acceleration. That is, the rate of change of the acceleration, or the 3rd derivative of position (position => velocity => acceleration => jerk).
Cars with big V8s or big turbos let you go from low levels of torque to high levels very quickly just by putting your foot down, and that feels fast.
Cars with smaller, high-revving NA motors don't have that same rush as the torque climbs (at least, not unless have a very fast transmission and downshift), so they feel slower even if they're turning the same times.
Cars with big V8s or big turbos let you go from low levels of torque to high levels very quickly just by putting your foot down, and that feels fast.
Cars with smaller, high-revving NA motors don't have that same rush as the torque climbs (at least, not unless have a very fast transmission and downshift), so they feel slower even if they're turning the same times.
Constant acceleration (corresponding with a flat torque curve) puts you back in your seat, and is objectively faster.
A turbo car with a higher boost threshold will be slower until the turbo spools, then you have a sudden increase in the rate of acceleration (Jerk) which feels subjectively faster then constant acceleration.
Sheds some light on why a manual is so fun to drive (and generally feels faster then an automatic). You have that pause in acceleration on each shift and then the rate of Jerk is high when you come back into the throttle in the next gear.
#7
I agree with Codrus about the perception of jerk vs acceleration being a big component of this.
BUT, one HUGE thing it looks like you are missing is gearing. You mention comparing an STI to a C5 Z06, well do the math on the gearing, you don't say what year STI but I'll just choose a new one, and I'm going to choose second gear to compare, STI 2nd gear 2.23, C5 Z06 1.78, so 2.23/1.78 is about 1.25, so right off the bat the STI is getting a 25% bump to acceleration in 2nd gear. Then the rear end ratio is STI =3.9, C5 Z06 3.42, so 3.9/3.42 is 1.14, so that's another 14% more. Then the rear tires on the vette are also taller so 26.7/25.8 = 1.03. The total gear advantage for the STI is about 47% looks like an STI is rated at 290 torque, and I think the vette is rated at 400 torque, well 290*1.47 is 426. The STI is a little heavier roughly 10% so then the acceleration you would expect between the two cars in second gear to be pretty much even.
This is far from a complete analysis of this, but I think it makes the point about gearing and what it's going to feel like. If you look at gearing those cars with big V8s usually have very LOOOONNGGG gears, whereas cars with small turbo engines usually have very short gears, which is going to make them feel like they are accelerating harder... for a little bit, until they have to shift up.
BUT, one HUGE thing it looks like you are missing is gearing. You mention comparing an STI to a C5 Z06, well do the math on the gearing, you don't say what year STI but I'll just choose a new one, and I'm going to choose second gear to compare, STI 2nd gear 2.23, C5 Z06 1.78, so 2.23/1.78 is about 1.25, so right off the bat the STI is getting a 25% bump to acceleration in 2nd gear. Then the rear end ratio is STI =3.9, C5 Z06 3.42, so 3.9/3.42 is 1.14, so that's another 14% more. Then the rear tires on the vette are also taller so 26.7/25.8 = 1.03. The total gear advantage for the STI is about 47% looks like an STI is rated at 290 torque, and I think the vette is rated at 400 torque, well 290*1.47 is 426. The STI is a little heavier roughly 10% so then the acceleration you would expect between the two cars in second gear to be pretty much even.
This is far from a complete analysis of this, but I think it makes the point about gearing and what it's going to feel like. If you look at gearing those cars with big V8s usually have very LOOOONNGGG gears, whereas cars with small turbo engines usually have very short gears, which is going to make them feel like they are accelerating harder... for a little bit, until they have to shift up.
#8
I agree with Codrus about the perception of jerk vs acceleration being a big component of this.
BUT, one HUGE thing it looks like you are missing is gearing. You mention comparing an STI to a C5 Z06, well do the math on the gearing, you don't say what year STI but I'll just choose a new one, and I'm going to choose second gear to compare, STI 2nd gear 2.23, C5 Z06 1.78, so 2.23/1.78 is about 1.25, so right off the bat the STI is getting a 25% bump to acceleration in 2nd gear. Then the rear end ratio is STI =3.9, C5 Z06 3.42, so 3.9/3.42 is 1.14, so that's another 14% more. Then the rear tires on the vette are also taller so 26.7/25.8 = 1.03. The total gear advantage for the STI is about 47% looks like an STI is rated at 290 torque, and I think the vette is rated at 400 torque, well 290*1.47 is 426. The STI is a little heavier roughly 10% so then the acceleration you would expect between the two cars in second gear to be pretty much even.
This is far from a complete analysis of this, but I think it makes the point about gearing and what it's going to feel like. If you look at gearing those cars with big V8s usually have very LOOOONNGGG gears, whereas cars with small turbo engines usually have very short gears, which is going to make them feel like they are accelerating harder... for a little bit, until they have to shift up.
BUT, one HUGE thing it looks like you are missing is gearing. You mention comparing an STI to a C5 Z06, well do the math on the gearing, you don't say what year STI but I'll just choose a new one, and I'm going to choose second gear to compare, STI 2nd gear 2.23, C5 Z06 1.78, so 2.23/1.78 is about 1.25, so right off the bat the STI is getting a 25% bump to acceleration in 2nd gear. Then the rear end ratio is STI =3.9, C5 Z06 3.42, so 3.9/3.42 is 1.14, so that's another 14% more. Then the rear tires on the vette are also taller so 26.7/25.8 = 1.03. The total gear advantage for the STI is about 47% looks like an STI is rated at 290 torque, and I think the vette is rated at 400 torque, well 290*1.47 is 426. The STI is a little heavier roughly 10% so then the acceleration you would expect between the two cars in second gear to be pretty much even.
This is far from a complete analysis of this, but I think it makes the point about gearing and what it's going to feel like. If you look at gearing those cars with big V8s usually have very LOOOONNGGG gears, whereas cars with small turbo engines usually have very short gears, which is going to make them feel like they are accelerating harder... for a little bit, until they have to shift up.
#9
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There's something about a big cube small block pushing you back in the seat from 1800rpm all the way to 7000rpm that a turbo car just doesn't give you. C6 Z06 comes to mind. Even my measly LS3 has this to some effect.
Ride in a supercharged vette or 5.0 mustang and you wont have this same opinion.
Ride in a supercharged vette or 5.0 mustang and you wont have this same opinion.
#10
Aside from huge engines and horsepower with huge torque and horsepower, na engines aren't known for "pushing in the seat" at least there isn't the typical turbo back shove. I'm not the only one to think that. it's a fact and if it wasn't the case nobody would have found a c63 w204 which seems "slow" or slightly disappointed with the power compared to a turbo tuned car like focus rs, 335i less powerful and not much less light etc etc while it is a big v8 with torque. that said, I agree, with a c6 zo6 or even zr1 we reach completely crazy weight/torque+hp ratios.now look at how a big turbo gtr33 of equivalent power works... it feels awfully brutal once on boost however, at low revs there isn't the torque of the 7l ls
#16
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Hilarious!
Was just telling someone how slow my car feels next to a fast car, literally feels slow. On the other hand, next to a comparable car, it feels damn fast when I am pulling a tiny bit on them. Next to a normal car, my car feels boring.
The point is, it's all relative at a given moment in my opinion anyway.
Was just telling someone how slow my car feels next to a fast car, literally feels slow. On the other hand, next to a comparable car, it feels damn fast when I am pulling a tiny bit on them. Next to a normal car, my car feels boring.
The point is, it's all relative at a given moment in my opinion anyway.
#18
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The jerk concept is correct. The last factor in all of it comes down to mental surprise. When you have a high torque n/a car - you slam the gas pedal down and the torque is delivered. With a turbocharged car there's the SLIGHTEST lag (or big lag) from when you slam your foot down to when you accelerate. I think that's enough to play with the brain to make you feel faster. It's almost the "unpredictableness" of the torque delivery. n/a is like a stepwise function. Turbo can often have that asymptotic curve followed by tapering off. Maybe you can mimic the "feeling" with a corvette by rolling onto the throttle vs stomping.
PD = roots. Centrifugal is like closer to a turbo than no (increasing torque as the rpm's increase). Roots (or PD) torque curve is more akin to an n/a car.
PD = roots. Centrifugal is like closer to a turbo than no (increasing torque as the rpm's increase). Roots (or PD) torque curve is more akin to an n/a car.
#19
--Ian
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