feelings of being pinned to the seat

[Turbinox]

The initial message was deleted from this topic on 24 April 2024 at 22:49

[Super Sonic]

Aiui, turbo engines may not have much torque at low revs, but when the turbo spools up, the torque is increased, so if you look at the torque curve for a turbo engine, the peak while be at high revs compared to a n/a engine.

[Doofus]

Inertia pushes you back in your seat, not torque.

[popeyewhite]

Turbinox said:

...why mostly turbo cars feel faster yet sometimes with less torque

The turbocharged cars I've owned have always had plenty of torque. The whole point is to boost engine power. I've always gone for performance cars though. My reckoning is you need over 300ftlbs/tonne to start feeling pinned back properly.

[LennyM1984]

Super Sonic said:

Aiui, turbo engines may not have much torque at low revs, but when the turbo spools up, the torque is increased, so if you look at the torque curve for a turbo engine, the peak while be at high revs compared to a n/a engine.

I think you may have that the wrong way round... Turbo cars tend to be able to produce their torque lower down the rev range hence their popularity on low capacity engines

[BertBert]

It's actually the rate of change of acceleration (called jerk) that you really feel.

[98elise]

BertBert said:

It's actually the rate of change of acceleration (called jerk) that you really feel.

Yup. Acceleration will push you into the seat, jerk will will vary the push. Jerk will be felt more.

[MitchT]

Back in the day a guy I worked for had a new E36 BMW M3 and then a Lotus Esprit GT3. The Lotus was faster but the BMW felt faster. I concluded, in an admittedly uneducated way, that the Lotus, being lighter and with a lower centre of gravity, felt less dramatic even though it was significantly quicker on paper because it was more efficient at deploying its performance.

[LimaDelta]

98elise said:

BertBert said:

It's actually the rate of change of acceleration (called jerk) that you really feel.

Yup. Acceleration will push you into the seat, jerk will will vary the push. Jerk will be felt more.

This, which is why it is more noticeable with turbocharged cars, rather than a more linearly accelerating normally aspirated engine. The rate of change of acceleration changes as the boost pressure (and therefore power produced) increases.

There's probably a joke in there somewhere about jerks, and turbocharged cars, but I can't be bothered to find it.

the rate of change of jerk is snap. The rate of change of snap is crackle, and the rate of change of crackle is pop. I kid you not.

[Turbinox]

ok, ok, the rate of change of the acceleration changes when the turbo rolls up, but with the n/a I if I press the pedal the torque is instantaneous and therefore the The acceleration goes from zero to very strong immediately and continues linearly. In theory the jerk feel more brutal the moment I step on the pedal and give you more of a kick in the back with thé Big na than the turbo spooling up assuming the torque weight values ​​are close? yet it's still the turbos that have the reputation of the feeling of "kick in the back" strange...

[Krikkit]

98elise said:

BertBert said:

It's actually the rate of change of acceleration (called jerk) that you really feel.

Yup. Acceleration will push you into the seat, jerk will will vary the push. Jerk will be felt more.

Which is why peaky turbo cars of old were most effective at it - sudden boost = big jerk ()

Modern turbo cars with variable vanes and completely flat torque curves feel very boring by comparison, because their boost comes in very smoothly then hits its mapped peak.

Turbinox said:

ok, ok, the rate of change of the acceleration changes when the turbo rolls up, but with the n/a I if I press the pedal the torque is instantaneous and therefore the The acceleration goes from zero to very strong immediately and continues linearly. In theory the jerk feel more brutal the moment I step on the pedal and give you more of a kick in the back with thé Big na than the turbo spooling up assuming the torque weight values ??are close? yet it's still the turbos that have the reputation of the feeling of "kick in the back" strange...

More linear torque curve with lower peaks on NA, so less to feel.

[Turbinox]

https://youtu.be/ECrvyv4c_-U

for example, at 2m50 he surely accelerates in 2nd and pushes them both back into the seat, yet he says that it doesn't feel very fast for 500hp, from a "butt dyno" point of view I have read several other opinions on this same merc

[InitialDave]

Krikkit said:

Which is why peaky turbo cars of old were most effective at it - sudden boost = big jerk ()

Yep, in terms of feeling the performance, an old school turbo car that you can sense taking a big deep breath before picking up its skirts and fking off is great fun.

[Turbinox]

the curve is linear but there are a lot of them it should pin you incredibly to the seat when you put your foot down from revs above 3000rpm, yet many did not feel it as intense and fast as much less power and torque turbo cars . impreza turbo, stage 1 335i etc etc amazing

[popeyewhite]

Turbinox said:

ok, ok, the rate of change of the acceleration changes when the turbo rolls up, but with the n/a I if I press the pedal the torque is instantaneous and

No, the power is instantaneous with an NA but you get less torque (generally), you normally have to wait a bit for a turbo to spool, but when it hits you feel that shove more. The 'shove' is torque provided by the turbocharger. Bigger turbos generally take longer to spool, which is why some manufacturers install twin turbos - one for low rpm boost and a one for higher rpm boost

[Turbinox]

popeyewhite said:

Turbinox said:

ok, ok, the rate of change of the acceleration changes when the turbo rolls up, but with the n/a I if I press the pedal the torque is instantaneous and

No, the power is instantaneous with an NA but you get less torque (generally), you normally have to wait a bit for a turbo to spool, but when it hits you feel that shove more. The 'shove' is torque provided by the turbocharger. Bigger turbos generally take longer to spool, which is why some manufacturers install twin turbos - one for low rpm boost and a one for higher rpm boost[/quote

you say in general, that's why I take the example of a big engine na in the video we see the c63 and it has more torque than most old turbo cars known to give a big kick in the back but according to many people it does not hit like a turbo does with less torque.

[Turbinox]

InitialDave said:

Krikkit said:

Which is why peaky turbo cars of old were most effective at it - sudden boost = big jerk ()

Yep, in terms of feeling the performance, an old school turbo car that you can sense taking a big deep breath before picking up its skirts and fking off is great fun.

the first time i got in an old school turbo car and it started i thought it had more horsepower than anything i've ever ridden in, yet cars with 150hp more and less weight didn't feel as violent

[popeyewhite]

Turbinox said:

you say in general, that's why I take the example of a big engine na in the video we see the c63 and it has more torque than most old turbo cars known to give a big kick in the back but according to many people it does not hit like a turbo does with less torque.

The NA 63 is an old school big displacement V8. It does provide plenty of torque, but it is spread out more across the powerband. Torque delivery is different with a NA engine. If you want a big dollop of seat-pin in a smallish car go for one of those mentioned, ie a 1- 3 series BMW, and get it mapped. Go have a look at some engine map dyno graphs and you'll see the difference in how the power is applied.

[LimaDelta]

Turbinox said:

InitialDave said:

Krikkit said:

Which is why peaky turbo cars of old were most effective at it - sudden boost = big jerk ()

Yep, in terms of feeling the performance, an old school turbo car that you can sense taking a big deep breath before picking up its skirts and fking off is great fun.

the first time i got in an old school turbo car and it started i thought it had more horsepower than anything i've ever ridden in, yet cars with 150hp more and less weight didn't feel as violent

You have been given the answer several times now, but still seem confused. It is nothing to do with power, or torque, it is simply the change in the rate of acceleration.

[Turbinox]

LimaDelta said:

Turbinox said:

InitialDave said:

Krikkit said:

Which is why peaky turbo cars of old were most effective at it - sudden boost = big jerk ()

Yep, in terms of feeling the performance, an old school turbo car that you can sense taking a big deep breath before picking up its skirts and fking off is great fun.

the first time i got in an old school turbo car and it started i thought it had more horsepower than anything i've ever ridden in, yet cars with 150hp more and less weight didn't feel as violent

You have been given the answer several times now, but still seem confused. It is nothing to do with power, or torque, it is simply the change in the rate of acceleration.

ok thanks this explains why with less torque/hp from the remap or old school turbo cars hits you so hard and feels quick on boost