What makes throttle response feel sharp?
04-29-2013, 11:37 PM
#1
What makes throttle response feel sharp?
Stupid question, but is it just a factor of the curve of pedal movement to throttle opening? I know modern cars tend to have most of the throttle opening early on in the pedal movement.
Just drove a 2014 Cayman S, and in Sport Plus, it was quite nice. Got back in my 2001 Miata, and it was like my gas pedal was connected to a marshmallow, in comparison. Just feels squishy and unresponsive.
I'm not talking about power, but the feeling of the engine. I've noticed even with a severely lightened flywheel/clutch setup, there's still a bit of that squishy feeling.
Lower compression ratio? Restricted head? There's a lot of good information out there about how to get more power, but I'm looking for how that feeling comes about.
Just drove a 2014 Cayman S, and in Sport Plus, it was quite nice. Got back in my 2001 Miata, and it was like my gas pedal was connected to a marshmallow, in comparison. Just feels squishy and unresponsive.
I'm not talking about power, but the feeling of the engine. I've noticed even with a severely lightened flywheel/clutch setup, there's still a bit of that squishy feeling.
Lower compression ratio? Restricted head? There's a lot of good information out there about how to get more power, but I'm looking for how that feeling comes about.
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04-30-2013, 10:37 AM
#8
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The DBW in "extra sharp mode" is probably programmed to amplify the first half inch of throttle travel.
Personally I don't like those artificial modes (a la BMW "sport" button) because it makes the car harder to drive smoothly. Corolla and Camry gas pedals are irritating that way, gives the impression of "power". You step a half inch, it lunges, you floor it, and you don't get much more. It's also kinda like having brakes that are sensitive in the initial press (but not necessarily gives you lots of max deceleration when you step hard), as opposed to Porsche brakes, which are very linear.
Personally I don't like those artificial modes (a la BMW "sport" button) because it makes the car harder to drive smoothly. Corolla and Camry gas pedals are irritating that way, gives the impression of "power". You step a half inch, it lunges, you floor it, and you don't get much more. It's also kinda like having brakes that are sensitive in the initial press (but not necessarily gives you lots of max deceleration when you step hard), as opposed to Porsche brakes, which are very linear.
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04-30-2013, 10:40 AM
#9
The DBW in "extra sharp mode" is probably programmed to amplify the first half inch of throttle travel.
Personally I don't like those artificial modes (a la BMW "sport" button) because it makes the car harder to drive smoothly. It's kinda like having brakes that are sensitive in the initial press (but not necessarily gives you lots of max deceleration when you step hard), as opposed to Porsche brakes.
Personally I don't like those artificial modes (a la BMW "sport" button) because it makes the car harder to drive smoothly. It's kinda like having brakes that are sensitive in the initial press (but not necessarily gives you lots of max deceleration when you step hard), as opposed to Porsche brakes.
Though I have to say, that 2014 Cayman is a nice Mercedes. It's rather less of a nice Porsche. Everything is high quality and well done, but lacking in feel or passion. All that kept it from feeling like an SLK was the induction noise and engine placement.
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04-30-2013, 09:13 PM
#14
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Drive by wire is a fairly complicated beast.
Most DBW works by using the throttle to "request torque".
My subaru LGT feels like a slob in "intelligent" but throw it in sport sharp and its a whole new car.
Roughly the way 07+ CANBUS subaru logic works is:
There is a 3D table called REQUESTED TORQUE. This table is unique to the drive mode (sport, sport sharp, etc).
This compares ACTUAL Throttle Position vs. RPM and outputs a "requested torque value."
There is then a 2D table called REQUESTED BASE TORQUE. This gives a requested base torque for each RPM value. I suspect this is a table to display the max requested torque available from the engine at any given RPM. This should probably somewhat match the powerband of the engine.
From there we have a few final 3D tables (one for cruse, non cruise, limp home, etc.) that converts it to ACTUAL throttle plate angle through RPM vs. (REQUESTED TORQUE/REQUESTED BASE TORQUE) ratio.
Strange and compounding. Boost is also related to these tables... and I suspect timing may be in some cars too.
All this works together to essentially make the car smarter than your foot. It provides more linear and gradual torque throughout the power band so that the throttle pedal is more of a "go faster" pedal & it takes the engine dynamics out of it.
Hope any of that makes sense?
Most DBW works by using the throttle to "request torque".
My subaru LGT feels like a slob in "intelligent" but throw it in sport sharp and its a whole new car.
Roughly the way 07+ CANBUS subaru logic works is:
There is a 3D table called REQUESTED TORQUE. This table is unique to the drive mode (sport, sport sharp, etc).
This compares ACTUAL Throttle Position vs. RPM and outputs a "requested torque value."
There is then a 2D table called REQUESTED BASE TORQUE. This gives a requested base torque for each RPM value. I suspect this is a table to display the max requested torque available from the engine at any given RPM. This should probably somewhat match the powerband of the engine.
From there we have a few final 3D tables (one for cruse, non cruise, limp home, etc.) that converts it to ACTUAL throttle plate angle through RPM vs. (REQUESTED TORQUE/REQUESTED BASE TORQUE) ratio.
Strange and compounding. Boost is also related to these tables... and I suspect timing may be in some cars too.
All this works together to essentially make the car smarter than your foot. It provides more linear and gradual torque throughout the power band so that the throttle pedal is more of a "go faster" pedal & it takes the engine dynamics out of it.
Hope any of that makes sense?
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05-01-2013, 10:31 AM
#16
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240_to_miata:
For turbo engines the OEs target MAP for a given torque request; (some use a closed loop system), instead of targeting throttle butterfly angle. The throttle butterfly angle is sometimes a 3D table function of RPM and pressure drop across the throttle butterfly (some OEs have a pressure sensor pre-TB).
For turbo engines the OEs target MAP for a given torque request; (some use a closed loop system), instead of targeting throttle butterfly angle. The throttle butterfly angle is sometimes a 3D table function of RPM and pressure drop across the throttle butterfly (some OEs have a pressure sensor pre-TB).
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05-01-2013, 10:33 AM
#18
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the nuge_26:
Yes you could program it so that while the oil is cold only the last 10% of throttle travel will give you the upper 40% of engine torque and allow max RPMs in the tranny. Not allowing it completely when floored would be a safety issue.
Yes you could program it so that while the oil is cold only the last 10% of throttle travel will give you the upper 40% of engine torque and allow max RPMs in the tranny. Not allowing it completely when floored would be a safety issue.
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