Progressive Throttle Mod (Anyone Done It?)
Discussion
Just chewing over the idea of a progressive throttle on my Chim.
As we know the throttle pedal has a 1:1 relationship with the throttle butterfly.
IE: 10mm of throttle pedal movement = 1mm of movement at the throttle butterfly (example only, not measured yet)
Obviously leverage plays it's part here but from what I can see the relationship remains 1:1 throughout the full range of movement.
What I am trying to achieve is:
A) Retain the 1:1 relationship between the pedal & butterfly for the first 25% of the throttle pedal movement to provide manageable low speed town driving characteristics
B) An exponential relationship between the pedal & butterfly there after
IE: From the 25% travel point on it stops being a 1:1 relationship and would look something like this:
And so on, obviously this would be a smooth progressive ramping effect not stepped as above.
I would have thought a simple snail cam should do it.
With the throttle cable running over the right ramping profile it should give the feel of a much faster throttle & less travel at the pedal.
Many cable operated carbs I have worked on used a snail cam to great effect & this type of mod is also quite popular in the motorcycle world where kits offering a selection of snail cams to play with are readily available.
I would hazard a guess that the long travel of the throttle pedal in our cars has more to do with it's Range Rover origins, rather than (as folk-law would have us believe) an attempt by Peter Wheelers's team to create a crude form of traction control.
A long travel throttle is perfect on the rough stuff as you don't want to be lurching on & off the throttle when bouncing over rocks.
However a sports car lends itself to different throttle characteristics, a faster shorter travel throttle should help to make the car feel more urgent & responsive.
But has anyone fitted a snail cam to the humble 14CUX throttle body on their Chim or Griff?
Thoughts
As we know the throttle pedal has a 1:1 relationship with the throttle butterfly.
IE: 10mm of throttle pedal movement = 1mm of movement at the throttle butterfly (example only, not measured yet)
Obviously leverage plays it's part here but from what I can see the relationship remains 1:1 throughout the full range of movement.
What I am trying to achieve is:
A) Retain the 1:1 relationship between the pedal & butterfly for the first 25% of the throttle pedal movement to provide manageable low speed town driving characteristics
B) An exponential relationship between the pedal & butterfly there after
IE: From the 25% travel point on it stops being a 1:1 relationship and would look something like this:
- First 10mm of throttle pedal movement = 2mm of movement at the throttle butterfly
- Second 10mm of throttle pedal movement = 4mm of movement at the throttle butterfly
- Third 10mm of throttle pedal movement = 6mm of movement at the throttle butterfly
And so on, obviously this would be a smooth progressive ramping effect not stepped as above.
I would have thought a simple snail cam should do it.
With the throttle cable running over the right ramping profile it should give the feel of a much faster throttle & less travel at the pedal.
Many cable operated carbs I have worked on used a snail cam to great effect & this type of mod is also quite popular in the motorcycle world where kits offering a selection of snail cams to play with are readily available.
I would hazard a guess that the long travel of the throttle pedal in our cars has more to do with it's Range Rover origins, rather than (as folk-law would have us believe) an attempt by Peter Wheelers's team to create a crude form of traction control.
A long travel throttle is perfect on the rough stuff as you don't want to be lurching on & off the throttle when bouncing over rocks.
However a sports car lends itself to different throttle characteristics, a faster shorter travel throttle should help to make the car feel more urgent & responsive.
But has anyone fitted a snail cam to the humble 14CUX throttle body on their Chim or Griff?
Thoughts
Edited by Chimpafrolic on Wednesday 22 June 17:02
I think my Datsun has this arrangement and a number of 'modders' pay good money to change it to 1:1. spend said:
Converting angular opening into 'pull' is absolutely nothing like you describe.. It is by nature progressive due to converting arcs blocking effect on diameter as you rotate in 3d. Just think of butterfly at 45degs it is still blocking more than 50% of the throttle...
If the relationship between the acting and receiving levers is truly creating a progressive effect as you suggest, its certainly not that pronounced.
I am talking about altering the long liner travel of the pedal to something noticeably faster (in a progressive way) over the last 75% of its range.
I am sure you are aware this type of cam arrangement as been employed on carbs for donkey's years, it's purpose is to change the relationship between pedal travel & butterfly articulation in a progressive way over its full range.
Apologies if you didn't grasp the gist of my post, the question I am asking the less pedantic amongst you is simple.
Has any one tried a throttle cable snail cam on a 14CUX throttle body?
Experiences and constructive comments welcome
Edited by Chimpafrolic on Wednesday 22 June 17:53
is that a sexual connotation
hiltonig said:
Or how about drive by wire ? Is this possible, I have the ecu to control it
Good point, and in truth that's the 21st Century way of doing things.Completely adaptive and user configurable if you have the ECU output and some software, a drive by wire throttle has to be infinitely better than the simple cam arrangement I am proposing.
It's a bit like comparing a mapped ignition advance/retard with the springs & bob weights in a distributor.
However, I am old school where the throttle is concerned.
Call me a Luddite but I still like a mechanical connection between my foot & the throttle butterfly, it just feels safer that way.
(says he who drives a Toyota Prius company car with drive by wire everything
)So back to my stone age throttle cam.
Anyone tried it?
As it not occurred to you there is more useful jobs/mods on these cars than this? NO! then move your foot quicker if you want quicker action your left leg seems to cope OK,I bet you can dip the clutch quick enough when giving your car the berries and tearing through the box 
Haircut as far as "drive by wire" is concerned in my opinion its just more to go wrong(and does)for what is in effect small benefit just my cents worth as always 
Haircut as far as "drive by wire" is concerned in my opinion its just more to go wrong(and does)for what is in effect small benefit just my cents worth as always 
Chimpafrolic said:
I would hazard a guess that the long travel of the throttle pedal in our cars has more to do with it's Range Rover origins, rather than (as folk-law would have us believe) an attempt by Peter Wheelers's team to create a crude form of traction control.
I dont think this can be attributed to PW or the team at Blackpool. Most race cars have long travel throttles - been accepted wisdom for a long time now. Even if you pick modern super saloons (M5, XJR, Quattroporte etc.) you will find they all have long travel throttles despite the aids and electronic remapping.Edited by Chimpafrolic on Wednesday 22 June 17:02
Personally, I would caution against your idea, if things get unexpectedly sideways you need the fine control a long travel throttle gives. At the end of the day though its your car and your choice.
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