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throttle body cable wheel
Craigorypeck - 22/2/13 at 11:42 AM

I have a 75mm throttle body on my inlet piping which is too big and makes driving at low revs difficult as the slightest opening lets alot of air in. So i was gonna make an eccentric off centre wheel for the cable so it would move less at the beginning of throttle pedal travel, giving more control at part throttle..
Would this work?? moving the centre hole closer to the cable ferrule??



I could make any shape so doesn't need to be circular, if anyone has any suggestions.

Thanks


Charlie_Zetec - 22/2/13 at 12:04 PM

I see your point of having an offset centre on a standard circle - essentially you're making the equivelant of an eccentric cam profile (egg-shaped).

Without making a new item to replace, I would think this is as good an option as any, however it would need proper investigation to see how much the throttle would need to open as to where the new hole would need to be placed, otherwise you could end up with it not opening enough (if that makes sense).


Craigorypeck - 22/2/13 at 12:22 PM

yes indeed WOT needs to be WOT too.. If the the first 25% of pedal travel controlled the first 10% of the throttle body movement it would be better, then the last 75% of pedal travel would contol the remaining 90% of throttle opening but ultimately making sure that when pedal is buried in the carpet its actually open fully...
I've seen a TB from a sierra cosworth that uses a lever system which adjusts the pedal travel away from a linear motion.... hmmm


alladdin - 22/2/13 at 12:38 PM

i remember dave walker mentioning this solution in an article. would be usefull on bike bodies. if you can swap quadrants easily then try it - its going to be suckit and see really. someone must make them already im sure ?


Craigorypeck - 22/2/13 at 01:10 PM

I'm running 2 throttle cables which is the root of my problem.. one goes to carbs and the other to a throttle body that regulates inlet to super charger, i am running similar diameter cable wheels so they open in parallel but the large TB inlet to charger is allowing too much air past at minimal throttle openings and building too much boost too quickly. i have boost gauges either side of the bike carbs, one is MAP and the other is from plenum and it makes interesting reading sometimes! An offset cable wheel should sort it and balance it out a bit better.


r1_pete - 22/2/13 at 01:15 PM

I'm 99% sure I have an eccentric cable wheel in a box of GSXR TB parts, I'll have a look tonight if you think it would be any use to you.


Craigorypeck - 22/2/13 at 01:27 PM

that would be fantastic!


matt_gsxr - 22/2/13 at 02:13 PM

GSXR600 throttle bodies have an elliptical cable wheel.
Just the idea you are describing.


rusty nuts - 22/2/13 at 07:56 PM

I have the same problem with my car on bike throttle bodies, probably made worse by having a lightweight flywheel and have been thinking about making a progressive throttle linkage . I've looked at loads of throttle linkages on various cars and have yet to find something suitable .


rdodger - 22/2/13 at 08:09 PM

quote:
Originally posted by Craigorypeck
I'm running 2 throttle cables which is the root of my problem.. one goes to carbs and the other to a throttle body that regulates inlet to super charger, i am running similar diameter cable wheels so they open in parallel but the large TB inlet to charger is allowing too much air past at minimal throttle openings and building too much boost too quickly. i have boost gauges either side of the bike carbs, one is MAP and the other is from plenum and it makes interesting reading sometimes! An offset cable wheel should sort it and balance it out a bit better.


This is very common. I am using a supercharger on my MX5 engine with dual throttle bodies. Standard on inlet and 70mm on the charger.

I use an eccentric wheel to open the charger throttle slower.

I will look for a picture.

Found one!



[Edited on 22/2/13 by rdodger]


Craigorypeck - 23/2/13 at 12:49 PM

nice one! thats the sort of thing I'm after but would need to be way smaller..


r1_pete - 24/2/13 at 12:56 PM

Here you go PM me if its any good

TB Cable wheel
TB Cable wheel


FASTdan - 25/2/13 at 08:37 AM

We are currently working on a few ideas for products to resolve this issue on bike carbs and bodies, but its quite a tricky one to make something thats universal.