mechanical throttle linkage, what's the problem ?

[madkaw]

I'm with the crowd that says the linkage is NOT a bad design, but these are old cars and will have issues. I stuck with rods on my Mikunis and they work flawlessly, better then I ever expected. So I am saying there is a fix for the rods, just need to find it. I'm almost sure you can buy all new ball ends and that's where I would start. I would also look at the long main rod that has the fork end hooks to the balance tube.

[bartsscooterservice]

Maybe the butterfly axles in the carburetor are just sticking in the closed position due wear overtime, i'll have a look next week.

Because it's the heavy point I need to overcome then suddenly it goes, I can't see how this got to do with even a linkage with play.

[Mikes Z car]

I notice my DD uses a cable that feeds to a round "pulley" on the butterfly shaft so the mechanical advantage is very close to the same throughout gas pedal depression meaning the rate of rotation of the butterfly shaft is linear. Pedal action is very smooth and the car uses a carburetor. I don't know if linear action matters for racing. Does vacuum pull on the butterfly to make it stick? Maybe unhooking the return springs and the linkage to the pedal when the car is running would answer that. Maybe compare that linkage friction to the friction when it is not running. Just ideas.

[240260280z]

Dang now you got me interested in this... I'll have to take measurements, draw the linkage, model it in excel then do what-if's....curses for taking my toys apart and an interest in applied physics.

I'm thinking what Mike says as well as Karl and Dan's findings...maybe an eccentric wheel is the way to go... maybe an adjustable eccentric is even better.

[Mikes Z car]

Blue, I just figured if we could get you dragged into this discussion we would get another valuable point of view. heh heh

[z boy mn]

Hi Mike (and all), I also have triple Webers and there's a point in the linkage movement that sticks a bit. I was going to replace some of the linkage points with Heim joints, but I'm thinking now a cable might be easier/better. Do you have any pictures of your set-up? I'd like to see what I'm getting into as I'm still learning the basics!

[Mikes Z car]

z boy mn.

I only have cable on my daily driver which is an old '83 Toyota SR5 wagon though I am also curious about using cable on a Z if anyone has pictures of their setup.

For Blue, I'd love to see how linkage modeling might be done with excel. I saw some two dimensional (in a flat plane) linkage modeling using a microsoft office product (might have been excel or powerpoint) a year ago somewhere on the net but couldn't see how to make it work for a Z multiple link setup. It might be possible to do 3D dynamic linkage modeling in sketchup, but is the output desired a graph showing gas pedal linear mm input movement VS rotational degrees of butterfly shaft movement? A goal might be your eccentric idea with a slow take off that gets faster at mid pedal depression and then tapers off at maximum gas pedal depression? I don't know what might be ideal for street driving other than slow or linear butterfly movement as the pedal is pushed off of idle.

[Reverend]

I'd personally love to see dozens of pics of triple linkages.

[Travel'n Man]

 

Edited March 2, 2019 by Mike
Updated link

[Mikes Z car]

Another one (mentions a cable that does not require grinding off anything on Datsun gas pedal):

Throttle cable setup - Lockar & custom bracket - Drivetrain - HybridZ

Edited August 26, 2013 by Mikes Z car

[z boy mn]

Great pictures everyone, thanks for the link. Installing a cable seems much simpler than trying to get the linkage worked out, especially for me. My linkage needs a "repeater" of sorts because the linkage to the carbs doesn't line up with the stock one on the firewall. It binds right when the mechanical advantage is worst/best and the first axle grabs the rubber washer inside the stock firewall bracket. Makes for slop and stickiness. An upgrade sounds like a good winter project!

[jfa.series1]

I'd personally love to see dozens of pics of triple linkages.

Carburetor porn??? Sounds a bit kinky!