Shifter

[ericjon262]

I always hear complaints about the Fiero's shift quality, and most people attribute that to the long shift cables. Well how about doing away with the cables altogether and going with a hydraulic "linkage"? four small double action cylinders and some lines, wala, smooth precise shifting.

Thoughts?

[Series8217]

I wouldn't want to have to bleed it.

Besides that, you have other things to consider like how the "pull" motion is going to work.

[ericjon262]

I wouldn't want to have to bleed it.

Besides that, you have other things to consider like how the "pull" motion is going to work.

already thought of that, by using a double action cylinder, you gain "pull" capabilities, without adding 4 extra cylinders.

basically, put a seal on the end of a cylinder where the rod goes through, so you can have fluid on either side of the piston.

I made a quick and dirty "diagram" in paint to illustrate what I mean...



now the question this raises, is how much effort would it take to shift the car like this? but I don't see how it could be hard with appropriately sized lines.

[The Dark Side of Will]

Are *YOU* dissatisfied with the Fiero shift quality? If not, why would you build this?

It's not an external linkage Muncie, S2000 or Mjata, but for a cable shifter, it's not bad. Go drive a MkII VW Golf if you want a vague shifter... and that's a bar linkage rather than cable.

The MR2 Spyder is cable operated and has very good shift feel.

Simply being cable operated is not a problem.

*I* think the Fiero shift linkage works just fine. I have a stock shifter, Rodney's cables and short shift linkage at the transmission. I can do clutchless up and downshifts all day.

[ericjon262]

Are *YOU* dissatisfied with the Fiero shift quality? If not, why would you build this?

It's not an external linkage Muncie, S2000 or Mjata, but for a cable shifter, it's not bad. Go drive a MkII VW Golf if you want a vague shifter... and that's a bar linkage rather than cable.

The MR2 Spyder is cable operated and has very good shift feel.

Simply being cable operated is not a problem.

*I* think the Fiero shift linkage works just fine. I have a stock shifter, Rodney's cables and short shift linkage at the transmission. I can do clutchless up and downshifts all day.

I don't mind the feel as much as I do the packaging, you could loop around the engine bay with a hydraulic setup and not sacrifice feel at all.

the cables must approach the transmission from a fairly straight orientation, where-as a hydraulic setup wouldn't have to.

I've driven a MKII jetta, I imagine they drive about like the golf did, and it wasn't fun.

[Series8217]

Well, you could make it work, but four (eight?) hydraulic lines and four cylinders seems like it just trades off cable/line routing for bulky assemblies at each end.

I feel like it would be pretty slow because you would actually need to move a significant amount of fluid to achieve the necessary stroke.

The BMW SMG II operates at like 1200 PSI to achieve good shifts. It's a hydraulic pump for shifting a transmission that normally is shifted with a manual linkage.

[The Dark Side of Will]

If both master and slave cylinders were, for example, 1/4" bore, then the system wouldn't need to move much fluid at all.

I've been musing about using the electric pumps and accumulators from the old Teves ABS systems, which operate at 1900+ psi, to operate a small diameter master cylinder for use in a DIY paddle shift. The transmission would be operated by a stepper motor turning the shift shaft (the job of the select cable) and a solenoid operating moving the shift shaft axially (the job of the shift cable).

[ericjon262]

I was thinking along the lines of keeping the line size almost equal to the piston size, so that there is minimal restriction to flow, and equal size pistons all around. the shift mechanisms aren't very hard to actuate so mechanical advantage won't have to be high

[The Dark Side of Will]

The MA of a cable is 1:1, so unless you wanted to shorten the shift throw, the hydraulic actuation would be 1:1 also.

[ericjon262]

The MA of a cable is 1:1, so unless you wanted to shorten the shift throw, the hydraulic actuation would be 1:1 also.

I was thinking about going lower to gain a faster actuation.

[The Dark Side of Will]

High end bicycles have hydraulic disk brakes these days... you may be able to borrow some of that tech/parts for the lines, fittings and reservoirs. That will probably be the only way to build this system WITHOUT making it MUCH bulkier than the cables you want to replace.

Due to the necessities of fitment, cylinders will most likely have to be custom.

How are you going to bleed these hydraulic circuits?

[ericjon262]

High end bicycles have hydraulic disk brakes these days... you may be able to borrow some of that tech/parts for the lines, fittings and reservoirs. That will probably be the only way to build this system WITHOUT making it MUCH bulkier than the cables you want to replace.

Due to the necessities of fitment, cylinders will most likely have to be custom.

How are you going to bleed these hydraulic circuits?

I've seen hydro bike brakes, and they are way tighter than anything cable actuated, it's nuts how tight they are...

I was figuring on custom cylinders, I've never seen anything with an appropriate form factor for the Fiero.

I don't know how it would be bled yet, I know hydro bicycle brakes are bled with a syringe to draw vac on the lines, I would imagine that would be the best way to bleed these too, but I'm not 100% sure how I would do it yet. I have more research to do on that.

[Series8217]

I hate (actually I like) to be a constant force of pragmatism, but have you already taken all of the slop & free play out of your existing linkages? You might find that the cables work fine once you do...

[The Dark Side of Will]

I thought I tried talking sense at the beginning of the thread, but maybe I was wide of the mark...

[crzyone]

I would say a swap to cables would be an upgrade from a leaky hard to bleed heavy hydraulic system.

If it's sloppy, buy new cables.

[ericjon262]

my point in starting the thread was to brainstorm a bit, I haven't driven my current setup yet, hopefully I will get to fire it off for the first time next month. right now, I have Isuzu cables and shifter setup to control a F23 from a 01 sunfire behind a LX9 3500. I built the linkage around the Isuzu cables, but they are running pretty close to the hotside of my crummy turbo setup. Right now, I don't really see a better way to run the cables, which is the beauty of a hydraulic setup, you can mate to the transmission wherever it's convenient, not just from the front. but as has been pointed out, it brings it's own set of problems that have to be sorted out. we'll see what happens.

[Series8217]

they are running pretty close to the hotside of my crummy turbo setup

Why not spend the money and effort on making a nicer turbo setup, while at the same time adding some clearance for your cables?

[The Dark Side of Will]

Doesn't California Push and Pull make custom cables? Do some mockups of different routing and order cables that will do what you want.

[ericjon262]

both of those are probably what will end up happening. the main reason I see is getting the shifter side packaged into the console would be a PITA.