clutch assist

[Waitey]

Are you also a member of the "failed pump" club? Mine died on the entrance of the busiest roundabout in Bracknell when I lived there - very inconvenient! Not too bad a job to change DIY, thankfully, but it didn't help my feelings for the gearbox (Since then I've also owned a Smart - well, the wife did - and driven an S-tronic R8, and my feelings for automated single-clutch manuals have not improved

Small world, we also had a Smart Brabus too, the most hilarious gearbox in the world.

My E46 was good though! Didn't break.

[Waitey]

has anyone actually fitted a clutch servo, and if so how successful was it

Lots of people have used the MG 1.6 ratio one in the TVR world with good success.

You might need a vac res though.

[gnc]

has anyone actually fitted a clutch servo, and if so how successful was it

[aaronjb]

I had an SMG E46 M3 too!

Are you also a member of the "failed pump" club? Mine died on the entrance of the busiest roundabout in Bracknell when I lived there - very inconvenient! Not too bad a job to change DIY, thankfully, but it didn't help my feelings for the gearbox (Since then I've also owned a Smart - well, the wife did - and driven an S-tronic R8, and my feelings for automated single-clutch manuals have not improved

I was thinking more of the electric assistance Bosch rolled out in Honda's and then latterly Tesla's etc etc.

I had completely forgotten those exist for some reason (despite watching every video Matt puts out)! Interesting idea and certainly solves the 'low vac' issue nicely, possible you could get better feel than a vac servo too as you could dial in the assistance level.

You also get a lot of standalone vac pumps now. VW ones from older diesels are cheap and compact.

Something else that is permanently leaking oil on all the BMWs I own (not standalone, to be fair, cam driven)

[Waitey]

If vacuum is required for a servo, why not use an alternator with vac pump mounted on the rear .
Magnetti Morelli did these for the diesel Transits back in the nineties .

You also get a lot of standalone vac pumps now. VW ones from older diesels are cheap and compact. 

[Waitey]

A few* more steps and you've got yourself an SMG system 

*OK, quite a few. Plus SMG was hydraulically actuated w/ electric pump. And awful (I was a glutton for punishment and had an SMG-I E36 and SMG-II E46  )

How will you solve the issue of feedback, though, as surely there'll be no pedal 'feel' anymore, you'd have to rely on engine note to gauge the bite point, no?

[edit] Apologies for the drift from the actual topic at hand!

I had an SMG E46 M3 too!

I was thinking more of the electric assistance Bosch rolled out in Honda's and then latterly Tesla's etc etc.



Swap the MC for a single port of of your desired size and bob's your uncle.

You'll still have *some* feel.

Just a bit bulky.

Good video on how one works.

https://www.youtube.com/watch?app=desktop&v=SRZ8XDNz2vU

[JON1D]

I understand that some times the pedal is slow to return with servo assisted and you can get a pulsing effect.
Having a vague bite point does not appeal so I would stay with a heavy clutch.
This is also dependant on a good vacuum. A low vacuum from a radical cam might struggle to give you sufficient vacuum at idle.
Going with a smaller cylinder and longer travel to achieve a lighter pedal would be the best option IMO.   

[GDCobra]

I went the opposite way on mine (RV8 with TL77 gearbox and standard SD1 clutch), wanted to reduce the pedal travel in the, quite confined, pedal area so went from a 3/4" to 1" master.  This did result in slightly heavy pedal but I could (and still can) live with it.  Later on I changed the slave to a concentric type and this is, maybe, slightly lighter and, as the system reduces lost motion could probably go back to the smaller master if I wanted while keeping acceptable pedal travel.

I guess the problem with a servo is the clutch is used more frequently than the brake and more fluid flows each time so pressure in the reservoir (servo body) rises quite quickly.  Perhaps a separate vacuum reservoir tank and electric pump could be used to suplement the engine? 

[Chris]

If vacuum is required for a servo, why not use an alternator with vac pump mounted on the rear .
Magnetti Morelli did these for the diesel Transits back in the nineties .

[gd427man]

Never had any issue with mine, but a mate has a mustang which he finds the clutch heavy.
He spoke about maybe looking at fitting a 'gas strut' to assist.
Is this even fesable?
Just a thought.
Ian

[aaronjb]

I'm going to try to use an electric actuator for mine, its only mocked up in my head for now, so its hard to explain!

A few* more steps and you've got yourself an SMG system 

*OK, quite a few. Plus SMG was hydraulically actuated w/ electric pump. And awful (I was a glutton for punishment and had an SMG-I E36 and SMG-II E46  )

How will you solve the issue of feedback, though, as surely there'll be no pedal 'feel' anymore, you'd have to rely on engine note to gauge the bite point, no?

[edit] Apologies for the drift from the actual topic at hand!

[Waitey]

"So if you are at 0.75" master cylinder size and you need 50kg of force on the pedal, which moves the master cylinder rod 1", going down down to 0.625 MC, would mean you'd need 41.5kg of force, but the rod would need to move 1.2"."

To compensate for the smaller MC by reducing the pipe diameter you would reduce the required distance of the rod to travel. Giving you a lighter pedal.

The other solution is to fit a servo boost assisted hydraulic clutch unit, giving you a light pedal but you loose the feel of the bite point.

In a closed hydraulic system like a car clutch line, the ID of the line that joins the two cylinders doesn't effect stroke of the cylinders. The only thing determining the movement needed at the rod is the ratio of bore diameters between the master and the slave. X movement in, will always equal Y movement out.

The only effect up or down sizing the ID of the connecting line will have is a lower of the effective energy needed to transfer the fluid forwards and back between the two cylinders. In the sizes and lengths we have in cars, this only amounts to less than 1% of pedal effort in transition. The apertures in the cylinders themselves are generally smaller than the smallest ID line you'd ever run, so most of the resistance to movement, other than moving the load itself, comes from those.

It comes more into play when you have powered hydraulic systems in things like excavators, where running larger lines in a system that are actuated many times, saves 'x' amount on energy in a day. Even then, going beyond 2" ID only gives diminishing returns and lots of packaging issues.

[gnc]

there seems to be a lot of different opinions on this,  so im going to take the  suckit and see option.
3/4 cylinder and 3/16 pipe.     ok but heavy
0.65 cylinder and 3/16 pipe.    longer travel  but still heavier than id like
next 0.65 cylinder and 5.16 pipe
after that a servo
geof

[JON1D]

"So if you are at 0.75" master cylinder size and you need 50kg of force on the pedal, which moves the master cylinder rod 1", going down down to 0.625 MC, would mean you'd need 41.5kg of force, but the rod would need to move 1.2"."

To compensate for the smaller MC by reducing the pipe diameter you would reduce the required distance of the rod to travel. Giving you a lighter pedal.

The other solution is to fit a servo boost assisted hydraulic clutch unit, giving you a light pedal but you loose the feel of the bite point.

[gnc]

thanks, makes sense too me. will try the options out
geof