New guy necroing a thread... I signed up because of this thread; I have a leg injury and desperately want to do this mod.

How much did the booster change your pedal travel?

 

I think it cut clutch pedal travel by 1/3 to 1/2, never measured it. I added a stop bolt under the pedal to eliminate wasted motion.

 

so, 1/3 less travel... *and* reduced tension? about how much was tension reduced?

any advice for me? what tools will I need to install this

I have v6 m5 firebird. should I expect reduced travel on mine, too?

 

you can get the boosters in several different assist ratios. pick whatever assist works for you, I'm sure you can get that clutch so light that you can barely feel it if that's what you need for your condition.

 

I haven't seen different ratios; where do I find this?

and can I convert increased ratio to reduced travel? I suppose that has to remain strictly tension?

 

you can change travel and pressure, travel is controlled by the master cylinder size and pressure by the assist ratio. There have been cars modified before with hand operated clutches, this being the extreme example:

if you have left foot issues, perhaps a motorcycle style clutch handle on the shifter is a better idea for you.

 

you can change travel and pressure, travel is controlled by the master cylinder size and pressure by the assist ratio. There have been cars modified before with hand operated clutches, this being the extreme example: https://www.youtube.com/watch?v=ZmcCoDmwhXc

if you have left foot issues, perhaps a motorcycle style clutch handle on the shifter is a better idea for you.

Negative on the hand shifter, but thanks! my issue affects my hands too, lol. thankfully, steering wheel isn't as difficult to use as the clutch pedal . (plus, that would be an expensive mod -- probably.)

So, I would need to swap out the clutch's stock master cylinder? Got it... I don't think there are any significant aftermarket options for my car, though.

... actually, did the OP change his master? he said his travel was reduced with the VH44, without changing master - I thought?

 

I'm actually not sure why he said his travel was affected, the booster is just suppose to boost the pressure, not the volume. but perhaps another change was done at the same time. you'll reduce the travel slightly since you're not fighting firewall flex but that isn't that much.


you're pretty much out of the stock realm for any of this, you'll need some custom fabrication. but the good news is it really isn't that complicated.

What is the idea for you in terms of travel and pressure?

where are you located?

 

1/2 travel and 1/2 pressure would have been good.
I believe this would require 1/2 (or double??) cylinder size, and 4:1 boost ratio. (1/3 pressure might be better, then 6:1; doubt I'll find this? lol)
If I focus on more of one than the other, then I want to reduce tension more than travel.

It's possible that I *only* need the boost, but would be nice to do travel too to help make sure I don't have an issue. Neither I nor any of my doctors have been able to firmly comprehend what's going on, so I can't say if it's primarily tension or position that affects me. lol

I'm in South Dakota.

I've done a decent amount of work on my car, and I like to DIY; woodwork, kydex, etc. so, I think as long as I don't have to weld (don't have one), the modding won't be too hard to comprehend. lol

 

yeah, you've got it, double the piston area and a 4:1 assist ratio.

Talk to these guys: tech talk there's actually something on that page about an option to change the travel at the booster, they certainly know more about these than i do.

 

Okay, I sent them an e-mail. Thanks.

Hello!

I have an injury to my left leg, and it's very painful to use the stock clutch pedal; the tension is too high.


So, I'm considering adding a VH44 inline between the clutch's master and slave cylinder.

Do you have any advice for me? I read that I should install a check valve on the vacuum line, for example.

Does the booster affect pedal travel, or only tension? Is it possible to change travel, without getting a different clutch master cylinder?

I read I can change the boost ratio easily; how is this done?

Thanks for your advice!

 

This is the reply I got from them:

Hi , the unit we supply for clutch is a vh44d ratio is 1.73 to 1, please call for more info 0415 532 153 regards terry

So, if any of you gents can answer any of my questions....... lol

 

I added the VH44 inline to the clutch hydraulics with no changes to either the master or clutch slave cylinder. I do not know which boost ratio (VH44 model) I got. I am positive there is a change in volume of fluid pushed: As I mentioned, I added a clutch pedal stop bolt to eliminate wasted travel. So I have my clutch rigged to work with boost. If I push the pedal down without starting the engine first, it will not disengage the clutch. (Won't push enough volume to do the job. Pedal pressure is also back to non-boosted force)

This can create a problem if the car is parked on a hill and loads up the gearbox to where the shifter won't slide out of gear. Obviously I can't start the engine to get vacuum (clutch boost) so I must loosen my clutch pedal stop-bolt to get the extra pedal travel. I carry a wrench for this purpose. However I live on the coastal plain so very few hills within 300 miles.

======
Trying to puzzle out the volume/pressure question:
Is the published 1.73:1 ratio a volume ratio? Then of course the volume changes, between input and output. Or is that 1.73:1 pressure ratio? It seems like the pressure ratio would be determined by the diameter of the vacuum diaphragm. I've seen pictures VH44 style booster with both large and small diaphragms.

Internally the VH44 essentially has a small piston pushing a larger piston. The piston rod gets assisted by a large metal plate and rubber diaphragm assisting via vacuum.
The small/large piston have a valve between the two, allowing the booster to work in "un boosted" mode producing a 1:1 volume. The valve opens when there is no vacuum assist.

This site has some nice colored schematics of the VH44 function. You can hit the links in sequence and get an "animation" of how it funtions. http://falconccwa.stormloader.com/vh40hint.htm

 

I added the VH44 inline to the clutch hydraulics with no changes to either the master or clutch slave cylinder. I do not know which boost ratio (VH44 model) I got. I am positive there is a change in volume of fluid pushed: As I mentioned, I added a clutch pedal stop bolt to eliminate wasted travel. So I have my clutch rigged to work with boost. If I push the pedal down without starting the engine first, it will not disengage the clutch. (Won't push enough volume to do the job. Pedal pressure is also back to non-boosted force)

This can create a problem if the car is parked on a hill and loads up the gearbox to where the shifter won't slide out of gear. Obviously I can't start the engine to get vacuum (clutch boost) so I must loosen my clutch pedal stop-bolt to get the extra pedal travel. I carry a wrench for this purpose. However I live on the coastal plain so very few hills within 300 miles.

======
Trying to puzzle out the volume/pressure question:
Is the published 1.73:1 ratio a volume ratio? Then of course the volume changes, between input and output. Or is that 1.73:1 pressure ratio? It seems like the pressure ratio would be determined by the diameter of the vacuum diaphragm. I've seen pictures VH44 style booster with both large and small diaphragms.

Internally the VH44 essentially has a small piston pushing a larger piston. The piston rod gets assisted by a large metal plate and rubber diaphragm assisting via vacuum.
The small/large piston have a valve between the two, allowing the booster to work in "un boosted" mode producing a 1:1 volume. The valve opens when there is no vacuum assist.

Is there any way you can link me to the one you bought, so I can try to find the ratio? Thanks!

Also, is the stop bolt necessary? Won't it become very firm to press near the end of travel, without the bolt, like with brakes?

 

Go ahead and email Peter Ni. He has no problem selling individual units.

 

Clutch is not as light as the 2GR throttle. The throttle is stupid easy, since it's just a rheostat and a little spring. Clutch is probably equivalent to a stock Toyota Corolla. I don't keep my heel planted to use the clutch. It might be possible, if the pedal was rigged to engage closer to the floor. I have mine rigged so that the clutch pedal hangs even with the brake pedal - then added a spacer to kill the wasted travel by the floor.

 

Corolla's gas (not sure if you were referring to DBC vs DBW) or clutch?

 

I estimate the clutch pressure with the booster installed, feels similar to the clutch pressure of a stock four cylinder car.

I'm trying to think of a way to get some actual pedal pressure measurements. I'll see if I can cook up something using a stick and a fish scale.

 

VH44 pedal pressure comparison!



I did my best with a fish scale and a stick.
With boost on (engine running) my clutch pedal is 25lbs to depress.
With boost off (engine not running) my clutch pedal is over 60lbs to depress. I'm not positive about the non-boosted pressure, since I would have to re-rig the clutch pedal linkage to allow full stroke of the pedal without boost, but it is at LEAST 60lbs.

 

Ugh!!!
Got my car back today.
ALL of the VH44 boosters on ebay are now gone or twice the price... sigh

sent peter ni a message a few days ago, no response yet.
also, their sales history is incredibly... low and sporadic?.. odd.

 

This is supposedly identical to the VH44.. anyone know anything about it?

.. does the kit look complete, at least?
BEK028 MGB Brand New Brake Servo Fitting Kit TT3949Z | eBay

 

This is supposedly identical to the VH44.. anyone know anything about it?... does the kit look complete, at least ?

That kit looks very complete. My kit did not come with the coil of flared hydraulic line shown in the ebay ad. The booster diaphragm looks like a smaller diameter, but deeper than the one I bought. Supposedly there are about 20 different variants of that booster, with different boost ratios, volumes, piston diameters etc. I pasted a summary below that I found on the 'net. The eBay listing would certainly give you some clutch assist. it just might be more or less than you want. I'd give it a try. That's what I did when I picked mine at random!

 

VH44 bore is 5/8"
My bore is 3/4"

I'm screwed, aren't I? Pedal travel will increase.......?

 

VH44 bore is 5/8"
My bore is 3/4"

I'm screwed, aren't I? Pedal travel will increase.......

Is that your master cylinder bore, or your clutch cylinder bore?

Actually, I think it does not matter what size cylinder is installed in the middle of the system. You are not replacing your input or your output cylinders. You are just adding another cylinder in the middle. And that middle cylinder has vacuum assist, PLUS a step-up cylinder internally. (Small piston pushes a larger piston internally). I believe the internal step-up pistons will guarantee that your pedal stroke will be reduced.

 

Somebody please correct me if this thinking is wrong!

Volume of output from two hydraulic cylinders is proportional to the bore diameters. Say your current cylinders are 1 (master cylinder) and 2 (slave cylinder). The ratio is 1:2.

If you add a third cylinder in the middle of this system with diameter 3; then the ratios are 1:3, and 3:2. Thus the volume from input to output remains 1:2. It doesn't matter what size cylinder you stick in the middle of the system.
*edit* Yeah, I think this explanation is really inaccurate - but the concept works.

However, all the VH44 boosters have an internal step-up, where a small piston area pushes a larger piston area. This guarantees that you will get more volume out of the booster, than you put in. You are guaranteed a reduced input pedal travel by installing a booster - in any hydraulic system.

 

Somebody please correct me if this thinking is wrong!

Volume of output from two hydraulic cylinders is proportional to the bore diameters. Say your current cylinders are 1 (master cylinder) and 2 (slave cylinder). The ratio is 1:2.

If you add a third cylinder in the middle of this system with diameter 3; then the ratios are 1:3, and 3:2. Thus the volume from input to output remains 1:2. It doesn't matter what size cylinder you stick in the middle of the system.

However, all the VH44 boosters have an internal step-up, where a small piston area pushes a larger piston area. This guarantees that you will get more volume out of the booster, than you put in. You are guaranteed a reduced input pedal travel by installing a booster - in any hydraulic system.

Sweet!
Do you happen to know your master cylinder bore size? That would be a simple way to know for sure.

 

I'm not sure I mentioned - I did remove the clutch pedal overcenter spring by the clutch pedal pivot. With the pedal pressure so much lighter I did not need the assist of the spring. Plus the overcenter "sweet spot" didn't fall in the right place any more with the shorter pedal stroke.

*edit*
Another tip for final rigging. A pedal-travel block off may be necessary (not just nice to have). Another forum guy was having trouble with the clutch pedal sticking to the floor with a (new) booster engaged. It may be possible for the clutch pedal to travel so far, that most of the return force exerted by the pressure plate is lost. This is because the boosted fluid volume is greater than not-boosted.
Conclusion, plan to add a clutch pedal travel limit of some sort. Find where the new clutch engagement point is, and block off the wasted travel of the clutch pedal. I used a block of wood for a while. (Zip tied to the back of the clutch pedal arm) Later I added an adjustable stop bolt to limit wasted travel.

 

That's awesome for you, Cyclehead.

My booster got here.
Of course, I need 3 lines going to it - input, output, and vacuum.

Which are they? I think I use the one on the back for input, the far top one for output, and the black pivoting line on the large, black round part is vacuum.. right?
Do I plug the top-near line? What with?

What's with the soft fabric on the round part of the gray piece that's held in by a spring?..

How must my booster be oriented?

Last, I assume it has two outputs. Is there any way to rig them together and get double boost? I imagine if I tried that, one output would be fighting the other output and I'd get nowhere except maybe a blown booster?

 

...What's with the soft fabric on the round part of the gray piece that's held in by a spring?..How must my booster be oriented?...

The fabric looking material is an open cell foam air filter. The booster draws outside air when you actuate the booster. The filter is behind a large washer with breather holes. Remove this vent washer and the foam filter to access the control spring if you want to fiddle with boost adjustment. I glued a washer inside the vent washer to reduce the boost.

The booster is supposed to be installed with the long cylinder pointed up 30 degrees. I presume that aids bleeding the cylinder.

 

bump

 

Is this correct?

I've gone through 10-20oz of fluid and I still hear air on the slave side and the pedal falls to the floor.

What the heck!?
Help!

 

... vacuum bled, fixed that issue

but now it doesn't drive.......

I bring clutch pedal all the way up and the clutch is still mostly disengaged.
Ideas?

 

So sorry I missed your earlier questions! (I got a new bicycle recently...and I have too many projects!)

Clutch still disengaged with the pedal up - is bizarre! That means there's residual pressure in the output line. And likely residual pressure in the input line also. I'm trying to think how that could happen.

 

Well, I can't keep it anyway - even with the boost, it still hurts my leg too much. my car is for sale ;(


fyi: if I limit the pedal travel distance to where it disengages *with* boost, I can fix it not engaging fully..

what happens: I shift from 4k rpm, then clutch stays partially disengaged, even if I shift again.
I turn off car, pump pedal, resume - works now.

thanks for trying

 

Sorry to hear it didn't work. On the bright side, now you can consider an MR2 Spyder with SMT transmission. It's a standard 5 speed, shifted with switches and hydraulics. The SMT system runs the clutch for you completely, and even blips the throttle on downshifts.

 

I had a 3 inch diaphragm seal fail last week on my clutch booster. It was a little aggravating diagnosing and finding it, but all fixed now.

I looked up my records. My first VH44 booster lasted 51,000 miles before the central shaft fluid/air seal failed and it sucked all the fluid into the big rubber diaphragm. My second VH44 booster lasted 18,000 miles before the small 3 inch diaphragm seal failed.

After the most recent failure, I drove home without any clutch assist. What a pain! If I can't find a complete set of rubber parts, I'll just order another booster for spare parts. They seem to be dropping in price.

 

After the most recent failure, I drove home without any clutch assist. What a pain! If I can't find a complete set of rubber parts, I'll just order another booster for spare parts. They seem to be dropping in price.

Paul, I know how much you love to tinker, so why not adapt an MKII turbo clutch pedal to your Spyder. It is double-sprung, for mechanical assist.