Vacuum Canisters/Reserviors. Do they work?

I'm looking for the low down on vacuum canisters in the brake booster vacuum line and if they work. Seems like a low expensive solution to avoiding the wooden pedal syndrome while LFB'ing.

Thoughts?

Eddie Fiorelli Wrote:
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> I'm looking for the low down on vacuum canisters
> in the brake booster vacuum line and if they work.
> Seems like a low expensive solution to avoiding
> the wooden pedal syndrome while LFB'ing.
>
> Thoughts?

They work, and are easy.
But correctly sized dual masters probably work more predictably.

Not dragging you brakes for impossible to quantify but likely neglible results might work even better. 8)

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

If all you're looking for is consitency in pedal feel, then do what a lot do as well, and remove the vacum signal from the booster. It will make the pedal harder obviously but if you put on a real race pad then that hard pedal will give you lot more control and mudulation.

What car is it?

Cosworth Wrote:
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> If all you're looking for is consitency in pedal
> feel, then do what a lot do as well, and remove
> the vacum signal from the booster. It will make
> the pedal harder obviously but if you put on a
> real race pad then that hard pedal will give you
> lot more control and mudulation.
>
> What car is it?

VeeWee Gowlph

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I prefer the inconsistency of power brakes over the leg work required for de-boosted stock breaks. However, here's is what the internetz says about dual master cylinder setups, I'm sure its been said here before as well:

For over 30 years race cars have used dual master cylinders, this is the use of two master cylinders that are side by side being applied at the same time. The mounting is generally done on the fire wall, but special applications have made it possible to mount these on the floor, under the dash or in a remote location. A balance bar is used to balance the force to each master cylinder. Think of a bar with a pivot point in the middle, when pressure is applied to the pivot point both ends move the same distance. Now think of the same bar with the pivot point move more to one side, when pressure is applied the shorter end will move before the long end. That is basically how the balance bar works. In a race car there is a cable connected to one end of the balance bar, this cable would go to a knob in the drivers compartment, so he can make adjustments as the condition of his brakes and road condition changes. The balance bar also eliminatesthe need for a proportional valve. On certain applications a remote reservoir(s) are used, in these applications it deletes the use of residual valves on disc brake applications. Master cylinders of this type do not have built in residual valves in them so if you have a drum brake application you will still need an inline ten pound residual valve, this is needed to retain pressure against the cups of the wheel cylinders.

There are major advantages to using dual master cylinders: (1) Smaller diameter master cylinders can be used to increase output pressure. The design allows the application of two master cylinders being applied at the same, thereby doubling the volume output. Because of this high pressure output you will not need a vacuum booster. If you are running any type of camshaft, chances are you do not have enough vacuum to run the booster anyway. (2) The balance bar eliminates the use of a proportional valve and gives you the optional remote adjustment. (3) The remote fill applications deletes the need for residual valve normally used when the reservoirs are lower than the calipers.

Question: Do dual master cylinders use a vacuum assist at all? Sounds like no.




Edited 2 time(s). Last edit at 04/06/2009 03:13PM by Eddie Fiorelli.

Not typically, but sometimes. There is a company called Comp Brake out of the UK that makes a setup to use booster and dual master setup.

http://nocoastmotorsports.net/Build/Merkur/Aug07Master.JPG

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Grant Hughes

Eddie Fiorelli Wrote:
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> I prefer the inconsistency of power brakes over
> the leg work required for de-boosted stock breaks.
> However, here's is what the internetz says about
> dual master cylinder setups, I'm sure its been
> said here before as well:
>
>
>
> Question: Do dual master cylinders use a vacuum
> assist at all? Sounds like no.

Correctly sized, it's not like its a vacuum system with the motor not running.
It's a bit more pressure depending bit not bad.
Hell when i was at a dry Monte Carlo looking at cars braking down from top speed to 25mph for tight T junctions I was wondering but seeing these skinny ass, no leg Eyetalians drivers in the service answered the question: they didn't have any muscles at all and they were doing just fine.

Did you have polio as a small child?

Note that my beloved Xratties have a pedal ratio of about 4.4:1, far less than many of the fancy pedal assemblies and say Volvo 240 at about a bit over 6:1 and the brakes work fine with completely acceptable effort.

The dual masters are cheap enough, and an easy mod to the pedal, and the ability to swap in whatever size ya want for the fronts if you got calipers with more area than your stockers is a big plus.

More room is a plus in a VW engine bay.

And if you decide ever to get a fun-ner cam, there goes vacuum at idle.

Sounds like win-win-win-win for the win
>
>
>
>
> Edited 2 times. Last edit at Apr 6, 2009 by Eddie
> Fiorelli.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Well, I am a not so tallish italian but my question was to understand what a dual MC install looks like.

ok so no vacuum booster, unless you go with the system Grant referred to.










Edited 1 time(s). Last edit at 04/06/2009 09:55PM by Eddie Fiorelli.

Eddie Fiorelli Wrote:
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> Well, I am a not so tallish italian but my
> question was to understand what a dual MC install
> looks like.

Here's one on Skye's Xratty:


modded pedal in the box---very similar to VW (it's upside down)



'nother view:


Complete thing.
Box is fully boxed for strength and stable pedal, sprigs between the pedals replaced with alloy spacers.



You do know that there are detailed instructions on building your own box---which you can adapt for a Golf since the instructions are for a MkII Escort---linked to here in the "Escort Rally Preparation" book dontcha?

And excelled clear line drawings on EVERYTHING you need in all the Ford books...

>
> ok so no vacuum booster, unless you go with the
> system Grant referred to.

Yeah.
Here's the other car everybody should be in a nice 240 Volvo, very similar again to both VW and Xratty, probably bought in from same supplier.




Again just a simple tube welded into the pedal.


A bench and a jig saw and a vswe and half a relaxed afternoon, its easy.


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>
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> Edited 1 times. Last edit at Apr 6, 2009 by Eddie
> Fiorelli.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I'll try to snap some pics of Scott Leonard's dual master setup in his Golf. He also loves it. It takes a very minute amount of time to get used to having to use a little muscle to brake, but not really. It's worse when you get back in your street car with mushy brakes after a weekend of rallying and can't operate the clutch or brakes because you're so adapted to the rally car.
I tend to find that I am braking way to early. People in some cars talk about modulating the braking, which to me means your riding the brakes, which means your not on the gas pedal. I try to go with Derek Bottles' wise philosophy, which was something along the lines of, "Hold down the gas pedal, as soon as you feel like you should brake, wait a three or more seconds then pound on the brakes, get back on the gas as soon as possible." I still find I'm usually on the brakes too early, but I'm working on that. At our test facility CORE I find that I tend to be too late as I'm always trying to push the limits out there. Heaven help me if there's a girl riding along as I always tend to show off. I've blown through a hairpin at 90+ because I was trying to see how long I could wait until I absolutely had to brake. I waited way too long.

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Grant Hughes

NoCoast Wrote:

> I waited way too long.
>

QFTW haha

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Welcome to the cult of JVL drink the koolaid or be banned.

Awesome pics thanks. On to the Escort Rally Prep link.

And Grant, if you could snap some pics of Scotts setup that would be cool. I'll be at Idaho and if he's there as well I'll make sure to talk to him about it there.

-e

NoCoast Wrote:
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> I'll try to snap some pics of Scott Leonard's dual
> master setup in his Golf. He also loves it. It
> takes a very minute amount of time to get used to
> having to use a little muscle to brake, but not
> really. It's worse when you get back in your
> street car with mushy brakes after a weekend of
> rallying and can't operate the clutch or brakes
> because you're so adapted to the rally car.

It's pretty entertaining when I get back in my street
car with the power-assisted brakes after driving one with
unboosted brakes around on a track. Generally I forget and at
the first stopsign I stomp the pedal like I would in the track car.
My poor ol' OBS then comes to a screeching halt about 20 feet
short of the sign.

> I tend to find that I am braking way to early.
> People in some cars talk about modulating the
> braking, which to me means your riding the brakes,
> which means your not on the gas pedal. I try to
> go with Derek Bottles' wise philosophy, which was
> something along the lines of, "Hold down the gas
> pedal, as soon as you feel like you should brake,
> wait a three or more seconds then pound on the
> brakes, get back on the gas as soon as possible."
> I still find I'm usually on the brakes too early,
> but I'm working on that.

I think Derek may've been simplifying things a bit. That's
a seat-time thing. I'm pretty sure he went to a practice
facility and spent a lot of time blowing turns, figuring out
what the threshhold of braking is for a car like his until he
could nail it every time. Then you take that mental picture and
apply it to every turn, tweaking it for road conditions, tire wear,
camber, bumps, etc.

And modulating the braking isn't about riding the brakes, it's
about getting on them and off them smoothly and holding them just
below lockup. If you stomp the brakes abruptly, your suspension
dives and then rebounds and wobbles and so on and you're now fighting
it and whatever the road's giving you. And if you just mash the pedal
to the stop, your wheels are going to lock up, and it's only very
rarely that a locked-up wheel slows you down faster than a rolling
one.

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Self-righteous douche canoe

Well put Michel!

Robert.

---

Robert.

"You are way too normal to be on Rally Anarchy." Eddie Fiorelli.

ok, so on to calipers. What is their role in this whole story? I've never felt that my baby calipers (oem GTI calipers, single piston) were lacking..ok with the exception of the time my pad disentegrated at Prescott.

Since the MCs feed the caliper pistons does it make sense to change one part of the system and not the other?

Given my thinking is correct, if a stock single MC generates a certain line pressure, if you increase the caliper piston surface area, you will correspondingly increase your braking force (and thus pressure) at the pad (for a given pad surface area). So if I double my effective piston surface area, then I can double my braking pressue. That's assuming the same MC can generate the same line pressure for both piston arrangments. (enough caveats for you?)

So, calipers, what's the story overall...