Can I please get some advice from the group? My 914 has been sitting for far longer than I care to remember, so what to do with the brake equalizer? It's only got very minor surface rust and Haynes says dismantling is verboten. So, do I leave well alone or what? Advice please. Thanks.

i do not know what the test procedure is for these.

i hear they are prone to being difficult to bleed if removed from car and reinstalled. some say you must bench bleed before reinstall. this does not address your question, just info. eric shea is our resident brake expert and rebuilder. he may comment or pm him with your exact situation.

oh, i think it is called a proportioning valve, designed to stop brake pressure to rear brakes in an emergency braking situation to avoid car from spinning around.
something like that?

Toss it in the garbage or use it as a paper weight, put a "T" fitting in its place and you no longer have a spongy pedal. I'm sure I'll get some flack from posting this, but I don't have a proportioning valve in any of my 914's...and no, I can't lock up my rear brakes.

I'll let other give you flak for your suggestion, but this statement jumped out at me.
Even WITH a prop valve, a properly operating system should be able to lock the rear brakes with no problem.
Even with what looks to be a lot of rubber on that car in your pic.

If you have a spongy pedal and cant lock all of your brakes there is something wrong.

That is one of my tests for a properly operating system.
I verify when & how the brakes lock and in what order but that's with my old hard "street tires"

A proportioning valve reduces hydraulic pressure to the rear brakes - to reduce the tendency for rear brakes to lock up before the front brakes. However, it's not as simple as that:

http://stoptech.com/technical-support/tech...rtioning-valves

The above StopTech web page begins the discussion with mechanical brake bias via a race pedal assembly with a balance bar. Disregard if that isn't attached to your brake pedal.

Further down, they discuss the objectives of a true proportioning/brake balance valve. Not all valves are the same.

Some racers use different F/R brake pads to help maximize vehicle braking, but that would be considered fine tuning with experience and available materials.

Sherwood

I don't have a proportioning valve (or an equalizer) in any of my 914's either. In fact, none of us do. It's a pressure regulator. If you can't lock up your rear brakes, you may want to rebuild them, put good pads in them and adjust them. Then, when they kick in on a curve, with a deer in front of you, you'll at least know "why" you spun off the road.

A pressure regulator acts like a T-fitting until you get 525PSI on the system. Then it temporarily prevents fluid from going to the rears. It's the first anti-lock brake device. It was installed by Porsche on purpose. "Anything" in a mid-engine'd car to prevent you from polar moment inertia induced spin is not something that belongs on a desk holding down papers. That's what A-Calipers are for.

That said... ders a lots of guyz out der dat are smartr den me.

Just my experience; both street and track 914;s I have run have deleted the valve, and used the "T" fitting with good brake feel, and performance.

So Eric, maybe you should restore these too!?
... especially since they're NLA new AFAIK!


Tom
///////

He does. On his website and announce on world some time ago. DIY & PMB full service.

Running a "T" only for 8 years on a vintage 914 E Prod race car with the recommended calipers by PMB. Listen to Eric.

I recently had mine refinished by pmb. I'm no hydrolic engineer, but I would not replace it with a simple "T" fitting

Here is a post that gives good info, the whole thread is educational:

http://www.914world.com/bbs2/index.php?s=&...t&p=1158590

In fact here are some plots from davesprinkle:





At least according to that model, operating the car with the prop valve gives better overall performance. (Adhesion limits with p-valve > Adhesion limits without valve )

I sent Eric the pressure regulator out of my Six to have it rebuilt. That was the single brake part we had yet to touch. Now all of my brake components are new.

Come on guys, it is really the only safety system we depend on every single time we drive the car, regardless of speed and conditions. I wanted mine at 100%.

Forgot to mention that I have larger front calipers and 19mm M/C, I have much better control and balance with the "T" fitting over the stock prop valve, just my own personal preference and experience. Any yes all of the brake system is new and works perfectly. (meant to say I can't lock the rears before the fronts)

This came up recently and I'am pleased that Eric chimed in to clear up the matter,porsche don't generally put bits in the cars that they make for no reason.
Mine stays and won't ever be a paperweight,besides I spent time replumbing and remounting it to clear my stock 6 mount.

No you don't. You just think you do. The pressure regulator (not a prop valve) and the T fitting operate exactly the same until a panic stop. You have changed your brake bias from a more even 1.6 to 1 to something more like 1.8 to 1. The T fitting and/or the pressure regulator have nothing to do with that. The bias is determined by your new 48 mm front pistons and your original 33 mm rear pistons. Your rears are now barely working.

Which, brings me to my point, (which is not to argue with people online); altering your brake bias and your brake system by removing a critical safety component is a prerogative all your own. I just don't think it's a good idea to recommend it to other people.

I am assuming (always dangerous) that you and your car only drive on the street...otherwise, it probably wouldn't have been put up for so long. Correct? If so, I'd say whatever margin of safety can be had to protect you from yourself would be a good call. The limits of a 914, short of emergency situations, shouldn't be reached on the street and unless you have allot of high-speed track time with a 914 (and how one reacts at the limit) - the safest option would probably be the wisest choice. Good luck.

Tony

Now we can answer the original poster and the original question. Sorry.

If the system appears to be clean, leave it in place. Bleed your brakes and get a good pedal. Then in a quiet garage, simulate a panic stop by pressing your foot hard on the pedal. Listen for the click. If you hear the click, the unit should be working as expected. These generally last a long time because the plunger seal gets very little use and or movement in its daily operation. It's the same seal they use in the master cylinder which gets much more use and much more travel. That said, we have seen quite a few seals that are beginning to wear and fray.

I would base my decision on hearing the click or not. If not, the unit is probably frozen and needs to be rebuilt. This is something that everyone can do tonight in a quiet garage. Simulate to panic stop and listen for the click from your pressure regulator.

Eric - Now why didn't you just share that with him to begin with? LOL!

Tony

Because in a public forum, bad advise can go a long way toward perpetuating a myth.

Actually what I have found is that the aftermarket "Brake Proportioning Valves" like the one sold by tilton:
https://tiltonracing.com/wp-content/uploads...oning-Valve.pdf
are advertised to work exactly like the stock "regulator".

Here is a plot of the stock regulator output pressure:


Here is a graph of the behavior of the tilton in the various lever positions:


You can see that they are identical except with the adjustable valve you can "move up" the transition point to a higher value.
In position 7, you essentially have a "tee".
In position 3 you would be close to the same as the stock valve in a 914-6 @500 PSI
And position 4 for a 914-4 @650 PSI

I am a smart man. Not smarter than Eric when it comes to brakes for sure. But I have not seen many that were smarter than the orginal engineers that designed the systems in our cars. Are the better more modern options for some of our components? Yes for sure but I can't see eliminating a part in the brake system is a true step up.

Where as I agree with your general opinion, it greatly depends on how you intend to drive your car. I drive a heavily modified 914 and the stock system is not nearly up to the task on many levels. Just sayin' but not necessarily disagreen'. The stock system would most certainly be the achilles heal of a true performance car...

PS: I do agree 100% on the "Eric" part - he advised me as to how to optimize my system - he spoke, I listened, I implemented.

Tony

Perhaps an unlikely scenario but lets say you are involved in a serious accident, perhaps with a fatality. Insurance company discovers that you modified your brake system from original based on some "shade tree engineering". Can you cover the cost of your liability which may be far greater than the $150 dollars you saved by going to a T-fitting?

I have often wondered the same thing.
I have a 914 race car that I drive on the street. It is highly modified so this question applies.
However I have liability through Haggerty and they know beyond the shadow of a doubt that the car is a "vintage race car" and they even have a list of modifications.
So I assume in my case, I am covered, but not sure with "regular" insurance companies.

I have often wondered the same thing about turning off systems in new cars like vehicle stability control and traction control.
Could you be held liable if you were involved in an accident and the black box data shows that you had disabled certain safety systems prior to the accident?

...........Porsche does offer to allow you to "turn off" many systems in their very high end cars.........

Normally the system (in my DD) only lets you "partially" disable the systems but they are still holding your hand.
And in some cars there is a hidden "secret handshake" that disables the "nanny" systems completely.
In my BRZ it is called "the pedal dance" that completely disables VSC & TC.

I have even heard of people removing the ABS fuse entirely

I agree to a very small degree - I completely agree with the "unlikely scenario" opinion. This would not only apply to the brake system but ANY modification to the car - cams, exhaust, bushings, shifters (and on, and on, and...) - the minute difference in performance would be nearly impossible to "pin as" the reason for a fatality. This falls under the "worry wort" explanation as to not change anything - I mean ANYTHING. Do what you want - you'll be ok.

Tony

Good point and as Eric, I believe, said, manufacturers rarely put stuff on their cars which is superfluous to requirements!

Thanks to all who replied.

P.S. I really dig Amphicars. Used to see loads of them growing up in England in the sixties. Now, not so much.

I thought I was so smart!

My brake Master Cyl DOES say "14" on the part that can be seen from under the car. So, I bought a new "19" to to compliment the Big Black 911 brakes.

Here's the new one clearly marked "19" at the red arrow on the part you cannot see when installed and no "19" is seen anywhere else on the main body:

Click to view attachment

Surprise!

I started to pull out the old "14" (see yellow arrow) and their is "19" (see red arrow) in the same location as the new one described above!

Click to view attachment

HELP! Is the old one a 14 or 19 confused24.gif

The size markings are consistently in the same place. You now have two 19mm master cylinders.

E.

Eric,
Thanks..............good to know I have an "extra" ....

If you'd like to 'relieve' yourself of the extra 19mm M/C, I'd be more than happy to help you out....