Compensating for a Tee, Deleting the brake compensator Options

[914_teener]

Not to hijack, but in addition to Forrest's question about the brake compensation valve, what do most here think about keeping the stock 914 sway bar in place on a /6 conversion?

My opinion is that depends on tires and spring rates....but for sure I believe more needed on a 6 conversion then on a -4 that is in stock config. Also depends on how you drive the car...as you can tell by some of the racers that responded.

I.m a civl engineer and not a mechanical engineer so I know enough to get into trouble and know I.m in trouble.

[Mike Bellis]

The PO of my car or PO,PO,PO of my car removed the bias valve and replaced with a T when he switched to 930 brakes. It was a dedicated race car at that time.

I can tell you my brakes work fine and the car stops on a dime. I have no intention of putting it back.

[mgp4591]

So far it seems that the valve is designed for lighter stock type engines and trans combinations. Are there any experiences for the heavier drivetrains? The weight transfer issue is still there but would the heavier mid weight setup keep the car more stable or exacerbate the tendency to spin at the limit? I'm thinking that the car would tend to stay planted. If the brakes had been upgraded all around, they'd respond as designed with the additional weight being controlled with the valve if it was still installed. What are the racers doing with the additional power and weight on the track?

[Cracker]

...not a "racer" but I do have a hot-rod with more mass (mike) - I obviously do no run a "T" in my car. Also, the hydraulic (plunger) style proportioning valve does not provide enough adjustment for my application. My "large" changes are made with the balance bar - the plunger style valve mounted on the console is for the fine-tuned, on track adjustments. The only "914" I have ever spun (on a track) was a stock-ish car, with all OE installed.

T

[brant]

So far it seems that the valve is designed for lighter stock type engines and trans combinations. Are there any experiences for the heavier drivetrains? The weight transfer issue is still there but would the heavier mid weight setup keep the car more stable or exacerbate the tendency to spin at the limit? I'm thinking that the car would tend to stay planted. If the brakes had been upgraded all around, they'd respond as designed with the additional weight being controlled with the valve if it was still installed. What are the racers doing with the additional power and weight on the track?

With a -6 and the in creased weight, I run an adjustable valve. Not a T

[914_teener]

...not a "racer" but I do have a hot-rod with more mass (mike) - I obviously do no run a "T" in my car. Also, the hydraulic (blade) style proportioning valve does not provide enough adjustment for my application. My large changes are made with the balance bar - the blade valve mounted on the console is for the fine-tune, on track adjustments. The only "914" I have ever spun (on a track) was a stock-ish car, with all OE installed. These cars are dangerous when driver quickly, in stock trim/set-up.

T

I quess Tony with consideration of the OP and what Brant said is that these things or answers may of may only partially apply. There are so many considerations when setting up a car. Braking and suspension are but a few. When I say "racer" it involves a lot of seat time and experience dinking around with what works. So seat time is important to know what these things "feel" like and what they do. I know how the math works and I have enough track time...twice..to be scared.

I asked the late Ron Mier (Slits) one time...many years ago now.. how it feels going into a corner and how to brake. He said at the old Riverside track that he knew it was time to brake when his asshole would start to quiver.

You have an awesome car BTW.

[stugray]

One thing to keep in mind: The stock prop valve will actuate ONLY when you stomp on the brakes in a (mostly) panic situation. That is because the prop valve acts like a tee until the brake pressure exceeds something like 650-750 PSI.
If you are driving normally you will never know it is there.

And the people who race will likely not ever "stomp" on the brake as racers are more skilled and would rarely ever depress the brakes so abruptly.

And this statement is incorrect:

. . Therefore no matter how hard you press the pedal, no more pressure goes to the rear calipers. . there is an external adjustment to preload the internal valve spring which regulates the valve psi cut-in pressure. .

The pressure to the rear brakes WILL continue to increase as you apply more brake pressure only at a reduced rate compared to the fronts.

This graph shows that the rear pressure does not go "flat" at the transition point, it still has a slope, just less slope than before the transition:

(IMG:http://www.914world.com/bbs2/uploads/post-14886-1390702515_thumb.jpg)

[JmuRiz]

Interesting stuff, maybe that's why only in the emergency braking drill at an HPDC i had one rear wheel locking. We thought it was the vent spacing on that wheel (rear passenger-side), but maybe it was since I removed the T.

I'll have to look at my car and see how easy it'd be to add the stock prop valve back in, since I kept all my old parts (IMG:style_emoticons/default/biggrin.gif)

[forrestkhaag]

In summary, I am going to move the damned thang once I get my motor mount in the car and I know where it will fit without interferring with oil lines, thermostat, wiring, fuel lines, brake lines thereto, and a host of other simple things to deal with....... (IMG:style_emoticons/default/hissyfit.gif)

Thanks for the input.

Sidebar: My attorney recommended deleting it...... after carefully documenting which engine mount supplier directed me to delete the valve, then,.. right after I kill myself in a hideous fiery accident, allow him to help my lovely wife sue the supplier so they can live happily ever after. With friends like that, (IMG:style_emoticons/default/WTF.gif)

(IMG:style_emoticons/default/lol-2.gif)

[Larmo63]

Forrest, your motor mount should not get in the way of the brake valve, Relax.

Put the mount in, and then re-attach the valve.

Have a bottle of wine, and forget what you did until the next day.

You'll be fine.

[mtndawg]

I had mine refurbished by pmb and it looks brand new. Since a team of engineers put it in the braking system I kept everything original.

[Steve]

I've been running a "T" for over 20 years on my car. Many auto crosses and trips to willow springs including "big willow". Now that my car is a street car again. I might look into the factory valve again. Can it be modified for a six conversion with boxster brakes?

[jim912928]

I converted my car to a six with parts from an 84 3.2l donor car. I also put the 84 disk brakes on all around. My proportioning valve was pretty grungy. The 911 donor car had what's called a brake "regulator" that is inline in the rear brake line just beyond the master cylinder. So far seems to work fine and I have had a few "hard stops". The pressure calibration isn't identical to the 914 prop. valve but it's darn close.

It's part number: 930 355 305 00

The "bar" is set at 33 with a reduction factor of .46

[rick 918-S]

I have the "T" but 255/50/16's and 225/50/16's have increased the contact patch and the rolling inertia which requires more clamping force on stock solid rotors. Oh and I am running a 19mm master and BMW 2002 4 piston calipers on the front. It woes the car down in a straight line. Considering my engine weighs as much as a big block Chevrolet I guess I'm satisfied.

[bdstone914]

I know there are early and late brake valves. The line routing on one causes some interference. Anyone know what that is ?

[mepstein]

I know there are early and late brake valves. The line routing on one causes some interference. Anyone know what that is ?

The late often has to be adjusted/moved on 6 conversions.

[Larmo63]

I'm doing my engine compartment right now with the Patrick mount. Everything fits fine, and I will be re-using it.

[mlindner]

This is mine, stock lines on a 74. Best, Mark

[stugray]

I hope that all of you worrying about relocating the stock valve know: You CAN make your own brake lines for a couple of dollars.

OR you can order some premade from belmetric.com

https://www.belmetric.com/475mm-brake-line-...59lcfa53lhceir1