Compensating for a Tee, Deleting the brake compensator Options

[forrestkhaag]

Does anyone have the experience and time to briefly describe any needed tricks to delete the brake compensator on an early car / This, so as to make way for a 6 engine mount?

Things like / Is more brake line needed in addition to the "tee" fitting? And is the tee a hardware store item or another "porsche-priced" item that would be metric, brass, and overpriced by 3x?... (IMG:style_emoticons/default/sheeplove.gif)

Sounds like a good time to change out all brake fluid as well.

I have heard the warnings if one is running 914-4 brake calipers / I am not and have nice beefy 911 calipers which will do the job up front verses in back.

Thanks in advance.

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[ConeDodger]

Relocate. And delete this thread before Eric Shea sees it and calls in an air strike! (IMG:style_emoticons/default/blink.gif)

[914_teener]

My experience is limited to the theory as I.ve kept my car mostly in stock form and went through my suspension with the weight ratios in mind.

In stock form the car was almost perfectly balanced. The valve as I understand it is like a antilock device or prevents brake bias....meaning if the car is balanced for the midpoint it will spin at that center of inertia.

Since you are converting you car to a heavier motor...its a tough question since you will be altering this balance. Have you considered this in the suspension on tje car? Probably need more info on tires...brakes...suspension mods if any to get opinions.

So this are some things to think about before you go to Home Depot.


Like your Moniker....there is some inherent risks in your Traunches.

[914_teener]

Rob gave you the short answer.

[ConeDodger]

Rob gave you the short answer.

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[mepstein]

I figure the engineers's at Porsche added it for a reason and Eric Shea agrees. So I kept it on all my cars.

[porschetub]

I relocated by moving it further left,I had to replace both rear brake pipes anyway but you could get away with replacing only the right hand side pipe only.
Its an easy enough job,never for a minute thought of removing it.

[JmuRiz]

I had mine removed when I put boxster brakes on the front with stocks on the rear. Should I re-install my stock proportioning valve when I put my car back together again?

[mepstein]

I had mine removed when I put boxster brakes on the front with stocks on the rear. Should I re-install my stock proportioning valve when I put my car back together again?

Chances are the rear brakes aren't really going to be doing much against the fronts but I'm all for following a system. When we put boxter fronts in a 911 we usually had SC's or Carrara''s on the back.

[forrestkhaag]

Interesting and sage advice / thanks to all for input.

Just got off the wires with Rich Johnson who has a 3.0SC motor in his conversion of many years back and has had no issue with brake performance in the snow,rain, and icy condition of Texas w/o the compensator. That said, I will retain this piece of Porsche engineering after removal and test the brakes under several conditions without it to see if there is appreciable difference in performance.

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[Mark Henry]

The correct Tee is a VW part, the VW aircooled shops sell same part for a 1/3 of the price of most porsche shops.
Often a VW shop will have a good used one for dirt cheap.

[Larmo63]

I'm keeping the compensation valve in my car for the same reasons stated above. Plus, I don't want Eric getting mad. (IMG:style_emoticons/default/biggrin.gif) One could install a racing/adjustable type valve, but with most engine mounts such as the Patrick Motorsports mount that I'm welding in, it isn't in the way. It's close, but a non-issue. I'd keep it, Forrest.

[GeorgeRud]

It would be interesting to see if some of these big engined conversions (running 915 transmissions) would lock up the stock back brakes with the additional weight in back. A 911 uses the T fitting, I assume because of the heavy rear end bias in the car.

As a safety feature, no reason not to keep it.

[brant]

just a point of reference and it only partially applies to the Original posters question:

back when I had a 4cylinder race car I installed a T fitting and had a terrible experience.

the car was a 4cylinder (so did not have the extra 150lbs of weight changing the overall balance)

but the car also was running 911S calipers front and stock 914 rear calipers

Further I varied the pad compounds for more brake balance to the rear with much softer compound pads on the rear compared to the front

I had run an adjustable proportioning valve and felt that I need test the next step of increasing rear bias by trying out the T fitting, once my adjustable valve was fully open to the rear brakes.

Well I went down the back straight away at our now defunct 2nd creek track.

hit aboult 105/110mph going into the braking zone for a 90degree rt hand turn.

the rears locked up (while in the braking zone and going perfectly straight) and within a flash the car did a 180 spin and continued on into the corner at 100mph going back wards.

it happened so fast there was nothing I could do
I went off the corner backwards at an excessive rate of speed


So my opinion on the stock valve, is that you will rarely ever need it
but when you do need it, there will be no warning and no time to correct. This will likely only occur at a high rate of speed where traction is imperative. and you will have very little control in the extreme situation where you do need it.

I still run an adjustable proportioning valve on the track, now in a different car. I change my brake bias on a nearly daily basis for nearly each different track I go to. I have a pretty good feel for the balance and make very very small adjustments.

but the one time a person is on the street and over their head... it will be a hard lesson to learn in an emergency situation

[jor]

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The proportioning valve is there to keep the back brakes from locking up when you need them most. When you slam the brakes, the car's weight moves forward and the rear end gets light. The proportioning valve reduces braking power to the rear as the weight transfers forward. Without the valve, the rears can lock and disaster can follow. I was having trouble bleeding the lines with the valve and considered removing it as a quick solution. Sage advice on this forum kept me from removing and, whenever I read something like Brant wrote above, I'm thankful.

[toolguy]

(IMG:style_emoticons/default/agree.gif)
The proportioning valve is there to keep the back brakes from locking up when you need them most. When you slam the brakes, the car's weight moves forward and the rear end gets light. The proportioning valve reduces braking power to the rear as the weight transfers forward. Without the valve, the rears can lock and disaster can follow. I was having trouble bleeding the lines with the valve and considered removing it as a quick solution. Sage advice on this forum kept me from removing and, whenever I read something like Brant wrote above, I'm thankful.

FWIW, this is the best explanation so far, with one clarification . . the proportioning valve does NOT reduce braking. . it LIMITS the max psi to the rear calipers. .until the proportioning valve operates, brake line psi is relatively equal front and rear. {Any difference is due to the twin valve master cylinder's design}. when the rear fluid psi reaches a factory preset level, the internal valve plunger in the proportioning valve moves and covers the fluid outlet port to the rear calipers. . 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. .

Apparently 911's didn't need such a valve, because the motor was rearward and weight transfer / lift was less noticeable. . with the mid engine 914, the tendency in hard braking for a stock suspension car is to lift the rear end weight off the rear wheels. Therefore the brakes will then tend to lockup. The non rotating wheels render the rear end to become squirrelly and tends to slid the car around sideways. Remember, brakes are most effective at the point just before lockup. . a sliding tire has no traction relative to a still spinning-braking front wheel causing an unstable skid rather than straight line braking

[PanelBilly]

I relocated by moving it further left,I had to replace both rear brake pipes anyway but you could get away with replacing only the right hand side pipe only.
Its an easy enough job,never for a minute thought of removing it.

I also did this.

[914_teener]

If you read Brant.s post about what happened and you believe in one of Newtons law of physics.....you may not notice the affect when braking in a straight line. The moment of inertia will shift when going into a corner fast and braking hard.

Just sayin. (IMG:style_emoticons/default/yikes.gif)

[mlindner]

YUp, I feel the missiles coming in from Eric........I put the T" in about 1980, Stock brakes, high performance pads, race fluid. Engine was a big bore four, Webers and cam. Very fast in the day, lots of auto-crosses (Scca, Pax, PCA) and three plus years of Road America....high speed, wet, dry...Went home with a few/lot of Chicago PCA trophies....and never a braking issue. My 914-6 GT Tribute will still have the original T. And NO, original lines do not need modification.....Eric's stand is on the mark, he is selling top shelf products to keep you safe if you have not done the testing or have the understanding. Best, Mark

[Larmo63]

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?