94eg!

iTrader: (2)

The DA valve is the same as the DC non-abs valve (94-97 RS). Only difference is the mounting bracket. These are the ONLY two "4040" valves that exist. Everything else is stamped with something else (or not at all).

1tuffbb6

iTrader: (1)

So is there a such thing as an 'EK 4040?'

94eg!

iTrader: (2)

No there isn't. Some people call it that, but the EK valves don't have any stamp on it, so it can't really be called a 4040.

1tuffbb6

iTrader: (1)

Good shyt, thanks homie!

Mr. Winky

This thread has been very helpful. Definitely a lot of useful information.

heel_touge

how does one test their prop valve for proper function?
Right now I'm boiling RBF600 pretty quickly on track days, we've found that the left front caliper does not release well, and the right rear caliper, when bled, trickles out. there is very little pressure to that caliper, or the rears at all for that matter.

im suspecting something going on with the proportioning valve, maybe corrosion or an obstruction. are there any moving parts? I have to order the part and have the car ready by wednesday next week. so im in a crunch and any thoughts would be greatly helpfull.

MAD_MIKE

For understanding Brake Bias I recommend reading this.
StopTech Brake Bias White Paper

Then read up on Proportional valves
Brake Proportioning Valves

Too much to read? Here's a simple explanation.

To keep the masses safe from themselves during braking, manufactures front bias cars. This keeps the car going straight under hard braking. If cars were set up with optimal brake bias, the common citizen under duress would more than likely slam on the brakes and put the car into a spin.

Then the street racer fanatic decides he/she wants better brakes and the first mod is to 'upgrade' the front brakes with larger rotors, bigger calipers and so on. This furthers the front bias, which in turn hurts overall brake performance. Causing the car to take longer distances to stop. Not good.

As for prop valves, they reduce the pressure to the rear brakes. Depending on how the proportioning is done varies. But usually with typical hydraulic proportional valves, there will be a knee point where the pressure rise slows and tapers off.

Easy way to test a PV would be to check pressure at the PV inlet port, and compare it to the PV outlet port. The PV inlet and MC outlet should be the same pressure, and the PVoutlet pressure would taper off after ~600psi or so.

But a PV will do squat if the initial brake bias is incorrect. It is merely a fine tuning device. The brake system is just that, a system. Not a cobbled together mess of random parts off multiple cars.

Kozy.

Ej8_KiD

i have sort of a weird question , i.e the 2 ports on the prop valve that go to the front calipers one for the right and one for the left if i invert those lines at the prop valve will the valve still work the same way? not sure how to explain it

Kozy.

Unless you're also swapping the inlet ports, the ABS is going to get mega confused when the wheel it's pulsing doesn't unlock...

94eg!

iTrader: (2)

If it's non-ABS it will work. But you will be eliminating one of the safety features designed into the car. Either brake channel leaving the master cylinder is meant to power opposite calipers (one left & one right). This way if you get a leak or failure within one channel, the other will still function normally and you will still be able to brake in a straight line.

MAD_MIKE

Invert the lines in which way?
Switching the lines from Left to Right, or do you mean from Inlet to Outlet?
What do you want to do exactly?

Mr. Dabolina

I know this is an old thread, but after getting in a debate about these things with a friend of mine the other day, and since I'm stubborn as hell, I decided to do some research.

I started out by reading this nice entry by the Brake Man. The graphs at the bottom are especially helpful if you're a visual person.

Then I stumbled on a nice thread on Rennlist (Click me) regarding Porsche proportioning valves. That's when it dawned on me. These numbers may be pressure cut-offs given in Bar rather than just a random production code. The first number being for the front cut-off and the second number being for the rear cut-off.

1 Bar = 14.5 PSI for those who aren't used to Bar as a pressure unit. Its very commonly used on Metric manufacturing machines that I've worked on / with in my day job.

For example with a 3040 prop valve, under heavy braking the master cylinder will put out more and more pressure relative to how hard you push on the pedal. The fluid pressure is the same in the lines leading to the prop valve. Rather than feeding the full pressure from master to all 4 corners, the prop valve cuts off the pressure at a predetermined high limit for the front (30 bar or 435 psi) and another predetermined high limit for the rear (40bar or 580 psi). Under normal or light braking the line pressure is allowed to vary between 0 and the cut-off pressure.

Thinking about this logically it seems to follow for most of the cars I've looked at prop valves on. Smaller lighter cars like an EF hatch use something like a 2530. My EG sedan uses a 3030. And the heavier of the bunch DA/DC use 4040's. Lighter cars generally need less overall braking pressure before lock-up so it follows in my mind.

In my mathy mind, this seems like a nice clean way to quantify your brake bias under heavy braking. A little napkin math can give you a good idea of how your actual braking force is split depending on your rotor size, pad size, caliper piston diameter, and line pressure. It does get a little messy with drums though. I can guarantee I'll be giving this a shot before I chose a prop valve for my sedan.

I've never seen anyone relate prop valves like this before so I may be completely off base here, or maybe I missed something during my previous research, but I'm just curious what other people think about this as a possibility.

Thanks for reading!

Kozy.

Nice theory, but wrong. There is never any proportioning to the front wheels. Ever. It's really, really bad, there is always hysteresis in the valving which is acceptable on the rear brakes but totally unacceptable on the front.

I can however see how you came to that conclusion.

Mr. Dabolina

Are you using hysteresis to refer to the lag in the pressure change due to the valving? If so, that makes sense.

Tyson

thinking of the pairs of numbers, and clearly there is a relationship between the first pair, and the 2nd pair of numbers, as ultimate pressures is a BETTER way of thinking about it. rather than a ratio, as commonly and mistakenly conveyed with a /.

but until someone actually does some measurements and a complete breakdown of a prop valve, its still a mystery.

ive done a bit of that research, but nothing worth sharing.

Bense

Bump