Adjustable proportioning valves (APV)

[Dave M]

To build from the discussion starting on 05.07.06 here (see a bit more than 1/2 way down the page),

http://lotuselancentral.com/forum/viewt ... 0&start=20

I thought I'd start a new thread as this topic gets away from the original topic there (Are bigger brakes better?). A quick summary: I have the AP front upgrade kit and find the car fading during track days. I attribute it to the fact that at a given pedal pressure, the fronts do much more work as a result of the upgrade than the rears to. Hence the fronts get hotter quicker on track, and the rears show very little wear.

ESM has some fantastic info in the above thread and it's worth the read of the bottom of page 2 and page 3 as part of the APV discussion. I agree that on a standard car, simply adding the big front brake kit will throw off the braking bias. However with stickier tires, race pads on the front for track days, adjustable dampers which have lowered the car, and removal of weight throughout the car, I've done more than just add the front kit.

I understand that you can only put so much pressure to the rears before they will lock, especially when weight shifts forward under heavy braking and the thought is to bias a car such that the fronts lock before the rears. My feeling is my rears aren't anywhere near locking by the time the fronts do, therefore I'm giving away braking ability of the car. If the rear pads aren't very worn, they aren't contributing anything! (And yes, I have new stock calipers on the rear).

That said, I have ordered Wilwood APVs and have begun re-plumbing the brake lines in order to get them into the system. I hope to mount the valves under the driver's seat so they are accessible when driving. That way it's not a "brake, stop, get out, adjust, get back in, brake again..." kind of test to set them up or adjust when different pads are put on either end. Last night I eliminated the stock proportioning/limiting valves witha simple piece of 8" hard line from NAPA and have begun to run other hard line where I can. The goal is to upgrade with the ability to return the car to stock specs if I need to.

I'll post pictures once I get the APVs in the mail and have a little more work done on the hard lines. Feel free to share your thoughts, concerns, or to confirm that I'm a wacko for going there. [/url]

[johnbenk]

Posting removed

[ESM]

Firstly can I strongly suggest no-one removes the existing brake proportioning without adding an alternative. Unless you like spinning it would be a very, very bad idea.

Dave, I reckon you will be able to set it up to be optimum on the limit, because they aren't two stage you will get low effort under lighter braking but I realise that's not a priority in a track car - might hurt you a little if you ever race in the wet but that's it really. It'll be fun to set up though - how do you plan to go about it?

[Dave M]

Ditto on ESM's point. The manual even notes that if an issue is suspected with the valves, to just replace them. NOT to take them apart and attempt a fix. If you pulled them apart and removed any portion you'd likely get much more braking in the rears than you'd ever want. My luck it'd be just before the time a car pulled out in front of me unexpectedly.

As for the set up, I will do some caliper pressure testing all around with various settings on the APVs. I want to do a little comparing to the charts you put together and the charts in the manual to see how things work out as far as slope and maximum pressures. Then it'll be off with the valves on their weakest settings (least amount of pressure to rears). I've got a great road 1 mile from my house that is empty and 4 lanes wide with no divider for some "lockup testing". I figure since my 2 current fronts have one or two flat spots from the last track day (they were 90% gone anyway), they can totally give it up in the name of science. I'll just keep adding pressure until I get a good balance - and then likely back off a little just to be safe. Hopefully the settings that produced the best outcomes in the pressure testing come close to the on-the-road settings.

You're right on the "kneepoint" adjustment...that would be nice. Hopefully the average overall balance is better than it is now, however.

[ESM]

If you give me the specs on the AP setup (pot size, disc size and pad depth) I'll stick its front/rear torque behaviour on a graph.

[Dave M]

If you give me the specs on the AP setup (pot size, disc size and pad depth) I'll stick its front/rear torque behaviour on a graph.

Thanks Alan!

Another nice surprise came last night when a box was waiting on my front step. It only took one day for the APVs to come, thanks to the fact the shop I ordered from is about 2 hours north of me! Using a piece of aluminium, I made a mounting bracket that will fit beneath the front seat and uses the seat bracket connections to bolt in. Now it's just bending brake line and getting the correct fittings.

The only trick with the fittings is the APVs use a 1/8"-27 pipe thread while the car lines appear to be M10x1.0. A quick search on-line last night produced a number of adapters, and one option so far. However it involved 4 different connections. I'd rather have a male 1/8"-27 pipe thread that plugs into the APV and adapts to a female M10X1.0. Then I can just run the hard line right up to the APV. Less chance for leaks. Not a big deal, though. That's the beauty of searching on the internet...

Here are a few pics of the work thus far:

[Sy V]

Hi

I beleive it is possible to take apart these. See LEC repair article Proportional Valve).

If this is correct you could remove the compensating valve that stops fluid to the rears.

You could then reaseble leaving the pipes in place

Has any LEC member ever done this to see what the Braking Effects
would be????? regarding rear lock up and the pedal travel.

This is just about the most ridiculous suggestion I have ever heard.

You're plumbing new depths of insanity with this theory.

Please save your advice for areas about which you know something.

[TommyK]

Hi

I beleive it is possible to take apart these. See LEC repair article Proportional Valve).

If this is correct you could remove the compensating valve that stops fluid to the rears.

You could then reaseble leaving the pipes in place

Has any LEC member ever done this to see what the Braking Effects
would be????? regarding rear lock up and the pedal travel.

This is just about the most ridiculous suggestion I have ever heard.

You're plumbing new depths of insanity with this theory.

Please save your advice for areas about which you know something.

ouch Sy... that was a wee bit harsh, don't you think?

[Sy V]

Yeah, maybe a bit harsh, but where potentially fatal brake performance issues are concerned, there's no room for speculative theorizing.

I retract the last sentence of my previous post.

[DeeAitch]

I did hear a story of someone who removed the valves in search of greater breaking effort - sadly he did not live long enough to relay the results - DO NOT DO IT - unless you know what youre about & replace them with something, as Dave is doing, and even then stick to a track day.

[TommyK]

Points well taken. That's why I'm putting myself in the very capable hands of the professionals at Precision Brakes.

[Dave M]

Points well taken. That's why I'm putting myself in the very capable hands of the professionals at Precision Brakes.

Hi Tommy. Are PB doing anything as far as proportioning, or are you only upgrading rotors and calipers for now?

[Ashaman]

I have a really dumb question, but is there a way to do this safely/accurately? (Some sort of a reverse dyno seems like it would be necessary, LOL)

I mean, even once you have a target in mind after working the math or what have you -- how does one go about actually figuring out how much braking force the rears are actually applying?

I ask of course as I also have one of those "remote contact" stories of a guy who wrapped his Eclipse around a pole trying to get his set right; so I have always been a bit scared of them.

I guess mine are fine, but I have always wondered if they are optimal...and since I know nothing about it, I just have left it that way

[Dave M]

The math and pressure gauges I'm hoping will get me to a close approximation of stock. Bascially whatever "heavy" braking pressure is to the fronts (from measurement), I'll compute the rears to be whatever % of that based on the performance/specs of the stock proportioning valves. I'll then set my system up for that same ratio. I know this setup results in a front bias in my car, so then I can slowly add rear bias until I get to a comfortable, controllable threshold braking. This I plan to do on track, or under controlled conditions - NOT just driving around.

The standard to metric adapters came in yesterday (actually the shop I bought the APVs from had them - see http://www.chassisshop.com/ ), but unfortunately I won't be able to get to things until next week due to some travel commitments. I'm very anxious to get things assembled. While I still don't have an answer on the turbo, at least the car will be ready to stop, if not go.

[TommyK]

PB is helping me put together a 13" rotor at all 4 wheels "kit"... It's taking a wee bit of engineering due to the rear rotors housing the wheel bearings. They assure me that it can be done as long as I have money left in the checking acct. The new proportioning valves are pretty much a must since I'm upgrading the rears as well.

[Dave M]

PB is helping me put together a 13" rotor at all 4 wheels "kit"... It's taking a wee bit of engineering due to the rear rotors housing the wheel bearings. They assure me that it can be done as long as I have money left in the checking acct. The new proportioning valves are pretty much a must since I'm upgrading the rears as well.

Sounds interesting! However I wouldn't just assume the proportioning will be totally out of whack. It's a lot of work redoing the lines if you don't need to. Probably good to get the car out on track or under very controlled condiditons to try everything out first - maybe even try some different pad compounds if PB can help you out a bit. I'd be hesitant changing the rears and then driving on the street without some sort of testing. Let us know how you come out, though. Could be another very good option out there for folks.

[Monty]

Hey dave,

Haven`t a clue on brakes etc but don`t u need to keep the valves close to were the originals were?

[ailwyn]

Hey dave,

Haven't a clue on brakes etc but don't u need to keep the valves close to were the originals were?

Monty,

If the original valves were being replaced than I would agree, but as Dave is going to be setting these to provide a "like-stock" balance, the adjustment for the change in location would be included in the set-up.

Or to put it a slightly different (and possibly more intelligible) way, in order to correcly balance the fronts and rears the move of valves would have to be taken into consideration as part of the overall setup.

This does assume that there is an impact in moving the valve location, which, like you, I think there would be due to a different volume (hopes to use the correct terminology) in the rear section.

Ailwyn

[ESM]

The trouble with big brakes on the rear (taking as a given that the bias is corrected) is that they dissipate miniscule amounts of energy compared to the fronts. So adding disc area makes it hard to bed them and hard to keep the disc surfaces clean and corrosion free. Also adding all that extra thermal capacity makes them hard to warm up. Big rear discs offer only aesthetic advantage as far as I'm concerned, although getting rid of any single pot caliper is a good thing, personally, I'd keep the disc a bit smaller.

[Ashaman]

Sounds like a pretty good idea, should be interestijng/fun.

The gauges measure the line pressure to each caliper then? Then based on that pressure you know what kind of braking force is being applied, is that it?