Adjustable proportioning valves (APV)

[TommyK]

... 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.

I am doing my conversion for two reasons... the obvious one is, as Alan pointed out, aesthetics (the stock rotors look like washers sitting behind my 17" wheels). The other reason is that noody else has done it before and most everybody has said it couldn't be done... I'm just hard-headed that way.

[Dave M]

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?

That's my thought. We'll see how it all goes once things are together. I should have a chance this weekend to get back at it. If not, the family is going to be out of town for a bit in Aug, so I'll have lots of garage time! The turbo better be back by then!!!

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

Actually I don't believe the location should make a difference. Since the valve merely changes line pressure to the rears, as long as the valve is anywhere *after* the split from the front brake lines, it should be fine.

[Specky]

Actually I don't believe the location should make a difference

That'll be Pascal's law in action... ok i'll get me coat


TTFN

[F1 LOTUS]

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

.

I 'think' Monty meant setting them close to the original setting - Pressure not location?

[Dave M]

Now that I read it again, you may be right, Brian. In that case, yes - I will try to set them close to stock specs at first, but then add pressure to the rears so they actually do more work.

[Dave M]

It's been a while since I've updated this, but I've finally had the time to install all my new bits. Took a bit of searching to find the necessary adapters to absolutely minimize the number of connections I'd had to make (goofy things like a 10mm bubble to 1/8" NPT adapters that bend 90 degrees...), but so far so good. Everything is installed and no leaks!

Here's how I changed from the stock system:

1) I removed the stock proportioning valves and the small hard lines that go toward the rear brakes and connect with the first set of flexible lines. These pieces were replaced with one 10" solid hose.

2) The stock lines have a connection just to the rear of the main cat. The lines are held in place by blue clips mounted to the chassis. The hard lines were separated here to lead toward the adjustable proportioning valves mounted under the driver's seat.

3) Hard line extensions (20" and 32") were mounted to the stock lines from #2 to get to the APVs. The most difficult part of the install was getting the 2 lines bent into position leading from the master cylinder to the APVs. They make 3 90 degree turns and 1 180 degree turn along with snaking through the chassis/body/seat mounts. The lines from the APVs toward the rear were much easier.

4) Holes were made and grommets installed to run the lines under the seat. Once everything was fit, I used a healthy dose of caulk to make sure there would be no leaks.

5) The APVs were mounted on an aluminum bracket that fits between the seat rails.

6) All connections were made using Yamabond thread sealant to help prevent leaks.

Once my other projects are done, I'll have the car on the road to test things and adjust the valves.

[F1 LOTUS]

Should make an interesting development project. How are you planning to quantify your performance progress?

[Dave M]

8)
Should make an interesting development project. How are you planning to quantify your performance progress?

Well, for starters...if I can make it through a few 20 minute sessions at a track day without the brakes fading, it will be considered a success!

[Fubar1764]

Sweet!

[Dave M]

The car finally made its road debut after 5 months of hiding and I was able to get the first impressions of the new APV setup. I had set the knobs to allow the least amount of pressure to the rears. While the first one or two hard stops did lock one of the rears, once the front brakes were hot, they consistently locked first. I also attribute the rear lock up to a fair amount of surface rust burning of the rotors in the rear.

I didn't get a chance to play with the adjustments at all as I was working on other issues (see my Project thread), but the first impressions are good. Granted conditions were less than ideal (35 degrees and windy, which made the Kumho V700s feel like rocks), but by no means did the car feel loose or like the back end would come around under heavy braking. It felt like a front-biased balance at this point. Next week promises to be warmer, and once I've tamed the boost, I'll begin to play more with the rear bias.