Brake Upgrade - Proportioning Valve

Re: Brake Upgrade - Proportioning Valve (TwoDogs)

Mon, 26 Nov 2018 15:11:55 GMT

Actually moving the valve to the engine bay would add extra vacuum and compensate for reducing the tank ("thinner"). I wonder why they went thinner, when you read about people adding extra tanks to increase the amount of vacuum. (volume not pressure).

Re: Brake Upgrade - Proportioning Valve (TwoDogs)

Tue, 20 Nov 2018 23:41:21 GMT

I've been going through the part numbers and yes there are 4 different boosters from 90-97.
I still haven't found the specs for each.
I believe there are only 2 ways to vary the power of a booster. 1) diameter of the diaphragm
and 2) the number of diaphragms.
So, it is possible that even in the same housing, the outer "clamped" edge of the diaphragm could be reduced thereby increasing the swept area of the diaphragm. Or they fit another diaphragm in the housing.... or....multiple things were changed to ....
re the check valve location - I don't think it matters. If I use one of the boosters without a check valve, I would install the check valve near the booster .

Re: Brake Upgrade - Proportioning Valve (Reddtarga)

Tue, 20 Nov 2018 18:35:41 GMT

Stuff you need to know if you are looking to replace your booster:
I have seen 4 different boosters fitted to SW20's as OEM.

The 'fat' body boosters on early model JDM cars, (don't know much about those) and 3 other different 'thin' body boosters that have the same size body.

With the 3 thin body boosters the only visible difference was that the ADM '90-91 thin body booster had the vacuum valve mounted on the booster.
The '92 - '94 booster and the post '94 booster just have a pipe outlet (no valve) and they both look identical. (With these the valve is mounted in the engine bay)
However, all 3 thin body boosters must have different internals even though the body size is the same, because the power in each case is different with the later model one the most powerful.
I don't know how Toyota achieved that.

Re: Brake Upgrade - Proportioning Valve (TwoDogs)

Tue, 20 Nov 2018 10:16:17 GMT

I'd like to talk about the boosters for a minute ?
As I see it, there are only 2 pressures involved, your engine’s vacuum, and atmospheric, it seems the only way to increase the power of the booster, is with a larger diaphragm. I see the later MR2 versions are called “thinner” and I can only imagine that reducing the volumes of the 2 chambers would make a small change to the speed they react. Bite? Otherwise I don’t think thinner means more powerful.
I haven’t been able to find specs (eg diaphragm diam.) on the various boosters Toyota has used or whether a Rav4 or Corolla unit fits…. Hoping someone can confirm or correct my “understandings” above…. Thanks.

Re: Brake Upgrade - Proportioning Valve (Falcon)

Tue, 20 Nov 2018 07:35:21 GMT

Ian. Regarding those front brake air scoops you showed me in Adelaide. Engineers mind and artists hands.
Really very well done. Way too flash for me though. But I'll take two sets if you make em !!
And I like the way you tested them. Real world, sensible. No BS.

Re: Brake Upgrade - Proportioning Valve (TwoDogs)

Mon, 19 Nov 2018 21:55:23 GMT

Ok now I think I've got it. When you said you were getting lockups very easily, you meant your ABS activated.
This clears my confusion, and only supports my opinion of the early ABS trials.
thanks for the clarification.

Re: Brake Upgrade - Proportioning Valve (Reddtarga)

Mon, 19 Nov 2018 18:21:25 GMT

TwoDogs
I am most confused that Redd says, going to 15/16" MC (which I have already) AND a later booster is too powerful.
Then wouldn't 15/16" M/C with my early booster be close ?

Well I didn't necessarily say that combination would be too powerful without ABS.
However with my early ABS connected it would have activated too easily with heavy braking, even on smooth dry bitumen, but it is fine with the 1" M/C.

I once tried a 15/16" M/C with my early booster, and it was sorta OK.
The travel was reduced but actual stopping power wasn't that impressive, and it needed a lot of pedal pressure.

Re: Brake Upgrade - Proportioning Valve (TwoDogs)

Mon, 19 Nov 2018 13:35:07 GMT

Redd, Falcon,
thanks for the responses.
I have ABS and don't like it. It can activate miles before lock-up. Almost sent me out onto a busy road due to lumps of dried concrete in the braking area. Not sure if I will deactivate it or remove it totally, but it is bad.
I am most confused that Redd says, going to 15/16" MC (which I have already) AND a later booster is too powerful.
Then wouldn't 15/16" with my early booster be close ?
I think I need to check the boost is working properly.
For some reason our booster units seem to cost a fortune where other cars cost $200 ! Are there other Toyota boosters (non-MR2) that might be suitable ?

Re: Brake Upgrade - Proportioning Valve (Carmikey)

Mon, 19 Nov 2018 10:18:45 GMT

Nice, simple yet effective mod. I like very much. Good work mate!

Sent from my SM-J320ZN using Tapatalk

Re: Brake Upgrade - Proportioning Valve (Reddtarga)

Mon, 19 Nov 2018 10:11:20 GMT

TonyMR2
Reddtarga - there is an awesome item to reproduce and sell :)

Yes I suppose it would be, but I have no interest in doing that because of the huge amount of time needed to make them. I think these are more for do it yourselfers with plenty of time to spare.

They were are made from 1 mm aluminum 'coaxed' into a rough shape, then overlaid with fiberglass tape and resin making them surprisingly stiff. They also have a rear support bracket.
Quite apart from the time it took to get the design right without fouling anything on hard lock, the finished articles took a lot of shaping, sanding, and filling needed to get them right not to mention getting the LH side one a mirror image of the RH.

Do they actually work?
When I first started this project I did some tests with a rough scoop only on one side. see pic.
I did a series of tests with 4 consecutive hard braking stop from 100 kph, then again quickly accelerated to 100 kph and coasted to a stop to allow the scoop to work if it was going to. I stopped the car and quickly compared rotor temps on each side using an infrared tester, finding that the side with the scoop was cooler, so I then went ahead and made the finished scoops for both sides.
Doing the same tests later with the finished scoops first fitted only on one side then only on the other side indicated the rotor with the scoop was about 15% cooler. Of course tests of this type are only a rough indication, but I think the project was worth the effort.

Re: Brake Upgrade - Proportioning Valve (5SGTE)

Sun, 18 Nov 2018 19:58:51 GMT

That is definitely spare time well spent.

Re: Brake Upgrade - Proportioning Valve (Guest)

Sun, 18 Nov 2018 19:27:36 GMT

TwoDogs you want awesome braking, purchase from DVS_MR2 has two brake upgrade packages from his cars, gen 3 turbo (around $550 from memory) or full deltaV upgrade (around $1400 from memory), complete with all components.

Re: Brake Upgrade - Proportioning Valve (Guest)

Sun, 18 Nov 2018 19:25:26 GMT

Reddtarga - there is an awesome item to reproduce and sell :)

Re: Brake Upgrade - Proportioning Valve (Reddtarga)

Sun, 18 Nov 2018 18:55:43 GMT

Falcon

I have had plenty of difficulty trying to work out brake problems on my car so I'm particularly interested in any discussions that this may generate on here.
Does your car have ABS fitted from factory ?
Will PM you.

I'm sorry if this is getting away from the original subject.
Doug, I don't know if this may help your brake problems, but if you have heaps of spare time here is something that may interest you for your track car.
Front brake airscoops fabricated from 1 mm aluminum, and fiberglass that direct the air right into the center of the rotors.
With these fitted I have found the rotors actually run cooler under heavy braking!!
They have lasted a couple of years on my car without getting destroyed, and they don't foul the caster rods.
Ha ha, yes, I know. I just have too much spare time on my hands, but it's fun making things.

Re: Brake Upgrade - Proportioning Valve (Reddtarga)

Sun, 18 Nov 2018 18:09:39 GMT

TwoDogs: "I'm also a bit confused as I would have thought it possible to just modulate the pedal pressure to prevent lockup"

Well yes it would be, but modulation preferences vary with different people, and there are other variables as well.
I use stock Toyota pads that have plenty of bite, even when cold. I imagine 'performance' pads would probably be different. Also in my case keep in mind that I still have the early small brakes and not the later ones.

With the 15/16" M/C, once I fitted the later model booster it made a huge difference to the pedal feel using the small brakes. I would even use the word 'deadly' to describe it compared to with my OEM '90 model booster.
I would have had to disconnect the ABS if I had wanted to keep using it, but being a road car I wanted my ABS operational.
I happened to have a new 1" M/C sitting around from an earlier project so I didn't hesitate to try it.
Anyway, even forgetting about the ABS it turned out that the 1" M/C gave me the perfect balance between brake modulation, pedal pressure, and pedal travel. The ABS also appears to work normally with it.