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Brake Upgrade - Proportioning Valve

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TwoDogs
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Re: Brake Upgrade - Proportioning Valve 2018/11/19 13:35:07 (permalink)
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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 ?
  
 
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Reddtarga
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Re: Brake Upgrade - Proportioning Valve 2018/11/19 18:21:25 (permalink)
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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. 

1990 ADM NA
 
 
 
 
 
 
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Re: Brake Upgrade - Proportioning Valve 2018/11/19 21:55:23 (permalink)
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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.
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Re: Brake Upgrade - Proportioning Valve 2018/11/20 07:35:21 (permalink)
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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.
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TwoDogs
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Re: Brake Upgrade - Proportioning Valve 2018/11/20 10:16:17 (permalink)
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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.
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Reddtarga
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Re: Brake Upgrade - Proportioning Valve 2018/11/20 18:35:41 (permalink)
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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.
 

1990 ADM NA
 
 
 
 
 
 
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TwoDogs
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Re: Brake Upgrade - Proportioning Valve 2018/11/20 23:41:21 (permalink)
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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 .
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TwoDogs
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Re: Brake Upgrade - Proportioning Valve 2018/11/26 15:11:55 (permalink)
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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).
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