Brake booster and ITB's on 16v

[Uzelac]

How does AE86 stock setup (with booster) react when used without vacuum ?

[jondee86]

Back in the day when cars were pretty much all drum brakes, boosters
were rarely seen on small family cars. But when disc brakes came into
wide-spread use, boosters too became commonplace. Essentially,
because disc brakes are not self-energising, the booster was needed to
keep brake pedal effort at a comfortable level.

Deleting the booster is perfectly acceptable for a dedicated race car with
a custom designed Willwood or similar system. The disc sizes, caliper and
master cylinders are carefully selected to give the required dissipation of
energy, without requiring excessive pedal travel of effort.

However, on an everyday driver, deleting the booster will need to be
certified/engineered, and offers little if any advantage (other than extra
space for quad throttles). I run a booster with my quad conversion, and
it works fine. The stock AE86 4-wheel disc brake setup is more than
adequate for standard or mildly modified cars. With upgraded pads and
fluid, they will cope with all but the most highly modified road cars.

Sorry about the rant It's only that the brakes are the most important
safety system in your car, and I cringe to read some of the modifications
that wannabe racers make to their braking systems. This not something
to practice your DIY skills on. If you must change calipers/discs/masters,
at least consult a qualified race car builder, to make sure what you are
considering will be safe

Cheers... jondee86

[Ivan141]

It's a problem us LHD guys aren't faced with fortunately. But your point is valid.

[4000GT]

Again, remove the booster... problem solved

[harkes]

Thanks for the replies. Not possible to remove brake booster in DK if you want to pass vehicle inspection.

[allencr]

harkes Wrote:...Compared to a blacktop the vacuum is ok but the amount of air being sucked by the itb's is much lower... Is the best sollution to mount fittings (green) and use a plenum?

Less cc's, hotter cams?
Use the stock setup, drill/bore out its fittings a mm or 2, fit a vacuum tank/reservoir/accumulator. If it holds vacuum for a hour, let alone over night it's OK.
If it still doesn't work as well as stock it must be something you've changed.

[jondee86]

I'm running ST ITB's on a smallport 16V with 272 cams and ST ISCV.
Typical MAP vacuum readings from my logs...

Idle = 75-80kPa (1000-1100rpm)
Cruise = 90kPa (12%TPS, 3500rpm, 5th gear, 100km/h)
Decelerating = 55-60kPa (50kPa decel from high rpm, throttle closed)

As you can see, the only time I get much vacuum is when I decelerate
with closed throttle. All the same the stock brakes and booster work good
enough for all round town and "spirited" driving on twisting backroads.

The FSM for the stock bigport 16V with single throttle intake suggests
47kPa at idle, and it would probably get down to 30kPa on decel. So while
I am a bit short of vacuum assist, I still have as much braking as I need.
This makes me think that you might have another problem if your brakes
are feeling inadequate ?

Cheers... jondee86

[Bean]

shot wide into the blue: is your oneway valve still working as it should?