Unintended acceleration

[LL - NY]

Sad to say, but Subaru didn't see fit to have ANY vacuum reservoir on a
turbosupercharged car, just a check valve. I swear that the only difference
between the aspro Impreza/Linear braking system and the turbo WRX/Aero is
the size of the front brake rotors (and associated added front brake torque
and bias, with the added heat sink).The Impreza shop manual seems to bear
this out (there is no reservoir in either brake system diagrams, nor does
there appear to be one or the required plumbing to have one.

Then again, in "normal" driving, you wouldn't likely end up with rapid
re-applications of brake and WOT, so in "normal" driving, you would unlikely
end up with the brake boost loss situation. That being said, when the boost
runs out and you're on the edge of ABS intervention, the pedal going hard
and the sudden loss of brake force for a given pedal effort can be
disconcerting at the least. When I "switch" (pull ABS fuse) to "manual ABS",
the loss of boost is more progressive (since ABS isn't making any demands)
so it's easier to compensate for the loss of brake boost and the increase of
required pedal effort. That being said, the effort is really exceptionally
high at Autocross speeds, I'd hesitate to think of how much braking
distances would increase at highway speed...

LL - NY


On Thu, Oct 22, 2009 at 11:21 PM, Cody Forbes <cody at 5000tq.com> wrote:

> One would think that the suggestions of a larger canister would be easily
> negotiated with Denver. Anybody that knows half of anything can see that
> it's a safety feature and not a performance gain. You may do the club a
> service if you bring it up and it makes the rule book as an acceptable mod.
> Especially if the solution was specifically adding a second identical
> duplicate to the stock resoviour (tee'd in) to eliminate people using tricky
> canisters for who knows what reason.
>
> -Cody
>
>
>  Just to be clear, I paraphrased the rulebook. But it's pretty definitive.
>> It
>> only allows changes to what is specifically mentioned that can be changed.
>> If it's not mentioned, it's generally not allowed. However, I had a
>> question
>> for National regarding swaybar end links on the same car (Subaru uses a
>> molded polymer of some kind, no idea why, other than there is no way for
>> them to squeak) and it's not specifically mentioned that those can be
>> changed. National confirmed that the end links are part of a "sway bar" so
>> that they could be changed. So, I do have to contact National to be sure,
>> THEY are allowed to interpret, we the minions just follow along.
>>
>> On Thu, Oct 22, 2009 at 9:47 PM, Brett Dikeman <brett.dikeman at gmail.com
>> >wrote:
>>
>>  On Thu, Oct 22, 2009 at 9:09 PM, LL - NY <larrycleung at gmail.com> wrote:
>>> > I haven't checked with National on the reservoir (I've thought about >
>>> it),
>>> bu
>>> > the pump is definitely out for at least Solo2 stock and Street >
>>> Prepared.
>>> .
>>> > No mods to brake system except pads/fluid, all else should be OEM
>>> > equivalent.
>>>
>>> Well, "nothing except pads and fluid" sounds like a pretty strong "no"
>>> to me.  Pads with a really high CoF would help with pedal force, which
>>> MIGHT get you some more brake-presses?  Probably not much.
>>> Regardless, seems to be a common problem, so...you're all in the same
>>> boat.
>>>
>>> By the way, it turns out there's at least one company that makes
>>> hydraulic boosters which run off the PS line, mostly for people
>>> running weird cams in big 'murican V8s.  Mini bomb and everything in
>>> one cute little package, very smart, but probably pretty expensive
>>> (and certainly against those pesky SCCA rules.)
>>>
>>> Brett
>>>
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>
>