hey all, i am having a specialised power porting plenum installed on my car at the moment, for those who havent seen one, they are massive (im talking twice the volume of a nispro or similar). but they are also apparently one of the best flowing around, now before the old argument of flow and flow under pressure starts that is not what this thread is about.
today at the shop where its all getting put on one of the guys commented along the lines that i may have no breaks for up to 5 seconds after idle because of the lack of pressure? would this be just after starting? or would this be on all occasions when driving and the throttle isnt open? if the car isnt idling will there simply be less breaks because there is less pressure or vacum (whichever it is) in the plenum?
i'd really like someone to explain this to me, im not afraid of a little maths, so please you car brains out there dont be afraid to unleash some equations on me.
if there is a problem would it be easier overcome with a vt/vs master/booster upgrade?
Ive been to Andys work shop numerous times and seen plenty of cars with his big plenum on their rb30s and no one has ever talked about lack of brakes when driving a car wit this manifold on it - if it was note worthy they would definetly have said something about it.
Even if you do have a lack of vacum for your brakes you can just add a vacum tank. I can see where they are getting with this as when using the brakes while there is positive presure in the intake (on boost) starves the booster of vacum but as soon as you snap the throttle shut there is instant vacum.
lol at sig....
i've heard of guys using inline one way valves as well as or replacing the stock one on vlt boosters.
i dont have 'instant' brakes when trying to stop from anything over 150kph, there is a delay.. more than likely to do with exactly wat your mate is talkin about, the booster pressurising while ur flat stick for a bit..
thats why you have a one way valve in the booster vac line, this holds wat vac is ther when the eng was last under vac, unless you pump the brake pedal with the engine off, in which case u will have brakes still but a hard pedal...
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Originally Posted by Cocopopz
If you hit the brakes while under boost you can loose some feel. This is unlikely as you dont seem to be accelerating as you are braking.
unless you're doing sick skids on the footbreak bro!!!!
alright cool, thanks for all the info guys, ill try and remember that at times when i want to stop i should not be holding down both the accelerator AND the brake at the same time.
anyone running a 1 way valve to their breaks? any draw backs?
im sussing a vs/vt booster/master convo 2moro, will be installed before the car is done.
Quote:
Originally Posted by R34NRG
normally its the cam that will stop you getting a decent pedal, never heard of plenum being an issue
yeh +1 for cam being the cause as well
brakes + throttle everyone has done it its just you are generally not travelling all that fast
correct me if im wrong but i pretty sure your car (if originally a turbo) will have a one way valve in the booster already.as this is to stop seals leaking in the booster as they were never made to have positive pressure .
i have never heard of a cam doing this.....unless it has so much inlet valve lag after bdc. that ut pushes air/fuel back out of the cyl at idle?
Quote:
correct me if im wrong but i pretty sure your car (if originally a turbo) will have a one way valve in the booster already.as this is to stop seals leaking in the booster as they were never made to have positive pressure.
Yeah the point I was trying to make was that the factory 1 way valve was probably chosen for a car making no more than 7 pounds of boost LOL...
once you start running 25psi+ there tends to be a bit of boost gettin past that 20 year old 1 way piece of **** valve.
I've heard of guys off here running 'inline' valves ASWELL as the factory one. must all help.. specially if u need to stop in a hurry.. kinda strange jumping on a hard pedal with nothing there at 150+kph..
