what is the difference between mbc and bleed valve

[Lmason]

what is the difference between mbc and bleed valve, have read mbcs only have 2 pipes and bleed valves have 3 pipes, but i have also read some mbc`s have 3 pipes for emissions reasons.
any feedback would be interesting.
s70 1997 t5

[Jod T5]

Originally Posted by Lmason

what is the difference between mbc and bleed valve, have read mbcs only have 2 pipes and bleed valves have 3 pipes, but i have also read some mbc`s have 3 pipes for emissions reasons.
any feedback would be interesting.
s70 1997 t5

as i have explained in previous posts a MBC holds the boost from the actuator until the point at which the setting has been made is met, it then releases the boost to the actuator allowing the wastegate to open...
a bleed valve, bleeds boost across the boost range allowing the actuator to open the wastegate later...
both options ensure the engine runs lean......
cheers
jod

[Pedro Fandango]

a MBC works by having a spring pushing a ball bearing into the pipe blocking it, the more you tension up the spring the more boost it takes to move the ball bearing clear so the actuator can be opened. As Jod says this stops the air altogether until it hits the required boost, giving quite an aggressive burst till the actuator opens

a bleed valve always sythens off a certain amount of air (setable by turning the adjuster) fooling the actuator into thinking the turbo is creating less boost than it actually is. But some air is always getting to the actuator you still get the wastegate creep of the actuator slowly opening before the set limit making the ride smoother. The third terminal is simply an outlet for the sythened off air, so it doesn;t matter if it goes back into the air inlet like you have done or simply released into the atmosphere

[Jod T5]

Originally Posted by Pedro Fandango

a bleed valve always sythens off a certain amount of air (setable by turning the adjuster) fooling the actuator into thinking the turbo is creating less boost than it actually is. But some air is always getting to the actuator you still get the wastegate creep of the actuator slowly opening before the set limit making the ride smoother. The third terminal is simply an outlet for the sythened off air, so it doesn;t matter if it goes back into the air inlet like you have done or simply released into the atmosphere

exactly....could not and did not put it better myself...lol
siphons tho duano........
cheers
jod

[Pedro Fandango]

Originally Posted by jod t5

siphons tho duano........

near enough lol

[Jod T5]

Originally Posted by Pedro Fandango

near enough lol

there is very little to pull you up on mate........
and BTW colin sorted a new VW lump from VW heritage £1400!! ouch but brand new....
all the best
jod

[Pedro Fandango]

Originally Posted by jod t5

and BTW colin sorted a new VW lump from VW heritage £1400!! ouch but brand new....

youch i did mean to ask you how he was getting on, glad he's got it sorted & back on the road tho, what size lump is it he's got?

my bro's gone & brought another air-cooled VW

[Jod T5]

Originally Posted by Pedro Fandango

youch i did mean to ask you how he was getting on, glad he's got it sorted & back on the road tho, what size lump is it he's got?

my bro's gone & brought another air-cooled VW

lol....mad man!!!
im not sure what it is, the only thing i can guarentee is that it is bloody slow!!
cheers
jod

[Pedro Fandango]

Originally Posted by jod t5

im not sure what it is, the only thing i can guarentee is that it is bloody slow!!

just how they left the factory lol, you think his is slow imagine going around Newquay in a stretched camper with a air-cooled 1.6 & the throttle linkage decides to snap so only got 1 carb & 2 cylinders working, it weren't good lol

[Jod T5]

Originally Posted by Pedro Fandango

just how they left the factory lol, you think his is slow imagine going around Newquay in a stretched camper with a air-cooled 1.6 & the throttle linkage decides to snap so only got 1 carb & 2 cylinders working, it weren't good lol

the only benefit is the copius amount of newquay steam lager available there, in particular in the Newquay Arms...Quality..........
cheers
jod