Dump valve questions...

imp124

Buy & Sell Member
Hi

When i rebuilt the ST the dumpvalve had sized itself shut so i took it apart to free it off which it now is. Now i have to set it up again as i had all the screws and spring out, there is the screw on the top which alters the pressure of the spring. When i rev it the piston moves and the valve opens i take it that it should not do this?

Cheers

Steve
 

Baz

Ex. Club Member
Hi

When i rebuilt the ST the dumpvalve had sized itself shut so i took it apart to free it off which it now is. Now i have to set it up again as i had all the screws and spring out, there is the screw on the top which alters the pressure of the spring. When i rev it the piston moves and the valve opens i take it that it should not do this?

Cheers

Steve


If it a hks one its ok, thats screw tighten it up all the way
 

gtsnissanb

Official MSC Trader
This is confusing it's not a ####ty baileys one there prone for seizing mate, if it is baileys ones from experience off being a apprentice watching a rover turbo engine rev up, the piston rises as the revs build then when you drop off the revs it drops down again
As I said I'm confused and just guessing this is what your talking about?
 
why you say dump valve do you mean what i know as a "blow off valve"?

if so, it opens when the pressure before the throttle is higher than the pressure after the throttle (to let the air in the inlet out instead of smacking back into the turbo). The reason I ask is that my car does not have a BOV.

Anyway, if so, it will flutter open on any boost unless you have a pressure/vacuum line from after the throttle to the other side of the BOV spring.

where exactly is it plumbed it, and do you have a pic?
 
sounds reasonable to me, I don't have the car handy but brake vacuum should be on the engine side of the throttle which is correct.

BOVs with an adjustable spring allow you to change the preload on the spring a little, which will help it open later (not a huge difference though). Adjust it all the way in both directions to see if it works properly. Or maybe it is just assembled incorrectly.

Kinda sucks to run around without any boost though :(

BTW why did you add a BOV? Or is there one in the stock system and mine is jammed shut too :blush:
 
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imp124

imp124

Buy & Sell Member
It was added by the previous owner so i kept it on. The valve works as it goes woosh! of you let off when on boost but only if you give it some, if your on boost at lower revs 3-4k then it chatters back through the turbo i think? well it chatters anyway. When i first set it up after i un-sized it as soon as it came on boost it opened, so i adjusted to stay closed a bit more but every now and again when i come on boost it goes up, drops about 0.25bar then back up again as if the valve is opening then closing again?

Steve
 

linz0577

Ex. Club Member
hi steve it did used to work very well i tested the system and there was no pressure drop until you let off the gas.. it was an expensive bov cost me £165 but if its playing up maybe its best to get a new 1 mate (Y) p.s hope the cars still going well mate
 
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imp124

imp124

Buy & Sell Member
Hi yep cars going great, the bov should be sorted now just having a few teething problems with the clutch on the manual box now :)
 
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