boost valve?

clio_rsi · Post by **clio_rsi** » Fri Dec 30, 2005 7:51 pm

just wondering, what would be the symptoms of a faultly boost valve? is it poss for it to boost somtimes and not others?

haz@nocturnal_development · Post by **haz@nocturnal_development** » Sat Dec 31, 2005 9:19 am

have u tried by-passin the valve to see if its that at fault?

clio_rsi · Post by **clio_rsi** » Sat Dec 31, 2005 4:10 pm

no i havn't tryed that, how would i go about doing it? thanks.

haz@nocturnal_development · Post by **haz@nocturnal_development** » Tue Jan 03, 2006 8:02 pm

gentley remove the vac pipes and hook up a vac pipe from the turbo compressor to the actuator. fittin a bleed valve into the system will allow ya to run more boost.

haz

rapid R5 · Post by **rapid R5** » Thu Jan 05, 2006 8:20 pm

if ya running a standard volvo actuator, they are piss weak anyway when doing the test haz is on about above, chuck it and get a stronger one.

steve

clio_rsi · Post by **clio_rsi** » Fri Jan 06, 2006 7:49 pm

i see, the thing is, i dont know much about this side of things. would you be able to describe how this bleed valve works? and where to get one from? plus if the standard boost valve is 'weak', what shall i use?

haz@nocturnal_development · Post by **haz@nocturnal_development** » Fri Jan 06, 2006 9:15 pm

the std boost valve is fine, the std actuator is weak. you can operate the actuator arm by hand !
hmmm, bac 2 basics, i'm not being rude,

the turbo spins creating boost throught the engine, if the actuator is a fixed rod then it will continue to make boost until it spun itself to bits.
but its not. the actuator has a diaphragm and a spring. the manifold pressure pushes on the diaphragm, which in turn pushes against the spring. wat happens is that when the boost overcomes the spring rating in the actuator it opens the wastegate, allowing the turbo to make no further boost, and the more the throttle opens the more air flow there is so the more the actuator opens, but at the same level of boost.

a stronger actuator will hold more boost before the manifold pressure tries to open it. weaker actuators will spike and cause wastegate chatter.

here's the simple bit

a bleed valve is fitted between the manifold and actuator ( ignoring the basic set-up ) OR between the volvo solenoid valve and actuator ( std or rich mod ) .

the valve simply bleeds off the air, so the actuator receives less than manifold pressure accordingly, opening the actuator less, thus making more boost. a bleed valve will only bleed off so much, depending on the size of the outlet. i suppose it fine tunes the actuator.

the reason this method is not liked is because you can turn the boost up, which feels faster, but without checking fuelling is not safe.
BUT the std or rich mod will allow for any lean mixtures

hope this makes sense

haz

clio_rsi · Post by **clio_rsi** » Sat Jan 07, 2006 4:57 pm

i see, thanks alot for that. so where can i get one of these valves?

JohnTurbo · Post by **JohnTurbo** » Sat Jan 07, 2006 6:21 pm

Ebays a good start for an mbc. I've run one @1bar for 18 months without any problems...inline, upstream of the actuator.

robkendall · Post by **robkendall** » Sun Jan 08, 2006 7:44 am

johnd used to make mbcs didnt he?
dont know if he still does but you could pm him......user name johnd
rgrds
rob

johnd · Post by **johnd** » Mon Jan 09, 2006 4:53 pm

Hi,

Don't use a bleed valve!!! They are very crude at controlling the signal and can lead to some awful boost spikes. Most of them cost the same as an MBC.

I still sell MBC's and do various types......

Basic ball spring...available in aluminium, yellow or real carbon fibre. Â£16.50 std Â£21.50 carbon

Precision MBC....Â£20

Dual stage precision MBC. First controller controls boost onset/rate and second controls max boost. The best control this side of an EBC.....Â£35

I run the dual stage type and also have an air recirculating valve that opens upon gearshifts removing all pressure from the wastegate line, closing it, ensureing you are straight on boost afterwards. These can fit any MBC........Â£15

As you can see there is a lot of variation on types and methods of control for MBC's whereas a bleed is purely and uncontrolled pressure leak.

If you want any further info. drop me a line

John

Murf · Post by **Murf** » Mon Jan 09, 2006 6:22 pm

Are you using one of the dual stage ones in your celica?
where is it plumbed in, presuming the 3S-GTE celica has the same setup as the MR2?

johnd · Post by **johnd** » Tue Jan 10, 2006 9:53 am

Mi Murf,

When I got the celica I just transferred the MBC straight over. It's plumbed in the compressor-->wastegate line and the line to the Turbo VSV is capped off. It 'should' be the same on the Mister 2.

John

chris1roll · Post by **chris1roll** » Tue Jan 10, 2006 4:56 pm

clio_rsi wrote:just wondering, what would be the symptoms of a faultly boost valve?

Notice this hasn't really been answered directly...

I have just discoered my boost solenoid was a bit on the knackered side....Was investigating my 27mpg "problem" (which after achieving 33 on longer journeys I now must put down to doing 90mph on the M5 every morning/evening for 2 junctions with a not fully warm engine)
and swapped mine for a random spare I had lying about.

So a faulty one will make fluttering noises whilst the turbo builds up boost, and will create more lag.
I thought my car was going well before, but now...2nd and third gear wheelspins from an _unmodified_ turbo engine, on 15" michelins, and a hell of a lot more kick.
More torque steer too...

clio_rsi · Post by **clio_rsi** » Tue Jan 10, 2006 5:22 pm

i see, well thanks everyone for your info, from the last post, i think i do need to change my boost valve. johnd, i'll be in contact soon, thanks.

Volvo 480 Club Europe

boost valve?

boost valve?

Re: boost valve?