MBC and Boost Gauge

[MattB]

Having completed a stage 0 tuneup, and with a wastegate actuator tweeking session planned for the weekend, my thoughts are that an MBC and Gauge are next on the list.

But.... which gauge is best - PSI or BAR???
Also, any recommendations on where to purchase either product from and which one/s to buy?

:shifty:

[p fandango]

PSI or bar is just what the gauge measures the pressure in, it won't make a difference to how accurate it is thats down to the manufacture

i got my MBC from DBS Motorsport (01522 856045/07961 973382) but i've had mine 3 years now & believe he's changed the design so no idea how good the new 1's are

[Wobbly Dave]

I would not mess with your wastegate unless you have an accurate pump that can measure in 4.5psi into the actuator - that is the standard pressure it should be. If you over do it then you can create nasty boost spikes that will damage stuff.

Gauge - It matters not which is best - 1 BAR = 14.7psi. Most aftermarket gauges are not that accurate so should only be used as a rough guide.



. . . the weight of the earth's atmosphere pressing down on us constitutes atmospheric pressure and is 14.7 "pounds per square inch" (14.7 PSI).
namely 1 bar is 1 atmophere. If you actually think about it - the pressure in the turbo is actually 1 bar all the time and you are measuring the additional pressure. At full chat the stock 850 should do about .6 bar.

The TIM gauge (Halfords ~£25) I had initially was about the most accurate but the range became insufficient.
The next gauge - the BSR gauge (which you can have for nowt) was woefully out (parts for volvo online)
I liked the stealth gauge (Auto Gauge from Ebay) but you couldnt see it at all well in the day time - thought it did hide away at night. Pretty accurate.
IMHO you will need to spend over 100 quid to get anything decent/reliably accurate - and I aint that bothered now.

[MattB]

Many thanks for your input guys. I think I'll leave the wastegate alone.
Is there any harm in fitting an mbc on its own, without a gauge?
Or do you need the gauge to measure the boost, so as not to exceed a particular maximum setting?

[p fandango]

it is advisable to use a boost gauge to set the MBC up yes, i think 13psi was the recommended limit but the ecu won't let you go over 15psi anyway (engine starts knocking then & ecu cuts ignition)

there is nothing stopping you bodging a gauge in just while you set up the MBC, then removing it when your happy its set right

[MattB]

cheers pedro.
btw - how are you running 20psi on a stock ecu????
:confused:

[p fandango]

btw - how are you running 20psi on a stock ecu????
erm pass, for years the ecu shutdown the ignition at the quoted 15psi as it supposed to, but when i changed the the vac pipes i found 2 quite bad air leaks she was happy to give the extra

[MattB]

erm pass, for years the ecu shutdown the ignition at the quoted 15psi as it supposed to, but when i changed the the vac pipes i found 2 quite bad air leaks she was happy to give the extra

cool! I need to check my vac pipes for leaks etc - car is approaching 100k - i've had it nearly a year now and haven't checked them yet. can you give me some pointers as to which pipes to check etc?? forgive me for appearing dumb, but I have preiously removed the plastic throttle cover and thought I could hear a leak aroungd this area - am I looking in the right place??



there is nothing stopping you bodging a gauge in just while you set up the MBC, then removing it when your happy its set right

does anyone have a spare boost guage that I could 'borrow'? I would obviously cover postage and would be more than happy to send a 'holding cheque' to ensure safe return etc??

[p fandango]

cool! I need to check my vac pipes for leaks etc - car is approaching 100k - i've had it nearly a year now and haven't checked them yet. can you give me some pointers as to which pipes to check etc?? forgive me for appearing dumb, but I have preiously removed the plastic throttle cover and thought I could hear a leak aroungd this area - am I looking in the right place??
yes, i just replaced all the pipes from the vac tree with silicone pipe. I think the main leak i had was from the vac tree to drivers side just under the fuel rail (rubber elbows had gone)

[MattB]

Sorry to drag on with this, but I just want to make sure that I am going to install the correct piece of kit:

I have visited my local motor factors, who want to seel me an 'in-car' mbc kit (£41), which will allow me to adjust the boost from inside the car as and when i want.
Halfords have a 'bleed control valve' which is situated in the engine bay (£17). I assume this is best as once set to the required setting, ie 13psi, you simply leave the valve alone - having an in-car control will increase the temptation to over increase the boost and cause damage to the engine??
Also, once I purchase the right piece of kit, can someone give me some direcetions as to where it is fitted.
Thanks in advance....

[p fandango]

first off ask as many questions as you like, thats what the forum is here for

i don't think either of the valves you've looked at are actual MBC's, i think they're both bleed valves which are totally different (but often mixed up)

MBC = completely blocks the air to the actuator until it reaches it set limit then lets the actuator open as normal, so it lets the turbo spool up as much as it can until ? psi then the actuator opens & takes control

Bleed valve = is basically a controllable air leak, it sythons off an adjustable amount of air out of the line to the actuator fooling it into thinking the turbo isn't making as much boost as it is. As some air is still getting to the actuator it allows it to open early so losing some of the pressure straight away

i've got about 9 pages of diagramed instructions on how/where to fit an MBC (as mentioned earlier my MBC may be different to one's available now) which i can scan in & email to you to help you out

[MattB]

Many thanks Pedro.
I think I'll agree with you in that both examples that the guys want to sell me are bleed valves or variations of.
I'll give DBS a call tomorrow - tried looking online and there's no website :bricks:
In the meantime, does your MBC look like these?:
eBay MBC 1 (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7990042657&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1)
eBay MBC 2 (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7990184834&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1)
eBay MBC 3 (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7991316553&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1)
eBay MBC 4 (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7991381925&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1)

[p fandango]

http://img17.imageshack.us/img17/3707/dsc000285af.jpg
my MBC, to adjust it all i have to do to adjust the boost is screw the end in, this puts more tension on the spring inside so needing more boost to open it

i think all those ebay links are for MBC's

[MattB]

ahh! thats great - now i have something physical to go by. both gadgets that halfords showed me must be bleed valves as they both had either a hole or an additional port.
I think I have come accross one like yours on the net somewhere for about £40?? - I'll have a look tomorrow and let you know how I get on.

have fun....
:wiggle:

[p fandango]

think i paid about £30 for mine but that was about 3-4 years ago now.

the actual mechanics of the valve are unbelievably simple so i think any of those off ebay would do the job just as well

[Tomcat]

How much of a difference do these things make Pedro?, I'm thinking of getting one soon'ish.

[rick2]

they make a huge change in the torque and reducing lag ..my car(94 auto t5) felt `top endy` in the rev range but after fitting one of these (with a boost gauge of course..no more than 14 psi!) the difference was,.well,.huge..different car altogether. i bought the no.2 type of ebay and it works spot on,but setting the correct pressure takes a bit of time.also make sure which vacuum lines you want to fit it into,there are a couple of variations..the set up i use(and most i guess) bypasses the bcs (less spikes).but for £20,and 1hr of your time its the cheapest £/hp you`ll get....

[p fandango]

How much of a difference do these things make Pedro?, I'm thinking of getting one soon'ish.
it turns them into an absolute animal mate, alot more aggressive than a remap

Think about it, its letting the turbo spool up as quick & as hard as it can, then at ?psi the valve suddenly opens, stops its fun & keeps it in order.

[p fandango]

MattB, any joy getting a guage & mbc yet? you have email

i've scanned in the instructions for the MBC (8 pages not 9 sorry) so if anyone is interested send me your email address & i'll email them to you

[MattB]

MattB, any joy getting a guage & mbc yet? you have email



Thanks for the instructions Pedro.
Got a few expensive trips coming up, so may have to leave mbc and gauge until next month. :frown:

I'll let you know how I get on...