Manual Boost Controller

[MattB]

Found a boost controller with 3 ports...


http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7969218384&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1

are they any good or different from 2 ports???

[steveT5]

Matt, when i was thinking about an MBC, there was a lot of confusion from various people about MBC's being different from bleed valves and so on. I have come to the conclusion that the two things work in exactly the same way. My valve has two ports, but has a hole in the valve body for air to bleed from. The valves with three ports are just the same, but i beleive can be fitted in the car, so they can be adjusted while driving. the 3rd port in this case has a tube fitted to it which terminates with an open end anywhere in the engine bay. I would imagine that this particular valve could be fitted in-car or under the bonnet.

[Pedro Fandango]

no thats a bleed valve mate, there is a big difference between a bleed valve & a MBC.

A Bleed valve is basically a controllable air leak, syphoning out an adjustable amount of air going to the wastegate so it doesn't open as soon creating more boost. With air still getting to the wastegate it will start to creep open early slowing how quick the boost pressure builds

A MBC is a pressure release valve, it actually stops the air going to the wastegate altogether until it reaches the set limit, it then opens allowing the air to open the wastegate suddenly giving a more aggresive build up of boost.

[steveT5]

Thanks for the description Duane, and my apologies to Matt for my inacurate description. I obviously have a bleed valve then. I assume that the MBC is a better bit of kit as it holds full boost for longer ?

[MattB]

Many thanks for your input guys.

So which is best?
MBC or Bleed Valve?

[Wobbly Dave]

Neither are great, IMHO. But if you must then I would say MBC. Fitting an airleak into a metered system can be problematic.

[Pedro Fandango]

Neither are great
they are for £30 :wink: (MBC's rule :nutkick: )

[Pedro Fandango]

I assume that the MBC is a better bit of kit as it holds full boost for longer ?
they will both hold what ever boost you've set them to, but the MBC gives a more aggressive drive low down because the wastegate isn't getting any air till it hits the preset level, were a bleed valve allows the gate to creep open letting boost out before the set limit

[Mrsmopp]

Neither are great.

In your opinion!! :troutslap

x

[Wobbly Dave]

In your opinion!! :troutslap

x

You disagree?

[Mrsmopp]

Yes!

x

[Wobbly Dave]

Why?

[Mrsmopp]

It never did my car any harm, I never had it turned up particularly high but got a significatly better response from the car - as well you know because you drove it with the MBC on.

Be careful that you state when giving opinions that it is it just your opinion not fact :wink:

x

[Wobbly Dave]

OK then if you find my opinion misleading then allow me to clarify it. I have after all only my own knowledge, experience and research to base my opinion on.

I didn't say "They don't work" - I just feel that they can be problematic, if set up incorrectly. Again the question in my mind is

"Is it good practice to fit an airleak into a metered system?"
and
"Is it good practice to fool a system into doing something it wasnt designed to?"

That said, if due caution is applied then I am sure everything will be fine.

I play devils advocate on this topic to help people decide.

[Mrsmopp]

It's very simple really.

Ultimately the best way to get more out of your T5 is to have an ECU remap - However, not everybody can afford this and as such have to source another method of modifying. There is no right or wrong just personal preference and we'd all do well to bear this in mind sometimes.

x

[Wobbly Dave]

In that case I would re-enforce my message which is "Be careful".

[Murphy]

What is up with you two. Have you fallen out !?!? Some serious bitching going on !?!?

[Mrsmopp]

What is up with you two. Have you fallen out !?!? Some serious bitching going on !?!?

I think you have read too much into it - Dave's on of my best VF buddies, doesn't mean we cant have debate tho!! LOL

x

[Murphy]

Dave ?

[sizzlechest]

Just bear in mind if considering a MBC or bleed valve that you need a boost gauge to see what kind of boost levels you're hitting. Otherwise it's kiss your honey goodnight!
:remybussi

[rich850t5]

OK so i have a boost gauge set up to monitor mbc settings,i have it currently set at 13psi however i can turn up the boost to 21/22psi and as long as i stay in sport mode it wont cut the timing but if i use econ mode it will cut back at 15psi QUESTION 1:WHY IS THIS?when it reaches 15psi it just picks up the front end points it at the sky and screams off up the road as if ive hit the nitro button boost goes up to 21 then drops back to 15 and holds this through the rest off the gears(auto)QUESTION 2 AGAIN WHY IS THIS? a confused t5 owner!oh and QUESTION 3 WHAT IS GOING TO HAPPEN IF I KEEP LETTING THE TIMING CUT BACK(IE DAMAGE TO ENGINE)?

[CAMO]

Just changed my bleed valve for a MBC- a great deal better+ now running nearly 1.0 bar boost on standard chip!

[dj_rog]

OK so i have a boost gauge set up to monitor mbc settings,i have it currently set at 13psi however i can turn up the boost to 21/22psi and as long as i stay in sport mode it wont cut the timing but if i use econ mode it will cut back at 15psi QUESTION 1:WHY IS THIS?when it reaches 15psi it just picks up the front end points it at the sky and screams off up the road as if ive hit the nitro button boost goes up to 21 then drops back to 15 and holds this through the rest off the gears(auto)QUESTION 2 AGAIN WHY IS THIS? a confused t5 owner!oh and QUESTION 3 WHAT IS GOING TO HAPPEN IF I KEEP LETTING THE TIMING CUT BACK(IE DAMAGE TO ENGINE)?
The ignition timing does not effect the boost level at all. The boost levels should be the same for both sport and econ mode if you have a MBC fitted (and even if you don't I think).

21 psi sounds rather too high to have set the MBC - but I am not sure that this is the pressure you have set it at. I think you are getting serious pressure spikes which are taking you up to 21 psi. This is because you have tightened the waste gate actuator. You don't need to tighten the WGA if you have got a MBC installed. The reasons for tightening the WGA are to keep the WG shut for longer when the boost is building. As you have a MBC installed, waste gate creep will not occur as the WGA will not "see" any pressure until the MBC pops open. Running with a tighter WGA will just give you potentially dangerous spikes. Put it back to standard!


Hope this helps and you haven't trashed your engine already...

[dj_rog]

Matt, when i was thinking about an MBC, there was a lot of confusion from various people about MBC's being different from bleed valves and so on. I have come to the conclusion that the two things work in exactly the same way. My valve has two ports, but has a hole in the valve body for air to bleed from. The valves with three ports are just the same, but i beleive can be fitted in the car, so they can be adjusted while driving. the 3rd port in this case has a tube fitted to it which terminates with an open end anywhere in the engine bay. I would imagine that this particular valve could be fitted in-car or under the bonnet.

I replied to a similar sort of question in another thread.
I bought a MBC (2 ports) off ebay and fitted it to my car. I could not adjust it to give me low enough boost levels. I took it out and had a look at it and noticed it had a hole on the body of the MBC. I worked out what was happening - when the ball baring in the controller was lifting to moderate the pressure on the high pressure side, air was bleeding out though this hole causing a low pressure in the line to the WGA which closed the WG which caused the turbo to generate a higher pressure than I wanted.

I blocked the hole on the body of the MBC and found that I could then adjust the MBC to give me the pressure I wanted (about 0.9 barg).

So, if you buy a MBC and it has a hole on the body, block it up!

any questions - please ask me...

R