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The mkiv Supra Owners Club

manual boost controller issues


dcarrter21

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OK so now everyone agrees its all good :D

 

EBC and MBC do the same thing : check

Do it by doing the same thing : check

Can work with/without VSV: check

 

Right we are sorted, we all agree, we got there eventually :lol:

 

I will agree when someone explains how the original diagram posted can be used to plumb in an MBC.

 

IF someone can explain that to me I will admit I was wrong and that the original diagram was in fact the answer to the OPs question.

 

Of course this will never happen, so I am right and you are all wrong :p

 

For some reason you guys think I am disagreeing with you on the way an EBC and MBC operations are similar. I am not, I am disagreeing on the way the original person thought the plumbing was exactly the same, and that the diagram was relevant.

 

So :p again

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The plumbing is the same isnt it?, all they're both doing is bleeding air off? If you showed me a EBC install I could remove it and place a MBC in it's place to do the same job?

 

Dunno, I know I couldn't do it and I have fitted about half a dozen MBC's.

 

If you follow that you take out the wastegate VSV. The green bits are where the MBC would go. If you plug off the other bits it wouldn't work as efficiently with an MBC.

 

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I've never actually fitted an EBC/MBC to a Supra :D, but I can't see how a MBC couldn't directly replace an EBC.

 

It could, if you plumbed back in the VSV at the same time.

 

Edit: The wastegate VSV is there for a reason. The way the EBC works means that it can adapt to any changes in the pressure. The MBC can't do this so IMO it relies on the ECU working the wastegate to keep it running right.

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I dunno, I'm out my depth talking Supra specific plumbing here :D

 

My understanding of it basically comes from Max-boost and Ian C's post on the workings of the sequential system. Max boost...

 

 

The wastegate actuator of turbo#1 is always connected to the boost signal. So when the engine is doing 2 psi, that's what the back of this actuator is filled with.

Or is it?

Looking closely we see another connection at the back of the actuator, on the same side of the diaphragm. It goes back to the unpressurised side of the intake, via the VSV.

Aye, 2 psi may be squirting through the actuator, but if the VSV is wide open then there is a generous 'relief' path for the pressure, so in reality the actuator never sees more than a fraction of a psi.

If the VSV has been shut by the ECU however, then the actuator will be filled with boost gases, and will be at the same boost pressure as the intake manifold (a bit higher actually, since it receives hot gases before the intercooler, which have a higher pressure compared to the manifold, where boost gauges typically get their signal from).

If you use a 'bleed valve' it won't matter a lot if you use either of the two pipes coming off this actuator. In both cases you'd be depressurising (partially) the actuator. How much would depend on the position (pulse duty-rate more accurately) of the VSV.

If you use a 'ball and spring' boost controller then it does matter which pipe you use. It has to be the one shown above - the 'pressurising' one.

Electronic boost controllers usually ask for the VSV to be blocked off so that they can fully control the boost pressure behind the actuator. This is normal, otherwise the ECU would be trying to undo the actions of the boost controller, and the result would be a funny boost curve.

 

Notice the last part, thats what I'm tongue in cheek getting at.

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