Need some information on boost control in the EVO.

I have read many times about running a MBC on the EVO, and some places regard that as one of the first mods to make. But my question is - does it alone really allow you to hold a steady boost level?

The reason I ask is that I think I read on the Dynoflash forum that the ECU actully controls boost taper. After about 2 seconds of full boost (19psi) it pulls it back to about 16psi. If I remember correctly from what I read, part of the Dynoflash tuning is to remove this boost cut parameter (example - change it from 2 seconds to 2 minutes or infinity before taper).

So I will restate my original question. If the ECU really does control boost taper, does a MBC alone eliminate boost taper? More specifically, if I crank the MBC up so that I get 22psi max boost, will it hold steady there until redline?

Thanks for any information you can give!

By the way, with my current mods (intake, exhaust, S-AFCII) I am getting 22 psi max boost at 2800 RPM, tapering to ~ 17psi, then slowly climbing back up as it revs out.

EVOlutionary

 

When you install an MBC you remove the factory solenoid (controller). So the ECU might think it's tapering the boost after an MBC install, but it really isn't.

To answer your question in a nutshell.. Yes, just an MBC alone will help you hold as much boost as the turbo will allow, all the way to redline. And it should be one of your first mods (after a boost gauge of course).

Now, if you really want to take advantage of the power the car really has, get the MBC and a flash (even a mail-in flash). It will raise your rev limit, remove the speed limiter, and tune your A/F ratios a little better than stock.

Hope that helps. PM me if you want any details about the stuff I mentioned.

:edit: BTW, yes, you can hold 22psi to redline with just an MBC (or darn close, not as low as 17psi for sure).

 

Thanks for all the information! That really helps.

What is a really good brand? Hallman? Buschur?

And how long does it take to install one? Thanks again!

EVOlutionary

 

I dont really know about the buschur MBC but I do have the Hallman and I couldnt be happier. You can get it from Al at dynoflash.com for like $100!

Edit: It takes about 45 min if you know what you are doing.

 

With tha Hallman MBC that I sell - the boost is virtually stable, it just falls slighly about 1 psi towards the red line cue to the small size of the stock turbo

Once you install a MBC the ecu no longer adjusts boost

Although the tune and timing can effect the boost curve