correct, proper tuning and youre all set.

 

I made the switch from mbc (Forge Unos) to 3 port with ecu controlled boost because it makes it much easier for me to switch between maps and not have to worry about adjusting the mbc any more. Spool up feels about the same with the 3 port as it did with the mbc, I haven't noticed an increase in lag at all. I also picked up a decent bit of power in the top end as boost is holding all the way to redline with less taper than i had with the mbc.

 

Does anyone know for sure why the 3 port holds boost better than the MBC? I think it may be because of inertia in the ball and spring setup or is due to vacuum on the wastegate diaphragm when the three port switches causing the wastegate to close more quickly?

Do the ceramic ball MBCs hold boost better?

 

ECU-controlled boost with a 3-port BCS allows you to increase WGDC as RPM increases in order to maintain your desired boost curve. An MBC only has one setting, so you set that to whatever peak boost you want. For instance, if 70% WGDC gets you the peak boost you want, with an MBC it's like if you had 70's in your WGDC table for all RPM points. With a 3-port you can have 80 or 90 WGDC at higher RPM to maintain a higher boost.

 

But an mbc has a feedback system of sorts that should allow it maintain a set boost pressure. If boost falls the spring should force the ball on to its seat,so the wastegate would then not see pressure, causing boost to rise again and so on and so forth. Similar to a solenoid rapidly opening and closing.

In practice it doesn't work like that and I am wondering why.

 

I would imagine it has a great deal to do with the spring,ball and bleed system of the MBC to maintain a good balance. That's why all MBC's aren't created equal. My guess as to why a ceramic ball is considered superior over a standard steel ball is because the air pressure has to overcome the weight of the ball AND the spring pressure rating. If the ceramic ball weighs next to nothing, the only mathematical factor is the spring rate. Thats probably more predictable and has a quicker response, since the air pressure doesn't have to overcome the steel ***** resting weight before the spring begins to move. If the bleed system is too large or too small, the pressure on the back side of the ball may not be balanced well with the pressure on the bottom of the ball. Thats probably why your theory about the feedback system may not work as well with some MBC's. Just my assumption though.

The 3-ports can be superior to many MBC's on the market when it comes to spoolup but the very well designed MBC's will have nearly identical spool characteristics. My favorite perks to a 3-port is the error correction and the ability to have the turbo spool LATER, which is very helpful on turbo's that ride the surge line in 4th and 5th gear. Most people mistake this sound as a BOV thats fluttering open. Even the FP Red's with the anti-surge cover can still ride the surge line with a MBC.

-Jamie

 

I dont know why everyone is still hyped about 3ports. A MBC spools faster and hold a better boost curve IMO. From this post in this thread https://www.evolutionm.net/forums/9511550-post64.html



The only two times I feel a 3port is better then a MBC is:

1) When you have to delay the boost spike to make sure you dont hurt stock blocks or to avoid surge.

2) When you run duel maps (ie pump gas and E85), so you can change boost levels when changing maps.

 

Hybrid: MBC -> EBC = yay!

 

 

Can you explain these graphs a little better? They're not making sense to me based on your argument. It looks to me like your starting WOT at different RPMs and it also looks to me like the 3-port hits peak boost around 3600 and the MBC doesn't hit it until 4500. Either way, I'm not sure I follow how you can compare spool up between the two when you start the pulls at different RPMs.

 

3 port < MBC, that's all there is to it.

 

All the info is typed on the chart. The 3port pull started earlier and still spooled later.

Its impossible to start the runs at the exact same RPM. The difference in starting RPM was only 60.

The bottom axis is TIME, not RPM.

 

Sorry but no, that's not all there is to it. For ease and speed of adjustment? Yes, absolutely, MBC wins there. But for ultimate control over the boost curve in each gear and switching between 2 maps, no, 3-port wins that IMO.

 

Gotcha. Any chance you could repost the graphs with RPM as your bottom axis? That would make it a lot easier for the rest of us to see what you're talking about.

 

You cant plot vs RPM with evoscan. Well there is a plot vs RPM button, but it doesnt work correctly.

Everything is as its typed on the chart. The 3port run started sooner (lower RPM), and still spooled later (higher RPM).

Also, even though the ECU boosted is tuned great, so great, that its never more then .4 off it target boost and doesnt even use error correction, the boost curve is not as "solid" and as stable as the MBC boost curve.