I've seen it a few times when customers came to me with somebody elses tune. we swapped in the mbc and it started behaving like that setup should.

 

You most definitely can configure a 3-port to spool equally as fast, if not faster than some MBC's.

 

A 3-port should out spool a mbc. I get my green hitting 25+ by 3750 and sometimes hit full boost at 3500.

 

Do you have data to back that up?

I have tuned many ECU boost setups and have gone back and forth between ECU boost and MBC more then anyone I know. I know how to tune perfect ECU boost. But even with perfectly tuned ECU boost, I always see the MBC spools faster.

I have explained why this is and will explain it again if you'd like. But for now, here is some data ..

As the data shows, the ECU boost run went WOT first and still didnt even spool faster then the MBC. Also, this perfectly tuned ECU boost. If you notice, error corr. is not even needed, as it is tuned perfectly.

Someone may say that I need to hold the WGDC @ 100% more, but doing that on this setup led to spikes.

 

this may just be my tired eyes playing tricks on me, but it looks like on the ecu boost graph there is a secondary peak?

can you overlay the two?

 

Currently I'm running a Grimmspeed 3 Port but I haven't dismissed the idea of moving to an MBC at some point. Like Turco said on the first page, the main advantage of a good 3 port is using gear based boost control with Tephra's V7. It allows me to hit 26psi in all gears rather than only hitting 22-24 in 1st and 2nd and then overboosting in 4th and 5th. I do have to agree with Mellon though- ECU-controlled boost can be a real pain to get dialed in and very time consuming. Using an MBC probably would have saved me several hours of tuning. Also, depending on what turbo you're running, (again) like Mellon said- preventing boost taper with a 3 port is not always a good thing. In fact, currently I have my 3 port set up to basically work like an MBC in that I have it set to hold a certain WGDC in each gear once it hits peak boost so that it naturally tapers to about 22psi at redline. I was actually losing power trying to run more boost.

 

I will grab some Dyno graph results when I can for ya.

I also try running similar boost taper to a MBC with a 3-port. Depending on the turbo, it's not beneficial to force it to hold more boost up top. The real advantage to ecu controlled boost would be the auto-correction setup for drastic weather variances in certain climates and the ability to tailor the boost curve. An example where a 3-port can be helpful is keeping a large turbo from riding the surge line in higher gears. That can be a little annoying to people sometimes, so having the ability to have the boost come in LATER in a particular gear is very nice.

Like I have always said, I can certainly appreciate both methods of boost control. Each have their perks and downfalls.

 

Care to share a couple? I am running a Perrin MBC with a 2.3 and EF3 Turbo and would love to be able to hold 28 out to 8k instead of tapering down to 23-24?

 

What WGA are you using with the EF3 turbo? Any preload on it? Have you done a boost leak test recently? I can't remember but does the Perrin come with a soft & stiff spring or no?

 

I haven't used ECU boost because when I got my Evo back in 05, those tables weren't tunable yet. But on all of my cars, DSM in the past, Evo now, I have always use an EBC.

The whole reason I used an EBC is because you control the flow of air with a solenoid valve, rather than a spring. If setup and tuned properly, there is no way an MBC can spool faster than a solenoid controlled valve, simply due to the fact that the MBC start bleeding air to the wastegate during the spring travel. Once that force is enough to crack the wastegate open, you are decreasing the spool time.

The only reason an EBC (or ECU boost if it works the same) would spool slower is if you are setting it to open the valve before the MBC spring would begin to open. It's a simple matter of setup and tuning.

As mentioned by Boosted Tuning above, he said that if he held 100% duty cycle longer (I would have guessed it should have been 0%, but maybe ECU boost works differently?), he got boost spikes. You get spikes more easily because an EBC setup (and I'm assuming ECU boost, since I haven't tuned it) is more of an on/off switch whereas an MBC is a gradual opening due to the spring.

But there is no reason that I see that a MBC should be able to spool faster. Both will be equal as long as they are 100% shut (not allowing any wastegate flow). The spooling slows when the wastegate is allowed to see some pressure, which an MBC will always do before an EBC. At a bare minimum, the EBC should be able to be tuned to behave like the MBC and better.

Of course, that's just my take on the subject, and can't offer data, but it's sound logic and based on my experiences in the past with MBC/EBC.

 

1 - wastegate selection (stiffer of course is better) and wastegate preload (more preload = less taper)

2 - MBC type and stiffness of spring - (Run the stiffest spring available for the MBC you have. Advantages of a stiffer spring in your MBC: less boost spikes, more constant boost curve and less taper)

3 - PORTING! - port everything you can. Porting parts and making the flow of the engine less restricted will lead to faster spool, a better, more solid boost curve and less taper, while using a MBC (or any form of boost control).

Theres a couple of tips.


IMO, the MBC spools faster as it seems to stay 100% shut (no flow to wastegate) longer/closer to peak boost then ECU boost can.

If I had to theorize, I would say my FORGE MBC with stiff spring stays 100% shut till a couple psi (1-5psi) before boost target. When I tried to hold the ECU boost to 100% till a couple psi before target, I got massive spikes. The highest I could hold the WGDC at 100% and not get spikes was about 15psi. In which then, it spools slower then the MBC.

Besides the spooling. If you look at my data I posted, the ECU boost tune is perfect and never more then 0.5psi off boost target and doesnt even use any error correction (error correction is enabled) since it so on target. Yet, its still not as solid and constant as the MBC boost curve.

With the MBC spooling faster, being more constant and the fact that its much easier to tune, its an easy choice for me to which is better.

Oh BTW, what EBC do you use? It woudl be cool to see some data from it.

 

I would venture to guess that meant that either the valve on the solenoid was too small or the actuation of the valve was too slow. Since I haven't been able to mess around with ECU boost and the 3port solenoids, these are only guesses. But, that's the only logical explanation.

In theory, if the actuation was fast enough and the solenoid flow large enough, you could hold the valve 100% shut until your target boost and then let a ton of air to the wastegate actuator (well the exact amount of air pressure to hold that boost level) and it wouldn't spike, but have fastest spool possible. Obviously, in reality it will depends on those variables, but the closer you are to the perfect setup, the closer to that theoretical operation you will be. It will be a very steep ramp to a flat plateau of boost.

You will never be able to reach that theoretical operation with an MBC because of the spring. Springs are not on/off...they are gradual, based on spring rate. So, you will always have to bleed airflow before your target.

I keep it very simple. I use a Profec Type-S. Similar to the old Profec B (if I remember correctly...it's been quite a while). No fuzzy logic crap.

It's the one that is just a simple solenoid and controller in the cabin that lets you adjust boost (like turning the MBC handle) and boost response (how fast or slow the solenoid actuates).

 

So, I thought one of the advantages of ECU boost is being able to use error correction to flatten the the peak. If you use a very aggressive wastgate duty cycle you will overshot your target, but error correction squashes it back down. On an MBC if you set it to high obviously you will just overboost.

I run a little HKS BB turbo and I need gear dependant boost control and % TPS/ WGDC correction to spool it as fast as possible and eliminate part throttle surge/ riding the surge line in each gear. I do not think this is possible with an MBC I would have surge in the higher gears and lazy spool and low boost in lower gears...

What am I missing? Maybe this is a big turbo thing?

 

Yes, but error correction is reactive, not proactive. So your boost still spikes if you have too aggressive of WGDC numbers. Then AFTER it spikes, it pulls WGDC.

 

Ya but with the correction interval at 3-5 times a second it's a jaggedy line not really a spike.

Not trying to argue, I have just seen many, actually almost all (good) pro tuners prefer MBCs and I'm still baffled why. Wouldn't you have to settle for picking one gear to set your MBC and have to compromise on the rest?

I have messed with an MBC before but don't have much experience.