What are the pros and cons of the 2 different types of mbcs?

Also, factory service manual suggest that the turbo actuator should not see pressure higher then aprox 16psi (1.13bar), in the case of spring and ball type mbc, I see that most people use tap into the bov line, as the input to the mbc. Suppose you set your spring and ball type mbc to 19psi, and when manifold pressure is at 19psi, wouldn't the output of the mbc be at 19psi also? and in turn the actuator will see 19psi?

I am no expert in how mbc works, so your experiences would be very helpful.

Thanks,
ob4

 

no one could help?

thx,
ob4

 

bump****

 

I've read that the stock wastegate actuator opens at 12 to 13 psi; the job of the MBC is to convert the manifold pressure of 19 or 20 psi to 13 psi via a calibrated restriction. The spring and ***** do this with a sort of pressure relief valve (open at whatever they're set to but delay and damp the pressure wave to open the wastegate) and the bleed valves leak a bit of the pressure, accomplishing the same thing. I've heard the ball and spring types are more reliable and reproducible over a range of loads, temps, etc., but I'm not sure if this is true.

Can anyone provide a better explanation?

 

I put on the Hallman Pro RX tonight, hooked it up with the compressor housing turbo nipple being the boost source, and the other hooked to the wastegate. So far it seems to be working awesome. Was a pain getting the thing on though.

 

rburris28, thanks for your input, that's also what i've heard too, but will the bleed hole(pressure relief hole) and the internal restriction of the mbc be sufficient to lower the pressure that the actuator will see? One thing to be sure is to hook up a pressure guage on that line and see what is the peak pressure that the actuator will see. I also went back and reread the factory service manual, the actuator should not see pressure above 1.17bar (aprox 16.5psi) and it should open at 1bar (aprox 14.5psi). If say you turn up the boost to 20psi, this means that the mbc needs to take off(by internal restriction and bleed hole) 3.5psi to avoid damaging the actuator diaphargm and if set your boost to 22psi, that's 5.5psi, I wonder if the mbc can take off that much pressure.

text from the service manual (page 15-4):
==============================================
TURBOCHARGER TURBOCHARGER WASTEGATE ACTUATOR CHECK
1. Connect a hand vacuum pump (pressure-application type)
to nipple.
CAUTION
In order to abovid damage to the diaphragm, do not apply
a pressure of 117 kPa or higher.
2. While gradually applying pressure, check the pressure that
begins to activate (approximately 1 mm stroke) the
wastegate actuator rod.
Standard value: Approximately 100 kPa
3. If there is asignificant deviation from the standard value,
check the actuator or the wastegate valve: replace if
necessary.
==============================================

Also, some people tap the bov line which is manifold pressure, but I have read the Hallman documentation, and they recomand using the turbo compressor value as the boost source, so what are the pros and cons for the 2 boost sources?

Keep the comments and experiences coming.

Thx,
ob4

 

The bleed type boost controllers hurt spool up, bottom line. The ball and spring type keep the boost signal from going to the wastegate actuator until the boost is high enough to take the ball off the seat in the controller and let the signal get to the actuator. This is the best type of manual boost controller I have ever seen.

There used to be only one out there. It has been copied over and over again by tons of companies. We have our own style of it that has a billet aluminum body with the mounting tab built right into the billet body. We sell them for $75 and when designing them had the EVO/DSM in mind mostly. This was the idea behind incorporating the mounting tab into the body. Makes mounting in our cars very clean and easy.

My biggest complaint on most manual boost controllers is the lack of or ****ty design of some type of mount. We addressed this and came up with what I feel is a super clean functional design.

David Buschur
www.buschurracing.com