just installed MBC's, little concerned

trev · 04-16-2008, 12:55 PM

So I added a set of MBC's per robrobinette.com I have been running 17-18 vac before I added them (I could only boost to 7psi of course) and after I added these, I have it at about 9 psi and the car is measuring 16/17 with a very rare dip to 15 if the idle drops a little. Car is still smooth and runs fantastic...just the haunting thoughts that I could have done something during my couple of boost pulls...any thoughts or am I just being a little too over concerned?

Trev

josh18_2k · 04-16-2008, 03:09 PM

this may not be the cause at all.. but any good MBC is vented, to prevent boost fluctuation. on mine, there was a small hole drilled into the part with the ball/spring. i'm thinking that the tiny bit of air sucked in through the vent is contributing to your drop in vacuum, and is totally normal.
if im wrong, my bad

David Jerome · 04-16-2008, 04:39 PM

I wouldnt worry, if it was blown you would know it. Could possibly be loosing a little vacuum where you added all the new lines also.

SPICcnmFD · 04-17-2008, 07:10 AM

^agreed, IMO vaccum is not a good indicator of engine health since their are so many things that can cause it change.

trev · 04-20-2008, 10:31 AM

well,

I did swap out the boost control with a new ball bearing controller, but left the needle valve in charge of pre-spool. I am getting a 7-3-5 pattern now...guess I need to tweek it more...

04-16-2008, 12:55 PM	#1
trev The Newbie Join Date: Apr 2008 Posts: 21 Rep Power: 0	just installed MBC's, little concerned So I added a set of MBC's per robrobinette.com I have been running 17-18 vac before I added them (I could only boost to 7psi of course) and after I added these, I have it at about 9 psi and the car is measuring 16/17 with a very rare dip to 15 if the idle drops a little. Car is still smooth and runs fantastic...just the haunting thoughts that I could have done something during my couple of boost pulls...any thoughts or am I just being a little too over concerned? Trev __________________ 2006 Porsche Cayenne Tiptronic S Silver FOR SALE 2002 Audi A6 4.2 Quattro 1994 RX7 Touring 5 Speed Black/Tan Leather SOLD 1993 RX7 Touring 5 Speed Silver/Red Leather SOLD 1987 Supra 1JZGTE 5 Speed Blue/Blue Leather SOLD

04-16-2008, 03:09 PM	#2
josh18_2k Rotary Fanatic Join Date: Feb 2008 Location: Gresham, OR Posts: 473 Rep Power: 18	this may not be the cause at all.. but any good MBC is vented, to prevent boost fluctuation. on mine, there was a small hole drilled into the part with the ball/spring. i'm thinking that the tiny bit of air sucked in through the vent is contributing to your drop in vacuum, and is totally normal. if im wrong, my bad __________________

04-16-2008, 04:39 PM	#3
David Jerome RCC Contributor Join Date: Jan 2008 Posts: 713 Rep Power: 18	I wouldnt worry, if it was blown you would know it. Could possibly be loosing a little vacuum where you added all the new lines also. __________________ David Jerome Broker for Speed For Sale LLC (David@SpeedForSale.com) (Pre-owned RX7/sports car sales & new parts sales/installs/tuning) PM me about low priced, high quality port work

04-17-2008, 07:10 AM	#4
SPICcnmFD Rotary Fanatic Join Date: Feb 2008 Location: B'ham, AL Posts: 329 Rep Power: 18	^agreed, IMO vaccum is not a good indicator of engine health since their are so many things that can cause it change. __________________ 1993 Rx-7 SM2 #11 At the local AutoX: http://www.youtube.com/watch?v=9VOSQkkSLQs Speed for Sale shootout 2007: http://www.youtube.com/watch?v=JiqlyAkGmpg A few laps at Barbers: http://www.youtube.com/watch?v=6_h5q...x=0&playnext=1

04-20-2008, 10:31 AM	#5
trev The Newbie Join Date: Apr 2008 Posts: 21 Rep Power: 0	well, I did swap out the boost control with a new ball bearing controller, but left the needle valve in charge of pre-spool. I am getting a 7-3-5 pattern now...guess I need to tweek it more... __________________ 2006 Porsche Cayenne Tiptronic S Silver FOR SALE 2002 Audi A6 4.2 Quattro 1994 RX7 Touring 5 Speed Black/Tan Leather SOLD 1993 RX7 Touring 5 Speed Silver/Red Leather SOLD 1987 Supra 1JZGTE 5 Speed Blue/Blue Leather SOLD