Cody 82 ZXT Posted May 15, 2001 Share Posted May 15, 2001 If I'm not mistaken the main gripe from most people running MBC's is that when the temp changes the boost changes. Thats one big reason I went with an electronic boost controller. I believe it has to do with the density of the air. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted May 15, 2001 Share Posted May 15, 2001 I want to make sure I understand exactly what you have. Unmodified wastegate rod, relief valve currently wide open and the boost controller which is what you are currently using to control the boost. How much boost do you intend to run eventually? I believe the stock wastegate cannister spring is rated at 7# and if you intend to keep the boost at 12# or less, I would just work with the adjustable wastegate rod. From personal experience I try to limit the preload the shortened rod will add to about 5-6# so anything above 12-13# I would use the MBC. I think I have stated before that the problem with MBCs that are not modified for turbos is that they are typically made for a wider pressure range, like 0-100#. As such they use a stiffer spring and do not have enough granularity to allow you to adjust in 1# increments. I usually try to find a softer spring. Having said all of that, I never had a problem with my MBC as a result of heat, but I would imagine with little or no granularity that extreme temp could cause metal expansion and cause the change you are seeing. I would make the wastegate rod mod and use that if the boost will only be in the 10-12# range. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted May 15, 2001 Author Share Posted May 15, 2001 I have a MBC (manual boost controller) set up to be very similar to what Scottie-GNZ is running with the exception of the shortened wastegate controller rod. I have not dialed in the pressure relief isolating the wastegate yet, it's just running open right now. My target boost, without an IC, is 9psi and my pop-off is adjusted to 10psi. What I am experiencing is fairly extreme variation in boost level, depending on engine temperature. I ran at the track Saturday under very warm condtions (road race), and my boost was over 10psi. I adjusted it down to 9, and now in cool conditions off the track, I am now only boosting to 7psi. I mounted the thing under the hood to the back of the strut tower, behind the heat shield, and the controller body doesn't seem to be getting that hot... What do I have to do? Mount the da@n thing inside the car? Put in a smaller flow restrictor? Suggestions? By the way, Saturday was awesome, Z's rule. With 225/50/15 Dunlop Z-rated tires, I was pulling over 1G in the turns. With a passenger, I chased down a Viper (a new driver, but still...) Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted May 15, 2001 Author Share Posted May 15, 2001 Thanks for the ideas. The MBC I have is just a pressure relief with a 10# spring in it (it's the MSA kit - $90 for $15 worth of parts). I have put the 0-100# pressure relief in line with it, in an attempt to speed the spoolup. Scottie - your point is well taken that I just am not boosting enough over stock to justify this complicated mess. I think I will try just shortening the wastegate actuator rod. Quote Link to comment Share on other sites More sharing options...
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