Hey all, I've done some searching through the forums, but wasn't able to find any answers to my specific issue. I've tuned my Hallman MBC to 20psi and have noticed that it holds the boost fairly well until about 5500-6000 rpm, which it will then taper down a few lbs. for the next 500-1000 rpm, then it will spike back up to 18-20 psi around 6500 - redline. I understand that there is boost taper, but I'm confused about the fact that it tapers, then spikes back to what I set the mbc to hold. If anything, I'd figure that it should hold 20 psi. until higher rpm's where it will obviously taper a bit. After installing my boost controller, I made sure to tighten all of the IC piping and whatnot, so I'm hoping it isn't a boost leak issue...but that wouldn't make sense if it were, because the boost is spiking back to what I've set it to after the short tapering. Anyways, my mods are...
-Defi Blue Racer Boost Gauge
-Hallman MBC (w/ the ceramic ball)
-Walbro 255 fuel pump
-Base flash
-Chopped Air box
If anybody could chime in and shed some light on what the potential problem might be, or inform me that I'm just being paranoid and this is normal...it'd be much appreciated. Thanks!
Also, did you do the install and tune of the MBC, or did someone else? Either way, if there is a way, could you post a pic of how its setup? Id like to help you resolve your problem.
Edit: and when you say youre running a chopped airbox, whats that mean, you cut the top off it??
I had JustDSM helped with my flash, he gave me the rom for a base flash which I flashed to my car's rom and I installed the boost controller myself. Here is a pic of my setup and a link to my logs, since I can't for some reason get this website to allow me to upload anything.
Ill have to look at this on my laptop because I dont have what is needed on my desktop. Ill take a look at your logs and then get back to you. Im hoping its just something that can be fixed in your tune.
For the MBC, where are you running the line for your boost source, to your turbo??
This is the diagram I used for my install. I was very careful and took my time with the install, so I know that it's installed properly. The only thing I could think of, is that maybe their is a leak at the T-fitting between the BOV and Intake Manifold. And if it's a boost leak, there is no way I'm going to be able to perform a boost leak test, because it was really difficult for me to access and take off the stock intake pipe when I installed the MBC and really don't want to have to go through that process ever again, lol. But anyways...I do appreciate your help, so thanks!
Yeah, I can check it out in Excel or I can use the playback and graphing functions in EvoScan...but for these, I used Excel in order to compare them to previous logs.
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