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!

 

Tuning, boost leak maybe??

Not sure what the chopped box is excactly but you could be choking airflow to the turbo. I'd have to log and see the car to know for sure.


Not too far away if you ever need a hand. Evans tuning is close to you too. I think hes in Mt. Bethel now

 

Here is a pic of my chopped box...it basically allows me a slightly bit more airflow, but I really mostly did it in order to make louder the sound of the turbo spooling and the bov


http://www.mediafire.com/?0tn2kzyddnj
-I ran 4 logs total...2 @ 20 psi. & 2 @ 25 psi...I'm running on 93 octane btw.

Thanks for the help!

 

Don't have winrar on GF's computer and she'll kill me if I DL anything HAHAHA. If no one gives you any feed back by tomorrow when I get to work I'll take a look man.

 

Sounds good. Thanks, much appreciated!

 

Turn your boost controller all the way down to its lowest setting. This should put you around 11 PSI base pressure. Then increase the boost via rotating the eyelet thingy on the end of the threaded wastegate actuator rod. Once you get the boost up to 17-18 PSI using this method, then you can dial in the final 2-3 PSI with your MBC.

 

Boost could just be creeping up. Try running wastegate pressure and see what it does.

 

Ok, so I turned the mbc all the way down, which put me at around 13 psi. and it only fluctuated about 1-2 psi. when it tapered down in the higher rpms. It seems that this boost issue is only when I have it turned up, where it tapers then spikes back up. That doesn't seem like it's a boost leak problem, because I should have the same issue with the mbc turned all of the way down as well, right?