boost drop

[demonchild]

I can't figure out what it is, but I can't get my boost to hold a specific psi. Right now with a 18G, 660 injectors, HKS blow off valve (vented to atmosphere :thumbdown ) and a Blitz dual SBC boost controller (gain at 19). I'm boosting to 1.25 bar and then rapidly droping to 1.14 bar and holding through the remainder of my RPM's. Why can't I get my car to hold boost. I don't think Tuning is the issue because I had RRE tune my SAFC.

any thoughts suggestions would be appreciated. All other info on my car is in my profile

 

[ACKERSON]

You said it holds 1.14 bar through the rpms after spiking to 1.25. So you are holding boost. It sounds like you have a slight creeping issue not an issue maintaing boost pressure. So if this is a boost spiking issue look around and you will find a ton of info on this subject.

 

[psychlow]

How long are your boost reference lines for your boost controller?

If they're too long, you may get boost spiking issues because it takes time for the lines to fill with air. If you shorten them, it should hold 1.14 Bar without spiking.

 

[demonchild]

the lines are as short as they can be. I had another question that's sorta related. When launching. when you hold the rpms at let's say 3500 should the boost level stay at 0 or rise quickly to 0 and then drop back to -30 or so. I was under the impression that it was supposed to hold around 0 to -5.

 

[psychlow]

Vacuum should go to around 0 as you open the throttle plate, then increase back to -20 to -30inHg as the RPMs catch up.

 

[demonchild]

perfect. Now, I'm off to fix the boost spike. I have a feeling this could just be related to the oh so fun fuzzy logic boost controllers.