HKS DSBC leaking boost....???

[chovis38]

I put my HKS electronic boost controller in about a month ago, and it was awesome at first; with the different settings, and boost would hold though the whole rpm bandwith (opposed to the manual boost controller, where as the boost would gradually creep down in the higher rpm's). Anyway, just last weekend, I got a 3" downpipe with no cat to go along with my 3" catback. Now, when I have a lower setting of boost dialed in, the DSBC holds the boost up untill about 4500 rpm's, and then the boost gradually climbs. On setting number four, I have it set for around 0.59 bar of boost..... well, it holds until about 4500, and then climbs to 1.15 or so..... Now, what I am thinking is that the selenoid might be leaking. I have checked all lines and hoses, but they are all fine. That is why I think it's the selenoid. Oh, and I have my rear O2 unplugged..... however, I don't think that would do anything except throw an engine code... I don't think it would cause the problem. Any help would be outstanding!!! Thanks.

 

[94EclipseGST]

Sounds like you may be getting boost creep, brought on when you changed to a large DP and eliminated the cat.

 

[chovis38]

Alright.... what should I do to correct that? I have tried to dial down my gain on my boost controller.... it is recommended that it be set at 10.... I had it set at 13... and now it is at 5, but it doesn't matter... it just takes a little bit longer to spool up, and then it does the same thing. The solution better not be to get a cat, b/c that's stupid!!!! Thanks for the help; keep it up.

 

[94EclipseGST]

There is a very good write up on boost creep and boost spike on Kyle Tarry's web page:
http://home.comcast.net/~tarryo/kyle/
Look under the tech articles section.

Basically, you need to look at your wastegate, possibly upgrading to a 34mm flapper. Also, do a couple of searches on boost creep, and see how other people have dealt with the problem, as there are probably more ways to deal with it.

The cat is definitely not he problem, so don't worry about putting it back on!!

Edit:

I also found this:

Quoting a posting from jb talons

It comes from a waste gate that doesn't permit enough flow by the turbo. An external gate does fix the problem, not because it is stronger, but that it flows better.

This definition comes from Extreme Motorsports

Boost Creep
A turbocharged car is a positive-feedback system. The faster the turbo's compressor wheel spins, the more horsepower the engine makes. More horsepower means more exhaust gasses are being expelled. The more exhaust that is expelled the faster the turbine (and thus the compressor) wheel spins, and so-on until the engine explodes.

The ECU (sometimes via a boost controller) controls the boost level by opening the wastegate. Boost creep, in which the boost level of your engine continues to rise despite the best efforts of the wastegate, is caused when a fully-open wastegate can't divert enough gasses around the hot-side turbine wheel.

Boost creep can usually be eliminated by porting the wastegate opening and O2 sensor housing or by using an external wastegate. Both of these allow exhaust gasses to vent more efficiently.

 

[chovis38]

Now it all makes sense...... the world is flat once again!!!! Thanks for the help guys!!! Right now, I will probably port the wastegate and the o2 housing..... I will go to external later on when I upgrade my turbo again, and when my internals are done. Again, thanks for the help!!!