Problem: Last night on my way in to work, I hit fuel cut due to overboost. I am using an HKS EVC 4 for boost control. Low boost is set to .78bar and high boost is set to 1.45bar. I thought maybe I was overboosting due to the cold, so I set the evc to low boost. 1st through 3rd, it would hold at .78 bar until just before redline, where it would creep just a little bit. 4th through 6th it would hold .78bar for a second then march up all the way until it hit fuel cut.

I've used this boost controller on my turbo'd spec-v and mkIII supra, without any issues. Its been on this car since I bought it with no issues.

I installed an agency power dp, perrin testpipe and turbo xs cb last week, and had no problems with boost creep until now. Weather has been about the same all week, cold as *****.

Unfortunately, the evc doesn't have a way to manually adjust the gain. Instead it has to "learn" the wg characteristics. I haven't done that yet because I'm not sure if its a wg preload issue or not.

Anyone who has seen this before, please feel free to chime in with your thoughts.

 

Anyone?

 

Chiming in with "you need an ECU reflash". Period.

Let me know if you are interested in proceeding with this service that will fix your problem as well as add 20+whp and tq to your car.

 

I know I need a flash, I'm waiting on the fuel pump to come in, then I'll be tuning myself. I have an LM-1 permanently installed and I've been doing a lot of logging. I'm stupid rich right now, low 10's across the board.

The boost creep is obviously a mechanical issue, which I don't see how a reflash will correct.

 

Edited: Inadvertently double posted, sorry.

 

I donīt think that itīs mechanical. I suspect, however, that it is wastegate flow related. Most likely a decrease in exhaust backpressure due to your exhaust mods, causing increased flow though the turbine housing and the resulting inability of the stock exhaust housing to divert enough flow out through the unported, restrictive, WG bypass port. The increased flow though the turbine scroll, and across the turbine blades results in higher turbine rotational velocity, without a parallel increase in the capacity of the WG bypass port to keep up with and bleed off enough of the increased volume and higher velocity main scroll flow.

 

Which would be completely mechanical, not electrical, lol.

 

If it is in fact boost creep, you have to make the WG flow less restrictive. Port the wastgate hole.
Boost cereep is cause from the exhaust flow taking the path of least resistance, through the trubine wheel. Meaning that the WG route is more restrictive than the turbine route.

 

You're right, it has more to do with flow mechanics, and not: 1) the mechanical bits of the WG assembly, ie. flapper valve, solenoid, WGA rod, etc., or, 2) the electrical circuitry of your EBC, both of which are performing their respective functions.

 

OK, my question now is, does everyone who installs a full 3" turbo back exhaust have boost creep problems?

 

sparky and EVO8emUp are correct. What you are experiencing seems to be very rare with EVOs ... happens a lot to STis after an exhaust upgrade.

 

So I have the best flowing exhaust evar?!?!

I'm going to go "relearn" the evc and see if that takes care of it. I personally think the evc isn't pulsing the wg open long enough now.

 

The most simple fix besides putting a more restrictive exhaust back on would be to pull the turbo, remove the turbine housing and port the WG hole. Be careful not to port too much and go outside the sealing area of the flapper.
Oh, and remember to debur the sealing surface so you get a nice tight seal. (flapper against the WG hole face)

Oh yeah.. I'm not sure if these turbine housings are similar to the 16Gs and such. With those, you had to use a smaller die grinding bit and remove some material from the corner of the housing so you could flip the WG flapper 90deg to get a better angle at the hole.

 

Its not caused by a TOO free flowing exhaust. The stock turbo is huffing and puffing to make the same boost above 6k that it does at lower RPMs (i.e. peak torque). I have heard of no one with an Evo 8 or 9 experiencing legitimate boost creep. In fact the higher the RPMS go with the stock turbo, the exhaust pressure inside the turbine housing starts to help the actuator open up the wastegate. So usually the reverse happens, i.e. Taper.

Something else seems not be functioning properly. I would put the EVC back thru its learning procedure, then see if the problem persists. You should let the EVC 4 relearn the characteristics of your wastegate system anytime you increase or decrease its efficiency, like you have done in this case. That could very well be the problem.

One last thing you shouldnt be running less than the stock boost pressure. So raise your low boost setting to at least 1.3 bar. That will help your problem also.

Brian

 

Yeah, I hope that you can fix the problem by getting your EBC to relearn the altered boost curve. That would be the easiest solution.

I went back and reread your original post and see that you still have the stock cat and the stock O2 housing on there. I donīt see how your exhaust could be way too free flowing if it still has these 2 major restrictions in place.

So, maybe you are right and it is your EVC not relearning the new boost curve. If you were to disconnect the EBC and install an available MBC just for test purposes you might be able to narrow down the problem.

If you do have to port your turbine housing, then focus most of the grinding attention on the initial turn in radius from the main scroll area into the WG bypass port(hole). You can openup the bypass port itself leaving about 3/16" of the port radius for proper puck sealing. This is with the single flapper 10.5, I am not that familiar with the double flapper 10.5 hsg.