Ok this is whats going on, when I first got my Evo the first mods were intake and ProfecB boost controller. The car held 20 psi all day long, no problem.

After I added the 3" turbo back exhaust I haven't been able to hold a steady constant boost pressure!!! I've tried several electronic boost controllers including manual, but NOTHING has help! When I go WOT it pegs to 21-22 psi and drops to 17-19 psi by redline 7k rpm, varies on what gear I am on. If I lower the boost it pegs to 18-19 psi and drops down to 15-16 psi by redline.

I've checked over my piping, intercooler and exhaust but everything checks out. I might have to pressure test it to see if I have any tiny leak somewhere.

Does anyone else have this issue?

 

I do. On my dyno graph its pretty damn noticable too.

 

Have you tried to pin point the problem? I wonder if it has to do with the o2 housing?

I am also thinking that if I don't find and leaks, I am gonna put back my stock exhaust and see what happens.

 

could be the ecu turning things down a notch. or ur bov is leaking. anyway, u shouldnt be too worried about it. im sure ur car still pulls harder than stock.

 

Hear is my experince Dr. I have the profec B spec II boost control and a 3" B&B catback. On the low setting, which I have set very low, I have the limiter set at 13psi. The boost is held steady between 11.3 and 11.5 in 3rd, 4th , and 5th.

In the high setting I have the limiter set at 19.5psi. The start boost and gain setting have been tweaked hundreds of times. The best I can do is a steady boost between 17.6 and 18.5 all the way to redline. I don't, as you want to do also, is not have it spike to 22psi or higher. I can get more boost with the same consistancy but it would spike during the RPM range which would set of the limiter. I could raise the limiter, but that is not something I want to risk. I would rather live with the boost presure in that range(which is way more than stock) than risk damaging the engine. It sounds like you have the same poblem. I have a feeling this is just the way it is.

 

I just figured it was the stock bov. I drove an Evo last night with a vishnu o2 housing and 3" exhaust and his boost dropped still. Its gotta be the bov or intercooler piping.

My boost drops about 2 psi in 3rd & 4th gear at 6500 rpm.

 

well im sure uno that stock the boost drops off to 16psi from 19psi around there don't you? *might* have something to do with it. don't know for sure tho.

 

We aren't talking about stock cars.

 

Yea, once you disable the factory boost control it *pretty much* takes that out of the equation.

I agree with Stinkapuss. It has to have something to do with the crappy factory BOV. I think if someone had the equipment to do it. It may be worth the effort to do some kinda pressure check/ leak down check on it to see exactly where its letting loose.

 

Try lower your GAIN setting to 5 or lower because when Gain is too high it cant HOLD BOOSt on high RPM. Try it and let me know what happens I have the same problem but I work everyday so I have no time to fool around with my car.

 

Thanks for the posts guys, it helps to know that I am not alone on this one.

evolutionist - I have both the profecB and the profecB spec II, but I had to take them out because they were giving me hell also, boost was WAY TOO eratic!! Once at the track I saw 30 psi, I thought I blew something up, but luckly I back off right on time! With the spec II sometimes it would hold steady boost and sometimes it wouldn't, it was speratic. I almost got my rear end spank by a turbo civic on the high way because of this crap, not cool !! So I yanked that freaker out and hooked up the HKS EVC and so far thats the one I have and its ok, but definitely not solid!

stinkapuss - The 6500rpm sympton is exactly what I am referring to, its only at high rpms where it drops off big time. Good thing you posted about the o2 exhuast, that takes care of one test.

There is a couple of things I am planning on doing, first of I will be pressure testing the system this weekend, w/ the HKS blow off valve and w/ the stock one, also w/ stock piping. HOPEFULLY I'LL FIND A FREAKIN LEAK . If not I am going to place back the stock exhaust and see if I can hold steady boost then. If none of these two work, I'll go after the wastegate itself and test that bad boy. I'll keep you guys updated.

 

DrEvo Did you try the GAIN SETTING at 5 ??

 

Start off by trying a new BOV and playing with the settings.

If that doesnt do it, you may need to get a more advanced EBC like the Greddy e-01 or the SBC-iD III which use solenoid motors that react many times per second to keep the boost steady. I believe the Profec B uses stepper motors like the HKS EVC. Stepper motors are much more reliable but they arent as quick reacting as the solenoid motors. Solenoid motors can break easier than stepper motors though.

You can probably sell both your profec Bs and pay for an advanced EBC.

 

I have to pile-on with stinkapuss and sr20det91 on the stock BOV/DV being the culprit. This seems especially likely since you mentioned even trying an MBC and having the same problem. I would keep the MBC on until you get it figured out, that way you know the EBC's program settings aren't affecting the condition in any way, which means easier trouble-shooting for you.

I mean there just isn't too much that could be causing this other than a bad DV/BOV, loose I/C hose, or other high pressure fitting/hose leaking boost off. Once you start pushing more boost pressure, the stock DV's days are probably numbered.

Oh and one other thing...there has been concern about the wastegate actuator canister as well. I read one little blurb about the canister being angled in a way that it holds water that is splashed into it. This in turn causes premature corrosion and performance degradation.

If you could get your hands on a pressure simulator tool as outlined in the MMC tech info, you could test the canister to see if its within spec. I can pm you some info on that if you want it?
Edit I noted after the post that you were already thinking in these terms. Let me know if you want me to forward the MMC blurb someone else sent to me.

Just remember following the logic path is your best bet when figuring out these kinds of boost problems.

Good Luck and let us know what you find!

N10S

 

I am using the e01 now and the problem I am experiencing is
I can not set the same boost on every gear.
For example if i set first gear 17 PSI my 3rd and 4th gear will be 19 psi. And if first gear is 19 then 3rd and 4th will be 21.