Boost drop from 3K-4K RPMs

CrookedH · #1 01-25-2010, 05:17 PM

So lately i've noticed my car dropping boost by 3-4psi between 3K-4K RPMs. I removed the CMD from my car for a day and still had the issue. With CMD, and the boost drop issue I peak about 20psi with a quick drop to 17, then straight back up to 20. Without CMD I peak around 14.x, drop to 10.x, then right back to 14.x. Probably does it once a day and only in that RPM range. I noticed a wierd flat spot on my baseline dyno in the same range, next pull with CMD it didn't do it. No boost leak at all, will hold 20.X PSI no problem.

See the baseline run on this for an example. A normal 2.0T has about 15-20 ft/lbs more than I was making in the 3-4K range.

Bad boost solenoid maybe? Other thoughts?

ragchaos · #2 01-25-2010, 06:37 PM

Are you saying that the needle goes crazy, mine does that when it raining and I WOT it from a stop, another thing i thought was weird is that i have the boost hit 20 psi on a dry day, but when it is raining the boost jumps up to about 24 psi, it freaked me the fuck out because when it did that the AFR was in the high 13's I dont have an explination for this maybe someone can chime in when the ground is super wet i wont hit it has hard. But yeah the needle does go crazy at about 3-4 RPMS but i doesn't happen everyday.

Tufast · #3 01-25-2010, 06:46 PM

Weird....I wish I was more knowlegeable regarding turbos & tuning.

ragchaos · #4 01-25-2010, 06:59 PM

Yeah me too i feel like an infant learning new stuff lol. I guess i gotta keep at it.

ragchaos · #5 01-25-2010, 07:09 PM

Found this on "THE OTHER SITE"

Direct quote from WHATNOT

Quote:
Originally Posted by AKGC View Post
wastegate actuator maybe? thats my first thought.

Time to upgrade
my thoughts exactly. I assume this is your track car, with BOV and whatnot? Not your other car with ATP wga?

The BCS, contolss boost with leak, not ball and spring. So if your wga is set for 5 or 10psi, that boost leaking by the BCS will go out the wga. My guess is the leaking the boost out the wga isn't consistent, so that is why you get it to 'bounce' back up. I think you are borderline on amount of boost the BCS will leak to the wga tension. So actually the loweer your boost is, the less leak BCS will leak, and the less you will see the boost leak.

solution, new wga with higher rating, or a MBC with spring and ball. Try your wife's wga on your car, I bet that resolves the issue. Even stock I never saw boost held so well than with my MBC. Its an on and off switch basically to the wga. It would go up to 16psi and hold to 14-15, and that leak Ibelive from from the CBV....if the CEL stayed off. That is why when I get my car back from the shop (transmission TSB) I am going to try the CMD with my MBC, since I still have OEM wga.

The stock GC leaking boost is two fold. the weak wga, and th CBV IMO.

END QUOTE

This makes sense to me as i too did not upgrade the WGA. Anyone else have any inputs

__________________
2.0T

genjuice · #6 01-25-2010, 07:46 PM

Quote:

Originally Posted by ragchaos

Are you saying that the needle goes crazy, mine does that when it raining and I WOT it from a stop, another thing i thought was weird is that i have the boost hit 20 psi on a dry day, but when it is raining the boost jumps up to about 24 psi, it freaked me the fuck out because when it did that the AFR was in the high 13's I dont have an explination for this maybe someone can chime in when the ground is super wet i wont hit it has hard. But yeah the needle does go crazy at about 3-4 RPMS but i doesn't happen everyday.

In order for it to rain you have to have low atmospheric pressure, which makes the air lighter and less dense.
That is the reason you are able to make more boost.
The same way when its very cold out the air is very dense and wont allow you to make as much boost.

CrookedH · #7 01-25-2010, 07:55 PM

I thought about wastegate but since it does it on stock boost as well as tuned and it's always the same RPM got me thinking electrical... Pretty much floor it, enjoy torque, think WTF, then power is back. Boost gauge will show ~20, quick drop to 17, then back to ~20. Doesn't spike above normal, it just drops off for about 700-1000 rpm. Same with stock and no tune.

Might just have to get the grimmspeed boost controller and forge wastegate. With my luck it still wouldn't fix it though.

ragchaos · #8 01-25-2010, 08:01 PM

This is a tough one. I have seen it happen and i just ignored thinking it might be the EBC and the WGA but i don't know for sure as I am still figuring things out on my own.

to Genjuice: I do see your point in this i never really sat down and though about it. Either way i don't punch it has hard if it is raining outside safety reasons apply too.

Edit: come to think about it when i first got my Boost gauge installed in the car( no CMD at the time) i did notice it too. I had also done the WGA adjustment. When i added the CMD i undid the WGA adjustment. Before i got the CMD i had a Turbo Xs boost controller on the car and not once did it spike like what you are explaining it was nice and smooth with a WGA adjustment and without it. Soooooooo it could be the EBC but unless other people are experiencing the same thing its hard to tell with out exp. and knowledge. The again my gauge doesn't spike everyday it just once in a while i have only seen it done three times( not in the rain) and I WOT my car at least twice a day everyday for about 150 plus miles a week.

YogiBear · #9 01-25-2010, 08:47 PM

My buddy gets that - all he has is CAI and WGA adjust 1.5 turns. It feel like TCS mildly kicks on for a sec for those of you who dont know what we are talking about.

Mcmonopoly · #10 01-26-2010, 11:15 AM

Wa...wait a sec there...I noticed the exact same thing, but only when I ran the PA reflash, I mean I physically felt a hole in the mapping, and TBH I'm pretty sure it's right around those RPM ranges.

I didn't/don't notice it when everything is stock, but I can really tell you that it feels exactly like what is described above....

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