Boost fluctuation

[Brock31]

This is a '04 wrx wagon. "stage 2" type setup


I'm getting a significant boost fluctuation at part throttle (~50-60%). What appears to be happening is that my WGDC's are set up for quick spool, but at part throttle, the boost level I am hitting is overshooting the target for that throttle/rpm range. I am logging positive boost error numbers and then immediatly after negative boost error numbers. This is causing my logged WGDC's to go from 55% to 32% then back to 55% in this one throttle/rpm spot. My TD's are pretty much factory settings.

Any advice would be appreciated.

Thanks,
Brock

[elevenpoint7five]

Your WGDC at 50-60% throttle should be different than your WGDC for 100% throttle. Your target boost should be different as well. It sounds like the target boost is spot on, but the WGDC's are all messed up.

[spulbi]

Your wastegate arm is too tight. Loosen it a couple of turns and see if that takes care of the fluctuation.

[Brock31]

Target Boost is spot on. I'm holding ~ 18psi till about 5800 then tapering to 15 at redline.
My understanding ,in regards to getting quicker spool, was to ramp up the WGDC's as you approach 100% throttle. In the RPM/ Throttle area where the surging is happening has WGDC's that go from:

23.8 47.3 57.8 57.8

The boost is overshooting in this area?

[elevenpoint7five]

Then lower the WGDC. What WGDC do you have in the 100% column?

[quazimoto]

Post screenshots of your boost maps.

[Brock31]

Originally Posted by dumdum

Post screenshots of your boost maps.

At the risk of sounding like an idiot, I don't know how to post a screenshot

[Brock31]

100% column from 2000 to 6500 rpm
68
68
64.8
57.8
57.4
58.2
69.5
71.9

[idipskoalmint]

Originally Posted by Brock31

At the risk of sounding like an idiot, I don't know how to post a screenshot

Alt + Print Screen

That will copy the image of the foreground window to the clipboard. Open up any image program (Start > Run > "mspaint") and paste. Save the image.

Upload the image to a site like Imageshack.

Insert the picture URL between [img][/img] tags

[Ysidro]

Mine does something similar. The turbo dynamic would give me nice positive numbers then bam! I get a negative overboost number like -160 or something like that then goes back to a positive numbers again.

Take alook at your Turbo Dynamics low course gain table or something like that, lookup the negative numbers thats affected and decrease the correction percentage that corresponds to that number in the scale, in small increments.
Then go out log, check, repeat until you are at your desire target.

you could adjust the wgdc but its also going to affect other values and change your target. this is more like a fine tuning. see if that helps.

goodluck

[Brock31]

Here are images of my WGDC and Target Boost maps for reference

Target Boost



WGDC

[elevenpoint7five]

WGDC is too high in those regions. Lower it. You're not ramping it up like you said, you're just running too high of a duty cycle at 50% throttle. Try something like 15,25,35,40,50,60,65,68. That's just looking at your 2000 rpm from 12 to 100. Then from there just keep similar ratios throughout the rest. I've never been in your car, driven your car, anything, so anything you use those numbers for is at your own risk I assume no responsibility.

[Brock31]

I scaled back my WGDC's to a more tapered look. I logged a few runs and WOT is still fairly solid. I didn't change my 100% WGDC's at all. I had the Romraider dashboard up reading my manifold relative pressure and it showed a max boost of 24.5 not good. Unfortunately I wasn't logging when that was shown. Apparently the cooler weather here tonight (50 F)is maybe playing a role in that.
Also, some surging is still occurring in the 3000 to 3500 range. I've still got work to do.

That spike freaked me out though.

[elevenpoint7five]

http://www.romraider.com/forum/topic1814.html

Read that.

Basically your understanding of boost control seems to be off. You don't need a taper. I could run 0 WGDC everywhere except for 100% throttle, then when i floored it, I would get whatever I have plugged in at 100%. Not saying you shouldn't taper it, but the taper should be consistant with the target boost, not with your WOT column.

Also, the spike may have been RR acting funny. It does that from time to time. But keep a close eye on it.

[Brock31]

Its been a while, but I have read that. It may be a bit of frustration on my part.
The idea I was going for, and I'm sure everybody else is too, is to get the quickest spool and hold boost the longest. What appears to be happening is that boost is coming on slower than the basemap specifies. Positive boost error. The TD tables then come into play to try to bring boost to where the basemap wants, but then overshoots the mark. Now negative boost error. It seems like the WG isn't reacting quick enough or something.

I do have a Grimmspeed BCS. Could the WG arm need adjustment? Too tight?

[Brock31]

double post

[elevenpoint7five]

You need that much WGDC for 19psi on a GS? If anything I'd say the arm might be too loose...

Messing with the TD Continuous might help the "quickness".

[Brock31]

Originally Posted by elevenpoint7five

You need that much WGDC for 19psi on a GS? If anything I'd say the arm might be too loose...

Messing with the TD Continuous might help the "quickness".

I just upped the WG duty correction in the upper boost error range to try to help with that. I also flattened out and significantly lowered my max WGDC table. I guess I'm sort of starting over here .

time for bed

[elevenpoint7five]

Lol! Sounds like tuning boost! I can't tell you how many times I've gotten frustrated with a car not doing what I want. I would leave it alone for a bit, or even just drive around and think about why, but by the time I was back to tuning it I had forgotten what I did or it didn't make sense anymore so I'd have to start all over. It seems to happen the most with getting boost under control. Good luck!

Andy

[Brock31]

If I increase the Max value in by TD continuous table like this:
-3.87 -1.93 -0.77 -0.39 0.00 0.39 1.55 4.00 6.01
-5.51 -2.20 -0.80 -0.30 0.00 0.20 1.21 7.00 25.00
will the increase in the positive correction area cause a more dramatic swing in boost? Or will it allow the WGDC table more "room" to correct the boost errors?

[quazimoto]

Originally Posted by Brock31

Here are images of my WGDC and Target Boost maps for reference

Target Boost



WGDC

Why are you trying to run 19 psi at redline with the TD04? That need to be like12 or 13psi. Thats probably half you problem. Also way too much WGDC at 49% and 63% throttle

[quazimoto]

This is what my TD04 maps looked like with a GMBCS:

[Brock31]

Originally Posted by dumdum

Why are you trying to run 19 psi at redline with the TD04? That need to be like12 or 13psi. Thats probably half you problem. Also way too much WGDC at 49% and 63% throttle

When i had my car on the dyno last weekend I was was dialing in boost at WOT. Having the target boost at 19 psi I realize is not acheivable, especially on the stock turbo. I was trying to get the boost to hold as long as possible and I was logging around 14-15 psi at redline. If I lower my target boost in that area will it still hold the 14-15 psi?

My WOT logs are pretty good as far as building boost and maintaining til redline. The part throttle boost is what has me confused.

It is clear that my WGDC in the mid range is too high. My understanding was that, to get quicker spool ( which is why I got the GS BCS) I wanted to increase the WGDC down low to keep the WG closed tight.

Is there a trade-off here between quicker spool and part throttle boost control?

[Brock31]

Originally Posted by dumdum

This is what my TD04 maps looked like with a GMBCS:

So you were running 99% max WGDC in the low rpm range? Wouldn't that cause a crazy overboost situation?

[Brock31]

These are the revisions that I made, but have not flashed yet.