strange boost occilation

[Broxma]

Need a little help figuring this one out so some background first is in order I suppose.

03 WRX Stage 2 XPT Map
Stock TD04 P&P
Gutted up
Catless TBE
Perrin EBCS running Interrupt

So before the P&P on the turbo I was running the EBCS in Bleed mode, hitting target boost everything was great except the spool was pretty slow.

So I P&P the turbo and run the EBCS interrupt mode, and I start getting wild Boost spikes, like up to 20 psi then dropping to 10.

So I cut the Dynamic Burst in half as per Jeff at Perrin, now I am hitting 17 psi but instead of it simply dropping down to say 14 and holding, it fluctuates between 12 and 17. Boosts up to 17, drops down, back up, repeat. Oddly, it only does this at WOT. If I am only about 75% throttle, it will hold at whatever the target boost is for that RPM, about 12 psi at 75%.

What tables specifically would affect that type of behavior? I haven't cut the WG Duty cycle down yet and that is my next step, but I was hoping some uber tuner with more experience than me might have some idea's.

/Brox

* Registered users of the site do not see these ads.

[quazimoto]

Are you still using the restrictor pill?Have you tried adding more preload to the wastegate arm yet?Are you using just the plain XPT or the GM XPT map?

[Broxma]

I don't have the restrictor pill in as per interrupt style install instructions from Perrin. Have not set more preload on the wastegate. I am running the normal XPT map and adjusted the settings myself. I would be interested to know what changes are made to the XPT map for running the GM BCS as it should be the same.

From what Jeff said, the most important table when adjusting for interrupt control is the Dynamic burst. Cutting those numbers in half was what was suggested and that certainly did cut the spike out. WG duty is somewhat important but that one is honestly easy to tune for. I am just wondering how many of the tables affect the wastegate operation other than those.

My plan now is to reflash to the stock map and set the EBCS up in bleed mode and see if the boost normalizes. I have already ran the WG straight from the Boost source and I got an exact 8 PSI. I want to run an MBC at about 12 pounds just to rule out any possibility of a mechanical, non-ECU problem.

/Brox

P.S. Taking advice from a guy named "Dumdum" has historically not been a good idea. But honestly, I do appreciate it.

[brettm]

you need to drop your max WGDC table to about 70-75% of what it is set to for a bleed style bcs. Also the TD continuous table is more important than the burst one. Cut that table down by about the same % as the Max WGDC table. You can then up the values from there. Always start more conservative and tune up rather than down.

Here is a link with more info:
http://www.enginuity.org/viewtopic.php?t=1814

[Broxma]

Copy. I was just reading about the drop on the WGDC somewhere else and am planning on tuning it tonight. I didn't know about the necessity to drop the continuous table which doesn't surprise though.

Thanks for the help.

/Brox

[Broxma]

Wanted to post an update so people could possibly tune a Perrin EBCS themselves if they so desire.

First I Took the WGDC table and cut all the numbers by 75%. I also took both Dynamic tables and cut those numbers by 50%, making sure I kept my negative numbers negative.

I found stretch of road allowing for WOT pulls and places to stop to tune. My first run was showing boost error of about 9 lbs, RPM dependant. I started to blanket raise the WGDC up incrementally by 10%. The higher the WGDC numbers got, the smaller % I used since my base numbers were getting larger.

I compared the Boost Error numbers by RPM to my WGDC map and found places I could increase WGDC by RPM to achieve target boost at lower RPM's.

If I found that I was getting fluctuation in boost at certain RPM's, I would Decrease the Burst/Cont duty cycle for the given RPM.

Since this was my first real road tune it is taking me a long time but so far my results are showing good progress. I have cut my boost error down to less than 2 Psi after about 2 hours of tuning.

I ran into a problem where my IAM started to drop from 16 down to 12 at WOT for some reason. I was at about 1/8 tank of gas and per my own mantra, I figured easiest solution first so I topped it off with some 93 octane. 3 logs later I haven't dropped my IAM's at all.

I figure about 2 more hours of tuning and I will have the boost totally under control. Next step will be tuning the Ignition map a bit more.

I certainly don't have the knowledge to do this to someone else's car but for my own car I feel pretty good about it, plus I work cheap.

Thanks for the replies I got they did really help me out alot. I was beginning to doubt that anyone actually read the EM forum at all, which to me, is mind blowing.

/Brox - Amateur Open Source Tuner in Training

[Not-EWRX]

hey let use know how the tuning of the ignition map goes. I did this same process as you when first tuning my car for my bcs. It's fun to make changes and see results. I need to retune it though I'm over boosting again with all the colder weather

[brettm]

Originally Posted by Not-EWRX

hey let use know how the tuning of the ignition map goes. I did this same process as you when first tuning my car for my bcs. It's fun to make changes and see results. I need to retune it though I'm over boosting again with all the colder weather

You should tune the intake temp compensation table for this. No need to retune everything.

Also if you are planning on tuning fuel at all you should probably do this before timing.

[Not-EWRX]

I have a good starting point, I have a XPT map that was road tuned by ev8siv3. I have just been noticing some hesitation in the 2.5k-4k range. The boost is kind of jerkey and and unsmooth. I hope I can get some time to look at it this weekend.

[Broxma]

Just wanted to keep track of things and I am unlikely to do so elsewhere.

I got my boost error completely under control. My WOT boost error, once the turbo hits full pressure, is within 1/4-1/2 PSI +/-. I cut the burst and continuous dynamics down just the slightest bit more to fine tune the target boost. I'm not sure if I can dial in the boost any further, but I will be doing many more tuning pulls this weekend.

The dropping IAM problem was totally solved with the full tank of 93. I have seen a max KC of 8 which coincides with full advance of ignition timing. I haven't found a table that mentions this KC value so I assume it is hardcoded but am still looking. I am also working on finding out how much timing is too much timing. Currently I am running 8.09 advance, and the increase table is set at .35. I am going to drop the increase table number and raise it in very small increments.

I am not sure if it is a problem but the Initial IAM on the map I got is set at 16. This is fine if everything is running good and you know it, but I don't like the ECU allowing max values to run after I make changes so I set the initial to 12 and allow the ECU to regain the 16. This way I know the car is actually happy.

I'm currently in the process of looking at a few other maps I have collected and comparing them to decide on the best timing maps. This is probably going to take me a while.

On a side note, I did have a guy with a Turbo DET20 240 ask about my car. He wanted to know what I had done and how much I put into it. After he found that I had put less than 800.00 in power mods on it and I had tuned it myself, he seemed kinda pissed, considering how much he spent on the JDM motor, and that he had a much slower car.

Again, I am still amazed at the abject lack of people who actively are tuning their cars and posting into the EM forums, especially considering the relatively inexpensive open source methods available. I was hoping the EM forums would be a trove of really experienced OS tuners who say around and schemed up new ideas and plans for innovative tuning and whatnot, but I think Halo 3 is taking up too much of peoples time.

I think I'll just stay in the garage.


/Brox

[brettm]

KC is your knock correction and should tie very closely to the timing advance table (IAM/16 * Ignition advance = KC). There are probably other values in there that I am forgetting but those are the basics. As far as forum activity nasioc em forums really aren't that busy. You should hit up the enginuity forums as they are much more active.

[Broxma]

I've been over at the Enginuity forums but haven't spent alot of time there.. The OpenECU forums are pretty dead it seems as well.

I knew what KC was, I just didn't know how it was figured, but the formula makes alot of sense. At 16 IAM I do get 8 KC, and my max ignition advance is set at 8.09. I'm getting ready to tune for the next few hours before rush hour gets started.

/brox

[dynamix]

Brox - I am suprised that more dont tune opensource either. Especially as going the ecutek route gets really expensive when minor maps tweaks are needed or wanted for fuel changes.

Enginuity is a good tool to do the job and being the curious type and working with computers it is a easy step to start tinkering to understand cause and effect before trying more advanced techniques.

[Broxma]

Yesterday I had another NASIOC guy come over so we could flash an XPT Stage 1 map on his stock car. Should have been np, flash it, few logs, good to go.

Not so much.
I looked at the XPT stage 1 and stage 2 maps and compared them. Stage one has higher boost, and for longer than the stage 2. Stage 1 has way more timing advance, and has more aggressive fueling. To me, it looked like the maps had been switched or something. So, being one to follow rules, I flashed the Stage 1 map on the car, went for a spin, and started logging. 2nd gear it seemed happy but it started pulling timing about halfway through, although IAM's stayed at 16. Sometime between the 2nd and 3rd gear pull though, it dropped IAM down to 12 at 3200prm/1.8. took it back to the house, and looked at the map, figured I could smooth some of the fuel map, which has some wild swings in AF at totally random spots, on at the spot we dropped IAM. Reflash, back out, and it dropped to 8, same exact place. Now confusion set it, flashed stock map back on and figured id work on it later.

Needless to say, I am currently not to confident in any map I find there, be it XPT or personal custom tune. I am going to buy a staged map from XPT just to compare the differences between the paid for and free map. Im sure it will be extensive, considering how little work went into the free stage 2 map.

MotS? Maps are alot like free drinks from strangers in a bar. It's probably alcohol, but you have no idea how good it works.

/Brox

[WolfieTT]

thanks for this thread