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Old 06-01-2010, 08:29 PM   #1
RubbleDTD
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2004 PSM WRX wagon
18Gxt

Default ECU learning and Clutch Shudder...

***SOLVED*** Root cause of shudder was accumulating FLKC during the clutch engagement periods that was driven by too little timing (see post #3).



I apologize if this specific topic has been discussed before. If I missed something when searching, please point me in the right direction and I apologize in advance for wasting your time.

My post has everything to do with the ECU, please hang in there and read the whole thing!


Background:

Car currently has 80k miles. 20k miles ago (@ 60ish k miles) I installed a ACT streetlite LWFW, ACT HDMM organic clutch, and HDPP. I chose this setup because I had just been tuned with the VF-39 and I wanted a clutch setup that felt more "defined". The OEM clutch felt funny to me because it always engaged at the very top of the travel and felt like it lacked "grab" (I know grabby = drivetrain shock and eventually broken gears, but I know how to drive and I wanted a clutch that had a more defined feel and grabbed when you wanted it to versus the OEM clutch which felt like it was landing in a pile of fluffy pillows every time you let it at the end of a shift). My friend had this identical setup on his 04 WRX and I loved the way it felt. 3 weeks go by the new ACT clutch, PP and LWFW are installed.

I love the feel of this clutch/FW setup. The engine sheds revs quickly and the car is a blast to drive in a spirited fashion. However, ever since the upgrade, DD and driving in traffic have taken a bit of a hit. The clutch likes to chatter if you slip it gently when starting in first, and on/off gas in 1st and 2nd gear is noticeably more jerky (even with Group N motor mounts, trans mount, and Una's sexy rear end from TiC). I have been driving the car with the new setup for 20k miles now and had (glady) accepted the trade-off in DD and stop/go traffic for the much improved clutch feel & feedback.


Recent Events:

I recently changed my Fog light bulbs and to do so I pulled the negative terminal on the battery per the provided instructions. When I drove the car afterward it seemed all my drive-train related problems had vanished! The clutch no longer chattered under light starts in 1st, and the on/off gas jerking in 1st / 2nd was virtually gone. Then it hit me; perhaps the ECU learning is the culprit behind my minor low-speed drive-ability woes.

Over the next 150 miles the clutch started its old ways again: chatter in 1st when slipping the clutch below 1700 rpm and the jerkiness in 1st / 2nd gear was returning. I decided to reset my ECU again to see if it made a difference. Voila! right after the reset everything was smooth as butta... Over the next 100 miles I was careful to pay close attention to the way the car behaved and here is what I noticed:

Right after ECU reset:
-with very light application of throttle in neutral, the rpms rise very smoothly from idle (750rpm) and will hover right around 1500 rpm.

100(ish) miles after ECU reset:
-with very light application of throttle in neutral, the rpms rapidly jump up to 1700-1800 rpm and then smoothly drop back down to 1600 rpm.


The car currently has seen about 200 miles since the last ECU reset (mentioned above) and I cannot get the rpms to smoothly rise to 1500 rpm as the engine did right after the reset. No matter how easy I am on the throttle, the minium rpm I can get the engine to hold above idle is 1600 rpm and that's after it jumps up to 1800ish rpm. I believe this engine behavior is to blame for the jerky on/off gas transitions; In a parking lot I will lightly apply gas from a roll in 1st and the rpm suddenly tries to jump to 1800 and the car shudders. The behavior exhibited right after the reset (smoothly rises to 1500rpm) seems like it would help avoid the jerking and perhaps improve the clutch chatter as evident directly after an ECU reset.

So to all you EM/Tuning experts out there; Is it plausible for ECU learning to contribute to the low-speed drive-ability issues I mentioned (clutch chatter during light starts in 1st, on/off gas jerking in 1st/2nd)? If so could it be corrected with a re-tune? Is there something seriously wrong with the behaviors I described? Any input would be greatly appreciated.

Again, the drive-ability issues mentioned are not very severe and I have coped just fine but it would be nice to find out if a potential solution exists.



Car info / mods are listed below:

2004 WRX wagon (felmale front axels)

Engine:
-SPT intake
-VF39/up-pipe/Catted dp/exhaust/650cc injectors/walbro
-Protune by Seth @ Moonperformance Lake Placid, NY circa september 2008

Drivetrain:
-Motor mounts
-Trans mount
-Unabombers sexy rear
-ACT LWFW (13.9 lbs, no CELs)
-ACT HDMM organic clutch
-ACT HDPP
**FW/clutch/PP installed 5k miles after the pro-tune

Note: i have about +/-13 degrees of backlash in the prop-shaft where it meets the R160 with the e-brake engaged. Does this sound normal? seemed like a lot to me.

Again, thanks for reading and please don't hesitate to post if you have any thoughts!
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Last edited by RubbleDTD; 10-19-2012 at 07:07 AM.
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Old 06-02-2010, 09:20 AM   #2
BLSTIC
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One potential culprit could be your throttle position sensor. We were running into issues on our RWD H22A powered speedway car (don't ask). It would drive like ass at light loads, we initially blamed this on the throttle linkage (which opened it a lot for little pedal travel), but adjusting the TPS so it read a higher voltage (more opening) stopped the problem. The problem was the injector overrun cutoff when hot, it would cut the injectors at zero throttle above 1100 rpm or so. We just told it where zero throttle ACTUALLY was.

I guess one way to tell would be to reset your ECU and calibrate the TPS. In my 1996 Falcon (an Australian vehicle which you stateside boys never got) the process was to turn the key on for 5 minutes without any throttle (engine off, ignition on), then hold the throttle flat for 5 minutes (again engine off, ignition on).
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Old 10-18-2012, 07:51 PM   #3
RubbleDTD
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Fixed (more than 2 years later).

Root cause turned out to be too little timing. I had always gotten minor FLKC corrections after 50-100 miles of driving in learning view but hadn't paid much attention to it.

When tuning for the 18G I rescaled the MAF and actually added in 7% additional timing in the trouble spots (between 1200 and 1800 rpm & .50 g/s which is clutch engagement territory) and now my FLKC table is completely zeroed out and the chatter is gone for good.
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Old 10-18-2012, 08:18 PM   #4
Frank_Zuccarini
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Congratulations!
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Old 10-19-2012, 03:32 PM   #5
BlazeRex
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Curious : How much timing were you running before vs. now in the specific load areas that had knock? Also, whats your min load FLKC engagement?

I'm not sure how long you've driven it around, but sometimes it takes a while for that FLKC to show up. Also, dont forget, you changed turbos and MAF scaling. Which can affect load values which affects timing.
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Old 10-22-2012, 08:19 PM   #6
RubbleDTD
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Quote:
Originally Posted by BlazeRex View Post
Curious : How much timing were you running before vs. now in the specific load areas that had knock? Also, whats your min load FLKC engagement?

I'm not sure how long you've driven it around, but sometimes it takes a while for that FLKC to show up. Also, dont forget, you changed turbos and MAF scaling. Which can affect load values which affects timing.
Here are some before / after screen shots of my Timing Tables. Aside from the timing tweaks below, a bigger part of the problem was that my old tune (which was a pro tune) had grossly under compensated injector scaler and latency values. Target AFR was achieved by applying massive MAF scaling corrections which threw off my g/s readings. The "false" g/s readings, would achieve the AFR targets with the improperly scaled injectors, but also shifted all my CL timing values to the left.

Correcting the Injector Scaler & Latency solved 70% of the FLKC. The changes you see below mopped up the remaining 30% of FLKC accumulations.

What is interesting about this issue is that I did not notice the shudder / FLKC on my old tune until I installed the LWFW.


Timing Before:




Timing After:




Timing Advance for Reference:

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Old 10-23-2012, 02:42 AM   #7
NSFW
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Thanks for the update.

I just looked at a stock 04 WRX ROM, and the base timing is about like yours, but the advance table is zero at 0.7 g/rev and below. So in other words you seem to be running about 7 degrees more than stock at 0.7 g/rev and below. It looks like someone took the "flatten your advance table" advice without making the corresponding changes to the base timing table...

I'm not sure that's BAD, but I'm not sure it's GOOD either.

Consider zeroing out the left column of your advance table to see how the engine runs with timing that's more like stock. I know that's the opposite of the change you just made to fix your problem, but I still think it's worth trying.
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Old 10-23-2012, 06:53 AM   #8
RubbleDTD
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Quote:
Originally Posted by NSFW View Post
Thanks for the update.

I just looked at a stock 04 WRX ROM, and the base timing is about like yours, but the advance table is zero at 0.7 g/rev and below. So in other words you seem to be running about 7 degrees more than stock at 0.7 g/rev and below. It looks like someone took the "flatten your advance table" advice without making the corresponding changes to the base timing table...

I'm not sure that's BAD, but I'm not sure it's GOOD either.

Consider zeroing out the left column of your advance table to see how the engine runs with timing that's more like stock. I know that's the opposite of the change you just made to fix your problem, but I still think it's worth trying.
When I flattened the advance table I was sure that the sumation was equivalent to stock. I added the stock base + advance in excel, subtracted 7 deg from .7+ g/rev and added 7 deg in the advance table. Any deviations from stock in the advance region would be in response to tuning for the 18G.

Last edited by RubbleDTD; 10-24-2012 at 07:24 AM.
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Old 10-24-2012, 06:55 PM   #9
BlazeRex
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What I think NSFW is getting at is the advance table isnt set at zero below .7 load, even though the map stops at .7
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Old 10-24-2012, 09:44 PM   #10
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Right... At loads below 0.7, the ECU just uses the values in the 0.7 column. So at 0.4 g/rev, you're running 7 degrees more than stock.

You could fix this by changing the leftmost cells of the advance table to 0, and then change the leftmost column headers to 0.54 and 0.7.
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Old 10-26-2012, 01:50 PM   #11
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I'm having the same issue with about the same parts if i uploaded my accessport map could you take a look?
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Old 10-26-2012, 03:09 PM   #12
RubbleDTD
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Quote:
Originally Posted by NSFW View Post
Right... At loads below 0.7, the ECU just uses the values in the 0.7 column. So at 0.4 g/rev, you're running 7 degrees more than stock.

You could fix this by changing the leftmost cells of the advance table to 0, and then change the leftmost column headers to 0.54 and 0.7.
Quote:
Originally Posted by BlazeRex View Post
What I think NSFW is getting at is the advance table isnt set at zero below .7 load, even though the map stops at .7
The values from .7 and below ARE the same as my stock map as shown (with the exception of clutch engagement zone changes).


This thread shows the factory Timing tables for an 02 WRX (see post #11):

http://forums.nasioc.com/forums/show....php?t=2039943
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Old 10-26-2012, 03:13 PM   #13
RubbleDTD
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Quote:
Originally Posted by DjTalan View Post
I'm having the same issue with about the same parts if i uploaded my accessport map could you take a look?
PM sent.
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Old 10-26-2012, 03:17 PM   #14
jthatch12
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Quote:
Originally Posted by RubbleDTD View Post
PM sent.

Iterationnnnnnnnnnn
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Old 10-26-2012, 03:19 PM   #15
RubbleDTD
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Quote:
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Iterationnnnnnnnnnn
I know... I know... Your gonna have to come to me man. You free this weekend?
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Old 10-26-2012, 03:41 PM   #16
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Quote:
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I know... I know... Your gonna have to come to me man. You free this weekend?
Tomorrow after 1, talk to the wife
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Old 10-27-2012, 01:27 PM   #17
BlazeRex
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Quote:
Originally Posted by RubbleDTD View Post
The values from .7 and below ARE the same as my stock map as shown (with the exception of clutch engagement zone changes).


This thread shows the factory Timing tables for an 02 WRX (see post #11):

http://forums.nasioc.com/forums/show....php?t=2039943
I hate to tell you, but you are 7* above stock in those areas. Look at post 13 on the linked thread. It shows exactly what NSFW and I are saying.
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Old 12-18-2012, 11:47 AM   #18
RubbleDTD
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Quote:
Originally Posted by BlazeRex View Post
What I think NSFW is getting at is the advance table isnt set at zero below .7 load, even though the map stops at .7
Quote:
Originally Posted by NSFW View Post
Right... At loads below 0.7, the ECU just uses the values in the 0.7 column. So at 0.4 g/rev, you're running 7 degrees more than stock.

You could fix this by changing the leftmost cells of the advance table to 0, and then change the leftmost column headers to 0.54 and 0.7.
I understand what you are saying now. The timing advance in the minimum load colum (.7) applies to all loads less than that in the base table. I can't believe I missed that before.

Now I have to figure out why my car likes 20% more timing in the low load zones. My FLKC table was significantly improved when I "incorrectly" flattened the advance table.
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