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Old 03-14-2013, 04:53 PM   #1
Rymar
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Default 2012 Impreza Limited 2.0: Fix for Hypersensitive Accelerator Pedal

While my 2012 Impreza Limited 2.0 is a great car in many ways, the hypersensitive accelerator pedal is driving me a little bit (more) nuts. As with many modern cars, Subaru has amped-up the feeling of the the accelerator pedal by mapping most of the throttle plate opening (and CVT transmission response) into what feels like the first 1/16" of pedal travel. Makes me wish for the days of cable connected accelerator pedals...

As I see it, there are 4 options:

1) Ignore it (not happening!)

2) Take the car to my Subaru dealer, and complain, escalating to corporate after the dealer says there's nothing they can do. Then, hope that they release an ECU update which has a "non-hypersensitive" accelerator pedal mode.

3) Buy a "Throttle Controller", which plugs between the (Denso?) DBW (Drive By Wire) accelerator pedal and the ECU. These apparently reset on every start cycle to the "normal" position, which is not what I want. Also, I don't think they are maintaining the redundant nature of the Denso accelerator pedal, which has two independent outputs which must match, or the ECU throws an error. In other words, I think they use a single microcontroller to provide both signals to the ECU, so if that fails...

4) Buy the ECUFlash and Tactrix Openport 2.0 (don't know yet whether they support the 2012 Impreza ECU), and remap the accelerator pedal response, as outlined in this thread:

http://forums.nasioc.com/forums/show....php?t=1537010

5) Design my own throttle controller (I am an electrical engineer) which "dulls" the first section of the accelerator pedal response.

Any other ideas or info?

Thanks!
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Old 03-15-2013, 11:53 AM   #2
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I think my gas pedal response changed after I got the reflash for that temperature sensor recall a while back. I agree it was too sensitive but I really think that it changed after the reflash.

Did you get it done?
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Old 03-15-2013, 12:16 PM   #3
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No, I haven't had the ECU update done; the description on the recall notice says it only affects the display of an error if the engine fails to come up to temperature fast enough, but maybe they did make some other tweaks to the mapping at the same time. I did have an ECU reset done by the dealer when I only had about 3K miles on the car, and it did seem to change the throttle response for a while; I think that may have had to do with the ECU re-learning where the "zero" point (throttle closed) is in terms of voltage from the gas pedal. I guess I should give Subaru a chance to respond to this issue...

I did find out that RomRaider doesn't have an ECU flash definition file for the USDM 2012 Impreza 2.0 CVT (at least not yet), so the ECUFlash/Tactrix solution seems less possible. I'm in awe of the amount of work it must take to reverse-engineer the contents of the ECU flash memory!
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Old 03-15-2013, 01:38 PM   #4
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In my opinion, if you're going to do it, do it right and go with option #4

You will literally be waiting for years and years before someone comes out with a definition for your ecu, UNLESS you do what I did: I placed a $300 "bounty" on my ecu and had the definitions in days!

If you go that route, besides having access to fiddle with your accelerator tables, you have access to everything else too!

I can post images of my tables, but I have a 2013 with a manual, so I imagine mine would be different than the ones for a CVT.

Here's the thread for my ecu on the romraider forum:
http://www.romraider.com/forum/viewtopic.php?f=8&t=9126
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Old 03-15-2013, 04:05 PM   #5
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So, what did you want to tweak? Did it work as expected?
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Old 03-15-2013, 06:16 PM   #6
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I own RalliSport Racing and figured after I was finished using it for R&D, I would throw in a turbo just for fun. When it came to EM, I wasn't overly excited with going piggyback (and the headache that comes with it), so for the money spent using romraider to tune was a no brainer.

I only run 92-93 octane, so I've added in a little timing and leaned out the incredibly rich fueling in the top end a tad. I don't feel comfortable going much further without a wideband though.
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Old 03-15-2013, 10:00 PM   #7
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OK, maybe this is a bit off-topic, but I thought Subaru stated that the FB20 engine in the 2012-2013 Impreza was specifically "lightened" so that it was not suitable for turbocharging.

Also, by "incredibly rich fueling" are you implying that the stock engine could achieve better gas mileage by leaning the mixture/advancing timing at high rpms, and running premium gas? I'm definitely interested in any table modifications you made! Before/after after would also help in seeing whether the CVT vs manual tunings are different.

I'm assuming you had no problems using Tactrix Openport 2.0/ECUFlash with your 2013 Impreza. Always good to know that flash programming tools work reliably with a particular ECU.

You set the bar kind of high at $300 for the RomRaider bounty, though! I was thinking of offering $100... maybe now that yours has already been reverse engineered, this one will be easier. First, though, I'm having the dealer upgrade the ECU to the latest firmware, and give Subaru a chance to respond.
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Old 03-16-2013, 12:28 AM   #8
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Well, I never said slapping a turbo on an engine with 10.5:1 compression was a good idea... I figured that someone would eventually do it and I just wanted to be the first for bragging rights; at this point, no matter what you do to an EJ, you will never be the first. With the new FB20, I already have a number of firsts under my belt and wanted to keep the trend going. Unfortunately it's a moot point though, as I'm far too busy take on such a project.

This is what I mean by incredibly rich fueling in the top end:



If you drive like a normal human being, you will be at or near stoich, so fuel economy wouldn't be a concern. But look at how rich it gets as the RPMs/load climb.

I had to wrestle with the program a bit before I got it working, but we'll just call that operator error. Anyone that's more computer savvy shouldn't have a problem.

I've seen guys offer a $20 bounty and get attention, so I think $100 is more than adequate. I just went overkill with the bounty because I was impatient and wanted to be given priority... it worked.
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Old 03-16-2013, 11:18 AM   #9
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Quote:
Originally Posted by myrt1987 View Post
I think my gas pedal response changed after I got the reflash for that temperature sensor recall a while back. I agree it was too sensitive but I really think that it changed after the reflash.

Did you get it done?
i also just had a ecu flash done and i think the car is easier to drive now and throttle response is more normal (5speed)
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Old 03-16-2013, 11:26 AM   #10
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Quote:
Originally Posted by blk6s View Post
Well, I never said slapping a turbo on an engine with 10.5:1 compression was a good idea... I figured that someone would eventually do it and I just wanted to be the first for bragging rights; at this point, no matter what you do to an EJ, you will never be the first. With the new FB20, I already have a number of firsts under my belt and wanted to keep the trend going. Unfortunately it's a moot point though, as I'm far too busy take on such a project.

This is what I mean by incredibly rich fueling in the top end:



If you drive like a normal human being, you will be at or near stoich, so fuel economy wouldn't be a concern. But look at how rich it gets as the RPMs/load climb.

I had to wrestle with the program a bit before I got it working, but we'll just call that operator error. Anyone that's more computer savvy shouldn't have a problem.

I've seen guys offer a $20 bounty and get attention, so I think $100 is more than adequate. I just went overkill with the bounty because I was impatient and wanted to be given priority... it worked.
so how did you tune your car?
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Old 03-20-2013, 02:06 AM   #11
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OK, so I went with option #4, ordered and received the Tactrix Openport 2.0 cable, and uploaded the flash image from my ECU.

I also have an appointment scheduled with my dealer to have the WQC-39 (temperature DTC indication) update done to my ECU this Thursday; I wanted to look at the accelerator curves before and after the update to find out if they really did change, and how much.

I used the ROM metadata files for blk6s' 2013 Impreza (thanks!) to analyze my ROM image; most of the tables are at different addresses in memory, but the two tables I am interested in were at the same place in my 2012 ECU, so I lucked out. I'll post my updated ROM file on RomRaider after I get the update (and offer a bounty for decode).

I'm assuming that the 2013 Impreza maps will be identical to the ones in the update to my 2012 CVT; I'll check to make sure after the update is done.

As noted in other threads, the accelerator to throttle plate mapping is done in two steps, the first from accelerator position to "Raw ECU" value, and the second table from this value to the "Torque" value, which should roughly correspond to throttle plate position.

In both ROM images, the second table is identical. Since this is across two model years, and both MT and CVT models, it seems to indicate that this table is dependent only on the engine characteristics (or at least something that hasn't been tuned at all between the two versions).

Anyway, the first table (pedal to Raw ECU) is very different. Here is the first table from my 2012 Impreza CVT, before the update:



and here is the same table from the 2013 Impreza MT:



At first glance, they look roughly the same.. but look at the row of input values on the 2012: they are much closer together for low values, compressing the accelerator pedal active range.

Finally, here is the common table which translates the "raw ECU" values into requested torque:



So, how to analyze what these tables mean for accelerator pedal feel?

I decided to write a bi-linear interpolation function in Excel, which should do roughly what the ECU does in looking up values from the tables, and chain the two tables together, creating a composite response. For each car, this looks like a 3D surface, with engine RPM on one axis, accelerator pedal position on the other, and requested torque output on the vertical axis.

The short answer is: yes, the version of software in my 2012 Impreza CVT ECU has a ridiculous accelerator pedal mapping, and the 2013 map is much better.

Here is the composite map from the 2012 software. Note how steep the curve is, and how the torque request maxes out at very small pedal positions, especially around 1200 RPM.


Compare this to the 2013 Impreza MT composite map. While it's not really what I would like to see, the slope is a lot more gradual below about 2000 rpm.




So, if I'm still not satisfied after the ECU upgrade, I'll just tweak it to what I want!

These tools are freaking awesome!!!
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Old 03-20-2013, 08:12 AM   #12
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Fascinating tables and data. No wonder this 2012 2.0i 5MT I DD has always felt like there's basically no difference between 20%-60% throttle at regular rpms.

Thanks for the write up, keep us updated if the dealers reflash results in any changes.
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Old 03-20-2013, 09:30 AM   #13
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Quote:
Originally Posted by jbulls93 View Post
Fascinating tables and data. No wonder this 2012 2.0i 5MT I DD has always felt like there's basically no difference between 20%-60% throttle at regular rpms.

Thanks for the write up, keep us updated if the dealers reflash results in any changes.
They just did some update on mine last week and the throttle mapping changed, it is much more linear now
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Old 03-20-2013, 09:40 AM   #14
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Quote:
Originally Posted by flyboy1100 View Post

They just did some update on mine last week and the throttle mapping changed, it is much more linear now
Ic, which transmission do you have? Are you saying that based on feel or viewing the map?
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Old 03-20-2013, 11:02 AM   #15
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Quote:
Originally Posted by jbulls93 View Post

Ic, which transmission do you have? Are you saying that based on feel or viewing the map?
I have no way to view the map, but I do need to press the peddle further to get the same response. I have the 5mt. It is especially noticeable when starting from a stop (it is easier and less touchy) and all my downshifts. I'm used to it now and I like it much better.

I wish I knew what the software version was
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Old 03-20-2013, 02:30 PM   #16
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Yup, those mappings are every bit as craptastic as the ones I showed in the original DBW reprogramming thread.

Before you reflash your own tweaks, I would ask around on the RR and OSECU forums to find out if it's safe to use defs that only cause those two tables to appear.
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Old 03-21-2013, 11:17 PM   #17
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The WQC-39 ECU flash upgrade was done this afternoon. On the drive home, I almost had myself convinced that there was a difference in the accelerator pedal feel, but... there wasn't.

After uploading the flash, I discovered that the accelerator map data was still in the same place (although the table descriptors moved around a little bit), but the map was identical to the one I had before. Still the same twitchy response. I think Subaru is probably still shipping the 2013 Impreza CVTs with this stupid map.

So, I opened the 2013 MT ROM file in RomRaider, and copied the "Requested Torque A (Accelerator Pedal)" table into my 2012 CVT ROM image, saved it, and then opened it in ECUFlash to program into my ECU. This is a particularly nerve-wracking thing to do, by the way. I first did a binary diff on the file, to make sure that I had only modified the memory range I expected. ECUFlash corrects the checksum the first time the file is opened. After a few failed attempts to connect (because I wasn't turning on the key at the right time), ECUFlash worked flawlessly.

Anyway, it transforms my car! Holy crap! It's going to take me a few days to get used to the fact that you actually have to press the accelerator pedal down to make the car go. I will probably try a few other maps as well; there is a strange surge in the acceleration when holding at about 1/2 throttle, which I'm sure can be eliminated.

I think what is being done is equivalent to the way that LCD manufacturers have a "showroom" mode, which amps up all the colors to try and sell TVs in the store. Car makers want to make sure the customer thinks that the car "feels powerful" on the test drive. In return, we get twitchy gas pedals which are hard to live with in everyday driving.

I'm actually considering putting in a simple "cable" mode, which simulates a mechanical cam and cable setup, which would have no dependency on RPM at all... what a concept!
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Old 03-21-2013, 11:24 PM   #18
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Yup, just like what I discovered and published years ago, you've just proven to yourself that manufacturers do stupid **** to sell cars and then it's up to use to fix them once we get them off the lot.

I'd encourage you to keep playing with the numbers. It doesn't look like the 2013 mapping is that good, just way better than 2012.
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Old 03-22-2013, 08:13 AM   #19
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Damn it. Very disappointing that they didn't alter the throttle mapping. I'm scheduled for the reflash today :-(
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Old 03-22-2013, 08:21 AM   #20
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I still think the pedal feels different. What used to happen in that first 1/8" of travel now takes 1/2". Still not much but im convinced it changed.

Having no idea throttle response would even be affected, its not like i was looking for it to change. I just noticed it after driving it home.

You be the judge.
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Old 03-22-2013, 01:38 PM   #21
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Remember that I only have before/after data for the CVT. If you have the MT, then it's quite possible that they did change the mapping.
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Old 03-23-2013, 01:19 PM   #22
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Well, nothing is ever as simple as it seems at first...

After driving the car for a day, there seems to be pretty good evidence that the TCU (Transmission Control Unit) has its own lookup table from accelerator pedal position to gear ratio. What happens is that for intermediate pedal positions (20% to 40%), the transmission upshifts, and the engine revs to about 3000 RPM. However, since I reduced the "torque request" in the ECU so much in this range, there is not enough throttle plate opening to actually accelerate! This is equivalent to leaving a manual transmission in a higher gear, and only applying enough throttle to hold at a constant speed.

EDIT: I just confirmed, by using Romraider logging to read the TCU as well as the ECU, that the transmission sees the accelerator pedal after conversion to 0-100%, and so it definitely has its own map of pedal to gear ratio.

I think the ECU, which is actually connected to the accelerator pedal signal voltages (there are two separate inputs for redundancy), is doing some processing to convert the voltages to a 0% to 100% range, and then sending the pedal position to the TCU BEFORE either of the lookup tables.

In the 0% to 10% throttle range, and 50% to 100% range everything works as expected: the cruising response and WOT response are very good.

Also, the Romraider and ECUFlash definitions are done! I offered a $100 bounty, and it got done overnight; I also donated $50 to the romraider site itself. It's incredible that these tools are available! There are actually 4 accelerator pedal tables in the ECU: the one which is used, plus 3 "SI-Drive" tables, which are not available in the US (have you ever noticed the word "SPORT" in the instrument panel display?). The table which is used matches "SI-Sport" mode. There is one more edit which needs to be done to the XML definitions, however: the 4th table, which is actually the one which is used, was not included in the first pass. This should be done shortly. The link to the definitions is:

http://www.romraider.com/forum/viewt...hp?f=34&t=9390

These are the definitions ONLY for the ECU image AFTER the WQC-39 emissions recall, for CVT equipped cars.

The table I have been editing is:

<table name="Requested Torque A (Accelerator Pedal)" storageaddress="FA08C" sizex="20" sizey="18">
<table type="X Axis" storageaddress="F9FF4" />
<table type="Y Axis" storageaddress="FA044" />
</table>



I also started thinking about what I have been doing: it would actually be possible to remap the accelerator pedal so that idle was when you held the pedal to the floor, and the car would go faster as you let up on the pedal! I better get the math right!!!

The possible legal ramifications are mind-boggling, so I just won't think about them...

I need to start logging data to determine the response of the TCU: I'll capture engine RPM, accelerator pedal, requested torque, and road speed. Speed and engine RPM will let me calculate the CVT gear ratio, and I can figure out how to modify the ECU accelerator map to deliver more torque in the ranges where the TCU has shifted the transmission to a higher ratio (effectively a lower gear).

The good news is that in the range which is so twitchy (0% to 10%), the TCU is doing the right thing. What I may do is go back to the default map, and start editing it to smooth out the pedal response in the 0% to 10% range only.

I will post the table data when I am done.

Last edited by Rymar; 03-23-2013 at 03:29 PM. Reason: Transmisson Info
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Old 03-23-2013, 09:15 PM   #23
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So, after some thought, I realized that without also reprogramming the TCU, the power from the engine, and the ratio selected by the transmission, would not match: the ECU is working with adjusted maps, and the TCU with its orignal maps.

So, I tried only changing the ECU accelerator pedal maps in the 0 to 10% pedal range; typically the transmission does not change gear ratios (at least not from the accelerator pedal input alone) in this range. Also, I think the TCU actually looks at how fast your foot is moving, as well just the value of the pedal position, to determine whether to upshift or not.

I used all of the original table from 10% and up, and used the 2013 CVT manual transmission table from 5% and down, and then defined the column headings for the intermediate values as 6,7,8, and 9%, to make sure there was a smooth transition. Here's what I came up with:



I need to drive the car for a few days until the idle speed relearn, and return to idle relearn, are complete, but I think this one will work.

On the freeway at 65, it is much easier to control crusing speed; and putting around at 30mpg to 40mph, the on-off throttle transitions are much smoother.

I would post the surface (see above), but it's actually pretty hard to see. There is just a flatter surface from 5% and under.

So, at this point, for the $169 it takes to buy the Openport Tactrix 2.0 cable, and the nerve it takes to reprogram your car's ECU, I think this is a reasonable compromise. I'll add one more post in a few days to confirm that this map is still working well after all the learning adjustments in the ECU have settled out.


Here is the data in a form which can be pasted into Romraider:

[Table3D]
0.00 0.48 5.00 6.00 7.00 8.00 9.00 10.00 15.00 20.00 25.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 95.00 100.00
600 0.0 0.1 12.8 23.4 33.9 57.9 72.8 83.6 85.0 85.1 85.2 96.8 97.8 98.8 99.8 100.8 101.8 102.8 187.0 196.4
800 0.0 0.1 3.9 13.8 27.1 59.4 87.4 82.8 86.1 86.2 86.3 99.5 99.8 100.0 102.0 104.2 104.7 105.2 110.0 115.5
1000 0.0 0.1 3.4 6.6 14.2 39.0 73.9 87.5 92.7 95.2 95.3 105.3 105.4 105.5 105.6 105.7 105.8 105.9 106.0 111.3
1200 0.0 0.1 3.7 6.1 12.4 32.5 70.4 87.4 96.0 96.1 96.2 115.0 118.4 120.0 122.0 124.0 125.0 126.7 130.0 136.5
1400 0.0 0.2 3.9 5.5 10.6 26.1 66.9 82.2 98.4 99.7 99.8 120.1 124.7 126.6 126.2 128.8 128.9 130.0 132.5 139.1
1600 0.0 0.1 3.0 4.0 5.0 14.2 45.4 62.8 109.5 109.6 109.7 128.3 129.6 130.0 130.0 131.0 132.0 135.0 137.5 144.4
1800 0.0 0.1 3.4 4.2 5.0 13.9 41.1 61.0 109.4 111.4 111.5 131.9 150.0 150.1 150.2 150.3 150.4 150.5 151.0 158.5
2000 0.0 0.1 3.0 3.7 4.2 10.6 33.9 60.0 109.4 123.9 131.7 155.0 155.5 155.6 155.9 156.2 156.5 156.9 160.0 168.0
2200 0.0 0.1 3.0 4.0 4.5 10.2 29.9 54.4 100.0 118.3 131.5 154.7 155.4 155.7 156.0 156.3 156.6 156.9 160.0 168.0
2400 0.0 0.1 3.0 4.1 4.5 9.4 26.8 48.2 95.0 121.0 131.2 154.4 155.3 155.5 155.7 155.9 156.1 157.0 160.0 168.0
2800 0.0 0.1 2.8 3.8 4.5 8.7 24.8 45.8 92.4 109.1 131.0 160.9 163.2 163.3 163.4 164.5 165.0 167.0 169.0 177.5
3200 0.0 0.1 2.6 3.6 4.4 7.4 20.7 38.9 80.7 103.2 127.8 161.6 170.0 170.9 172.0 172.9 173.3 176.0 178.0 186.9
3600 0.0 0.1 2.4 3.4 4.4 6.1 17.4 35.0 72.8 94.2 120.6 152.2 164.4 170.0 171.3 172.6 173.6 175.0 178.0 186.9
4000 0.0 0.1 2.4 3.3 4.3 7.2 15.6 32.2 67.6 85.4 111.4 140.2 162.2 174.6 175.9 177.5 178.5 179.3 180.0 189.0
4800 0.0 0.1 2.1 2.9 3.8 4.9 11.6 27.8 57.9 73.5 96.2 123.7 155.8 170.0 176.9 177.1 177.3 177.5 178.0 186.9
5200 0.0 0.1 2.2 3.0 3.9 4.5 8.0 23.3 50.4 64.9 88.1 114.5 145.9 161.8 170.3 174.0 174.2 174.4 174.5 183.2
6000 0.0 0.1 1.8 2.5 2.8 4.1 4.4 18.1 40.7 53.7 72.7 94.6 129.5 146.7 154.0 157.3 158.3 159.3 160.0 168.0
6800 0.0 0.1 1.4 2.0 2.4 4.1 4.4 11.4 30.9 42.5 59.7 79.3 114.6 135.0 152.8 153.8 154.8 155.2 157.0 164.9
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Old 03-25-2013, 12:22 PM   #24
NH8991
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Chapter/Region: E. Canada
Location: Montreal, QC
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2009 Impreza 2.5i
Sport, DGM

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Good job with all this Rymar.

I've been in a similar position with my 09 auto, trying various fixes & my own values to get rid of the sensitivity, but i've ended up going back to stock for now until I get time to play with it again.
The TCU definitely is adding more complexity to things.

I know the CVT is a different animal to the 4EAT, but maybe some of the basic logic is the same.

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Old 04-01-2013, 01:22 PM   #25
Rymar
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2012 Impreza Ltd 5Dr
Dark Gray Metallic

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Quote:
Originally Posted by myrt1987 View Post
I still think the pedal feels different. What used to happen in that first 1/8" of travel now takes 1/2". Still not much but im convinced it changed.

Having no idea throttle response would even be affected, its not like i was looking for it to change. I just noticed it after driving it home.

You be the judge.
I can confirm that the pedal feel is affected, any time the ECU is reset (battery disconnect, or new programming). This occurs because the ECU has to relearn where the "0.00%" point is, as it converts from the accelerator pedal sensor voltage into the internal 0.00% to 100.00% range.

The pedal sensor voltage ranges from 0.68V to 4.00V, although the 100% point is mapped to about 2.7V. Note that there are two separate sensors for safety, and they must match or the ECU will throw an error.

After each reset, the 0.00% starts out at 0.92V. On each successive start cycle, the voltage for the 0.00% point drops, until after about 20 cycles, it reaches 0.76V, where it stabilizes. This is to prevent the zero point on the pedal from ever mapping to even a slight amount of throttle opening.

You can force a re-learn of this by turning the key from "acc" to "ign" 20 times; there is no need to actually start the car. (Of course, make sure NOT to have your foot on the accelerator pedal as you do this).

I'm pretty sure this is what happened; I noticed the same thing after my ECU was upflashed by the dealer.

More info on the overall project to follow... the summary is: it works!
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