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Old 04-01-2010, 06:58 PM   #1
Chrisgst99
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Default COBB tuning problem.......

I just recently had my motor build not to long ago and today i had it tuned from where it was built at, in when i was getting my car tuned there was a problem with it pulling timing at 5600 rpm, due to the knock sensor sensitivity. the car was checked for any failure and there was none. i have a built PPG straight cut tranny that is very loud like crazy and i was told that my tranny is causing the car to knock around 5600 rpm as the tranny gets louder. the car was dyno on was a dynapack they said the only way of getting around that problem was to buy a stand alone ecu like a AEM EMS, so they can control the knock sensor sensitivity threshold. my question is is there anybody with ppgs straight cut gears tuned with a Cobb v1 have the same problem on a wrx? and is there any way of getting around this problem with the stock ecu flashed with the Cobb access port? thank you
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Old 04-01-2010, 07:02 PM   #2
Chrisgst99
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Is there a way to control the sensitivity of my knock sensor using the accessport on a 02 wrx?
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Old 04-01-2010, 10:14 PM   #3
Ysidro
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I think there is a table in tuner race you can adjust.
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Old 04-02-2010, 10:38 AM   #4
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How many degrees did it pull? I'm just getting into tuning but I have heard a few people say the 2.0 usually has knock around 5k-6k. I don't see a table for sensitivity in Tuner Race.

edit - Maybe you can tweak the coarse knock learning tables?

Last edited by jasonspeed; 04-02-2010 at 10:59 AM.
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Old 04-02-2010, 01:02 PM   #5
Chrisgst99
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Originally Posted by jasonspeed View Post
How many degrees did it pull? I'm just getting into tuning but I have heard a few people say the 2.0 usually has knock around 5k-6k. I don't see a table for sensitivity in Tuner Race.

edit - Maybe you can tweak the coarse knock learning tables?
like 5 degrees of timing and i have a built 2.5 longblock
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Old 04-06-2010, 05:07 PM   #6
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Bump...
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Old 04-06-2010, 10:19 PM   #7
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There is no knock sensor sensitivity table. You can have someone tune it with det cans, which is a much cheaper alternative to buying a stand alone. There are also ways to shim the knock sensor, or reposition it to be less sensitive.

Andy
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Old 04-07-2010, 01:38 AM   #8
lazzer408
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Put a voltage divider on the knock sensor signal. If you want it reduced by 10% then build the divider for 10% voltage reduction. This is basic electronics and can be used to lower any voltage from a TPS, MAF, MAP, O2, ect ect.

Vo= Vin*R1/(R1+R2)

R1/R2= Vo/(Vin-Vo)

Example: R1=1k R2=9k will give you a 10% voltage reduction.

WiKi shows the resistors as "Z" but normally R is used in schematics to show a resistor.

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Old 04-09-2010, 02:12 PM   #9
Cobb Tuning
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Quote:
Originally Posted by Chrisgst99 View Post
I just recently had my motor build not to long ago and today i had it tuned from where it was built at, in when i was getting my car tuned there was a problem with it pulling timing at 5600 rpm, due to the knock sensor sensitivity. the car was checked for any failure and there was none. i have a built PPG straight cut tranny that is very loud like crazy and i was told that my tranny is causing the car to knock around 5600 rpm as the tranny gets louder. the car was dyno on was a dynapack they said the only way of getting around that problem was to buy a stand alone ecu like a AEM EMS, so they can control the knock sensor sensitivity threshold. my question is is there anybody with ppgs straight cut gears tuned with a Cobb v1 have the same problem on a wrx? and is there any way of getting around this problem with the stock ecu flashed with the Cobb access port? thank you
The ECU does not use logic to interpret the knock signal -- this is done at the hardware level.

As such, this is not a problem with the AccessPORT or ProTuner software...there is no threshold that can be adjusted. Knock is emitted at certain frequencies, depending on bore and stroke, and each ECU is calibrated to the engine it came on -- the 2L ECU hears knock correctly on the 2L engine; the 2.5L ECU hears knock correctly on the 2.5L engine. The 2.5L is quite a bit "noisier" and false knock is common in the ~5500 RPM range when using a 2L ECU.

elevenpoint7five and lazzer408's solutions have been known to work in certain cases. Disabling knock control and tuning the engine to MBT with det cans would also be an effective strategy.

Good luck and best regards,
Lance
COBB Tuning Surgeline
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Old 04-11-2010, 02:55 PM   #10
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thanks for all the advice guys, it just pissed me off that i spent so much money on my engine build and on tune day i was not able to get my car tune due to this problem.
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Old 06-24-2010, 03:44 AM   #11
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I was wondering if anybody else ever have this issue with tuning a 2.5l engine on a 2.0l ecu?
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Old 04-24-2012, 05:32 AM   #12
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I hate to bring this thread back from the dead...but I am having the same problem. My last engine setup did the same thing. I had a built hybrid 2.5 block / built 2.0 heads (tuned OS with stock 16 bit 2L ECU) and we would have knock right around that area. What we did was disabled the knock sensor and used DET CANS ...google them to build...very easy....and you physically listen for knock as you tune to MBT. We achieved our desired timing as intended and the car ran great...until I lifted my heads lol....so now I am on another build with a built 2.5 block and stock 2.0 heads and it does the same thing....so needless to say I am going to finish tuning it with det cans.
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Old 04-24-2012, 09:04 AM   #13
Cobb Tuning
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Quote:
Originally Posted by BlackJavaPearl04 View Post
I hate to bring this thread back from the dead...but I am having the same problem. My last engine setup did the same thing. I had a built hybrid 2.5 block / built 2.0 heads (tuned OS with stock 16 bit 2L ECU) and we would have knock right around that area. What we did was disabled the knock sensor and used DET CANS ...google them to build...very easy....and you physically listen for knock as you tune to MBT. We achieved our desired timing as intended and the car ran great...until I lifted my heads lol....so now I am on another build with a built 2.5 block and stock 2.0 heads and it does the same thing....so needless to say I am going to finish tuning it with det cans.
Hi there. In Feb. of last year, for all turbo Subaru ECUs we support, we added a number of knock sensivity tables to the AccessTUNER software that allow you to adjust how a knock event is determined based on input from the knock sensor. The logic is fairly complex and we have not received a lot of feedback from tuners specifically attempting to use it, but it is possible to tune it (albeit with some experimentation on your part). The previous assessment that this was all hardware based was incorrect.

If we look at the how the OEM calibration for this logic, the "Knock Threshold Weight Factor..." table(s) and "Knock Threshold/Filter Final Limit..." tables are the primary means by which they tune for different motors. That would be a good place to start if you are interested in attempting to tune knock sensitivity.

Bill
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Old 04-24-2012, 07:38 PM   #14
BlackJavaPearl04
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Thanks for the info Bill.

Quote:
Originally Posted by Cobb Tuning View Post
Hi there. In Feb. of last year, for all turbo Subaru ECUs we support, we added a number of knock sensivity tables to the AccessTUNER software that allow you to adjust how a knock event is determined based on input from the knock sensor. The logic is fairly complex and we have not received a lot of feedback from tuners specifically attempting to use it, but it is possible to tune it (albeit with some experimentation on your part). The previous assessment that this was all hardware based was incorrect.

If we look at the how the OEM calibration for this logic, the "Knock Threshold Weight Factor..." table(s) and "Knock Threshold/Filter Final Limit..." tables are the primary means by which they tune for different motors. That would be a good place to start if you are interested in attempting to tune knock sensitivity.


Bill
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