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Old 07-30-2003, 12:18 PM   #126
wolverine
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KoneKiller,

I am no automechanics, but facts show me that with 94 gas, I don't get any warning signal from the knocklink, while with 93 gas, I do (yes, all the leds lit!)--even though I could not hear it (maybe too much loud mp3 music at work ). So, you tell me, what gives? What is the expected behavior?
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Old 07-30-2003, 12:49 PM   #127
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We got our first reflashed ECM back from Subaru yesterday. We reinstalled it in the car and everything seems A-OK. No discernable loss in power, in fact quite the opposite. Everything seems good. I'll report more once the customer has driven the vehicle.
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Old 07-30-2003, 12:50 PM   #128
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Well I got my car yesterday. Drove around a bit and did a VERY brief 3rd gear WOT from 3500-4400rpm and the FIRST time I did it I heard about 2 audiable pings at about 4200rpm and then nothing. For the next 20 minutes I did the same thing in 3rd and/or 4th gear and never heard anything else in about 10 times of trying to induce it. I did feel an almost imperceptable dip in power at 4200rpm so it seems like it learned.

I am going to construct a very lengthy/informational email for the owner of the dealership and reference any/all info on the web on this issue since he has not heard about it yet.

Now keep in mind:
-this is on a tank of gas that the dealership put in so who knows the quality of the gas.
-This is at 6000ft above sea level where I thought we wouldn't have this problem due to the fact we are running 3.5psi less boost from atmospheric losses.
-It only pinged semi-audiably 2 to 2.5 times and only happened once = I am not worried about it since it was the FIRST time I took it over 4000rpm (and just barely at that).
-I am going to fill it up with 93 after this tank is done and see what happens from there.

Overall I am not too worried at this point but I still wouldn't mind a reflash for the 1-2 times I go to Arizona with thier CA like 91 crap gas.

Time will tell.
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Old 07-30-2003, 12:56 PM   #129
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Please wait until after your break-in period to approach the dealer about this issue. Wait until you have developed a routine of operation and an extensive degree of familiarity with the behavior of the motor before attempting any type of claim on this issue.
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Old 07-30-2003, 01:00 PM   #130
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Quote:
Originally posted by Porter
We got our first reflashed ECM back from Subaru yesterday. We reinstalled it in the car and everything seems A-OK. No discernable loss in power, in fact quite the opposite. Everything seems good. I'll report more once the customer has driven the vehicle.

Hey Porter,

Is there anyway we can get something from SOA regarding the context of the re-flash?

I am very interested what they did to correct the issue. I am in the process of checking here in Phoenix if someone wants to go halves on a before and after re-flash at the AWD Dyno in town.

I would really like some facts and data before getting the re-flash.
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Old 07-30-2003, 01:01 PM   #131
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Quote:
Originally posted by Porter
We got our first reflashed ECM back from Subaru yesterday. We reinstalled it in the car and everything seems A-OK. No discernable loss in power, in fact quite the opposite. Everything seems good. I'll report more once the customer has driven the vehicle.
Thanks, Porter. Please keep us posted!
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Old 07-30-2003, 02:55 PM   #132
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Your point is certainly valid and given the option, I'd run 94+ in it all the time. It IS after all, a high performance motor.

So, the knocklink raises two questions:

1. What level of pre-ignition is meaningful?

There are 'purists' who will tell you that any pre-ignition is harmful, because it raises pressures, etc. There are 'purists' who will tell you that every well-tuned internal combustion engine pings, even if it's inaudible. I think we will all agree that massive knocking (massive enough to feel it in the seat of the pants) is a death knell for a motor. FWIW, I'm in the 'a little ping is ok, camp.'

2. What does the knocklink detect and how does it do it?

Is your knocklink wired to the stock crystal? Or do you have a seperate crystal for it? Either way, is it located/tuned/calibrated/filtered/processed/interpreted in a way that makes the data meaningful? If I was getting the 'white' signal in the absence of audible knock, I'd wonder if it was valid information. But again, I haven't seen any technical information on the processing algorithms of the Knocklink. My guess is that they are pretty liberal in their definition of 'knock.' If a lot of people didn't 'detect knock' with this device, they wouldn't recommend it to their friends.

The reason I need a straightjacket is that it's so very, very clear that Subaru intended for this car to ping. It's not an accident, or a mistake from an engineering standpoint. It was an engineering choice STi made, but I think they misunderstood the tolerances of the buyers of this car. The expected behavior of this car on 93 octane is to ping. I don't see how Subaru could have been more clear about this -- it is written in the owner's manual! <shrug>

|Step away from my car with that reflash unit and no one gets hurt!| :

Quote:
Originally posted by wolverine
KoneKiller,

I am no automechanics, but facts show me that with 94 gas, I don't get any warning signal from the knocklink, while with 93 gas, I do (yes, all the leds lit!)--even though I could not hear it (maybe too much loud mp3 music at work ). So, you tell me, what gives? What is the expected behavior?
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Old 07-30-2003, 04:27 PM   #133
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Quote:
Originally posted by KoneKiller

Is your knocklink wired to the stock crystal? Or do you have a seperate crystal for it?
Mine is connected to a Bosche knock sensor; the receiving unit is, of course, the knocklink. I don't have any technical info on this device, but it is probably some op-amp type bypass filter with an A/D (Analog-to-Digital) converter to display the analog signal into an array of LED's.
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Old 07-30-2003, 04:53 PM   #134
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Quote:
Originally posted by wolverine


Mine is connected to a Bosche knock sensor; the receiving unit is, of course, the knocklink. I don't have any technical info on this device, but it is probably some op-amp type bypass filter with an A/D (Analog-to-Digital) converter to display the analog signal into an array of LED's.
The input voltage from the peizo is probably pretty high, so it might not need much amplification. The real question in my mind is what sort of signal processing is being done to weed out other forms of vibration from knock. Part of this is intrinsic to the mass of the sensor weight, but part of it has to be in the detector.

The simplest way would be to simply convert the voltage signal into a graded LED response, a la a VU meter. That really wouldn't be very useful, but it would be easy.

A better solution would be to detect frequency distribution, duration, intensity, etc, but our cost and sophistication just went out the roof. The ECU does just this. Some people are looking at the amount of knock retard to get a sense of what the ECU is seeing, by usings the SECS monitor.

It would be interesting to see how the knocklink and SECS correlate.

In any case, it's interesting to contemplate, for sure, but the real issue is whether the motor cares about the ping as much as the 'ping detector' does. My guess is the motor can handle a lot more ping than you are willing to listen to.
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Old 07-30-2003, 04:58 PM   #135
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I go in tomorrow to have my ECU reflashed. I will let you guys know next week what I think about it.
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Old 07-30-2003, 05:23 PM   #136
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Quote:
I don't have any technical info on this device, but it is probably some op-amp type bypass filter with an A/D (Analog-to-Digital) converter to display the analog signal into an array of LED's.
My question would be is it (it being the knocklink, or any aftermarket sensor for that matter) filtered in the digital domain (via a DSP) or is it a simple analog bandpass filter? I do believe that the stock Subaru sensor is at least partially analog as there are fixes to settle the knock activity on earlier Subarus and that was done by adding passive components to change the bandpass frequency. However, I have read that it only looks for activity in certain RPM ranges which I would suppose is a digital function carried out by the ECU. Does the knocklink account for the same factors? Is the knocklink filtering out different frequencies? I would expect a iron block and an aluminum block to have different frequency characteristics, for example (although it may be insignifcant). Is the knocklink ignoring signal above a given RPM? Is the stock ECU? If so, are they the same RPM? There are numerous variables here that must be answered before one can reliably count on an aftermarket sensor.

Just stirring up the pot a bit....

Christian
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Old 07-30-2003, 06:11 PM   #137
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guys, the knocklink has been used on Impreza engines for a long time. It is very well understood now.

You should never use the OEM knock sensor to trigger this as it reduces the knock signal to the ECU.

The SECS is just displaying what the ECU see's, and the ECU goes deaf with regards to high RPM knock. the knocklink is displaying what the bosche sensor see's and doesnt miss high RPM knock.

You should mount the bosche sensor directly onto the engine block, not onto the inlet manifold.



Set the knocklink sensitity to max.

It is normal on the STi engines to see both green lights flicker under load, at max revs you may see the two yellows flickering, but if the big red led lights you have definately got Det and you should back off.

My Knocklink and charge temp display (the charge temp display is also a temperature trigger for my water injection system which is triggered when boost and charge temp are in the correct ranges)


Last edited by johnfelstead; 07-30-2003 at 06:25 PM.
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Old 07-30-2003, 07:19 PM   #138
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Quote:
Originally posted by johnfelstead
guys, the knocklink has been used on Impreza engines for a long time. It is very well understood now.

You should never use the OEM knock sensor to trigger this as it reduces the knock signal to the ECU.

The SECS is just displaying what the ECU see's, and the ECU goes deaf with regards to high RPM knock. the knocklink is displaying what the bosche sensor see's and doesnt miss high RPM knock.

You should mount the bosche sensor directly onto the engine block, not onto the inlet manifold.
That's where I have my knock sensor mounted, thanks to someone here on the forum (PunkWRX, I think) to point it out for me. I figure if there is some problem with the stock knock sensor, I can count on my independent sensor... Simple logics: Eliminate as many variables/unknowns as possible in your experiment!
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Old 07-30-2003, 07:35 PM   #139
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if you share the OEM knock sensor with the knocklink you increase det and you dont display it either! Think about that!
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Old 07-30-2003, 08:05 PM   #140
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no, no , no ,no you guys are WRONG AGAIN!!!!

Like you guys said, this has been discussed many times... in short this is what you need...

- Use either a used or new subaru sensor, go to subaruparts.com and get a subaru knock sensor, for the STi, get the STi sensor.

- Do not use the supplied BOSH sensor nor the factory installed one. The BOSH microphone/sensor might be tuned to different frequency (aka, diferent motor, displacement, etc.) and if you tap into the stock one you will reduce accuracy or induce static noise.

- Set the KnockLink to MAX sensitivity and wire it up. MAKE SURE you run the provided shield wire all the way up to were you join it with the actual knock sensor (to protect the line against static noise). You might need to make ur own connectors to mate the knock sensor to the Knocklink harness.

- When you install the knock sensor in the extra BOSS shown in the above pic. on the engine block it must must at a 60 degree angle from the rear fo the car towards the passenger side. If you look at the factory sensor you will see it's wire is 60 degrees towards the passenger.

___________Firewall____________o_______ <-- Cabin Hole
..................................0^
...........................Stock New
............................\\60^\\60^
|------------90^----\\----\\-------------| Engine Block
|.............................O......O............ .....| Knock sensor(s)
|...................|Intercooler|................. ...|

*** Sorry for the mis-alignment, damm spaces.

- On the STi, there is a metal braket in the BOSS provided that holds 1 of the coolant lines for the Throttle Body, I just mounted mine on top of the braket and used a longer bolt (like the intercooler bolt). It might reduce accuracy/sensitivity but I still get red knock lights at WOT between 4-5k rpms. So it seems to be working properly.

Last edited by zacek; 07-30-2003 at 08:28 PM.
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Old 07-30-2003, 08:44 PM   #141
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i hope you arent trying to tell me i have the instalation wrong zacek, because if you are, you are wrong.
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Old 07-31-2003, 07:47 AM   #142
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John - Could you PM the details on your temp gauge when you have the time.

Thanks in advance,

Shaun
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Old 07-31-2003, 09:37 AM   #143
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Quote:
Originally posted by Porter
We got our first reflashed ECM back from Subaru yesterday. We reinstalled it in the car and everything seems A-OK. No discernable loss in power, in fact quite the opposite. Everything seems good. I'll report more once the customer has driven the vehicle.
How many days total to get it back?
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Old 07-31-2003, 10:20 AM   #144
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Quote:
Originally posted by johnfelstead
guys, the knocklink has been used on Impreza engines for a long time. It is very well understood now.

You should never use the OEM knock sensor to trigger this as it reduces the knock signal to the ECU.

The SECS is just displaying what the ECU see's, and the ECU goes deaf with regards to high RPM knock. the knocklink is displaying what the bosche sensor see's and doesnt miss high RPM knock.

Set the knocklink sensitity to max.

It is normal on the STi engines to see both green lights flicker under load, at max revs you may see the two yellows flickering, but if the big red led lights you have definately got Det and you should back off.

Ok... this raises more questions than answers.... Forgive my ignorance... but...

> Is the input impedance of the knocklink so low that it can drag down a peizo unit signal? Poor design?

> Why set the sensitivity at max? Has someone done a correlation between knock sensor sensitivity, knocklink sensitivity and combustion chamber pressures?

>The knock sensor is really just a microphone with poor frequency response. The reason ECU's are engineered to be 'deaf' to the knock sensor at high RPM is that regular engine noise is high enough to generate signal from the knock sensor in the absence of detonation. Does the knocklink have any algorithm to distinguish noise from knock? Given the 'flickering yellows' at high RPM, I'd surmise not.

The concept of high RPM knock is a bit odd to me. I'm sure we can create a circumstance where it can happen, but that isn't the usual way knock happens, it's usually low to mid RPM.

> If the knocklink shows full on detonation and it's not audible, which instrument is unreliable, the knocklink or the ear?

There is an old cliche in science: meaningful information always comes from meaningful data, but not all data are meaningful information.
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Old 07-31-2003, 11:19 AM   #145
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Quote:
Originally posted by KoneKiller


> If the knocklink shows full on detonation and it's not audible, which instrument is unreliable, the knocklink or the ear?

There is an old cliche in science: meaningful information always comes from meaningful data, but not all data are meaningful information.
In my case, I think the ear (well, mine) is unreliable Why? Because, like I said, if the knocklink is unreliable, it should show some activities on 94 gas as well; but it does NOT for several runs. For 93, however, there are occasions where even though I cannot hear it, the knocklink does show flashes of the knock LED.

I know, it is sometimes hard to discern what information is meaningful... To do so, you've got to have a controlled experiment like I did. I am very confident that what I see is knock (or vibration from the engine block, whatever you want to call it), may it be damaging or not, I don't know... But, it is definitely knock, and I don't get that with 94 octane.
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Old 07-31-2003, 12:00 PM   #146
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Quote:
Originally posted by wolverine


In my case, I think the ear (well, mine) is unreliable Why? Because, like I said, if the knocklink is unreliable, it should show some activities on 94 gas as well; but it does NOT for several runs. For 93, however, there are occasions where even though I cannot hear it, the knocklink does show flashes of the knock LED.

I know, it is sometimes hard to discern what information is meaningful... To do so, you've got to have a controlled experiment like I did. I am very confident that what I see is knock (or vibration from the engine block, whatever you want to call it), may it be damaging or not, I don't know... But, it is definitely knock, and I don't get that with 94 octane.
I agree, the 93/94 octane experience is compelling. I'm not concerned about a small amount of knock, even audible, but I do run the best fuel I can easily get (93) and haven't heard any significant knock to date, either on or off the track. <knock on wood>
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Old 07-31-2003, 03:10 PM   #147
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Alot of people are saying they have det and I am a little concerned. Either I have been very lucky or I don't know what det sounds like because I have not experienced it. It has been 100+ degrees here in Portland and we have some of the crappiest gas in the country (92 if you believe their numbers but it is still crap quality). I had my car at the drag strip and it was well above 4k rm most of the time and I never heard det.

Does anyone know if there are any correlations with location in the country or what the percentages among owners are?

Would I feel det or just hear it and what would it sound like? I have only heard det in old cars when trying to shut the engine off not while it is running.
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Old 07-31-2003, 04:12 PM   #148
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Quote:
Originally posted by Burke
Alot of people are saying they have det and I am a little concerned. Either I have been very lucky or I don't know what det sounds like because I have not experienced it. It has been 100+ degrees here in Portland and we have some of the crappiest gas in the country (92 if you believe their numbers but it is still crap quality). I had my car at the drag strip and it was well above 4k rm most of the time and I never heard det.

Does anyone know if there are any correlations with location in the country or what the percentages among owners are?

Would I feel det or just hear it and what would it sound like? I have only heard det in old cars when trying to shut the engine off not while it is running.
My ilttle experience, I started getting det during acceleration at about 3200 miles, before that smooth as glass... now its like, "Did someone drop a bunch of bbs in my engine?"
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Old 07-31-2003, 04:54 PM   #149
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Quote:
Originally posted by Burke
I had my car at the drag strip and it was well above 4k rm most of the time and I never heard det.
If you go full-throttle well above 4K rpm, that's probably why you don't hear it. My experience shows that if I don't WOT between the 4k to 5k mark, and then WOT after 5k up to red-line, I don't get det either. It is only when I WOT at low rpms and keep it there until I hit 4K-5K range, that's when I get det.
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Old 07-31-2003, 05:11 PM   #150
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Quote:
Originally posted by Burke
Would I feel det or just hear it and what would it sound like? I have only heard det in old cars when trying to shut the engine off not while it is running.

I work part time at a 2WD Dyno. Det or Ping can sound very differnet depending on the appilcation. It can be best described as Pop-corn popping in an aluminum pan. Either high in pitch or low in pitch. It is very distinct.

Good Luck, hopefully you will never have to hear it!
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