knock sensing on 86.5
12-23-2003, 06:47 PM
#1
Three Wheelin'
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knock sensing on 86.5
As I understand it, the 86.5 does not come with knock sensing capability. Aparently, Andy's '87 S4 does. He told me that there are a couple holes in the block where the sensors go, and he has seem them on other cars (like mine).
Now, I guess what i'm looking for is an explanation of how the knock sensing/retarding features work. What I'm assuming is the ECU monitors these sensors. When they sense knock, the ECU simply retards the ignition until the knocking stops.
Now, if that is the correct assumption, that means I would need to put knock sensors into my car, and install an ECU that supports this feature. Is that accurate?
With my ultimate goal being to get knock sensing capability into my car so that I may be safe when cranking up the boost on Andy's supercharger kit - does anyone have any other suggestions?
Thanks!
Now, I guess what i'm looking for is an explanation of how the knock sensing/retarding features work. What I'm assuming is the ECU monitors these sensors. When they sense knock, the ECU simply retards the ignition until the knocking stops.
Now, if that is the correct assumption, that means I would need to put knock sensors into my car, and install an ECU that supports this feature. Is that accurate?
With my ultimate goal being to get knock sensing capability into my car so that I may be safe when cranking up the boost on Andy's supercharger kit - does anyone have any other suggestions?
Thanks!
12-23-2003, 06:59 PM
#2
Nordschleife Master
Basicly, you got it.
The knock sensors are basicly microphones. Not normal mics mind you, but tuned to help filter out some of the noise. The ECU listes to the noise, and if it "hears" knocking, it retards the timeing untill the knocking stops. Then it advances the timeing, untill it starts again, and thus starts retarding it again. This is dove very quickly, so there is never any severe knocking, and no dammage to the engine.
I guess you could go to the S4 wireing harness, ECU and knock sensors. It wouldn't be cheap though. Failing that, you could go for a stand alown, but sometimes they don't work right, and it wouldn't be cheap.
There is a company that makes an intercepter box that goes, IIRC between the coil and the ECU, and will advance or retard the spark depending on if the knock sensor pick up anything. It's called safeguard, and is made by J&S electronics. I'm of no relation, bla bla bla. I've never used it, but it looks intersting and well worth the effort to investigate.
The knock sensors are basicly microphones. Not normal mics mind you, but tuned to help filter out some of the noise. The ECU listes to the noise, and if it "hears" knocking, it retards the timeing untill the knocking stops. Then it advances the timeing, untill it starts again, and thus starts retarding it again. This is dove very quickly, so there is never any severe knocking, and no dammage to the engine.
I guess you could go to the S4 wireing harness, ECU and knock sensors. It wouldn't be cheap though. Failing that, you could go for a stand alown, but sometimes they don't work right, and it wouldn't be cheap.
There is a company that makes an intercepter box that goes, IIRC between the coil and the ECU, and will advance or retard the spark depending on if the knock sensor pick up anything. It's called safeguard, and is made by J&S electronics. I'm of no relation, bla bla bla. I've never used it, but it looks intersting and well worth the effort to investigate.
12-23-2003, 07:07 PM
#3
Three Wheelin'
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well, i'm either gonna do it right, or not do it. That would mean transplanting the S4 harness/ECU/sensors into my car, or going stand alone. I kind of wanted to go full-standalone anyways as a project... maybe I should start looking into my options.
Maybe someone can chime in with a "Well actually, since this and that are the same, all you gotta do it put this over here and connect this wire and swap this part...", It would be awesome, but somehow I don't think that's gonna happen
Maybe someone can chime in with a "Well actually, since this and that are the same, all you gotta do it put this over here and connect this wire and swap this part...", It would be awesome, but somehow I don't think that's gonna happen
12-24-2003, 08:42 AM
#4
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mspiegle -
On the S4 and later cars, it is just the EZK ECU that deals with the knock sensors. As ViribusUnits says, the signal form the piezo-electric knock sensors is at a very low level. (that's why they have 3pin connetors with a screened lead).
The EZK amplifies and filters the knock signals out of the general engine noise, then retrads the ignition in 3 degree steps until the knock stops.
The problem for you is that on the S4 engine, there is a Hall sensor on the camshaft. This gives the EZK the information it needs to work out which knock sensor it should be listening to, so it can retard the ignition on just that bank. If the EZK doesn't get any signal from the Hall sensor, then it just reatrds the ignition on both banks by 6 degrees.
You would need to generate a camshaft signal. You could possibly use the injector pulses (once every engine rev) and with a simle divide by 2 circuit generate the equivalent of the camshaft (half engine rev) pulse, and feed that into the EZK to fool it that all was well.
I think it would be possible to use an S4 EZK with the LH for the 86.5
Hope this helps !
On the S4 and later cars, it is just the EZK ECU that deals with the knock sensors. As ViribusUnits says, the signal form the piezo-electric knock sensors is at a very low level. (that's why they have 3pin connetors with a screened lead).
The EZK amplifies and filters the knock signals out of the general engine noise, then retrads the ignition in 3 degree steps until the knock stops.
The problem for you is that on the S4 engine, there is a Hall sensor on the camshaft. This gives the EZK the information it needs to work out which knock sensor it should be listening to, so it can retard the ignition on just that bank. If the EZK doesn't get any signal from the Hall sensor, then it just reatrds the ignition on both banks by 6 degrees.
You would need to generate a camshaft signal. You could possibly use the injector pulses (once every engine rev) and with a simle divide by 2 circuit generate the equivalent of the camshaft (half engine rev) pulse, and feed that into the EZK to fool it that all was well.
I think it would be possible to use an S4 EZK with the LH for the 86.5
Hope this helps !
12-24-2003, 12:04 PM
#5
Chronic Tool Dropper
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M:
You will be dollars and weeks ahead if you just buy an S4 to use for your project. Do this now before you become attached to your current car, and you'll be driving sooner with more $$ left in your wallet. The 86.5 is a very nice car, and certainly the best option if you like the S body style. However, transplanting the S4 engine harnesses alone will set you back a pretty penny. Continue that harness down to the brains, get it all sorted, and you will easily cover the cost difference between the two cars.
I'm looking forward to seeing some more of these SC cars in service.
You will be dollars and weeks ahead if you just buy an S4 to use for your project. Do this now before you become attached to your current car, and you'll be driving sooner with more $$ left in your wallet. The 86.5 is a very nice car, and certainly the best option if you like the S body style. However, transplanting the S4 engine harnesses alone will set you back a pretty penny. Continue that harness down to the brains, get it all sorted, and you will easily cover the cost difference between the two cars.
I'm looking forward to seeing some more of these SC cars in service.