One quick question. When the J&S led light comes on at WOT, does that mean its detecting knock, or does it mean that its retarding timing? Or is it both? Im assuming that when the led lights up, that means its not good. I believe that a good setup would mean thats the light WILL NOT light up under WOT, is this true? Hope im not confusing anyone.

 

Chris, I think I was able to answer this on the phone, but for others who may want the answer.
John from J&S will hopefully clarify, if I am wrong.

The J&S LED above 1750 rpm's will light up when detecting knock from the stock knock sensor. The intensity of the LED is in direct correlation to the intensity of the knock and the amount of retard, depending on your dip switch settings.

 

Sell it.Question answered..

 

So when the light comes on, its not a bad thing? It just tell you that its sensing knock and pulling timing, right? So im guessing its supposed to be lighting up then?

 

No, its a bad thing..If the car is "knocking" then it is not tuned correctly.A properly tuned car should not knock.The J&S is a safety net and you should no rely on knock retard as a method of pulling timing.If your car was tuned properly it would not need to pull timing based on knock.

 

And how exactly does this help the poster?

 

Some tuners are using headphones to listen to a knock sensor. We've had reports from a couple tuners saying that the J&S hears knock that they can't hear with their headphones.

Here's a comment from a tuner on the Subaru forum:

Now moving on to the headphone users... I've personally built a couple units myself for use with noise canceling head phones and have added various levels of filtering and so forth. Simply put, the JandS id'ed and corrected detonation well before it was ever to a point of being audible and distinguishable to my ears. In other words, it was typically much higher level detonation. Keep in mind that by the time most detonation is audible a considerable amount of high level detonation has already taken place. Apparently John's algorithm is sensitive enough to detect it based on my experience. For those that will immediately jump on me to cry wolf that the JandS was false triggering... an adjustment of 3-4 degrees of timing on my EMS eliminated all triggers from the JandS and when added back in yielded the same response from the JandS. Again there was no hope or prayer of hearing this detonation through the head phones by any stretch. I tried quite a bit and ran numerous experiments to see if I could hear the detonation. So again, while headphones may work great (and do!) for hearing detonation in some cases, the underlying fact is there is considerable detonation occuring at high levels that are inaudible amidst the engine noise that the JandS is identifying successfully.

Complete thread here: http://forums.nasioc.com/forums/show...=831718&page=1

 

Good info John. Is this level of "inaudible" knock something that the stock ECU knock sensor would pick up and retard timing on? The reason I ask, is that the ECU needs to sense a certain level of knock, before it determines that its strong enough to cause engine damage. As you know, some knock is present in nearly all engines at some point...but the minor inaudible knock is not damaging, which is why the ECU waits until a certain knock threshold is reached before taking action and retarding the time. Can you tell us a little bit more about how your knock sensor algorithm determines what is harmful knock?