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Old 09-13-2005, 01:13 AM   #26
CMJ
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Hi jeff,

Thanks for your interest in the knock box.

the pricing for the knock box is
racer net $1537.26
plus tax if you are in Ca. or NC.


units are in stock
Like I said, over 1k
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Old 09-15-2005, 04:45 PM   #27
NSNMotorsports
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Hi Guys,

Just wanted to chime in here for a bit. I was talking with John some, and as one of the people out there that has really spent a lot of time trying things and fiddling with the JandS and as an electrical control systems engineer as my "day job" I wanted to bring my comments and perspective.

I have a Mazda MP3 boosting about 13 psi right now (due to wastegate issues) that is making a bit over 260 whp. I run a Microtech standalone system and the JandS Safeguard for my engine control electronics.

First of all... for the gentleman refering to the use of a knock window as being "not ideal" I have to ask how it is anything less than ideal? Yielding a specific TDC marker point yields no feasible gain. Ideal peak cylinder pressure is typically stated as needing to occur around 14 degrees ATDC for maximum power output. While this will vary to some degree due to how well it is being targeted by the tuner as well as by variations in mechanical aspects of the motor (but only marginally.. it is still commonly accepted that regardless of engine construction 14 degreest ATDC is ideal for peak cylinder pressure). The reason I bring this point up is that peak cylinder pressure is typically the most conducive to detonation. Additionally, any case where the flame front slams into the piston due to overly aggressive timing would typically occur within a few degrees of this location unless timing is so severely over advanced that most generalized scenarios are no longer applicable. Thus using the JandS scenario for the window locations of peak pressure are straddled appropriate and the range where piston rock is occuring (at top dead center) that can lead to false triggers in most systems, is avoided. Detonation is much more an effect of timing than of strict reference to TDC, and thus by using the window that John is using, you are much more relative to the appropriate measurement of location for this phenomenon. Additionally, in conversations I've had with John, he has indicated that it would be possible to move the window per request... have fun gettign any other manufacturer to adjust the software in their units for you.

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.

I'm sure there will be more to respond to when some of you read through and counterpoint to my statements. I'm happy to hear alternative points of view, but wanted to express some of my opinions on the matter (and no I do not profit from, sell, or carry any sponsorship or association with JandS... just am an avid user with experience that has shown me the value in the system).

Thanks!

Steve
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Old 09-15-2005, 04:51 PM   #28
cdvma
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Steve,

All good points. I want to believe that a proper knock box (like the J&S) can detect knock much better than I can since all I have is just very very cloudy auditory input. At that level where I cannot detect it but the J&S can, I must say that the knock is probably incipient and not that dangerous. You can never be too careful so if the J&S can even stop incipient knock then more power to the creator and the people who want to use it with that level of sensitivity.
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Old 09-15-2005, 05:40 PM   #29
NSNMotorsports
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Originally Posted by cdvma
Steve,

All good points. I want to believe that a proper knock box (like the J&S) can detect knock much better than I can since all I have is just very very cloudy auditory input. At that level where I cannot detect it but the J&S can, I must say that the knock is probably incipient and not that dangerous. You can never be too careful so if the J&S can even stop incipient knock then more power to the creator and the people who want to use it with that level of sensitivity.
Even if the knock is incipient for the mechanics, it typically leads to surface heating (spark plug tips, carbon deposits, etc) which can then lead on to pre-ignition which is even worse due to the fact that even timing control can't help and you get into the runaway conditions that rapidly result in total destruction.

It's really a great security blanket to have too, if you make a mistake tuning and alter values accidentally that results in very dangerous circumstances, it becomes a good system for protecting you from yourself too!

Last edited by NSNMotorsports; 09-15-2005 at 06:03 PM.
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