[RickyB]

I started this project do to the lack of availability of sophisticated aftermarket knock detection systems.

I think that it is great to do something like this, but I disagree that there is a dearth of good aftermarket knock detection systems. I am aware of systems that operate on both the time and frequency domain AND are fully integrated into the engine management so that ignition retard on an individual cylinder basis, additional fueling on an individual basis, cam control to reduce dynamic compression, TVIS or intake tumbler control to reduce VE and boost retard can all be properly applied. These system are usually a little beyond the pocketbook of many MR2 owners, but they are available for under $2000.

Most engine management systems ignore the knock sensor above a specific rpm. This is because it cannot differentiate between mechanical noise and actual knock at high rpm's.

Not really. Most gasoline engines do not detonate above 6000 RPM. There is simply not enough time for even fairly unstable fuel to start a detonation event at these speeds. Put a stethoscope on a crappy engine sometime and do a pull on it with too much timing in the 4000-7000 range. You will hear the pings start at 4K and run up through 5K and then vanish regardless of what you do. You can melt the engine easily at high engine speeds, but you cannot beat it to a pulp with detonation.

Given that, any decent knock control system is going to let the tuner taper response off at higher engine speeds since there is nothing for it to see there.

 

[RickyB]

I suppose I should reword my statement about the lack of solutions. The aftermarket lacks a solution that is easily attainable for the average car geek. I ran into this when trying to find a knock solution for my megasquirt MS2.

The low-price EMS market does not provide very sophisticated knock detection. By the time you integrate robust knock detection hardware and software, you have spent enough time and money that you would probably have been better served starting with a more expensive EMS platform. You should certainly price both options if robust knock detection is in your must-have list.

I have personally experienced audible knock at 5k+ rpm with a Mazdaspeed 3 that had entirely too much ignition advance.

The 2.3L in the MS3 is my daily driver and redlines just above 6K. This is not the optimal engine to base all your knock experience on.

If knock disappears at 5k+rpm, why do 12,000+rpm Indy Car ecu's have four knock sensor inputs? http://www.mclarenelectronics.com/Products/Product/TAG-400i

Knock sensors are rarely if ever used on race cars. Serious race cars are tuned for very specific fuel and conditions that are well known to the tuner ahead of time (and never driven under any other conditions). This unit has knock sensor inputs because it is a general purpose EMS and even though it can be used for race applications, it is not limited to race applications.

Certainly there would be an operating speed that this would occur, however, I have yet to see any technical documentation pointing out a certain engine speed.

It depends on many factors, so you cannot just pick single point. I have tuned hundreds of 3S engines on a dyno with a stethoscope and never heard a single ping above 6K regardless of conditions. There is no exact point, which is why most engine management systems with good knock detection capabilities will allow you to program in desired threshold across the entire engine speed range.