[EFI Tuning]

We've been a little quiet lately but we are still working on some cool things. I ordered the Plex Knock Monitor unit a couple of months ago and finally spent some quality time this weekend to get familiar with it on my personal car.

From the factory our cars are equipped with two knock sensors. A knock sensor is on each side of the block. The knock sensing capabilities have come a long way since the early LS1 days but there are still issues your tuner will face once you begin deviating from stock. As you change the configuration the noise characteristics of the engine may change. This can excite the knock sensors in unpredictable ways and may show up as false knock. It is also possible to have knock occur and your ears not detect it (age is a big factor here). Knock is brutal on the rod bearings when it occurs. It may not destroy your engine in seconds like pre-ignition can but it will slowly start to wear on the rod bearings which will eventually lead to some costly rebuild work.

As a tuner it is critical to be able to differentiate between false and real knock. There are indirect approaches to getting there but it isn't always easy and still leaves some gray area. The installation of the CA primary cat delete pipes can cause some significant resonance that causes the factory knock sensors to over react. To know this for sure you need to pull back timing and on top of that run some high octane fuel to convince yourself it isn't real. Once you determine that it is necessary to adjust knock sensor thresholds in the ECM to mitigate this condition or you will have timing pulled back and lose significant amounts of torque. The next question is... how much do you adjust the thresholds to mitigate the condition but still detect real knock? The answer is unless you have additional tools you can't be sure. On a FI or N2O build it is absolutely critical to have a tool like this to safely maximize the torque output of the engine.

The Plex Knock Monitor can work with two supplied Bosch knock sensors. For the purposes of getting familiar with the setup I used only one sensor. The stock locations are a bit of a challenge to get to so I placed the sensor at the front of the block. On a FI or N2O scenario I would have utilized the stock knock sensor locations.

Photo 1 shows the knock sensor mounted.



Photo 2 shows the inductive pickup on cylinder 1.



Photo 3 shows the knock threshold curve set to the noise floor of my actual engine.



Photo 4 shows an induced knock event on cylinder 1 around 3500 RPM. The Plex unit can be setup to show the noise floor and knock events on each individual cylinder. This information can also be relayed to HP Tuners so you have 100% correlation with your scan data.




Not shown are the headphones. The Plex unit also has very advanced audio filtering capabilities so that before the output of the knock sensors gets to your ears it has been filtered to the frequency band of interest. There is no guess about what is knock and what isn't when you listen via this method. It sounds absolutely horrible. It is something most would NOT hear while riding in the car.

We aren't the only tuning option available but we are very data driven and feel it is important to invest in tools that create a better (and SAFE) product for our customers. We just wanted to give a little bit of insight about how we go about this.

Thank you,
Tim

[parish8]

this looks interesting. how does it interface with hptuners and what does it look like when you log it there?

I have a ton of reported knock. ~3000rpm at wot, any time above 6200rpm, some other random places. I am only running 3psi and am running e85. I have also pulled a fair amount of timing with no change in knock. I have also added more to my knock tables than I am really comfortable with and I still have the reported knock.

how high can you take those knock sensor levels before you have effectively made them useless?

[EFI Tuning]

PM sent