Newbiata

After reading about the different ways of knock detection, I have been thinking about an easy way to detect knock with Megasquirt. After trying my hand at those electronic detcans to no success (Just heard a lot of ticking from the lifters), and the limited availability of working knock detection, I've been thinking of new ways to get a reliable knock signal. My 93 engine has one of those carbon resistance oil pressure sensors, and it would be interesting to use a voltage dividing circuit to input the signal into Megasquirt. Since the oil pressure should fluctuate during a knock event, my reasoning is that the data log will display the event and I could tune it that way. Any thoughts?

dglb99

Adding an actual knock sensor would likely yield better results. However, actually using det cans seems to be the best way to actually detect knock. Then when you know what is and isn't knock through the det cans you can set up the knock sensor filtering appropriately.

Newbiata

I'm using the DIY MS2, so I don't think I have any reliable signal filtering. From what I've been researching, the Knocksense seems like a sort of "meh" solution, and I haven't been able to find any other good filtering solutions. Either way, the oil pressure sensor will be a nice extra sensor input. I will try again with the detcan that I made with a spare microphone, do you have any recommendations for a proper rpm-based filter?

O R X O N

The Knocksense was described as "worse than nothing" by one of the gurus here.
Can't speak for MS2 based systems, but I have a Knock Module from DIYAutoTune arriving in the mail tomorrow for use on my MS3x.

Newbiata

Awesome, that sounds like a good solution. I wish I could do that but alas, I only have an MS2...

Mudflap

Newbiata - I'm sure you already know this. But you will go around and around and around about this issue. There is a reason that there is no "solution" to any electronic (audio) or sensor detection. You could throw a ton of money at it. Or you can go make the mechanical det cans...

The problem with any method is that you simply cannot prove what levels indicate knock without verifying with mechanical det cans. So I wouldn't bother with anything else.

You'll look dumb, feel dumb. But you drive around and turn up your timing (at low rpm/load) and listen for it. As you get better at detecting it, you can then switch to electronic sensors and correlate the two.

I challenge anyone who says they can hear knock. Especially a loud *** 4banger with turbo. It all just turns into a clangy mess.

sixshooter

iTrader: (12)

Electronic det cans are the best answer.

The knock sensor doesn't work well.

DNMakinson

iTrader: (3)

What brand do you recommend? Is this for an individual, or a dyno shop, $$$$ wise?

I liked the concept of the through-the-firewall mechanical setup that Hakan used

@Savington what have you found to work well?

Mudflap

That is what I use, but the absolute best sound and detection (that i've found) is to feed that tub directly into your ear hole. Both sides. It makes a huge difference.

Newbiata

I'll give the detcans another go then. I am picking up a lot of ticking noise, either from the IACV or the valves even on the motor mount bolt spot, so I'll try building myself a new setup and make sure I have the IACV to be closed during accel.

I did get the stock oil pressure sensor setup, but I think that the capacitor on the voltage conditioner circuit messes with the stock oil pressure unit since it seems a bit more wiggly now.

Savington

iTrader: (31)

Mechanical tube to your ear on the dyno is great if the car is quiet enough. There are instructions on how to make a set floating around here somewhere.

Properly tuned MS3 knock detection is more than good enough to do the job a knock sensor should be doing, which is saving the motor in the case of catastrophic failure (bad gas, slipped timing belt, etc). Looking at the invidivual channels in MLV will tell you whether you're seeing engine noise (all cylinders noisy) or knock (one or two cylinders spiking well above noise floor). Acamas had very finely dialed-in knock detection. My only gripe was that the sensors were noisier on E85 at 400whp than they were on gas at 300whp, so I ended up setting the noise floors higher than I would have liked.