Anybody Use Det Cans??
 

Hey,

I made some detonation cans to use while tuning. In boost i sometimes do here this sound, it sounds like a thick piece of glass cracking like a tick tick, i think its detonation? How severe would this be? Seems to only happen if AFR is leaner then 12.0. I also sometimes hear the same sound getting back onto throttle coming off over run fuel cut, just for a second.

Any one able to explain this sound a bit more to me?

Thanks in advance!

That sounds like det, and you shouldn't be 12 in boost.

It depends on how much boost. 12 is fine at lower levels.

I target 12 by 110kpa and 11.8 by 120kpa, carry 11.8 to 170kpa, then 11.5 by 200kpa. For the first 6ish psi my afr was a bit leaner then 12.0 in spots so i would hear that tick tick sound. Because my ve table needed work.

Would this be more of a mild detonation? Trying to figure out if this would cause any damage.

Detonation you can hear without Det cans is an 8 out of 10. The human ear can't pickup the kind of knock that won't hurt an engine. Det cans are good, but a knock sensor that can tell the ECM to retard timing is even better. OEM's have been doing it since the early 80's.

You need to know the knock threshold first. I wouldn't count on a na/nb knock sensor too much. And the settings in megasquirt are too modular to count on them either.

I'm not sure I'm following you here, what do you mean by knock threshold? You mean how much timing he can run without knock? How do you propose he figure that out without Det cans or knock sensors?

On the megasquirt.....I don't think "modular" means what you think it means. On a ms3 with the knock module I've got tons of resolution, per cylinder gain control, rpm and temp based knock limit curves. With sequential ignition I can even do per cylinder timing retard. That's plenty to be able to do it right.

I'm saying that I advise not to count too much on the knock sensor, i.e use det cans, figure out the threshold. The graphs in the log should almost flatten out by then and work with that.

electric det can into the mic jack of your laptop, nice ear muff head phones into the headphone jack. It's amazeballs.

http://www.absurdflow.com/miata/klde/detcan1.JPG

Engines make lots of noise. Knock sensors pick up lots of noise. You need to figure out what the threshold is that differentiates noise and knock.

Have you succesfully had knock appear and then go away with knock retard on an MS3? If so please share logs and settings.

Personally I have had trouble differentiating between noise and knock, and need to continue fussing with settings. I know I have heard knock on det cans that the MS3 did not see, and the MS3 has told me there was knock when there isn't any at times too.

This is exactly what I use. A clip on microphone off ebay epoxied into a battery terminal. I've also used copper pipe flattened out with a hole drilled through, works just as well.
I run the output through FL studio (a free to use digital audio workstation) and apply a bandpass filter that allows the filtered sound to play in real time.

As for what knock sounds like, its more than one sound.
It can be small snaps, ticking or crackles, barely audible. Its what we used to call BLD (Borderline detonation). We'd be like "Is that knocking?" Then you'd get a great big SNAP and you'd knock for sure.
It can also sound like a high tension steel cable snapping, or a stone thrown on to a frozen lake. I'm not sure how to describe it, if you listen to the engine enough you'll know when you hear it because its not like normal engine noise.
Pre ignition is unmistakable not least because its so much louder than a normal knock event! It sounds like some snapping a shatter proof plastic ruler but in time with the engine rpm. It goes off like a machine gun!

I'm still integrating and timing the setup, so far I have a fairly decent baseline level of noise established that rises with rpm as expected. I did find that cylinder 2 & 3 are "louder" than 1 & 4 which makes sense since they are further away. I've leveled them by adjusting the gain down on 2 & 3.

I haven't ran it for long but I have had some mild knock in transient situations where I've gone lean or lugged the motor. Seems the NB1 sensor works fairly decently. I was waiting for dyno time to push the limits.

I've also found that. I've also found knock situations that did not show up on the sensor.

Trust what you want.

Ehh you should have tuned with the crap from the 80's.... This stuff is way better. I think we can agree the Knock routine needs to be a last resort backup to a good timing table, bad gas, abnormally high intake temps, ECT. We tend to rely on a WB on the fuel side almost too much, can't really do that with the knock sensor.

So I have an 02 engine, which came with a knock sensor, in my car, which didn't. I can wire it up to the MS but has anyone soldered an 1/8" jack onto the end of the plug and used that in their detcan setup? Could be interesting.

So the tick and crackles is minor, but if it got worse would you still hear this noise and on top of it a different noise?

Also how useful is watching the oil pressure gauge flicker? How much would the needle move to indicate knock?