057 | Elite knock control - Haltech Elite 2500

A question was asked in the webinar about the ability of the Elite to handle individual cylinder knock control. Right now the Elite doesn't offer individual cylinder knock control however the knock detection is windowed to a particular cylinder. The retard is applied to all cylinders though.

Individual cylinder control will be added as a future firmware update at no additional cost.

I just watched the Elite knock control webinar and found it to be very helpful! During the video where you are setting up the knock detection in the software you jump the timing in the 2000-2500 RPM range up to 40 degrees under the -10 to 0 KPA part of the table in order to force a light knock so that you can adjust your spectrograph (16:29 in the video).

I have questions regarding this part of the process:

1) Is it always necessary to do this? Is the equation with cylinder bore just a good starting point for you to fine tune from or in some cases is it good enough as is?

2) The idea of forcing the engine to knock a little bit makes me nervous :). Can you provide guidelines on a RPM vs Load vs % timing increase on where we should be doing this? In the video you jumped the timing from 18 to 40 degrees. Is that what we should do or does it vary from engine to engine? I am just not sure how to approach this part.

Thanks!

It's best to double check everything, especially if your aiming for high power figures. the equation with the cylinder bore will get you close but again it's best to double check, that's why you'd introduce light knock at low RPM and low load. the low load and low RPM means that that there is not too much strain on the engine and therefore any knock created will not damage the engine, so long as you don't hold it in a knocking situation.

I believe Andre would have jumped from 18-40 as he knows the engine, he has already tried these values and therefore knows it will generate a good knock signal to allow calibration at this value.

If you are doing this yourself then advance the timing slowly, ~2 degrees at a time whilst listening to the engine until you reach knock, the knock level will vary engine to engine so there are no hard fast rules

Chris's reply is spot on. I've done these sort of tests on our 350Z many times now so jumping to 40 deg is something I've already tested and know to be enough to induce knock. Normally you'd slowly creep up the timing until knock occurs.

To answer your specific questions:

1. Yes, in order to set up and validate the knock control system you need to induce knock. Without this there is no way to prove the system is working correctly. The calculation for knock frequency in my experience has always worked out to be very accurate however many factory knock sensors are 2nd order sensors that are tuned to be most sensitive around double the calculated knock frequency,

2. The damage that knock can do is relative to the specific power level. What this means is that a low powered engine may well survive knock for 100,000 km or more (everyone's heard some old timer labouring their Toyota Corolla up a hill in the wrong gear with the poor engine pinging its head off - Chances are it'll just keep on going). A high powered drag engine on the other hand can be destroyed in seconds by aggressive knock. When testing and configuring knock control you always want to start with the lowest rpm and load that you can easily induce knock. This will ensure that minimal stress is placed on the engine.

Thanks for the detailed answers....that makes perfect sense!

Hello everyone. Going to revive the webinar thread. I'm ready to tune my fresh vq35de twin turbo G35/skyline. this is my 3rd build and first one i will tune myself. The last build had a knock issue. I've watched the elite knock webinar several times and appreciate the knowledge here. My question is will the knock frequency for an FI engine be the same under vaccum and boost? I.e. if i tune the knock detection like Andre did at light load and get 12khz frequency, is that the same knock frequency in my 15 psi of boost range? BTW I will be wearing knock listening equipment as well. Thanks HP Academy!

The knock frequency doesn't tend to change as it's really an aspect of the engine's mechanical design. You'll also find that the frequency filters used in the ECU aren't super specific so 12 kHz for example is just a centre frequency for the DSP filter but this still allows frequencies that are close to 12 kHz to come through too.

Thanks Andre! That helps!

I have a follow up question. So what is the approach to tune and verify the knock threshold table for a boosted application?

My thoughts are tune for vaccum as in the video. then set the threshold at a conservative/safe level and then proceed tuning with knock ear system. I know this could cause some false knock. As i am tuning the mid/high boost levels listen for knock throughout the pull. If there is no knock at a certain point then i can ease the threshold a little. Rinse and repeat for upper boost levels. Does that sound correct?

Andre, for your haltech elite setup on your 350z did you keep the oem knock sensor or go with a different one i.e. the haltech one. I remember you mentioning there is different filtering designs OEM manufacturers would use. The issue I am having is making sure that I am able to tell noise from actual knock while listening and using the elite spectrograph. Doing some driving and testing last month it seems I am getting some knock in vaccum when I get on the throttle. I just wanted to make sure I am good before I start adjusting the threshold. Thank you.

We're using the stock sensors on our 350Z. With a lot of the factory fitted sensors on late model engines you will find they are narrow band designs that are selected to provide a better signal to noise ratio on that particular engine. Usually this is a second order type sensor which is tuned around double the calculated knock frequency.

Thanks Andre. So with a 96mm bore I calculate I should see knock at the 6khz freq. With a second order I should be looking around the 12khz. Sound about right? Thanks again.

Yes that's correct. I'd try both frequencies as well as variations close to each frequency to see what provides the best signal to noise ratio.

I'm dealing with a rotary using an Elite2500 trying to do "banked" knock to listen to both rotors, but I can't seem to be able to find a center frequency. used new oem sensors, the graphic analyzer just goes full red even free revving. Haltech suggested to use a more modern sensor, so I replaced them with a pair of bosch sensors, and its the same. I'm suspecting there needs to be some filtering but there's none available in the software. I've researched and found that the correct frequency should be somewhere around 3.5KHz but its just as noisy past 20KHz. Any ideas?

it's possible that you just have too much vibration in the system. What engine and transmission mounts are you using? I wouldn't trust anything besides OEM. Even the "street" aftermarket mounts vibrate a lot more than stock.

All oem. This car is a unicorn...14k miles on it!

Its possibly you've got an electrical noise issue there, have you got access to an oscilloscope at all?

Sorry to necro an old posting :)

I'm just starting to learn my Haltech e2500 that I got for my k20a ep3 civic type r - and after getting the base timing sorted (not as easy as you'd hope on this particular car - thanks honda) I'm starting to learn about the knock monitoring system that the ecu has.

The e2500 has several channels of knock related information

"knock signal" - the raw signal coming in from the sensor (honda OEM at the moment)

"knock threshold" - which in the webinar was explained basically as the "background noise level" of an engine at a rpm point (if using a 2d table) when its not knocking

"knock level" - I don't know what its for or how to make use of it - it steps up and down fairly aggressively and doesn't always seem to be related to knock signal exceeding the threshold

"knock count" - increases usually when knock level goes up - but not always - what use is it other than a flag that "something didn't go right many times"

OK - now for the questions :)

what is the knock level channel? is it just a rough indicated value of how bad it thinks the knock event was at that point in time? What should the correct use of this be?

what is the knock count channel? obviously it counts knock events - but what is a knock event trigger? is it when signal exceeds threshold or is it related to the knock level channel in some way?

The knock threshold table (in its optional 3d format) has a top axis set by default in the haltech provided base map to use TPS rather than map - is there a good reason for that? Wouldn't MAP be a better axis to use than TPS so that you can match it against load on the engine "better"?

Yes - I'm going to be using audio knock monitoring as well - the TunerNerd kit has been ordered - and I do understand that the knock control is an extra layer of protection AFTER a correctly tuned ignition table and you can do without it entirely if things are initially tuned correctly and safely - but I'd like it to be working - and I'd like to know exactly what the channels are and what they mean when viewing the datalogs - I've not found anything in the comprehensive Haltech help file - or the forums there - about what these unknown (to me) knock channels are or how to make proper sense of them.

I'm asking in here first - in case someone knows whats what - failing that I'll fire yet another query off to Haltech support to find out more - They're really good guys - but I'm sure I'm about to be added to the Haltech spam filters soon lol:)