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-   -   Factory PCM knock control discussion (https://www.rx8club.com/series-i-engine-tuning-forum-63/factory-pcm-knock-control-discussion-200224/)

MazdaManiac 01-29-2012 09:37 PM

The timing retard value that we log doesn't care what the "source" was. If there is a value shown, then that is what is pulled from the calculated timing value.

Why can't you guys just go outside and try the experiment? Is it really that hard or do you just prefer to throw ideas around without having to be responsible for them?

FazdaRX_8 01-29-2012 11:30 PM

I did do the experiment, and yes there is a knock detection when hit hard enough.

but when my car pulls timing at 6000rpms there is no knock detection!!!

MazdaManiac 01-30-2012 04:24 AM


Originally Posted by FazdaRX_8 (Post 4176941)
but when my car pulls timing at 6000rpms there is no knock detection!!!

How do you know it is pulling timing?

TeamRX8 01-30-2012 08:45 AM

some things just aren't meant to be ....

http://www.chapso.de/galpics/2010/12...1291868783.jpg

FazdaRX_8 01-30-2012 09:55 AM


Originally Posted by MazdaManiac (Post 4177007)
How do you know it is pulling timing?

The datalogs, that are posted in this thread....

TeamRX8 01-30-2012 11:08 AM


Originally Posted by FazdaRX_8 (Post 4177187)
The datalogs, that are posted in this thread....

you continue to miss the point, entirely ...

FazdaRX_8 01-30-2012 12:07 PM


Originally Posted by TeamRX8 (Post 4177240)
you continue to miss the point, entirely ...

Enlighten me,

Btw I emailed you my timing map and u never replied....

TeamRX8 01-30-2012 12:29 PM

edit: apology my bad, sent you email

.

MazdaManiac 01-30-2012 06:57 PM


Originally Posted by FazdaRX_8 (Post 4177187)
The datalogs, that are posted in this thread....

You show the timing being pulled, but you don't show anything that indicates it is knock. Because it isn't.
I already explained to you what is happening back on the 18th.

FazdaRX_8 01-30-2012 07:53 PM


Originally Posted by MazdaManiac (Post 4177671)
You show the timing being pulled, but you don't show anything that indicates it is knock. Because it isn't.
I already explained to you what is happening back on the 18th.

Whats wrong with the IAT?

oltmann 02-10-2012 03:51 AM


Originally Posted by MazdaManiac (Post 4168765)
No - the RPM delta table is the RPM delta table.

Obviously, RPM delta is affected by throttle opening angle and rate, but it is not the same thing.

Those tables are looked up based on the difference between measured RPM and desired RPM. Desired RPM looks to be set by the the idle tables, or when off idle it is set to RPM itself. I don't know it this ever actually amount to anything like a delta. No reason to speculate though, you can log desired RPM with any scan software that has the Mazda enhanced parameters. If anyone uses Torque for Android, it is mode 22 pid 0x96e. Scaling is x/4. I broke my Elm327 dongle or I'd do it myself.

In any case, this correction seems to be mainly for controlling hunting idle.

Desired rpm isn't used for much else, but it also looks up base idle timing. I'm not really sure why you can cause feedback knock retard at idle, but it is tangential to the candidate issue. It does highlight one important point: 0.5 load is the maximum for feedback knock retard. This is mislabeled in my version of AccessTuner.

Meanwhile, one of the knock learning strategies only starts at 0.5 load. There are also IAT limits for this stuff, so you could probably disable the whole system by miscalibrating it...

I think we need a utility like Learning View to look at the learned parameters. If you're satisfied with what has been divined from crescent wrenches and defended with hand-waving, I have not a fuck to give.

rotaryPilot 02-10-2012 07:00 AM


Originally Posted by MazdaManiac (Post 4147082)
Did you see this as a change in timing or an actual knock retard value?
If it is only the former, than the knock sensor had nothing to do with it.

It is likely that you have bad IAT values being reported sporadically.



Originally Posted by MazdaManiac (Post 4177671)
You show the timing being pulled, but you don't show anything that indicates it is knock. Because it isn't.
I already explained to you what is happening back on the 18th.

What FazdaRX_8 have to show in order to indicate that it is knock and not just timing being pulled ?

MazdaManiac 02-10-2012 04:53 PM


Originally Posted by oltmann (Post 4186047)
If you're satisfied with what has been divined from crescent wrenches and defended with hand-waving, I have not a fuck to give.

At the end of the day, that is all that matters to anyone that is tuning these things.
If you are only interested in parametric masturbation, I have an equal quantity of fucks to offer.

Originally Posted by rotaryPilot (Post 4186093)
What FazdaRX_8 have to show in order to indicate that it is knock and not just timing being pulled ?

The actual knock decrement value, which he has already said shows zero.

FazdaRX_8 02-10-2012 06:22 PM


Originally Posted by oltmann (Post 4186047)
It does highlight one important point: 0.5 load is the maximum for feedback knock retard. This is mislabeled in my version of AccessTuner.

Meanwhile, one of the knock learning strategies only starts at 0.5 load. There are also IAT limits for this stuff, so you could probably disable the whole system by miscalibrating it...

so anything above .5 load would not be logged in knock retard?

FazdaRX_8 02-14-2012 12:15 AM

? Bump

Flashwing 02-23-2012 09:26 PM

I have been experiencing this very issue and based on all my available data, the knock sensor is the culprit.

Looking at the code oltmann posted, there does appear to be an error present with regards to the logging capability. If I'm reading it correctly, any timing retard value less than 10 will always show as zero. It just so happens the max knock retard value is -10.

I have been running a very conservative timing map so my issue would compound itself. The sensor would think it hears knock (due to unknown reasons), pull timing which would then actually create a misfire causing further timing to be pulled. IAT's were all normal during this time and the RPM delta tables were zero'd which did not solve the issue.

After reading a post previously made by Kane regarding the knock tables, I zero'd all of them and the problem has gone away. No misfires and my timing is being set to what I have in my base table.

For all I know I have a failing left motor mount that is causing the sensor to freak out.

I think the jury is still out on this issue but removing the knock tables from the equation completely fixed the issue for me.

Brettus 02-23-2012 10:20 PM

Good work Flash .
Is this under boost or NA ?

I always limit the knock retard value by about half anyway and don't see any misfire either .

FazdaRX_8 02-23-2012 11:11 PM

I am keeping mine stock,

I mean if you flat line them all and you get bad gas, what keeps your motor from blowing?

dannobre 02-24-2012 12:26 AM

Proper tuning ;)

FazdaRX_8 02-24-2012 12:44 AM

Yeah, where do you get one of those?

Flashwing 02-24-2012 09:58 AM


Originally Posted by Brettus (Post 4196623)
Good work Flash .
Is this under boost or NA ?

I always limit the knock retard value by about half anyway and don't see any misfire either .

This is under boost.

Something has clearly changed in my setup as I never had this problem previous to doing the Turbo rebuild. For all I know I damaged the driver side motor mount with all the moving of the engine and the knock sensor is picking it up.

While removing the knock sensor's capabilities might not be ideal, no one should depend on it to save your engine. With the sensitivity to knock that the rotary has it is very possible you would destroy something before the PCM had time to react in the first place.

FazdaRX_8 02-24-2012 10:20 AM

I have been looking into the mazdaspeed 3 ap, and knock stuff. Cobb gave up early on us. The knock sensor I think works fine, we just cant see what is acually reported. Other then logging timing and compare to comanded.

I do think that the kr system can save an engine from predetination, due to bad gas, that is why mazda has the system, incase someone put in 87octane.

The only way to get a "proper tune" for it is to tune with bad gas...

Flashwing 02-24-2012 10:50 AM


Originally Posted by FazdaRX_8 (Post 4197014)

The only way to get a "proper tune" for it is to tune with bad gas...

Not at all. You can build in safety margins within the tune to account for poor quality fuel. That said, the best thing you can do is ensure you use quality fuel with octane ratings that can be accounted for and stick with it.

I've made a habit of carrying a couple gallons of Xylene with me when I make road trips to areas of AZ that I know have crap gas. In the end, that stuff is cheap while engines are expensive.

TeamRX8 03-03-2012 03:04 PM

You could zero the table out for a test just to see what the result is :dunno: just make duplicate map with the tabled cleared and do a simple back to back comparison under the same conditions. It doesn't get any easier than this.

cwatson 07-23-2013 11:59 AM

So, sorry to bring this up from the dead:

Am I to understand the cobb does not log knock retard because it has filtered out all values below 10? And our knock retard is negated? Is there a workaround for this? I was thinking of getting an AP but am not very comfortable tuning w/o being able to monitor knock levels.


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