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Old 07-22-2017, 04:38 PM   #1
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FLKC in high gears (e.g track). What is acceptable?

For many perhaps not that relevant (unless you are not worried about your license) or for those tracking their cars:

What FLKC should we accept at 4th/5th gear at high rpm?

I'm not sure I can live with this. And I really don't want to pull 2 deg timing out of Base Timing B either. I suppose there is no solution except going Ecutek?

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Old 07-22-2017, 05:47 PM   #2
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Adjust cams/add fuel/add DI/add EcuTek.....

Or a combination of the above.

What's your FLKC regard value set to?
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Old 07-22-2017, 07:12 PM   #3
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Quote:
Originally Posted by Kodename47 View Post
Adjust cams/add fuel/add DI/add EcuTek.....

Or a combination of the above.

What's your FLKC regard value set to?
-0.65

It's running 20.3 port from 2k to redline. Above 6k exhaust is at fixed 25 retard and intake advance is 28, 21, 13, 10, 5, 3.

This is more zoomed in and filtered for AFR above 13:


I suppose "per gear timing" is the only solution if I don't want to sacrifice performance in lower gears? Or should I just live with it and leave it to the ECU to retard the timing?

Timing Compensation per cylinder A and B is zeroed out. I'll try to restore that to stock and see if it makes a difference. In lower gears my experience is that TCPC doesn't make a difference at all.

The fuel used it 102 octane and the IAT was 29 deg. I have 100% IAT comp activation at 6 and 7k (the definitions I have the value is positive for retard) and the retard value in Timing Compensation IAT is -1.05. I checked the tables and the values add up to the log.

Last edited by Tor; 07-22-2017 at 07:23 PM.
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Old 07-26-2017, 09:32 AM   #4
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The FLKC graph illustrates perfectly where you are hitting the wall of the capabilities of your header.
You can't ask it to do what it's not designed for.

Bite the bullet, take the timing out and spend the money on track time where it belongs.

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Old 07-26-2017, 09:40 AM   #5
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Quote:
Originally Posted by Tor View Post
For many perhaps not that relevant (unless you are not worried about your license) or for those tracking their cars:

What FLKC should we accept at 4th/5th gear at high rpm?

I'm not sure I can live with this. And I really don't want to pull 2 deg timing out of Base Timing B either. I suppose there is no solution except going Ecutek?

AFAIK the ECU detects FLKC off the sensors that are meants to monitor knock on a STOCK car. Once you have done modifications, such as upgraded exhaust, headers, tune, the FLKC does NOT provide accurate information, as even rasp from the aftermarket exhaust can cause some FLKC to appear. If your AFR is within the normal range, IAM is steady at 1 and you don't hear any knock and car behaves fine, then don't worry about FLKC. Having said that, 11.6 AFR is tad bit low, might wanna get a better tune and get it steady north of 12 throughout the RPM range.

Last edited by tdotBRZ; 07-26-2017 at 09:42 AM. Reason: additional info
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Old 07-26-2017, 10:44 AM   #6
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Quote:
Originally Posted by Wayno View Post
The FLKC graph illustrates perfectly where you are hitting the wall of the capabilities of your header.
You can't ask it to do what it's not designed for.

Bite the bullet, take the timing out and spend the money on track time where it belongs.
If it's the headers capability to move the exhaust fast enough, why is only showing in higher gears? Wouldn't the capabilities of the header relate to rpm and mass airflow only regardless of gear? Or what am I missing.

Also as far as I recall I didn't get nearly as bad FLKC when it was colder (this log had 30 deg C IAT). I might make IAT compensation (even) more aggressive before I'll lose the timing. And as said above I'll put the TCPC back in first and see if it makes a difference.

This is how it ran on track with the same timing at 15 deg C IAT (actually more timing due to higher load and no IAT comp - knock corr is FLKC, and the data are Tactrix log overlaid):


Quote:
Originally Posted by tdotBRZ View Post
AFAIK the ECU detects FLKC off the sensors that are meants to monitor knock on a STOCK car. Once you have done modifications, such as upgraded exhaust, headers, tune, the FLKC does NOT provide accurate information, as even rasp from the aftermarket exhaust can cause some FLKC to appear. If your AFR is within the normal range, IAM is steady at 1 and you don't hear any knock and car behaves fine, then don't worry about FLKC. Having said that, 11.6 AFR is tad bit low, might wanna get a better tune and get it steady north of 12 throughout the RPM range.
Except for the header, I am running stock exhaust. I just don't know if I feel comfortable with the ECU pulling that much timing.

P.s.
Are you criticizing my tune? Auch, that hurt! It's the 33rd iteration. It's the set to target 11.6 AFR on purpose:

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Old 07-26-2017, 10:48 AM   #7
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Quote:
Originally Posted by Tor View Post
Except for the header, I am running stock exhaust. I just don't know if I feel comfortable with the ECU pulling that much timing.



P.s.

Are you criticizing my tune? Auch, that hurt! It's the 33rd iteration. It's the set to target 11.6 AFR on purpose:



Nono was not criticizing the tune. If your IAM is constantly at 1, the ECU have not pulled any timing, FLKC is just simply numbers from the stock sensor that is meant to monitor knock on STOCK car and STOCK tune. IAM is more reliable representation if your ECU is pulling timing due to knock.




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Old 07-26-2017, 11:20 AM   #8
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Hmmm


The knock sensors are basically microphones designed to detect certain frequency's which the ecu then processes through some algorithms. After processing this produces either flkc or fbkc signals which is the ecu's reaction to the inputs from the knock sensors.


If the ECU detects enough knock signal in certain time periods of large enough magnitude (ie you will initially see it as fbkc or flkc) then it will decrement the IAM value.


The flkc is likely real and even if it was false the ecu would react to it the same as it doesn't know the difference its just an input signal from knock sensor. IAM does not reduce instantly on knock its a derived value set by ECU dependant on its perception of the severity of the knock.


Their no separate sensor for IAM flkc fbkc its all derived from same sensors.


I don't think anyone has complete understanding of all the processing and algorithms used but theirs some good info over at the Romraider site.


But it was based on wrx ecu but likely similar, but best we have to work with.


http://www.romraider.com/forum/topic1840.html


I don't think header or aftermarket exhaust noise is going to cause false knock indication , unless its actually hitting on chassis or similar. Why because if you run good E85 fuel you will get virtually no knock even with 4 degrees or more timing than that.




To test if its real knock pull a couple of degrees out of the map or run higher octane fuel (unlikely you can find better than 102 ron easily).


If the knock persists at same levels it likely false if it reduces significantly it was likely real.


Its highly unlikely you will "hear" knock on these cars especially it higher rpm. Occasionally ive heard knock on stock cars , stock tune around 2 or 3 k rpm but they have quiet exhausts and they knock bad on stock tune in that area (on our crap fuel anyway)
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Old 07-26-2017, 11:39 AM   #9
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Quote:
Originally Posted by Tor View Post
For many perhaps not that relevant (unless you are not worried about your license) or for those tracking their cars:

What FLKC should we accept at 4th/5th gear at high rpm?

I'm not sure I can live with this. And I really don't want to pull 2 deg timing out of Base Timing B either. I suppose there is no solution except going Ecutek?




Probably have to run a "track" tune with less timing than your "road" tune or run some higher octane fuel on track day ??


Now you could do that with wayno's flex fuel tune, just disable all the flex fueling adjustments. Put a toggle switch to earth into the evap input on ECU.


Then you can just toggle between two timing and AFR maps with the toggle switch. Put track values in one set ie bit lower timing and maybe bit richer afr and road setting in other more timing leaner afr.
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Old 07-26-2017, 01:18 PM   #10
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Do you log oil temperatures? I also have built a tune for a cat less header (Ace 350) with the rest of the exhaust and intake being stock. I see similar knock to yours, where there is no knock for all sorts of street and autocross driving, but on track I get significant FLKC without an IAM drop. This only happens for me when oil temperature rises above ~ 240 F. I suspect cylinder head temperatures have risen to the point that knock becomes frequent.

The solution is probably a street map and a track map, or perhaps some sort of ROM hack where we replace coolant temperature timing compensation with oil temperature timing compensation. Not sure how well that would work with an oil cooler though.
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Old 07-26-2017, 01:26 PM   #11
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Old 07-26-2017, 02:33 PM   #12
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Quote:
Originally Posted by tdotBRZ View Post
Once you have done modifications, such as upgraded exhaust, headers, tune, the FLKC does NOT provide accurate information, as even rasp from the aftermarket exhaust can cause some FLKC to appear.
Erm.... No.

If you have built an engine, like changed internals, then it may be more noisy due to extra slack in the components. These are likely to be in the frequency range that the stock sensor and ECU filtering work and therefore it is possible to trigger the timing retard. Changes in general noise in the engine bay, like a change in exhaust manifold, will make no difference. It's simply not the right frequency and is not going to have an impact on the knock sensor output.

It's a shame that we can't adjust the OEM knock filtering, however unless you change to noisier internals then the OEM calibration is not an issue.

Also, if it was the exhaust causing the right frequency to trigger it then it would do it all the time in every gear
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Old 07-27-2017, 12:55 AM   #13
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I've the same issues mentioned including the 'phantom' knock not alleviated by dialing back base timing and increased KC in higher gears tuning with the OFT/Romraider.

Carry on discussion gentlemen.
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Old 07-27-2017, 02:25 AM   #14
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If it's the headers capability to move the exhaust fast enough, why is only showing in higher gears? Wouldn't the capabilities of the header relate to rpm and mass airflow only regardless of gear? Or what am I missing.
That's fine if you only want to think of things in two dimensions, but exhausts have a finite volume. You should think of them more like a buffer. After a certain period of time at a certain load, with certain egt's, etc, the buffer will start to fill and increase back-pressure.

You spend a lot more time above 6800 in 5th than 3rd don't you ?
Something like 12s compared to 2s ?

Your cattemp shows 600 in 3rd and 660 is 5th.
What happens to the volume of gas as you increase the temperature?

Maybe look at more of your data channels?

A stock header (with hollowed out cat or not) is not designed to flow well above 7k, as intended by the factory engineers. Any turbulence may also increase back-pressure.
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