Knock detected on baseline tune

Delox · Post by **Delox** » Sat Mar 07, 2009 12:18 pm

Hey everyone.

So I drove my car more than just in and out of the driveway today with nistune for the first time since install. I was receiving a knock code occasionally, but do not yet have a wideband to complete actual tuning.

I have injectors which are double the size of the stock (740cc vs 370cc) so I cut the K constant in half (144 vs 288 stock). In order to 'band-aid' the problem until my wideband arrives I simply increased the K constant up incrementally until I stopped receiving the code (around K = 160).

Of course this is not a final solution, and the wideband will be coming in within a week or two, but for now I figure running a bit rich is better than chancing anything.

I plan on building myself a knock amplifier as outlined in the other thread since I don't completely trust my stock system.

Also, is it acceptable to clear DTC codes while the engine is running in real-time mode?

thanks guys.

Matt · Post by **Matt** » Sat Mar 07, 2009 2:52 pm

you can only clear the codes in 'tuner mode' so that is fine

if you are getting the KNOCK DTC code then it means that occasionally your knock sensor may be going out of limits. what that means is that normally the ECU expects a reistance of about 500kohms. If it travels too far out of range from this value then the code gets raised

Check your connections to your knock sensor/s and make sure those are secure. if you disconnect the sensor this will raise the code also

That DTC should not be raised for when knock is occurring...

Delox · Post by **Delox** » Sat Mar 07, 2009 3:02 pm

hmm, I've never had that code before installing nistune, and when I rebuilt my engine the knock sensor read around 540kohms (which I compared to a new one which read about the same).

I rewired the entire knock sensor all the way back to the ECU because my harness had been damaged somewhere along its length.

If I receive the DTC again I will copy the exact dialogue.

TM_S13 · Post by **TM_S13** » Sat Mar 07, 2009 7:47 pm

haven't you used the "resize injectors" tool of nistune ?

chris2712au · Post by **chris2712au** » Sun Mar 08, 2009 12:11 am

Delox wrote:hmm, I've never had that code before installing nistune, and when I rebuilt my engine the knock sensor read around 540kohms (which I compared to a new one which read about the same).

I rewired the entire knock sensor all the way back to the ECU because my harness had been damaged somewhere along its length.

If I receive the DTC again I will copy the exact dialogue.

did you use screened cable for the rewire and ground it properly..

these knock sensors are prone to electrical noise that can trigger b/s error codes

Delox · Post by **Delox** » Sun Mar 08, 2009 9:51 am

TM_S13 wrote:haven't you used the "resize injectors" tool of nistune ?

Yes, and I put in the stock size and new size, so it should have a rough tune, however I was receiving the knock code so I was worried.

chris2712au wrote:
did you use screened cable for the rewire and ground it properly..

these knock sensors are prone to electrical noise that can trigger b/s error codes

Ive never received an error with my current wiring until installing nistune, therefore I assumed it was a real error. I ran a slightly thicker gauge wire to the sensor, and on 300zx's only one of the connectors on the sensor itself is utilized, the other does not have a contact in the (female) connector.

chris2712au · Post by **chris2712au** » Sun Mar 08, 2009 12:52 pm

can you get your hands on another ECU perhaps ? you can try the resistor mod to disable it just for test..

Delox · Post by **Delox** » Mon Mar 09, 2009 3:08 pm

chris2712au wrote:can you get your hands on another ECU perhaps ? you can try the resistor mod to disable it just for test..

I cannot get another ECU, and I don't see the logic in doing so.

Why would I disable the knock sensor, I don't see the benefit of running that "test".

I do not believe nistune is malfunctioning, nor my ECU.

chris2712au · Post by **chris2712au** » Mon Mar 09, 2009 5:28 pm

using a resistor to disable it will test your wiring out and take your sensor out of the equation... as long as you connect the resistor at the point where the knock sensor is..

If you dont get errors you cant blame the wiring nor the ECU, nor nistune for certain.

then it is definitely a sensor problem.. till then your guessing...

however you have not got the tune right, you don't have a wide band, and i think you said you are running 1 bar of boost ? maybe your engine is knocking so bad your ecu is complaining about it.. check your plugs out ? any signs of pinging ? hows your base timing ? hows your fuel pressure ?
I know matt said that it should not raise the DTC if knocking however I would like to see it tested..

all else is good just replace the sensor.. sounds like this guy had fun though..

http://www.wallpaperama.com/forums/p032 ... t6166.html

Delox · Post by **Delox** » Tue Mar 10, 2009 10:37 am

I will try the 1m Ohm resistor at the sensor point just to check, though again, I never had the code show up before installing nistune and new injectors at the same time. I highly doubt that the injectors are the problem.

as for the knock sensor, I know how to replace it and its not bad at all to pull the plenum and lower intake when you've done it as many times as I have. When I rebuilt my engine I tested the knock sensor and it was working perfectly.

when I turn the fuel K constant up to 155 (from 144) the knock error stops showing up. This is why I do not believe it is sensor related, but actually knock occurring, however matt mentioned that I should not see that error under normal circumstances of knock.

OEM_Z · Post by **OEM_Z** » Thu Mar 12, 2009 4:00 am

Interesting... Im having some similar types of issues with the knock code 34 that I also did not previously have. But I can say that I also dropped in a JDM engine and reused the knock sensor that was already on it. I upgraded to 740 injectors as well and had to make my own adjustments to the ecu. I resized the injectors and scales on my JWT bin.

Nistune set my k-value at 144 but that definitely seemed to be to low. So I doubled it for my dual intakes to 288 but then ended up adjusting it to 320 - 330 range. Ash goes as far as setting his to 340 with dual intakes as I have seen in his tunes.

I have been playing with the tunes for a while and the 34 DTC did seem to go away when i had k-value set higher but it could be coincidence. Im gonna really look into just trying to eliminate the knock sensor itself as the cause of the code. A friend of mine just got the nistune installed on his Z and has no codes running the Nismo 555's.

OEM_Z · Post by **OEM_Z** » Thu Mar 12, 2009 4:09 am

I also thought that I was knocking which I possibly was at times when I had it on the lean side of the k-value. Since I was knocking I thought that threw the knock code as well but thats not the case as Matt has explained. Pinging does not throw the code 34.

Now that Im pretty sure the k-value is in a good range based on torque and drivability now I have to figure out why Im throwing that code still.

Delox · Post by **Delox** » Tue Mar 17, 2009 5:36 am

I've just purchased an LC-1 so I hope I can resolve all this once I actually figure out how everything works.

Delox · Post by **Delox** » Tue Mar 24, 2009 10:39 am

This is the error I receive sporadically.

once this occurs, the car feels sluggish, seemingly because the ECU has gone into knock settings (retarded timing, extra fuel)

.

Matt · Post by **Matt** » Tue Mar 24, 2009 12:21 pm

The nistune firmware does not go near the knock sensor register or DTC codes. Even the Rev15 firmware monitors the knock sensor register and updates an internal knock counter. But it doesnt affect it ...

In all versions we only added some code to the consult firmware to communicate with the ECU and dont touch the diagnostics code stuff

So nistune firmware shouldnt be raising DTC codes for knock sensor. If you suspect it does (and LED is flashing knock code). Unplug the board and use the factory chip and see if it does it with factory ROM.

But there should be no link between Nistune and diagnostic codes raised as a result. You need to be clear on these forums which ECUs you are using also so I can check it here

So far I do not get knock sensor fault codes with Nistune boards installed on HCR32, BNR31, A31, Z32, S13 CA18, VL turbo etc on the rev15 firmware when testing knock out here. I am using one resistors to hold up the backup knock line on the bench and a real knock sensor on the primary line (to trigger the sensor and check the counts)