View Full Version : false knock methinks


ichpen
05-10-2012, 08:14 AM
To the guys that dabble with tuning here. I'm having a hard time finishing off my TVS road tune.

I'm running a 2bar SD OS, VVE tables are spot on, IATs are good, MAF is off, AFRs under boost are a nice 11-11.3 at max, so just working on finalizing the high octane tables. I'm doing pulls in 5th gear from 2-5k rpm. At around 4k (apcyl .98-1.00) I'm seeing 6 degrees KR. Pulled 6 degrees in the affected cells, did another run and I see 6 degrees KR again. Boost I'm pegging at 13 psi on the TVS. Running 91 ethanol free gas.

Was running 18 degrees in those cells, pulled it back to 12. Same result.

Car runs strong, don't hear pinging or anything out of the ordinary.

Kind of baffled now and thinking this is false knock. My knock sensors are fresh. From what I read few things to check are torque on knock sensors and if anything may be making contact with the frame/engine. I know my driveline is a bit shot (diff on its way out, DS is not 100% balanced). Only other odd thing is my bank 2 precat o2 is sometimes reading 10% leaner than bank 1 but I see this in many other cars I've logged also so not sure.

Kind of curious if anyone has any outlandish ideas here.

DMM
05-10-2012, 09:22 AM
You should be fine at 18* if your fueling is spot on (fuel press, injectors, etc.). While this does not sound like typical "burst knock" conditions, there is a possibility that this could be what is happening.

I would try going into "Spark"--->"Retard" and under "Burst knock" select the "Enable Delta Cylinder Air" and desensitize the sensors a tad bit to see if this helps. I had to do this on the V and the truck, but I have the knock sensors in the valley...and I was having issue's like this at around 2k RPM.

Even though you are pretty safe at 11.0-11.3, I would add a little more fuel JIC you have a single fuel injector that's lagging behind the rest.

This is the PITA stuff that could be caused by any number of things and it gets really frustrating. Good luck!

CancerJCC
05-10-2012, 10:06 AM
I'm with DMM. Disable burst knock COMPLETELY and see if it goes away. Mine is off all the time, thats burst knock not regular knock retard. (Before someone tells me I'm crazy).

wcryan
05-10-2012, 10:12 AM
^ your crazy..... just cause

CancerJCC
05-10-2012, 10:16 AM
^ your crazy..... just cause

Damnit. Haha

ichpen
05-10-2012, 03:39 PM
You should be fine at 18* if your fueling is spot on (fuel press, injectors, etc.). While this does not sound like typical "burst knock" conditions, there is a possibility that this could be what is happening.

I would try going into "Spark"--->"Retard" and under "Burst knock" select the "Enable Delta Cylinder Air" and desensitize the sensors a tad bit to see if this helps. I had to do this on the V and the truck, but I have the knock sensors in the valley...and I was having issue's like this at around 2k RPM.

Even though you are pretty safe at 11.0-11.3, I would add a little more fuel JIC you have a single fuel injector that's lagging behind the rest.

This is the PITA stuff that could be caused by any number of things and it gets really frustrating. Good luck!

Good suggestions guys.

Burst spark I've always zeroed out as I know it always used to introduce KR even just blipping the throttle from idle. I'll desensitize the sensors a bit but...

Having said that the KR is now gone. I'm effing confused.

2 things that changed:
1. I refueled
2. I upped my boost a pump level from 20 to 30% just on the off chance that pressure is dropping albeit AFRs are good

Low and behold it seems to have disappeared in those cells so it was/is either a) bad gas b) fuel pressure drop but AFRs were perfect (maybe this is the small delay factor) or maybe I just was running borderline.

Could have been a fluke also but I did 4 solid pulls and 0 KR across the board.

Now not sure what to do. Guess I'll do more pulls and see if this comes back.

Thank you though.

DMM
05-10-2012, 03:47 PM
Now not sure what to do.


Leave it alone! LOL My guess is that you have 1 injector that does not flow the same as the others (unless they were flow matched) and the extra fuel made up for it.

ichpen
05-10-2012, 04:00 PM
Leave it alone! LOL My guess is that you have 1 injector that does not flow the same as the others (unless they were flow matched) and the extra fuel made up for it.

Allegedly flow matched but yeah will let it be. :burn: