Lets Talk About Knock

[SargeRX8]

Couple of things tha havent been mentioned.

Fuel pumps dont last forever but it could be a dying fuel pump

Engine breathng heavy. It could be flinging more oil into the PCV or intake

Weather is a big factor. The power fc doesnt have a great intake temp compensation, the oem sensor in the rb26 is coated so its slow to respond anyways.

If you get your car tuned in winter, there is a good chance it will knock in summer as you cant heat soak and engine or replicate 40deg c temps easily. However

it is possible to take an educated guess at it. Its a compromise but beats a retune for summer or winter whch isnt really feasible.

Fuel is an interesting one too. When vortex first came out, it was more oxygenated then BP/Shell/mobile however I found that you could run a bit more

timing on shell for example but it would run richer. It seems they have changed their fuel as now it is very similar to what shell used to be. Its not likely

that a tuner will tune so close to the edge that it will det on change of fuels, but if you have a combination of things going on it will contribute. Say your

pump is getting tired, engine is breating a bit more, hotter weather then when it was tuned, going through cells not ususally seen on the dyno

Biggest one, air temp compensation, the power fc's isnt great but it can be effective enough

I have been keeping a close eye on fuel as my old pump failed and now it is fitted with a GTR. When the pump was failing I was lean popping left right and center and the car was near undriveable. I won't rule it out but I am not leaning towards the fuel pump having an effect at this stage.

What causes the engine to breath heavy? I have fitted a sealed catch can into my car so I can pull it out to check oil levels. Although my dip stick oil level is practically exactly where I left it but I doubt the effect of heavy breathing and oil blow by is enough to drop that line. I am leaning towards either a one off where something, some cell, some air, something just triggered some detonation or tricked the sensor. With that said I'm not turning a blind eye to it. I just took the car for a drive. Done some 6krpm through the gears and max det was 9 or 10 on the power fc controller. Exact same roads, almost the same weather just didn't hit the limiter today.

Some good points made there sucram, however it sounds like it is intermittent and doesnt happen everytime on the one tank of fuel or temperature etc. To me the experience described by Sarge would be more likely that some of the tuning cells are not set correctly and it is only when it hits these cells that knock is experienced.

Sarge you seem to have glossed over PaulR33's update?? That is the first place I would be investigating.

I have indeed but fiddling with something I am not too confident with is something I want to avoid. The car is going to get a tune up soon for more boost so until then, ill just lay off the heated driving.

What condition are your plugs in?

Have you actually pulled them out and checked them yet?

I haven't. The current plugs have about 500km on them. When I have time I will pull them out and check for signs of det. I pulled one out for inspection and it looks more to the rich side if anything. Plug shape and structure still looks very healthy.

[Harey]

I didnt necessarily fiddle with the tune itself. I just meant keep giving it a hard time and watch the knock number. If you do get some knock then take note of the cells that have been used. Then you can tell your tuner this. Otherwise, when the tuner has the car he might not get to the same cells again and you will be in the same place.

[DVS JEZ]

Harey its not that easy on the handcontroller. U cant use map tracer to watch the cells and monitor knock at the same time unless the engine light flashes on the dash.

[SargeRX8]

Sarge it isnt a voltage it is an analog signal and you have to filter the knock frequency from the mech noise with a band pass filter, not exactly trivial unless you know electronics theory and opamps + building filters, you would then need to determine a threshold via inducing real knock, better to buy an existing setup, there is a reason why good knock ears

Cost 2k

I have no idea about half the things you just spoke of... What signal is the power fc unit seeing? Is the power FC doing all these conversions and calculations from the sound signal? Surely its not up to the ECU... Maybe I can intercept a wire to the ECU to read something from... I don't know.

I was just fiddling around before, on idle if I rev to about 5k the knock bar on the power fc won't sit still. It must be picking up noise. As soon as I back off the throttle it jumped to 10. It jitters around 2 - 3 constantly. I can't replicate this knock hit...

[JonnoHR31]

the knock sensor is just a microphone, it sends everything it hears to the ecu and the ecu simply ignores everything except a small frequency range in which knock usually lies. it then spits out a number based on how strong it was. this is why you can get false knock and also why its not overly accurate on some modified engines, as the sound/vibration knock makes changes.

those little jitters are just normal engine noise, ignore them. the one off knock you saw is almost certainly a false knock from hitting limiter, happens a fair bit.

[Rolls]

I have no idea about half the things you just spoke of... What signal is the power fc unit seeing? Is the power FC doing all these conversions and calculations from the sound signal? Surely its not up to the ECU... Maybe I can intercept a wire to the ECU to read something from... I don't know.

It is seeing a sound signal which it would then have the things I spoke of either in software or hardware to figure out if it is hearing real knock. So yes it is all internal, there would be nothing you could easily tap into.