Strange knock sensor values

[smart_garrett]

Hi all,

I have been tuning my 20det and have into a bit of confusion. When I log the knock sensor values, sensor 2 is has quite different values than sensor one, even at areas where there is little knock possibility. Is this because they could be wired in series? Although wouldn’t make much sense, I haven’t looked into it much. I will get large knock spikes at about 5500rpm -6000rpm, we have taken a lot of timing out down to about 11-13* and ran different types of fuel and have had no luck. I would think that the voltages of the two sensors would be more similar but I could be wrong. I’m not sure if this is false knock or not but I would like to bump the timing back up to 16* ish as the afr’s were spot on and it felt good or if anyone has any other suggestions that would be much appreciated. Unfortunately don’t have access to knock ears. Cheers

 

Set up is a rb20det

gt2860rs

440cc injectors

platinum pro

Edited October 4, 2020 by smart_garrett

[Duncan]

I'd start by swapping the front and rear sensors to see if the problem moves with the sensor (so replace it), or if it is the same (ie, there is a wiring or actual problem)

[GTSBoy]

Stock knock sensors are not really worth a knob of goatshit. They will miss real knock and detect non-knock. If there's a little more mechanical noise at one end of the engine than the other, ie valve train clatter or rod noise, then one will/may register knock that the other one doesn't.

You CANNOT tune based on what the knock sensors are telling you. You can only tune using knock ears or similar.

[smart_garrett]

2 hours ago, Duncan said:

I'd start by swapping the front and rear sensors to see if the problem moves with the sensor (so replace it), or if it is the same (ie, there is a wiring or actual problem)

Good idea mate, will give it a go

[smart_garrett]

2 minutes ago, GTSBoy said:

Stock knock sensors are not really worth a knob of goatshit. They will miss real knock and detect non-knock. If there's a little more mechanical noise at one end of the engine than the other, ie valve train clatter or rod noise, then one will/may register knock that the other one doesn't.

You CANNOT tune based on what the knock sensors are telling you. You can only tune using knock ears or similar.

Yep, makes sense could be picking up drivetrain “noise” as well. I had a great time helping tune our e46 race car here in the us for a series called lucky dog, had knock ears there and was able to hear it audibly, really helped make it perfect. Just my first dab dealing with rb’s, good to know they’re not reputable

[smart_garrett]

Update, I have played with timing and fuel bit more and retarded the timing 5 degrees and it still made little to no difference. It seems to detect the least knock competitively (if it even is real knock) at about 16* timing at high rpm/wot, which is conservative from what I've seen people online have their 20's at. I also put a tank of fresh 100 AKI (104 RON) and it seemed to make little to no difference of the seemingly high knock values that are spiking to 200+. This is leading me more to think one or more of the sensors is faulty.

[PLYNX]

From the United State of America:

[GTSBoy]

FWIW, I think even new sensors can be flaky wrt how and when they "detect" knock. The lack of reliability of RB knock sensors has been known for >20 years. They were still "new" back then.

[Murray_Calavera]

I'm surprised no one has mentioned this yet. The platinum pro has terrible 'knock detection' it's closer to 'random noise detection'. I'm not saying the ecu is rubbish, it just that it can't do proper knock detection.

The platinum pro is a very old ecu by todays standards. If you want better knock detection, get a haltech elite ECU or better yet, by a plex knock monitor.