GM knock detection reliability

[Daniel Souza]

I've just watched a webinar from HPacadamy about The Plex knock monitor. It is a impressive device and I can see it's a must have for a professional tuner. However its price is a bit scary for beginners. The initial buget of HP tuners + wide band is more than doubled after adding the Plex knock monitor.

So here comes my question. Based on your guys experiences, how does the GM knock detection strategies (E38) correlates to the Plex monitor ?

Would my beloved LS3 engine be safe if I tune it after a OTR cold air intake + headers just trusting the ECU knock detection?

 

[monstar]

I've just watched a webinar from HPacadamy about The Plex knock monitor. It is a impressive device and I can see it's a must have for a professional tuner. However its price is a bit scary for beginners. The initial buget of HP tuners + wide band is more than doubled after adding the Plex knock monitor.

So here comes my question. Based on your guys experiences, how does the GM knock detection strategies (E38) correlates to the Plex monitor ?

Would my beloved LS3 engine be safe if I tune it after a OTR cold air intake + headers just trusting the ECU knock detection?

Of course.

 

[07GTS]

ur not really ment to tune to knock, that is a by product of going past too far its best to tune to peak torque/hp and thats where the dyno comes in just so u can see where the gains stop, especially if u are running ethanol cos u most likely wont see knock so have to look for torque to level out or reduce means u have gone too far, u can tune for the majority of the ecu without a dyno but timing is best to have that reading to know where u are at, AFR ect can be adjusted with a WB on the street (i have one plumbed in full time) but also yes the GM knock works well or a little too well on some when using petrol, also everyone thinks the factory main spark timing is crap but in fact it is quite good and only needs little changes to suit mods the power gains are in most of the other areas

 

[_R_J_K_]

The LS platform is far enough along in life/aftermarket R+D/popularity that if there was a limitation it would be a known limiting factor. For example, the knock sensor in the HSV 304 based motors is pretty bad, to the point that if you move up in size of cam it will set the knock sensor off, so most tuners will disconnect it. It's pretty much purely because the type of sensor and way they used the knock sensor wasn't accounted for when the engine was being designed in the 60's when knock sensors didn't exist. Nothing like that has really happened with the LS.

Also keep in mind that the Plex is primarily an external tuning tool that has no interface with the ECU (so no ability to retard in the event of knock) and once you're away from the dyno, the Plex isn't there anymore and knock will happen in real world driving regardless of tune (bad fuel, heat, environment, some other failure etc...). Consider that in the event of knock you won't have anything to rely upon apart from the factory sensor to stop knock anyway as that's it's primary purpose rather than a tuning tool. For what you're trying to accommodate for the GM sensor is well within spec. It's not like it's a highly strung/racing build which is probably what tuning with the Plex is geared towards.

I wouldn't be surprised if a lot of shops don't have a system like this in their inventory anyway.

EDIT: It does look like there might be some Canbus ability to hook it up to an ECU but I can't find a lot of info about it. My point still remains though that it's overkill for what you're trying to achieve.

 

[monstar]

Had a friend who had troublesome burst knock being reported on his stroker build, logs really stumped him and conflicting pro advice for a good while trying to find whether real or false. So basically building on the stock tune base without adjusting noise characterisation caused a lot of unnecessary grief.
Took it to Harrop in Melb for a fresh tune, using these headphone cans on the dyno to recalibrate mic sensor profile basically carved out a brilliant tune.
In this case of petrol, noisey cam (klanky), stroker (unknown mic thresholds), once-up set-and-forget top dollar last ditch effort tune where legal action threatened left right and centre... yes helped someone über the berg. If I was charging guys a grand a flash then I’d want some theatrics like this too, maybe even a balaclava.
But like wearing flippers, goggles and a float ring when surfs up, its a lot of unnecessary real estate. I think it’s usefulness is too rare if you log, scan and tune regularly for a car you know intimately, perhaps overkill and practically counterproductive.

 

[Daniel Souza]

Thanks all for the info . I don't mean to tune to knock. I just want to be sure the knock protection is reliable on my application.
I am also aware of the KR strategies of the E38 ECU but if my log shows knock is being detected and acted upon more often than usual, something is not right.

I also want to tune the low octane fuel table for E10 which will make the engine more knock limited and I will rely on the knock sensor even more.

ur not really ment to tune to knock, that is a by product of going past too far its best to tune to peak torque/hp and thats where the dyno comes in just so u can see where the gains stop, especially if u are running ethanol cos u most likely wont see knock so have to look for torque to level out or reduce means u have gone too far, u can tune for the majority of the ecu without a dyno but timing is best to have that reading to know where u are at, AFR ect can be adjusted with a WB on the street (i have one plumbed in full time) but also yes the GM knock works well or a little too well on some when using petrol, also everyone thinks the factory main spark timing is crap but in fact it is quite good and only needs little changes to suit mods the power gains are in most of the other areas

You mentioned you keep the wideband connected all the time. What sort of life span you are getting out of the sensor? Does your controller turns on the sensors heater as soon as the engine is on ? Do you use one for each bank?

 

[monstar]

I also want to tune the low octane fuel table for E10 which will make the engine more knock limited and I will rely on the knock sensor even more.

LS3 specs:
Target EGT= 736.2 degrees C at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 96.3 to 98.5 Octane required range
Air Standard Efficiency = 61.79940 % for 10.700:1 Compression Ratio
... maybe burn and break things with 91 octane, made for 95 minimum. Pouring that sulphurous unrefined sludge upped pig rich into this V8 CO2 generator ain't gonna save your wallet, or the planet.
Must be a long way between servos and no PULP availability?
Later intake close cam (any aftermarket) would solve your ASE / low octane issue, as would VVT.

You mentioned you keep the wideband connected all the time. What sort of life span you are getting out of the sensor? Does your controller turns on the sensors heater as soon as the engine is on ? Do you use one for each bank?

FWIW my wideband is connected on-board all the time, controller is TechEdge 3A2 running TE 2.0. Been running Bosch LSU 4.2 daily with heater since 2013, 200k km. Does need free air recal now though.
Single wideband after 100 cell HFCs (bank 2 rear) tuned open loop, I log and correlate narrowband and injector pulse width to report and maintain parity between banks.

 

[Daniel Souza]

LS3 specs:
Target EGT= 736.2 degrees C at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 96.3 to 98.5 Octane required range
Air Standard Efficiency = 61.79940 % for 10.700:1 Compression Ratio
... maybe burn and break things with 91 octane, made for 95 minimum. Pouring that sulphurous unrefined sludge upped pig rich into this V8 CO2 generator ain't gonna save your wallet, or the planet.
Must be a long way between servos and no PULP availability?
Later intake close cam (any aftermarket) would solve your ASE / low octane issue, as would VVT.


FWIW my wideband is connected on-board all the time, controller is TechEdge 3A2 running TE 2.0. Been running Bosch LSU 4.2 daily with heater since 2013, 200k km. Does need free air recal now though.
Single wideband after 100 cell HFCs (bank 2 rear) tuned open loop, I log and correlate narrowband and injector pulse width to report and maintain parity between banks.

The low octane table would be tuned to E10 (94-95) and not 91. I use the car for work and the company gives me a fuel card. Because Holden states the car is E10 compatible, the company wants me to use E10. So my strategy is , I start using E10 and from time to time I snick in a 98 tank. With time i start using more more 98 until they complain, then I go back to E10 and the cycle starts again. That is the price to pay for free fuel in my case. For track days or drag days i make sure i have 98 even dough i didn't see much difference on the 1/4 mile times between caltex E10 and 98.

I haven't started tuning it yet, I'm just building up knowledge and budget. I got a baby due in a few weeks and the $$$ is flowing out more than ever. Soon the time to learn EFI tuning will be also consumed by the newborn creature.

I will probably go with HPTuners but I am still open to EFIlive , please feel free to try change my mind. At the moment I am just capturing logs from OBDLink and Torque App to backup my studies. I know it is far from ideal but it is something.

There is also the warranty, still 4 years left or 100Kkm, issue which is bugging me. The engine is not much my concern, if it goes it would be a good excuse to get better internals, but the auto transmission could have some issue not related to the tune and I wouldn't be covered for. How do the Auto transmission have been performing on the older HSVs ?

 

[monstar]

I will probably go with HPTuners but I am still open to EFIlive , please feel free to try change my mind.

Same principles of course, EFIlive have traditionally had the edge re 3D VVE, now just different screens and terms. I think there is generally less known about EFIlive, so seems more P-plate first time easy fix tune swappers use HPT plus is free for young blokes to play with hence the more common (inexpensive) setup. So from your perspective I think having a Flashscan V2 handheld is the core difference vs always buggerising around with a laptop and bluetooth dongles.
I use my iPhone VPN to EFIlive desktop in office, so anywhere simply transfer microSD from FlashScan to iPhone and scan and tune. Handy, anywhere, anytime, family think I am struggling with tech to type an SMS or something but I send tunes and receive logs from mates as an SMS attachment, same speed as an MMS. Data calibration doesn't need headphones, laptop, AFR gauges, tin foil hat. WBO2 controller has no gauge or lights, just audible alerts from behind glovebox.
EFIlive is the best software for our e38, discrete, cool, just works and full featured. I bought pre-wideband sensor, controller, FlashScan and one licence neat in box for $900, definitely the best toy I've had in years!

There is also the warranty, still 4 years left or 100Kkm, issue which is bugging me. The engine is not much my concern, if it goes it would be a good excuse to get better internals, but the auto transmission could have some issue not related to the tune and I wouldn't be covered for. How do the Auto transmission have been performing on the older HSVs ?

Nah forget the warranty, just do it. good 6l80 goes for $750 as is, brand new $2750. Complete short block a couple of grand, not worth waiting, grow a pair.
My trans is original, carries decent load at a decent clip for over six years 300k km still kicks arse zero probs. I was an early proponent of the deeper trans pan and wide mouth filter though, seems to have paid off.

 

[_R_J_K_]

Not that it's that important anymore, but check out the knock sensors Plex has on this page next to their Knock Monitor - https://www.plex-tuning.com/5-tips-...ng-a-knock-sensor-that-everyone-should-apply/

They look like standard Bosch donut sensors. My SR20 has one of these from the factory (an over 20 year old engine). This would make me believe that the Plex system is only advantageous because of the way it presents data rather than having a higher quality sensor.