Knock Sensor readings - What is a normal ? V6 3.8L

[vlad01]

From y pipe onward a stock exhaust generally doesn't impede performance or knock limits much in my experience. However proper long tube tuned headers vs stock cast exhaust manifolds makes a huge difference.

At least on the older Buick engines you go from being totally knock limited and lower performance at about 22º total timing vs 29º and just under the knock limit with good headers.

Not sure on timing requirements for ecotec, will be a lot lower than Buick. Iirc around 16-18º ?

Ideally you need to get knock headphones and confirm there actually is knock or not.

[JohnDee68]

Why can’t you trust the software? Even the factory scan tool has one for each cylinder. It’s easy for the pcm to pick up each cylinder by knowing which one is going to fire. That way it can tell if it detonated on the last cylinder that fired it will take whatever actions it’s programmed to do via calibration. Later cars are done the same way to pick up which cylinder is miss firing in the event it’s not open on the coil driver side. They are smart enough and quick enough to calculate the mixture from a certain cylinder is not right via o2 sensor and throw up a code.

Well, with one software it shows a knock retard anywhere between 30 and 90 degrees ( seemingly not possible). Where at the same time on each cylinder it doesn't show any knock for any cylinder at the times it is showing the 30-90 values for knock retard.
The other software (TunerProV5) doesn't even register any knocks for any cylinders, presuming that is set correctly by who ever set it up in the VX_V6_$BD_Enhanced_v0.9c.adx definition file I am using. Or even if that is the adx file I am meant to be using. As I have had other values in the past which displayed so far off that they had to be wrong. ie, L/100, MAF G/s.

I guess without a proper ALDL GMH scanner device or even another vehicle to compare readings, I am really just flying blind and feel to be getting misled by the readings from the current software, which is of concern when trying to diagnose anything in the first place.

The other issue is that being a 2002 vehicle, most people have moved on to more current models these days which I can understand. So I am left to sort out things where i can myself. Along with help from guys of course, which i do appreciate. I like to try and solve as much as i can on my own first so I don't bother people too much.

[JohnDee68]

From y pipe onward a stock exhaust generally doesn't impede performance or knock limits much in my experience. However proper long tube tuned headers vs stock cast exhaust manifolds makes a huge difference.

At least on the older Buick engines you go from being totally knock limited and lower performance at about 22º total timing vs 29º and just under the knock limit with good headers.

Not sure on timing requirements for ecotec, will be a lot lower than Buick. Iirc around 16-18º ?

Ideally you need to get knock headphones and confirm there actually is knock or not.

Thanks, I presume you are correct with the eccotec being at around 15degrees mark retard for knock. Well that is what i gather also from looking in to the TunerProV5 software. I am unclear if that is the max, or does it retard 15D each time it detects a knock. I don't fully understand what the PCM does to resolve knock (yet).

I presume knock headphones is like a stethoscope? I have one, though I would find it hard to use while also driving along at 100kmph.

I am looking to make an attachment to use via one of the O2 sensor points that will allow me to measure the back pressure in the exhaust. Because I am unable to confirm there isn't a restriction at this stage sufficient to cause the fuel economy usage of around 12L/100 when it should be more around the 7-8L/100. The exhaust is still original and at 505000km. What sort of back pressure would I expect from a good standard exhaust? You Tubers say less than 3psi at idle ideally, would that be right?

[v6bucket]

https://tunertools.com/products/link-g4-knock-block
This is the "knock headphones" that was referred too above.
At 505000km, I'd say that the catalytic converter is u/s, possibly restricted.

[vlad01]

Those sound recording on that link are great. For those that never heard knock via knock ears should def have a listen.

[vlad01]

These are expensive but are a good kit. Each ear has it's own volume as well on top of the gain of the box. Comes with everything you need.

https://www.ebay.com.au/itm/32462350261 ... Sw1ANgnnes

[Charlescrown]

What about the Jaycar kit. Cost abt $20 and you can hear a bee fart.
Make that $10.95 plus ear phones etc. KC5152

[JohnDee68]

https://tunertools.com/products/link-g4-knock-block
This is the "knock headphones" that was referred too above.
At 505000km, I'd say that the catalytic converter is u/s, possibly restricted.

Thanks for the link. So they basically convert the knock sensor to an audible range and amplify it. Which is what the software is meant to do, but in a visual way rather than audible.
I am yet to test the Cat, but at this stage it doesn't show restrictions in the Cat. But further testing needs to confirm 100 percent. There is no signs of deterioration when looking in to the Cat from the exit end, in fact it looks new internally. But that isn't a sign it is good either.

I'm on the scrounge now for an old used O2 sensor to make up a O2 fitting pressure gauge adaption. As I don't think i would have a bolt with thread for them that I can use as an adapter. Any one know what thread the VX O2 sensors are?

[v6bucket]

18mm x 1.5.

[JohnDee68]

18mm x 1.5.

Thanks V6bucket. I have today made up an adaptor and managed to check back pressie in my exhaust.
At quick throttle opening and red to red line, it flashes almost 2.5psi briefly. Then returns to zero where it remains all other times. So no exhaust restrictions at all.
This now leads me to either crank/cam timing not set right or just the tune not right.
I'm trying to see if I can check the cam timing without dismantling and removing the front timing chain cover.
I think it can be possible if I mark the harmonic balance at 12 o'clock when piston 1 is at Tdc. Then with just the 135 valve cover off, rotate crank till inlet valve starts to open, at which point note the harmonic balance position. It should show if the crane gear has been fitted on 0, 2 or worse spline. I think that can work? It I'll need to know, at what degree the valve should start to open as, to ensure the crank is at that point.
Anyone know if I'm on the right track with that thought?