I tried to locate mine today from above and below with an inspection mirror, I could see the front one barely and really couldn't tell the angle in the mirror, too much stuff in the way.
Found the lead for the rear one, but not the sensor. Mine isn't that bad since the GMPP base tune my tune is built from so if I have to take the TB or lower CP off sometime I'll dig further. I think they might have changed the sensitivity in the later tunes a bit. I know it got a lot better with the GMPP OS.
Garage Queen-'12 T3 2SS/RS LS3 M6 Camaro. TVS 2300 & stuff on corn squeezins
Any results yet, Shabby?
Still need to do more testing, its been 100F+ here lately and i have one log that has plenty of kr during cruising but when it was 80F i had none.
If you can easily reach the rear sensor you should still give this a shot, you have nothing to lose.
Last edited by shabby; 07-09-2010 at 05:52 PM.
I have the '08 Sky RL so I've got the vacuum pump like yours.
Thanks for the feedback!
Yogi
Ok, I've run several tanks of gas through my Sky since I turned the knock sensors, I'm gonna call this a fix, on my car at least.
I'm not getting the random knock from one cylinder only anymore, and I haven't had the massive amount of KR in the first couple minutes of cold start in the mornings either. I was actually getting as much as 8* KR AT IDLE on a cold start, not anymore. When I do get KR it's almost always from multiple cylinders, and it's when I would expect to show some KR. I can actually tune my timing now, getting actual realistic knock feedback when I get the timing too far ahead in spots. And when I back it off, the KR goes away like it should. Before I had tried several tanks of straight 100 octane and was still showing KR in random areas. I had been backing off timing trying to get rid of the KR and was pretty surprised when the 100 octane had no effect on it.
I have no explanation or reasoning that would substantiate why turning the knock sensors would have any effect on sensitivity except for the fact that GM mentions making sure they're at 90 from vertical in SI. Mine were most definitely NOT 90* from vertical from the factory, and most of the LNF's I've looked at lately aren't either. Even the Bosch technical info on their knock sensors says "knock sensor position- arbitrary". I have seen lots of comments on knock sensor torque, the general consensus is tighter torque makes the sensors more sensitive. I torqued mine to specs (18 ft/lbs) every time I rotated them. I'm not sure about torque being the issue, I could see super loose would make them rattle and pick up false knock, but tight is tight, I'm not sure torquing them down super tight would transmit any more knock than the recommended torque would. The center collar in the sensor is solid, it's not like you're compressing the actual ceramic part of the sensor. You would have to get it extremely tight (bolt would probably break first) to distort the brass collar. The bolt transmits the vibrations, but I'm just not sure 20, 30, or even 60 ft/lbs would transmit any more noise to the sensor. (???)
On a related note, I had increased my "tip-in timing retard" (burst knock retard) trying to get rid of KR (which ended up being false). After this knock sensor stuff I put the tip-in retard table back to stock, and happened to notice no change in my logs. I then went extreme on the tip-in retard (like 10 or 15 degrees retard) and again saw no change in tip-in timing in my logs. I then zeroed out the entire tip-in table and guess what, still no change and still no KR showing up in the logs! So here's the next experiment for you guys, try messing with your tip-in timing retard and see what happens. I've been running that table zeroed out for a week or so now with no ill effects or KR showing up. Isn't tuning fun?! Good thing I'm patient and don't get frustrated trying to figure things out!
BTW I'll start a new thread with this tip-in retard finding.
Last edited by gmtech16450yz; 07-10-2010 at 06:01 PM.
id love to get a mini how-to for this...
So on the cobalts should the pigtail be pointing to the passenger or driver side?
09 Cobalt SS/TC 1/4 mile of 11.952@117.62mph.
Front of the engine is passenger side.
Garage Queen-'12 T3 2SS/RS LS3 M6 Camaro. TVS 2300 & stuff on corn squeezins
just saw this thread tonight. is this still working for everyone?
so by the looks of it, on the sky the wires need to be pointed towards the front of the engine, correct?
2008 Sky RL
Yes that would be correct. I had a discussion with CBSSOB and I am going to check this today. Seems like on our cars best way is from underneath... I will keep you posted.Originally Posted by |V3nom|
cool cool ill have to check this out next time i get some free time. might fix some of my knock.
2008 Sky RL
ok so my front knock sensor is set correct at the 9 o'clock position but the rear is at 5 o'clock. now how the heck do i get to it to adjust it with a torque wrench?
i was able to get some extensions to reach it but once i got the torque wrench on it i couldnt turn it due to no space. do i need a swivel socket or something? i tried using a torque wrench with a swivel and it felt weird, like it wanted to torque it down more than i needed. is there another/better/easier way to do this or should i stick to the original plan?
2008 Sky RL
A knock sensor is an accelerometer and the ceramic pieces are the parts that produce an AC signal based on vibration. The way the sensor is clocked could have a major impact on the reading depending on the mode of the vibration the ECU is looking for, the direction of the sound wave and even the harmonics of other vibrations in relation to the location of the sensor.
I can't remember off the top of my head how the internals of the doughnut accelerometer are configured, but I recall the pigtail having a factor in the orientation of the accelerometer element.
In theory as long as your vibration is on the same plane as the accelerometer then you would be able to pick up the knock, but in function there are a lot of vibrations in the engine bay that could cause false knock. The clocking of the sensor would potentially shield normal vibrations as they will be out of phase with the sensor elements, but when real knock occurs it may excite the block in a plane that matches with the element and trigger as knock.
This is a very simplified example, but valid for this discussion.
Actually you could use a knock sensor to diagnose the condition and wear of not only the engine, but the components attached. Assuming you knew the harmonic for every component in the engine. This is how Jet engines are monitored using what is called a Plane 1 accelerometer. Mind you it's a much higher resolution sensor, but literally every bearing and fan blade can be monitored for abnormal wear based on the vibration coming from the engine. It's all based on a given noise level vs. RPM and frequency. etc..
With our car engines the sensor is monitoring the normal vibration and only looking for abnormal signals in that noise to designate as knock. Like with a select few advanced knock controllers on the market for auto engines, our ECUs are now so capable they can adjust for conditions that are precursors to knock.
IF the sensor is configured and installed correctly.
-Adam Chant SCdyne Performance "Tune it or lose it!"
which is why i need to know how to loosen and torque the rear knock sensor so i can adjust it to the proper position.
2008 Sky RL
I had the intake mani & injs off to replace inj seals & clean the valve stems when I did mine.
IDK any other way to get to them but mine was a Cobalt.
Garage Queen-'12 T3 2SS/RS LS3 M6 Camaro. TVS 2300 & stuff on corn squeezins
screw that lol, ill leave it the way it is before i do all that work.
2008 Sky RL
Just read page one of this thread. Easier on the Kappa
"The knock sensors are directly under the intake, right below the foam insulating material around the injectors. Not sure about the Cobalts but on the Kappas you need a mirror to see them without taking anything off. Pulling the dipstick tube off will make it pretty easy to get to both sensors."
2007 Saturn Sky Redline
GMPP + Westers
Whoa there skippy, go back a few pages and see the fun that i had getting to the rear sensor. The 08+ should be easier since they don't have a vacuum pump under the the manifold.
This thread is only 2 pages
Yeah I guess I was lazy and didn't read the entire first page. Oops
2007 Saturn Sky Redline
GMPP + Westers
i guess no one really read what i wrote.
i found both knock sensors, the front one was clocked correct but the back one is at 5 0'clock instead of 9 o'clock where it should be. i was able to get to both knock sensors, BUT i cant get my torque wrench on the rear one.
can i use a swivel adapter or will that mess with torqueing it back to spec?
2008 Sky RL
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