GM knock sensor thread Options

[brianforster]

and finally ....FOR THE WIN....

a copy of the toytoa bible (better then the bgb) from auto shop 101. that proves that each knock sensor is tuned to a specific frequency and that the ecu dosnt do any from of audio filtering to get its knock info from.

http://www.autoshop101.com/forms/h38.pdf

[Batman722]

after skimming through this post I have some newbie type thoughts....

the stock (toyota sensor) might tend to blow at times...so you want to put a different frequency sensor in so it blows less ? correct ?

isn't that the same idea as " I keep blowing a 15A fuse in the fuse box, so I will put a 25A one is so it doesn't blow anymore "

if the stock sensor blows, there is a reason why. Solve the problem - don't band-aid it until it is a bigger problem.

my .02

[jgreening]

My *opinion* is that the GM sensor is at least 90% as good as the stock Toyota sensor.

Although I am not sure how you quantified this, I generally agree. You have to ask yourself though, is the $40 extra worth the 10% (or whatever) chance that the GM sensor will not appropriately respond to catostraphic detonation?

In a modified motor, I would say this is a good mod as there is a larger chance of a big knock event that could blow a knock sensor but not the motor.

On the other hand, I have to part company with you on this one. To me, the increase chance of detonation on a modified motor increases the need for accurate knock detection. With modified (high horsepower) motors, the last thing you should be worried about is the $40 difference in the cost of these sensors.

[CelicaGT04]

after skimming through this post I have some newbie type thoughts....

the stock (toyota sensor) might tend to blow at times...so you want to put a different frequency sensor in so it blows less ? correct ?

isn't that the same idea as " I keep blowing a 15A fuse in the fuse box, so I will put a 25A one is so it doesn't blow anymore "

if the stock sensor blows, there is a reason why. Solve the problem - don't band-aid it until it is a bigger problem.

my .02

Makes sense to me batman!

ANYWAY... I read about 2 pages of this topic and figured i would just say that we all love celicas here! Why cant we all just be happy for fastbird, i mean im happy for you!! If he gets knock then he will learn! You gave your opinion and he gave his. I think we should all be happy for him, if it works, it works. If not well then i guess then you can say "I told you so!" !!! If it works then fastbird can say "I told you soo!!!" Either way im still happy for you!


Everyone on this site is a great member! Im glad we have great moderators like lagos and pressur2. I am also glad we have great people like doc to help those who dont want to get their hands dirty or want their swap done correctly. I think everyone plays a role and im playing mine! Lets just get along.

Doc great work on the swap

Fastbird- that is a nice car and i hope your happy with it! i mean hell, im happy to see it look like that!

Mario!

[lagos]

Im glad we have great moderators like lagos and pressur2.

im a moderator? woot!!!


keep reading the rest of the pages. it started out as lagos bash, but now is a cool tech talk thread.

This post has been edited by lagos: Jul 12, 2006 - 11:45 PM

[scothaniel]

the stock (toyota sensor) might tend to blow at times...so you want to put a different frequency sensor in so it blows less ? correct ?

No, thats not what ( some / few / many ) people are saying. When excessive knock happens, how long will the sensor last? All motors get knock, even when everything is running perfectly. Only in this case, the knock is like 4 counts / second (microphones pick up background sounds). When you get 50+ knocks / sec - something is wrong.

The stock sensor is known to be more fragile then most and fail after a few cases of excessive knock. The real question here is whether the GM knock sensor is listening for the correct frquency. Knock sensors listen for specific frequencies to determine knock - otherwise valve or injector tick would through off the system. Does the GM sensor listen for the same frequencies as the stock sensor?

From my experience, I believe so.

[phattyduck]

In a modified motor, I would say this is a good mod as there is a larger chance of a big knock event that could blow a knock sensor but not the motor.

On the other hand, I have to part company with you on this one. To me, the increase chance of detonation on a modified motor increases the need for accurate knock detection. With modified (high horsepower) motors, the last thing you should be worried about is the $40 difference in the cost of these sensors.

That's not quite what I wrote. I mean: A modified (ie stronger) motor can take knock events with less damage, and are often more likely to see those events (higher boost, racing, etc.). Both of these things point to the need for a hardier knock sensor, and *if* it is less sensitive it won't hurt things as much.

Its ok if you disagree though.

-Charlie

[phattyduck]

and finally ....FOR THE WIN....

a copy of the toytoa bible (better then the bgb) from auto shop 101. that proves that each knock sensor is tuned to a specific frequency and that the ecu dosnt do any from of audio filtering to get its knock info from.

http://www.autoshop101.com/forms/h38.pdf

Very good link. I probably have that downloaded in the tech director on my other computer... I just haven't read it yet!

So, here's my *opinion* on what's going on in the knock system: Knock sensor sees knock even and resonates at a larger amplitude (shown in the graph on the second page). This signal is sent to the ECU where there is an envelope filter that is able to grab the peaks of the knock events. When this peak reaches a certain value, the knock response of the ECU is generated. In this way, the ECU can have a simple comparator watching the knock system - cheap and effective. (at one time, started investigating designing something like a J&S with a friend of mine...). There is no need for complicated electronics or computation in the ECU.

The resonant effects of the motor (peaking at the same or similar frequency as the sensor) will enhance the sensitivity of the sensor to knock events. BUT... the bandwidth of the resonance of something as complicated as a motor (with a shape NOTHING like a tuning fork and made up of many materials) should be fairly wide - and thus a sensor that is less than 1kHz away in peak frequency should still work well.

Once again, my opinion - but a fairly educated guess.

-Charlie

[jgreening]

In a modified motor, I would say this is a good mod as there is a larger chance of a big knock event that could blow a knock sensor but not the motor.

On the other hand, I have to part company with you on this one. To me, the increase chance of detonation on a modified motor increases the need for accurate knock detection. With modified (high horsepower) motors, the last thing you should be worried about is the $40 difference in the cost of these sensors.

That's not quite what I wrote. I mean: A modified (ie stronger) motor can take knock events with less damage, and are often more likely to see those events (higher boost, racing, etc.). Both of these things point to the need for a hardier knock sensor, and *if* it is less sensitive it won't hurt things as much.

Its ok if you disagree though.

-Charlie

Good point Charlie. You may be correct but I will note that almost all of the high hp 3sgte's run stock knock sensors. That surely doesn't prove anything but may be worth observing.

[lagos]

and finally ....FOR THE WIN....

a copy of the toytoa bible (better then the bgb) from auto shop 101. that proves that each knock sensor is tuned to a specific frequency and that the ecu dosnt do any from of audio filtering to get its knock info from.

http://www.autoshop101.com/forms/h38.pdf

Very good link. I probably have that downloaded in the tech director on my other computer... I just haven't read it yet!

So, here's my *opinion* on what's going on in the knock system: Knock sensor sees knock even and resonates at a larger amplitude (shown in the graph on the second page). This signal is sent to the ECU where there is an envelope filter that is able to grab the peaks of the knock events. When this peak reaches a certain value, the knock response of the ECU is generated. In this way, the ECU can have a simple comparator watching the knock system - cheap and effective. (at one time, started investigating designing something like a J&S with a friend of mine...). There is no need for complicated electronics or computation in the ECU.

The resonant effects of the motor (peaking at the same or similar frequency as the sensor) will enhance the sensitivity of the sensor to knock events. BUT... the bandwidth of the resonance of something as complicated as a motor (with a shape NOTHING like a tuning fork and made up of many materials) should be fairly wide - and thus a sensor that is less than 1kHz away in peak frequency should still work well.

Once again, my opinion - but a fairly educated guess.

-Charlie

just read that pdf. tells you exactly how it works...lol

[presure2]

lets keep this thread on topic.

[Fastbird]

lets keep this thread on topic.

[phattyduck]

just read that pdf. tells you exactly how it works...lol

I did read it. Just because that's what they tell their mechanics what is going on, doesn't mean it is 100% technically correct.

In an interesting side note: There were some Subarus built with 'overactive' knock sensors. The recommended fix from the factory: a small amount of teflon tape on the threads to insulate it from the knock vibrations... On the flip side, some of the earliest US WRXs were shipped with almost deaf knock sensors. The result? About an extra 30hp and all those great reviews of the WRX (and that 5.4 second 0-60 time) and then the motors eating themselves alive after a while.

-Charlie

[lagos]

I did read it. Just because that's what they tell their mechanics what is going on, doesn't mean it is 100% technically correct. wink.gif

all the info in there is 100% correct when it comes to toyota knock sensors and how they work. its like the bible for that kind of stuff. you can bet your 1st born child on it.

[phattyduck]

I did read it. Just because that's what they tell their mechanics what is going on, doesn't mean it is 100% technically correct. wink.gif

all the info in there is 100% correct when it comes to toyota knock sensors and how they work. its like the bible for that kind of stuff. you can bet your 1st born child on it.

That said, my long post doesn't directly contradict anything in the document...

-Charlie