Idea for Phantom knock elimination.

[forcefed86]

I think this is the route I will be going. Plan on using a "NC" boost switch inline to ground on the knock sensor. This will disable the knock sensor until the desired boost level I wish, then the switch will open at my desired boost level and the knock sensor will work again.

Once I get into boost 9+ psi I don't ever see knock. (so far anyway) So I figure for now I'll set the Hobbs pressure switch to 10psi. This way I can keep the sensor inplace incase I get bad gas or clog in fuel system etc.... and it won't annoy me when cruising around town.

 

[gofer]

More than likely the sensor is bad or you don't have it torqued properly, 17 ft/lbs is what the service manual shows. If you replace the sensor and torque it and still get knock that you KNOW is phantom then put a plastic washer between the sensor and the block to absorb vibration from the motor.

I'm not sure what your rigging up or if your idea will actually work but it seems like your going WAY out of your way to get rid of phantom knock and it could be a bad sensor.

 

[Calan]

I think this is the route I will be going. Plan on using a "NC" boost switch inline to ground on the knock sensor. This will disable the knock sensor until the desired boost level I wish, then the switch will open at my desired boost level and the knock sensor will work again.

Once I get into boost 9+ psi I don't ever see knock. (so far anyway) So I figure for now I'll set the Hobbs pressure switch to 10psi. This way I can keep the sensor inplace incase I get bad gas or clog in fuel system etc.... and it won't annoy me when cruising around town.

Sounds like a bad idea to me, but that is just my opinion of course. I wouldn't take the chance of adding another point of failure to the knock circuit.

There's several ways to desensitize the knock sensor...some better than others. I would try to find the source of the PK, if you are sure that's what it is....or, if you are still on the JeffO chip, just have him change your PK limits. He might even be able to code the window you want instead of his basic "turn on" threshold.

Are you sure it isn't real knock that needs to be tuned out?

 

[Ceddy]

If the Knock Sensor is disconnected or grounded it will go into limp mode and put out a constant 9 counts of knock.

 

[forcefed86]

If the Knock Sensor is disconnected or grounded it will go into limp mode and put out a constant 9 counts of knock.

No, if it is disconnected it puts up a code. If it's grounded and left connected it will not. I know because mine is grounded right now. (this is a 1g not sure if that matters)

Sounds like a bad idea to me, but that is just my opinion of course. I wouldn't take the chance of adding another point of failure to the knock circuit.

There's several ways to desensitize the knock sensor...some better than others. I would try to find the source of the PK, if you are sure that's what it is....or, if you are still on the JeffO chip, just have him change your PK limits. He might even be able to code the window you want instead of his basic "turn on" threshold.

Are you sure it isn't real knock that needs to be tuned out?

Few months back on my oem motor this ecu and knock sensor were used and worked great. This is why I doubt the sensor is "bad". Since then I have changed alot.


From what I've read the knock sensor was designed for the factory motor. Once you go above and beyond it is pretty much useless.

I'm running forged pistons at 9.5:1 compression, aftermarket rods, large cam, and .020 over bore. I'm guessing this is why my sensor is spazing. I have the revised lifters and my valvetrain is not loud. Also running e85 @ 18-22* timing 10-12psi of boost max. On a e316g. Unless something is installed improperly there is no way this thing is knocking. Esp in the no load conditions. Also there is no sign of detonation on the plugs. Tuning with a WB02 high 11's AFR.

Wwitched over SD jakal setup for my fuel management. This is another change that may or may not be realated. I have the phantom knock option on and that does help, but it still jumps around at times. Mainly light load accel no boost.

This may also be an part due to the SD swap. Or so I've heard this is common when eliminating MAF's. Not sure if the circuitry is tied in in some way.

All that being said I'm planning on giving it a try shortly.

 

[gofer]

The knock sensor doesn't become less useful just because the motor has been built. Your on E85 and running 12psi, its definitely PK especially if its at low load conditions. Like Craig said though, your just adding another point of failure that could for whatever reason ignore ACTUAL knock and destroy those forged pistons, aftermarket rods, etc etc. It sounds like you have a laundry list of expensive parts in that motor, that knock sensor is free insurance you just have to make sure its installed and working like it should.

Try doing what I mentioned above (torqueing it or using a plastic washer) to eliminate that PK your seeing, a bad sensor will look burnt or leaking. My NEW knock sensor would pick up road noise at low load conditions but with ECMLink you can enable your knock sensor at a set RPM and throttle position, I'm not familiar with Jackal but they might offer something similar.

 

[dsm-onster]

Which wire on the knock sensor harness did you ground?

 

[Calan]

...the knock sensor was designed for the factory motor. Once you go above and beyond it is pretty much useless.

I would say right the opposite. The more power you make and the closer to the edge you are, the more critical it becomes...not useless.

The biggest problem with the factory sensor on a built motor is engine noise harmonics; sounds are amplified more or less at different frequencies compared to stock. It is a tuned system; once you change engine geometry, sound travels differently (at different amplitudes) and can confuse the knock sensor circuitry. (Of course sometimes it is just noisy stuff like lifters, etc). The other problem is that due to the 1G sensor being overly sensitive, it picks up these changes in the noise spectrum much more easily than it should.

1. Make sure you aren't actually knocking at low loads and RPMs; it's a lot more common than you'd think. I turned my PK threshold off after two years of having it set to 3k, and found the expected noise at 2.5k. But after some investigation, I found that I had really been knocking some there due to not-so-great timing and AFR values in the tune. Once those were nailed, no more knock. Now I just pick up occasional spikes under 3000 RPM, but it's pretty rare.

2. While e85 is a LOT less prone to knock, it does in fact still knock. In some cases, it is more susceptible to rich knock due to pooling on top of the pistons. In fact, I've found on my car that e85 is more likely to knock on low loads than regular pump piss (think pinging at low RPM's and medium loads). Make sure you aren't actually running overly rich at medium loads and low RPM's.

3. Make sure the sensor is in the correct (lower) hole, next to the freeze plug. There is another one about 4 inches higher closer to the head that has the exact same threads...it's extremely easy to confuse them.

4. If all else fails, look into desensitizing the knock sensor. I can tell you what worked for me after years of fighting with it, but do it at your own risk of course. I mig-welded the hole shut and then ground it to a nice flat surface. Since doing that, it reads knock when it should but hasn't picked up any PK at all above 3k RPM that I am aware of.

 

[forcefed86]

The knock sensor doesn't become less useful just because the motor has been built. Your on E85 and running 12psi, its definitely PK especially if its at low load conditions. Like Craig said though, your just adding another point of failure that could for whatever reason ignore ACTUAL knock and destroy those forged pistons, aftermarket rods, etc etc. It sounds like you have a laundry list of expensive parts in that motor, that knock sensor is free insurance you just have to make sure its installed and working like it should.

Try doing what I mentioned above (torqueing it or using a plastic washer) to eliminate that PK your seeing, a bad sensor will look burnt or leaking. My NEW knock sensor would pick up road noise at low load conditions but with ECMLink you can enable your knock sensor at a set RPM and throttle position, I'm not familiar with Jackal but they might offer something similar.

Not saying it's less useful, less accurate is more like it. The frequency the sensor is programmed to pick up on changes with changes in bore/stroke/compression(and dynamic compression from large cams). Or so I've read.

Not to mention I'm convinced the ECU ties the KS into the MAF somehow. Either that or my ECU has some sort of internal short. Even with my sensor complelty unplugged (CEL on) I would occasionally see my knock gauge (OEM boost gauge) jump up half way and I could feel it pull timing. Again this is at a low load low RPM. And I'm not overly rich, if anything I'm on the lean side

Which wire on the knock sensor harness did you ground?

Couldn't tell you off hand, I can check this weekend. Pretty sure it was the ground wire. Not sure though, I couldn't even tell you what I had for breakfast this morning.

 

[JayRolla]

I was pretty much in the same boat as the OP. No madder what I would get full knock count at neutral and just revving the motor. I fought the issue for years, rebuild head, new sensor, washer trick, everything.

After fighting for so long I ended up eliminating it. When the car wasnt PK'ing I would never get any knock in my tune on e85. So I got pissed and eliminated it. Ran for over a year like this on a very aggressive tune. 8.5:1, 30psi falling too 26, 22* timing and 12.0 AFR's. Car is still running like a champ other than drivetrain issues.

 

[GORBS88]

Which wire on the knock sensor harness did you ground?

All you have to do is ground the sensor body itself, not the wiring.

I have had years and years of PK issues and pulled all my hair out trying to fix it! Welded the hole closed with MIG welder, used plastic washer to space it from the block, put it in a different hole (even in the intake manifold) and STILL had terrible PK issues.
I think the prothane engine mounts are to blame for these issues as i don't remember it being that bad before the install of them.

I'm NOT saying to eliminate the sensor but that's what i had to do to have a car make ANY kind of decent power. It's been unhooked for 2 years now running 30+psi with ZERO issues. I have a very conservative tune and use a "chassis ear" to listen for any kind of knock.

For all the "nay sayers" that are going to pipe up you can save it! MANY MANY other people out there tune turbo builds WITHOUT knock sensors and it works JUST fine!! (turbo hondas,240's and such)
IF i didn't have these terrible PK issues i would have it still connected but this was the ONLY way to not want to BURN my car to the ground!

 

[gofer]

I'm not knocking (AHAH get it?) your ideas or setup, just wondering if you ever tried the less sensitive 2g knock sensor?

 

[Calan]

I'm not knocking (AHAH get it?) your ideas or setup, just wondering if you ever tried the less sensitive 2g knock sensor?

Different circuit design... don't think it would work in a 1G.

 

[GORBS88]

I'm not knocking (AHAH get it?) your ideas or setup, just wondering if you ever tried the less sensitive 2g knock sensor?

haha! GOOD ONE..

On a more serious note, yes i did try it but with NO success. For some reason they must be wired differently or somthing. It would default to the (9) counts of knock.

 

[dsm-onster]

All you have to do is ground the sensor body itself, not the wiring.

Hmmm, so all you have to do is ground the knock sensor case to disable it like forcefed86 is doing? Isn't it already grounded by being screwed into the block

Forcefed86, go find out which wire damnit!!!!!

 

[Steve93Talon]

DSMlink lets you control the knock sensor via RPM and TPS levels. Many of us have effectively disabled it and made more power than would've been possible with it enabled. There are many things that can cause phantom knock to read throughout a pull on a modified car, like different internals, tolerances, more solid engine mounts, different crank pullies, lighter clutches/flywheels, etc.

I've even experienced a car with severe phantom knock, and it went away by changing the head gasket from an MLS to a composite (obviously could've been some other variable that changed during the swap, but either way the knock was gone afterwards).

The bottom line is if you're running a known good fuel and are confident in your tune, you can probably get away with it. It's definitely not something everyone should be running out and doing though.

 

[GORBS88]

Hmmm, so all you have to do is ground the knock sensor case to disable it like forcefed86 is doing? Isn't it already grounded by being screwed into the block

Forcefed86, go find out which wire damnit!!!!!

Ummmm NO.

You have to take it OUT of the block so you don't pick up any more PK. This way it is STILL plugged in and the ECU is happy.

Then by grounding the sensor it is still functioning like it should but oviously can't pick up any sort of knock cause it's ZIP tied to the firewall!!

 

[dsm-onster]

AHA! I see. I've been thinking about the circuit this whole time. makes much more sense. You didn't need to rub it in

 

[GORBS88]

AHA! I see. I've been thinking about the circuit this whole time. makes much more sense. You didn't need to rub it in

Tee Hee! No worries, just giving you a hard time!

 

[dsm-onster]

Stop that. I have too much to do! . . .

 

[JayRolla]

AHA! I see. I've been thinking about the circuit this whole time. makes much more sense. You didn't need to rub it in

, I was confused just like you when I first was removing my knock sensor. Its ok, we are not all knowing wiseman or anything.

 

[ist dwa]

I think this is the route I will be going. Plan on using a "NC" boost switch inline to ground on the knock sensor. This will disable the knock sensor until the desired boost level I wish, then the switch will open at my desired boost level and the knock sensor will work again.

Once I get into boost 9+ psi I don't ever see knock. (so far anyway) So I figure for now I'll set the Hobbs pressure switch to 10psi. This way I can keep the sensor inplace incase I get bad gas or clog in fuel system etc.... and it won't annoy me when cruising around town.

If you don't have DSM link to control PK, I think this is a gret idea to get rid of PK IMO.

 

[turboglenn]

there's a million and one reasons the OEM KS isn't suited for a built engine and why it really isn't well suited for any engine in some peoples opinions. I ran without one for 9 YEARS, tuning the old fashion way and never lost an engine to detonation and only popped on HG in those 9 years from a faulty wideband reading at the track.

Now that i have a stand alone KS i still see PK rearing it's head as they are nothin more than piezo microphones based around a certain frequency range... google "big mooses knock sensor ramblings" there's other sensors out there that will wire into our cars, and are more tuned for the "knock sound" than hearing suspension, AC compressors and more... I run a saturn KS right now... although i do know bore size and stroke play a part in the frequency range it should be tuned to pick up i'm no knock guru, in fat i hate knock sensors but i HAD to have the J&S stand a lone knock system just for piece of mind but i ignore it half the time as its doing it's job and keeping my engine in one peice by pulling timing su[ppposedly before knock starts (Jon is a KS genius talking algorythims and more till your brain smokes )

Myt point... too many people look at the KS like it's the last leg before death of an engine and it's not... it's an OEM safeguard to keep warranty claims down for one, and on the other hand it's not meant for performance, it's meant to handle the soundds of daily driving... I liked notr having one, but i can deal with the J&S since i can program or eliminate it if needed

 

[asrdave]

my question is if another knock sensor would work? in the mr2 world we use a gm knock sensor, because faulty readings from a oem knock sensor from being very fragile, now would this in any way benefit us? i mean we use everything else GM anyway -=X
Parts :: ATS Racing
just a thought

 

[turboglenn]

there's a delphi unit for a porsche inline 4 (IIRC) that has an almost perfect response range and is 2 wire (most GM's are one wire)

here's a link to what i mentioned earlier

Big mooses page

BigMoose's Ramblings: Knock

and another that links to him and talks about similar things

Turbo Triumph Web Site