de-sensitizing knock sensor!!!

turboterror · Mar 11, 2008

Ok long story short doing some tuning on an evo 1. Anyways with stock cams we were able to hit 1.5 bar with about 20 degrees of timing and only about 6-10 counts of knock running 100 octane fuel.

Ok here goes the tricky part. We switched his stock cams in favor of FP1x cams. Now the car reads a linear knock count progression up to 25-29 counts on the logging. It doesn't matter what boost we run or how much timing I pull out of the CAS it reads 25-29 counts consistently in a linear progression. We are also using the Apexi RSM logging back to back. Long story short I am positive the 25-29 counts are not real knock. Its engine noise.

My question is to you guys I have heard of using lots of teflon tape on the knock sensor and re-torquing to a lower spec, to desensitize the knock sensor. How much will this desensitize the knock sensor? As we basically need to reset the baseline to 25 counts.

Any other tricks are anything that people know will desensitze the knock sensor and still retain it in the block? (no zip tieing it to the firewall...thats a bit too dangerous at this point).

thanks.

Infinity · Mar 11, 2008

Not sure how to fix your issue, but on my completely bone stock Evo, the knock sensor or some other sensor goes crazy when a loud truck passes by while it's idling. The RPMs are all over the place.

jeffgst · Mar 11, 2008

turboterror said:
It doesn't matter what boost we run or how much timing I pull out of the CAS it reads 25-29 counts consistently in a linear progression. We are also using the Apexi RSM logging back to back. Long story short I am positive the 25-29 counts are not real knock. Its engine noise.

How are you sure that this is really Phantom Knock and not real knock? Is it knocking 25-29 counts at vacuum conditions or under boost??

Phantom knock only occurs when you get large amounts of knock during vacuum conditions. If you are under boost and you are knocking I would suspect it to be real and desensitizing the knock sensor is not the recommended action.

When you installed the cams, did you reset base timing to 5 degrees BTDC?

I don't know how much teflon tape will help in desensitizing the sensor at all.

turboterror · Mar 11, 2008

jeffgst said:
How are you sure that this is really Phantom Knock and not real knock? Is it knocking 25-29 counts at vacuum conditions or under boost??

Phantom knock only occurs when you get large amounts of knock during vacuum conditions. If you are under boost and you are knocking I would suspect it to be real and desensitizing the knock sensor is not the recommended action.

When you installed the cams, did you reset base timing to 5 degrees BTDC?

I don't know how much teflon tape will help in desensitizing the sensor at all.

under boost...and based upon RPM. knock sensors pick up engine noise. Engine noise goes up as RPM's goes up. Its shown as a linear progression (logged on more than a few AEM EMS). It just seems that the knock curve has just moved up.

Also...like I said. the timing has been changed...no matter if it is set at 5 BTDC, or 2 or 0 BTDC. Nothing changes. Can run 10 psi of boost and it still knocks 20 counts.

Before the cams was running 23 PSI 6-10 counts, 20 degrees of timing all the way to 7.5K

HOT97ECLIPSEGSX · Mar 11, 2008

I remember when my knock sensor causes me all kinds of hell. Random studdering, problems under boost, hardcore timing retard after 4.5k RPM, etc.

Replacing the knock sensor took are of my problem.

Steve93Talon · Mar 11, 2008

Do you have the ability to control timing at different RPM points? If so, pull alot of timing through the midrange and see if the knock goes away. You're dealing with a very aggressive cam profile, the FP_X series cams have been known to cause knock until they're dialed in correctly and tuned.

Black_ bullet · Mar 12, 2008

Steve93Talon said:
Do you have the ability to control timing at different RPM points? If so, pull alot of timing through the midrange and see if the knock goes away. You're dealing with a very aggressive cam profile, the FP_X series cams have been known to cause knock until they're dialed in correctly and tuned.

Agreed.

Have you verified your AFR is still good?
Possibly the increased ramp rate of those cams dont like timing...
You may have to pull timing like mentioned in the post i quoted.

I wouldnt be surprised if thats true because i had to pull 2 degs of timing after i installed the bc272s. Lower boost helped but not much, air temp was fine the whole time, i suspect it was just that the Increased cylinder pressures i suppose are causing the different need in the engine ign timing.

And also just gone and replace your knock sensor but dont fiddle with how tight it should be. Tighten it to whatever factory specs are.

turboterror · Mar 12, 2008

Black_ bullet said:
Agreed.

Have you verified your AFR is still good?
Possibly the increased ramp rate of those cams dont like timing...
You may have to pull timing like mentioned in the post i quoted.

I wouldnt be surprised if thats true because i had to pull 2 degs of timing after i installed the bc272s. Lower boost helped but not much, air temp was fine the whole time, i suspect it was just that the Increased cylinder pressures i suppose are causing the different need in the engine ign timing.

And also just gone and replace your knock sensor but dont fiddle with how tight it should be. Tighten it to whatever factory specs are.

Using a wideband. at the moment running extremely rich to try to compensate. running in the 10.6 range.. I have also ran up to 11.0 with a few more counts of knock (about 29-35). Its not he midrange thats causing me problems. Its from 5.5k-7.5k. I have pulled up to 5 degrees out of the timing map using the CAS with no difference. Timing at 17 psi was 19 degrees on the map (something like 12 degrees or something like that with the knock retard) with the CAS pulled for timing...Don't forget I am also running 100 octane fuel...everything considered 19 degrees of timing with 100 octane should be good to go. But it isn't of course.

Black_ bullet · Mar 12, 2008

turboterror said:
Using a wideband. at the moment running extremely rich to try to compensate. running in the 10.6 range.. I have also ran up to 11.0 with a few more counts of knock (about 29-35). Its not he midrange thats causing me problems. Its from 5.5k-7.5k. I have pulled up to 5 degrees out of the timing map using the CAS with no difference. Timing at 17 psi was 19 degrees on the map (something like 12 degrees or something like that with the knock retard) with the CAS pulled for timing...Don't forget I am also running 100 octane fuel...everything considered 19 degrees of timing with 100 octane should be good to go. But it isn't of course.

What turbo is this on again?

Yea thats pretty weird. On 100 octane i can run 25-26psi on my evo3 w/ no knock. Have you done a compression test lately. Do you have really high compression pistons, or maybe some bad carbon build up raising your compression... That would make it more prone to knock.

Another question, what spark plugs are you running. Believe it or not but the spark plugs can also affect knock.

I recently found that running the BR7ES plugs calmed some random detonation in my engine. I was running BRP6ES before that.
The colder range plug helps a bit but the main importance is making sure you get non projected plugs... If it has a P in it is projected... The projected tips arent ideal in a high boost motor.

Id like to assume with you that your not getting that much real knock but is it worth the risk ? Ok, how about this, is your timing getting pulled or is it just saying your knocking without the timing actually getting pulled back significantly?

I used to be able to get another 2-3 degs more before installing my Fp race mani and cams. Now my tune is something like this -

3k- 13 degs
4000-11 degs
4500-11 degs
5000-12 degs
5500-13 degs
6000-14 degs
6500-16 degs
7000-19 degs

With 10.8 AFR thru torque peak and 11.2 afr after 5500 rpm,
and thats not aggressive by any means but its allowing 24psi on 93 crap tane without any concernable knock or timing getting pulled...
You want a smooth timing increase, if its jumping around it will knock that way too...

Post me a log of your pulls.

soldave · Mar 12, 2008

Running on a Small 16G turbo, and with new NGK Iridium BPR7EIX plugs gapped to 0.65mm (recently changed from HKS Racing Plugs). Got 3 logs for you here. The first one is pre-cams installation and is when I was boosting about 22psi/1.5 bar. Second log is with new cams in and running about 18psi/1.25 bar. Third log is post-cams and running stock boost on the car (11psi/0.79 bar).

Pre-cams
Post-cams, 18psi
Post-cams, stock boost

90_talon_matt · Mar 13, 2008

First things first, I'd suggest getting those Iridiums out of there and swap in some BR7es plugs. I've never had any luck with Iridiums in many different boosted applications from DSMs, to Sr swapped 240s to a boosted Ecotec.

soldave · Mar 13, 2008

But similarly, I had iridium-tipped HKS racing plugs in my car for over 12 months boosting to 1.5 bar with no problems whatsoever. And the early Evo generally recommend iridiums for stock and higher-boosting applications.

Having said that, in the process of problem-solving this knock, we may try different plugs.

Black_ bullet · Mar 14, 2008

Black_ bullet said:
What turbo is this on again?

Another question, what spark plugs are you running. Believe it or not but the spark plugs can also affect knock.

I recently found that running the BR7ES plugs calmed some random detonation in my engine. I was running BRP6ES before that.
The colder range plug helps a bit but the main importance is making sure you get non projected plugs... If it has a P in it is projected... The projected tips arent ideal in a high boost motor.
.

I will just quote myself...

And Soldave; thanks for putting those logs of your car.
Your pulls get some good timing adv,what octane are you using?

Black_ bullet · Mar 14, 2008

<< Edit from my last post right above this one>>

Soldave your first log had good timing adv on the pre cams pull,what octane were you using there?
But the post cam pull looked pretty bad... Your timing adv wouldve done good if it was done similar to how i said my timing adv is currently (in an earlier post in this thread) and I run 23 psi right now on the evo3 with that tune and no knocky. When your 2nd log tried to ramp up to 16deg the knock got much harsher, and with dsms, once you get any considerable knock, its very likely the rest of your pull will continue to knock even after the ecu has retarded timing.... It shouldnt have went up past 15 degs until around 6500 and you wouldve been ok... No more than 5 counts is acceptable for an aggressive everyday tune in my book.

soldave · Mar 15, 2008

But would the iridiums cause knock? I thought they would just cause misfiring, which is definitely not happening.

Was using the same fuel for all the runs: 100 octane here in Japan.

A couple more logs for you to analyse here. First of all, this morning I put the stock chip back into my Evo to compare with the newer chip I had in and see if it helped with the knock problems I was having. I think the timing is better with the stock chip to be honest, and the only problems with it are the lack of launch control and the speed limiter is back on. And I was making just about the same amount of power with the stock chip. See the first link below for details of this run. We were still getting the knock though, and now we are pretty sure that the knock is real. We confirmed this by taking the car to redline in 4th gear but staying off boost. At the most we had 1 or 2 knock counts. On boost we were getting 30+ counts again.

We then adjusted the cam angle sensor to 2.5 degrees, and then proceeded to remove the knock sensor and teflon tape it. The knock sensor could probably do with being replaced with a new one, but without having one to hand, we put this back in and loosely torqued it. It did its job partly, reducing knock counts to around 20. This was also shown in our power figures, and we ended up doing one run and hitting 323HP according to our Apexi RSM - an increase of 19HP from the start of the day.

So getting better but still plenty of knock that needs to be removed somehow.

Here are the logs:
First run of the day on stock chip
Final run of the day after teflon taping knock sensor and playing with cam angle sensor

Black_ bullet · Mar 15, 2008

soldave said:
But would the iridiums cause knock? I thought they would just cause misfiring, which is definitely not happening.

Was using the same fuel for all the runs: 100 octane here in Japan.

A couple more logs for you to analyse here. First of all, this morning I put the stock chip back into my Evo to compare with the newer chip I had in and see if it helped with the knock problems I was having. I think the timing is better with the stock chip to be honest, and the only problems with it are the lack of launch control and the speed limiter is back on. And I was making just about the same amount of power with the stock chip. See the first link below for details of this run. We were still getting the knock though, and now we are pretty sure that the knock is real. We confirmed this by taking the car to redline in 4th gear but staying off boost. At the most we had 1 or 2 knock counts. On boost we were getting 30+ counts again.

We then adjusted the cam angle sensor to 2.5 degrees, and then proceeded to remove the knock sensor and teflon tape it. The knock sensor could probably do with being replaced with a new one, but without having one to hand, we put this back in and loosely torqued it. It did its job partly, reducing knock counts to around 20. This was also shown in our power figures, and we ended up doing one run and hitting 323HP according to our Apexi RSM - an increase of 19HP from the start of the day.

So getting better but still plenty of knock that needs to be removed somehow.

Here are the logs:
First run of the day on stock chip
Final run of the day after teflon taping knock sensor and playing with cam angle sensor

I cant speak upon the iridium plugs because ive never used them but i did speak upon telling you plugs that are KNOWN to work... How bad could it be to just give them a try. How much boost was this on again and what are your air fuel ratios?

You have a lot of knock, and not to be the bearer of bad news, but every time you do a pull with that much knock coming up you are cutting into the life spand of that engine. I know your working out your knock issues, but you have either two reasonably safe options... Turn down the boost to a level that doesnt knock, OR, get a true tuning device that allows you to have full control over timing advance. You say you have a chip.. Ok, now send that chip back to whoever programmed it and tell them the type of timing it should have... ( Keep reading and ill get more into that.)

I dont trust your teflon taping of the knock sensor either to be honest.
Doesnt mean you were tricking the engine out of some phantom knock,
may mean that now your ecu is just not retarding timing as much to protect itself. :tat:

If your running any kind of leaned out afr or high boost ( 20psi+) then id say you have some pretty aggressive timing advance, even with 100 octane.
When it tries to shoot up too quickly thats were your knock began, and in the 5000rpm range on both of your pulls.

Once your knock begins; your timing shows itself dropping a deg to compensate, but a few hundred rpms later its already trying to go higher when the knock never stopped in the first place.( typical safc timing issues.)
Knock on a dsm isnt likely to stop once its started during a pull so as the ecu is fighting you to still advance to its next segment on the timing map, your knock will just get worse and worse like your log shows.

Just from eyeballing your log i can tell your timing is increasing too fast.
Starting from where i saw your knock issue begin; if instead your timing
increased in this manner -

5000- 17 degs
5500- still at 17 degs
6000-18 degs
6500- 19 degs
7000- 20 degs

that way ^, then id bet you wouldnt of had hardly any knock;
but your log is already way up to 21degs by 6300rpms while still pulling timing.

Try a cold air intake, drop the boost 2 psi or so, and change the plugs in the meantime, but mainly you need to get that timing map lower and smoother.
You have ideal race gas timing adv there my friend, not pump gas...

90_talon_matt · Mar 15, 2008

Does anybody know how the Evo timing maps compare to the 1g/2g maps? I think it would really help to take a look at the values that are added to your base timing during different airflow scenarios.

Black_ bullet · Mar 15, 2008

90_talon_matt said:
Does anybody know how the Evo timing maps compare to the 1g/2g maps? I think it would really help to take a look at the values that are added to your base timing during different airflow scenarios.

That, and their stock compression ratio?

I sort of forgot we were talking about an evo here.

The same theory of tuning i listed above should be the same though,
as the car is certainly getting too much timing advance for the boost, and octane its on currently.

soldave · Mar 16, 2008

Stock compression is 8.5:1

Black_ bullet · Mar 16, 2008

So stock timing maps are similar to 2g also i bet?

de-sensitizing knock sensor!!!

turboterror

Infinity

jeffgst

turboterror

HOT97ECLIPSEGSX

Steve93Talon

Black_ bullet

turboterror

Black_ bullet

soldave

90_talon_matt

soldave

Black_ bullet

Black_ bullet

soldave

Black_ bullet

90_talon_matt

Black_ bullet

soldave

Black_ bullet

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