Knock voltage readings and thresholds

[Force Fed Mopar]

Those that have logged it, what kinda of knock voltage do you see? I have .04 under pretty much all no-boost conditions (varies a bit, .02 or .06 max). I see .96 sometimes when I am feathering the gas trying to get traction. I am using the knock threshold table from the T-LM 2.5 MTX Cust cal.

[shadow88]

Agreed with the .04v under normal driving conditions.

I found anything above 2.5v is more than just engine noise. When I make any changes to my car, I find if I keep it under 2.5v, nothing gets damaged.

[Force Fed Mopar]

Agreed with the .04v under normal driving conditions.

I found anything above 2.5v is more than just engine noise. When I make any changes to my car, I find if I keep it under 2.5v, nothing gets damaged.

That's good to know. What's your setup? I have a 2.5 w/ Wiseco's and a F3 cam and 2.4 lifters. Lifters are slightly noisy due to no preload (shimmed them for a stock base circle and haven't felt like re-doing it yet). I ran the engine up to 4k+ though out of boost and never saw more than .04v.

[shadow88]

Oh, that list is huge.

Points of note for detonation are forged wiesco's, swirl head that's been machined a few too many times. non-projected spark plugs, stock smec with 32 psi and 70hp of nitrous and 8 degrees base timing.

All my problems come up after 2.8 volts, so I keep it to 2.5v or less.

[Force Fed Mopar]

Oh, that list is huge.

Points of note for detonation are forged wiesco's, swirl head that's been machined a few too many times. non-projected spark plugs, stock smec with 32 psi and 70hp of nitrous and 8 degrees base timing.

All my problems come up after 2.8 volts, so I keep it to 2.5v or less.

2.5 or 2.2?

[shadow88]

My shadow is a 2.2L

[1BADVAN]

Agreed with the .04v under normal driving conditions.

I found anything above 2.5v is more than just engine noise. When I make any changes to my car, I find if I keep it under 2.5v, nothing gets damaged.

This makes sense for being conservitive, but ALL the knock sensor curves i see in MPTuner have the limit at 3+ volts at about 5500 RPM. Shouldn't that mean that the engineers felt like that was a safe limit? The 2.5 MP cal has it go up to 4.0 volts at 6000 RPM. To me if that is safe you are limiting power by restricting it only to 2.5v.

Again not trying to argue or disagree just trying to understand the different things i am seeing.

[Force Fed Mopar]

This makes sense for being conservitive, but ALL the knock sensor curves i see in MPTuner have the limit at 3+ volts at about 5500 RPM. Shouldn't that mean that the engineers felt like that was a safe limit? The 2.5 MP cal has it go up to 4.0 volts at 6000 RPM. To me if that is safe you are limiting power by restricting it only to 2.5v.

Again not trying to argue or disagree just trying to understand the different things i am seeing.

Engineers have a lot of things to take into account, like loose 100k mile engines that make a lot of noise at higher rpm and people that like to fool with things like g-valves when under warranty :D I ran the MP timing and knock tables on mine, and was seeing the knock light at 14 psi. Whether it was really knocking or not, not sure. I didn't have the datalogging set up at the time. It was worse at the lower revs. I am running the knock threshold from the T-LM 2.5 MTX Custom cal with the T-SMEC B151 timing tables (MP 2.5 MTX cal) w/ 1 degree less timing at 14psi on both full and part throttle tables and do not see the light. I took a datalog of it this morning, when I have a chance to review it I'll post what it saw.

[shadow88]

This makes sense for being conservitive, but ALL the knock sensor curves i see in MPTuner have the limit at 3+ volts at about 5500 RPM. Shouldn't that mean that the engineers felt like that was a safe limit? The 2.5 MP cal has it go up to 4.0 volts at 6000 RPM. To me if that is safe you are limiting power by restricting it only to 2.5v.

Again not trying to argue or disagree just trying to understand the different things i am seeing.

Your results may vary. I have never dug into the program side of things to see where the computer begins to pull timing. I have broken the insulation off spark plugs when the knock sensor reads 2.8v even if it's just for a moment. I have broken ring lands on hyperutectic pistons at 2.8v as well, and no I don't have teflon tape wrapped around the threads of my knock sensor.

What I am suggesting is anything above 2.5v is more than just engine noise. Detonation of any amount is not helping your engine produce it's maximum power when it makes too much cylinder pressure for the fuel being used.

[Force Fed Mopar]

Your results may vary. I have never dug into the program side of things to see where the computer begins to pull timing. I have broken the insulation off spark plugs when the knock sensor reads 2.8v even if it's just for a moment. I have broken ring lands on hyperutectic pistons at 2.8v as well, and no I don't have teflon tape wrapped around the threads of my knock sensor.

What I am suggesting is anything above 2.5v is more than just engine noise. Detonation of any amount is not helping your engine produce it's maximum power when it makes too much cylinder pressure for the fuel being used.

So what do you run yours at? Do you set it to run at 2v on the knock sensor? Or do you set it to see .04v? Just went over my datalog from yesterday, at 15 psi full throttle or part, never saw more than .04v.

[shadow88]

I set mine to run a maximum knock voltage of 2.5V. There's always some noise that brings the knock sensor output to above .04V when it's being pushed. Seeing 1.4 - 2.2 volts under hard, high rpm acceleration is pretty normal on my car.

[Force Fed Mopar]

Yeah, I know that it's been said that more boost makes the block ring more.

[ShelGame]

Yeah, I know that it's been said that more boost makes the block ring more.

More power in general...

[Force Fed Mopar]

Here's a log I took at the track tonight, AFR's were in the mid-high 10's. Ambient temps were 89-91*F. Knock threshold is copied from the MP 2.5 MTX cal.

[Force Fed Mopar]

So I jacked up the threshold to 2v based on shadow88's experience, and no audible knock at 14-15psi on MP rpm timing and -11.5 map timing at 15psi. Logged it at the track last Thurs, it will jump up to 3v on shifts sometimes, but never goes past 2v otherwise. Here's the logs:

[shadow88]

I'm not sure how to open that. If you're staying under 2V wot you should be able to get away with more boost or timing assuming the a/f ratios remain cool.

[Force Fed Mopar]

My AFR stays in the 10.5-11.0 range. You need MPScan to view the log files.

I pulled timing down a bit more and it misfired out the exhaust bad under WOT and 18psi. Calculated WOT timing shown in MPTune showed the total timing to be 1*BTDC at 3k, 2* at 4k and 6.5* at 5k. So I'm still playing with it, I put it back to stock timing MP timing maps w/ a continued slope after 15psi and am slowly bumping the threshold up. Got more datalogging to do. Tried it out today and the knock light showed but I had taken my MBC apart to show my brother and didn't get it set back as low again, spiked 20psi lol.

Stock MP timing maps gives me 6.5*@3k, 9*@4k and 14*@5k.

[Force Fed Mopar]

Annnd now my laptop battery is messing up on me again....

[turbovanman²]

Can you post up your knock sensor table, pretty please, :nod:

[Force Fed Mopar]

Here it is currently.

[turbovanman²]

Thanks.

[Force Fed Mopar]

Looks like I'm gonna raise it a little more...

[wowzer]

off topic rob but NICE gauge setup if i may say so myself. obviously the PW readings are not right. still haven't figured out why. typically i think they would run around 1 mSec or less at idle and 11-12 mSec at WOT. i do have one suggestion. if you look at the logging info you will notice the max bytes returned are around 280 per second. with a 12 byte sample you are getting around 23 samples per sec, or a sample about every 40 mSecs. i see you have the logging rate at 7 mSec. i would suggest moving that up to around 35-40. otherwise, all you are getting in the log file are duplicate data entries. i had planned on having the program auto adjust to the max logging rate, but instead i have set up the new version to allow each gauge to have a sampling frequency setting from 1 to 10, so that makes it hard to do the auto adjust thing.

thx for posting these up.

[Force Fed Mopar]

off topic rob but NICE gauge setup if i may say so myself. obviously the PW readings are not right. still haven't figured out why. typically i think they would run around 1 mSec or less at idle and 11-12 mSec at WOT. i do have one suggestion. if you look at the logging info you will notice the max bytes returned are around 280 per second. with a 12 byte sample you are getting around 23 samples per sec, or a sample about every 40 mSecs. i see you have the logging rate at 7 mSec. i would suggest moving that up to around 35-40. otherwise, all you are getting in the log file are duplicate data entries. i had planned on having the program auto adjust to the max logging rate, but instead i have set up the new version to allow each gauge to have a sampling frequency setting from 1 to 10, so that makes it hard to do the auto adjust thing.

thx for posting these up.

I haven't set up the logging, that's just what it is default I guess. I'll set it to the settings you suggested and try it. Assuming my laptop battery is working...

Maybe the PW is in uSecs? Seems like I saw that measurement in Dcal.