I need help understanding knock retard. I get the gist of it but I'm new to tuning so my knowledge is limited.

so I need to be educated on how to look for it in logs like the "whys" I can physically find the knock in the log but I need to be schooled on why I'm getting it or if its really knocking to begin with and then what to do to alleviate it.

car is a 98z stock motor 3600stall, lts, udp, unoiled k&n, p&p stock maf, ls1 intake still, msd plug wires,3.42's

 

Anyone out there

 

Reduce the WOT spark timing to 24*. The 1998's have too much timing as stock. And there is something wrong with B2S1 O2, as it's over 1.1 V. What are the fuel trims doing on that bank?

Russ Kemp

 

Its a sim from the wideband on that side it's programable does it need an adjustment?

 

First off '98s had extra special knock sensor problems.
If you don't know the pedigree of yours, I'd replace
with whatever's the generally accepted.

Next, KR comes on too hard and hangs around too long
to let you see much about why. I like to cut the attack
rate by half and double the decay rate. You still keep
the protection but you can begin to tell whether the
ping at the time is a steady state load point kind of
problem (main mixture and spark, fuel pressure and
injector delivery) or is a transient thing (exhaust bang,
tip-in mixture, SD:MAF air mass mismatch). As stock
the retard hangs around while the condition gets away.

 

Many things can trigger knock sensors, they are able to detect specific frequencies of sound. They are designed to work with OEM components, i.e. the knock sensor for each engine is designed around that engine's parts, it is able to filter out noise that all engines of those types make. If you try to use a foreign knock sensor (lets say you tried a 4-cylinder knock sensor on a V8) it would not work the same, because the same frequencies of engine knock that the 4-cylinder would produce is not made by the V8 engine. The same thing can occur if you change internal parts, for example piston/rod/crankshaft. If you modify the bottom end, the new bottom end may produce a different, distinct frequency when knock occurs, that the original knock sensor does not detect well.

For this reason, it is important that when tuning an engine, we keep in mind that as parts change or even wear (bad engine mounts, new headers, anything that rubs/vibrates due to wear or because it was changed) might give us false knock.

And so, here are some tips and tricks for determining if a knock is false or not.
1. If you think there might be engine knock or pinging, reduce timing significantly, even if the engine performance suffers. For example if you had 30* of timing at WOT, and reduce to 20*, see if knock counts drop at all, look for any change, even a subtle one. If you have an EGT gauge and the correct octane of fuel then the EGT should rise, and knock count will remain the same, that is probably false knock.
2. False knock may tend to occur at a specific RPM. Check for consistency, if you get knock during WOT and CRUISE at exactly 3200rpm it could be false, something in the engine or drivetrain is emitting one of those particular frequencies that the sensor is picking up.
3. Run the car with normal fuel and make a log of the suspected knock, then fill up with race fuel (or much higher octane, like 105 octane if you were using 93 before). If you still see the same exact knock counts then it is probably not knock.

Sometimes all it takes is one modification, such as solid engine mounts, to completely wreck the knock sensors usefulness. In those cases you can try wrapping teflon tape around the knock sensor threads to help "dampen" its ability to detect, and also screw it in less tightly.


And finally, a dynojet session can help you sort out whether the engine is knocking, with a little experience tuning engines you should be able to compare torque output, EGT, wideband readings, and that experience (knowing what fuel is adequate goes a long way to preventing engine damage) to determine if the engine is running well or not. Set smoothing to ZERO and study the torque output, it should be smooth without little jagged ripples. If you reduce timing and those ripples/jagged edges become smooth, that was probably engine knock.

What I really like is a quiet engine that you can really listen to during a WOT run. No, you cannot hear ALL knock, in fact a knock sensor is supposed to be more sensitive to the pre-knock frequencies (sounds that occur just before engine damaging knock occurs) if that makes any sense, so often it will detect knock LONG before you can actually hear it. But it still helps to confirm that an engine is running right, when you can listen to it make a WOT pull without a hiccup or strange noises. Sometimes you can hear it knock and the knock sensor will be completely silent as well; so do not depend on the knock sensor, but rather, use it as an additional tuning tool.

 

I don't know it for a fact but I assume the sensors are the original ones from the factory, with that being said is it worth the trouble to pull the intake to find out I would prefer to not jack with that if I didn't need to. I see that tick sells a upgrade knock sensor kit for 97-98 cars for 175 so id be 200 deep into things by the time u do new intake gaskets. if it aint broke don't fix it ya know.

So lets say I just work from the log and don't know what sensors are in it. do I start with pulling some timing down to the 24 that was suggested then go log it? or is replacing the sensors with the newer ones basically a must
then log it again before pulling timing?

ok so if I cut attack in half and double decay then go for a drive log it and look for what? in that log

I'm normally running 91oct, 93 when headed to the track

jimmy you said something about sd:maf mismatch I've tuned on the VE tables but have never tuned the maf yet I'm learning as I go so do I need to recal the maf first before looking further into the knock retard?

also it was mentioned about my b2s1 NBO2 being at 1100mv is that and issue? I can adj the output of the simulated NBO2 if needed

sry for all the questions. Like I said before I'm new to this.

thanks guys

 

definitely dont worry about what sensor is in there. If the A/F value is ok and you just want to go for a quick drive to re-check, then reducing timing is a fast, easy, safe first attempt at sorting out a suspected knock signal. Always choose the cheapest/quickest method first.

 

k so don't mess with the attack and decay yet just pull some timing or do I need to do both ?

 

ok this maybe a stupid question but knock retard is logged in map kpa vs rpm and spark tables are cyl air mass vs rpm.
so am I able to copy special paste my correction with the row axis being differ or do I need to set up new graph based off of cyl air mass vs rpm

 

I made a new graph with same axis as in the editor and pulled some timing haven't been for a drive yet tho

 

You can follow the suggestions posted, they are great suggestions for controlling the amount of ignition retard you get with different knock conditions. But they by themselves will not "cure" knock. You never want to depend on the computer to pull timing out when it detects knock. That is more a safety feature for sheep to drive their car and use bad gas, and not really a solid tuning feature for the engine to depend on in a high performance application. Put it this way, many stand-alone ECU do not even have the capability to pull timing with knock detection. They depend on the tuner/user to determine maximum safe timing for the application/environment/fuel quality.

You reduce timing, and see how the sensor reacts, overlay the graphs and look for similarities. If there is an obvious decrease in detected knock with the removed timing advance, then you have some evidence that the engine really was knocking, but there is still more to do before you can be sure. Try a combination of some of the suggestions I posted and try a few different timing values to get a feel for how the engine/sensor responds. For example, you want to be pulling timing, and start seeing less knock signal, and then add the timing back in, and re-verify the knock re-appears. Then adjust fuel octane up, and verify it disappears again, back to the same way it looked when you pulled out the timing earlier, the overlay of your reduced timing vs the higher octane fuel with more timing should be similar. See how we can look at it from several angles to verify that it was real knock?\

If you post up your time vs knock vs rpm vs ign advance (and any other nifty variables logged) I can examine it for you. You can take a screen shot with "print screen" then paste it into a paint file, crop the picture, and upload it.

 

I'm sorry but I'm not follow you on what your asking me to log and post. I don't feel that this is what your asking for

 

The bottom part that shows the graph, you should be able to make it higher resolution, get closer, and zoom in on the wide open throttle portions. Make back to back runs, use the higher timing setting first (so any temp rise does not contribute to knock) and then use a lower timing setting.

Then examine or post the logs, both together, so you can compare them or I can compare them. We want to see the ignition timing vs RPM vs knock, with any extra data such as Inj PW you can fit in there without muddling it up. The knock output graph should appear obvious; if it isn't adjust the settings until you can clearly make out the difference. The whole point of this is to compare graphs, i.e. more than one at a time. If you need an example I can post one.

 

Ok gotcha I'll log everything I can timing wise rpm ect in one graph and get it posted up weather is **** today so won't be able to log anything til tomo

Thanks

 

here is new logs screenshots first one is with more adv sec is with less.

now I believe the knock retard is coming from a 3/2 down shifting and then it never goes ways threw out the pull the I think. I need to either back off my shift points or increase the limit a little to allow a hair more time for the shift to complete.

I did have all the torque mgt taken out of the tune but thinking back on things I believe after I rebuilt the trans and had some passes on things I put some torque mgt back in it becuz the rear end sounds so hammered on part throttle shifts.

I think that should account for the knock/spark retard right after a down shift.

Think it is retarding the timing all the way down the track after a burn out?Maybe that's why my 1/8 to 1/4 seems to not be what it should

 

The first graph shows timing is pulled exactly as you describe, during downshift. And then it comes back, as if real knock is occurring later.

The second graph is showing a knock retard as coming back, as you approach redline. That is more likely to be real knock.

The questions here are,
how does reduced timing affect the graphs (make identical runs with much less timing)
how does higher octane fuel affect the graphs (turn up the octane to 100+ and check for similar retard patterns)

Once you sort out how timing/octane affects the knock retard, you can make a call whether or not to disable which portions of it. Having the knock retard feature is a great way to protect the engine; but you certainly do not want it just pulling timing at the slightest tickle either. I was also kind of hoping you could post a graph of the actual knock sensor's output, I dont see it in any of your graphs and it might be worth looking at.

Once you make a call whether the knock is something to worry about or not, here is how it plays out:
1. you decide that there is knock at higher rpm as the second graph suggests because the knock retard goes away with reduced timing/higher octane, so you permanently reduce the timing in those regions and it goes away for good
2. you decide that there is NOT actual knock, and the sensor is too sensitive, so you adjust the settings (less sensitive setting) until the knock retard goes away(recommended for confirmed false knock), or, disable it in those regions (not recommended to disable the knock retard), or, do something to make it less sensitive i.e. teflon tape it, loosen the sensor, fix the bushing/mount making the "noise".

heres is a picture I circled the suspected area,

 

can you post your timing tables, not retard,to see if the peaks and valleys correspond to each other,if there is a big jump or lack there of, this can cause some timing to be pulled..

 

Ya I'll do that after work

 

wasn't sure if you meant the tune or log so here is both for both timing setups.

and the tunes