knock knock

09Laramie · Post by **09Laramie** » Sat Oct 17, 2009 1:41 am

I just got my predator this week for my 09 Ram 1500, 5.7L Hemi. I've also been doing some data logging, and I've noticed what seems to be a lot of knocking- KNK ST Retard and KNK LT Retard- with the 87 tune, even though I just filled up with 93 gas. No mods on the truck other than the predator.

Since I'm new to tuning, I'm looking for some advice from the more experienced tuners out there to make sure I'm on the right track, and maybe point out things I might be overlooking before I start attempting to tweak the tune for my truck.

Temperatures have been in the 40s for the past few days here (mid 40s for both of the logs posted below), and I found some posts on the forum that seemed to suggest that colder temperatures could cause the fuel/air ratio to be more lean, and that gas should be added in the tunes to correct for it. This sounds reasonable, although I would think that the MAF sensor would account for most temperature variations. Is adding more gas where I should start?

I have two logs from yesterday posted below, both with WOT runs and some cruising too.
For the morning log, the first WOT run starts at about 26 seconds in, and there's a second WOT run at 52 seconds.
The afternoon log has a WOT run at 4 seconds, and a shorter one at 1:15

Thanks in advance for your help

09Laramie · Post by **09Laramie** » Sun Oct 18, 2009 11:12 pm

the brand of gas that I've been using could have something to do with it (been using Sam's Club gas, which I know isn't exactly known for quality), although it still seems like even cheap 93 octane gas shouldn't have that much knock on the 87 tune.

Anyway, I added a can of NOS brand octane booster to my half-full tank today, and it seems like it at least reduced some of the ST knock. The log posted below was taken shortly after putting the octane booster in the tank. I'm going to fill up with Exxon or something in the next couple days when this tank runs out. Hopefully that will yield better results.

WOT runs in this log are at 11 sec, a short one at 44 sec, and another one at 3:30 that didn't have any knock while at WOT.

there are also some seemingly random jumps in ST knock at 4:12 and 6:22 that I'm a little curious about.

and just to make sure I'm understanding some of the numbers right- actual spark and base spark- positive numbers there are degrees before TDC, and negative are degrees after TDC?

Thanks again for any help you guys can provide.

lross78550 · Post by **lross78550** » Mon Oct 19, 2009 12:04 am

09Laramie would you mind sharing the settings you are using on your truck. I know i cant just take your settings and plug them into my truck but by looking at your settings i can at least learn how your going about modifying the basic predator tunes. If you get time just post or pm me the settings you changed and the results (positive or negative). I would really apprieciate it. I'm doing alot of reading and trying to learn all i can and it seems like we are both just starting on 09 ram hemi's.
thanks
Lee

09Laramie · Post by **09Laramie** » Mon Oct 19, 2009 12:24 am

I'm just running the 87 tune just like it came out of the box right now- I'm not confident enough yet to start adjusting things based on what I see in the logs, which is why I'm starting with things like the gas I'm using. I'll happily share whatever I learn or figure out with you when I get there though.

Right now I'm just starting by doing some data logging with the following parameters: BASE SPK, SPK ADV 1, INTK TEMP, KNK FUEL RET, KNK LT RETAR, KNK ST RETAR, ENG RPM, VEH SPEED, THR POS %

lross78550 · Post by **lross78550** » Mon Oct 19, 2009 12:43 am

I have access to 100LL fuel at the airport. Is 100LL low enough lead to keep from plugging up the catyltic converters if i run it often? Im running the 93 octane tune and i have run 93 octane fuel in the truck since it was new. However the only gas stations down here are valero stations so who knows if the 93 is really 93. I too notice a fair amount of valve clatter at different times and condiditons. I will hook the data logger up tomorrow and i bet the knock retarders are working overtime. A single tank full of 100LL would answer the question of weither a fuel is available that will burn smooth with that much spark advance. But a full tank of 100 LL might also turn my catylic converters in to plugged up bricks

Lee

airportdave · Post by **airportdave** » Mon Oct 19, 2009 3:03 pm

Use 100LL at your peril. Despite the term "low lead", 100LL aviation fuel has many times more lead than LEADED auto gasoline, and exponentially more than unleaded auto gas. Even a little 100L in your vehicle is liable to cause valve guide issues, catalytic converter destruction, spark plug fouling, etc. Additionally, aviation fuel uses a different octane measurement method than auto gas, so comparing aviation fuel octane numbers to auto octane numbers is comparing apples to oranges. See http://www.shell.com/home/content/aviat ... 71515.html for a great dissertation.

09Laramie · Post by **09Laramie** » Mon Oct 19, 2009 10:38 pm

I'm not sure about the other side effects that airportdave mentioned (not saying that I don't think they'd happen- just don't know either way), but 100LL will definitely clog up your catalytic converter(s). There was an FBO employee that I heard about who had been stealing avgas, and one of the reasons he got caught is because he clogged up the cats on his vehicle. You might be able to run on 100LL if you remove your cats, but even then, I wouldn't try it on my brand new truck.

back on the knocking though- haven't gotten to fill up with another brand of gas yet, but the log I took today looks more consistent than some of the previous ones. I was getting ST KNK of 2.5 degrees at about 4100-4200 rpm, which then dropped off .5 degrees every .5 seconds, and was back to 0 by the time I got to 4800 rpm

lross78550 · Post by **lross78550** » Tue Oct 20, 2009 8:07 pm

09Laramie Hows it going? Learned any tricks?
Thanks
Lee

09Laramie · Post by **09Laramie** » Wed Oct 21, 2009 10:24 pm

filled up with Exxon 93 octane last night, and took this log on my way back from work this evening. Seems to be a little less knock overall, but I'm still getting up to 3.5 degrees of ST KNK Retard at WOT.

Is there something I should be doing to fix this or am I overly concerned about nothing?

Quick · Post by **Quick** » Thu Oct 22, 2009 2:06 am

Well, that's not something to get alarmed over but it's too much and it too consistent. leave everything the same and add 5% fuel across the board. If that doesn't do it add another 5% fuel. What you're looking for is may a spike to 2.5* spark retard right when you drop the throttle or at the shift points and it should step directly down to zero.

2001z06 · Post by **2001z06** » Thu Oct 22, 2009 12:11 pm

I would take out the tune and data log with the stock tune

09Laramie · Post by **09Laramie** » Thu Oct 22, 2009 10:31 pm

Quick wrote:Well, that's not something to get alarmed over but it's too much and it too consistent. leave everything the same and add 5% fuel across the board. If that doesn't do it add another 5% fuel. What you're looking for is may a spike to 2.5* spark retard right when you drop the throttle or at the shift points and it should step directly down to zero.

Thanks for the feedback- I'll try this tomorrow morning and take some more logs.

At what point would you get alarmed about the knock? One of the reasons I'm focusing on the 87 tune right now is because I want to make sure that I know what I'm looking for and how to fix it before I put the 93 tune on.

2001z06 wrote:I would take out the tune and data log with the stock tune

I actually did exactly that the 2nd day I had the predator. That log was done with the Sam's club gas and before the octane booster though. Saw a little knock- 2 degrees at about 4700rpm, tapering off .5 degrees every .5 seconds
I'll probably try taking another log of the stock tune tomorrow while I'm messing around with it.

Quick · Post by **Quick** » Fri Oct 23, 2009 1:25 am

What you're seeing is how much timing the PCM is pulling to eliminate knock. It does quite well at that within it's limits. It detects A knock and pretty much pulls timing before that cylinder fires again. So maybe it's better not to have that first knock but it's not going to do any harm in the short term. What you're losing is power/performance. You would be making more power if you maintained the timing with no knock that might be being caused by the gas you're using or oil/oil vapors being burned. The PCM has limits to the timing it can pull. If it's worse than that then you have sustained knock which will do damage in a hurry.

So, alarmed? I'd be alarmed if you started seeing knock up towards 9 under 4K rpm, up towards 7 in 4k-5k rpm, and 5 above that.

09Laramie · Post by **09Laramie** » Fri Oct 23, 2009 10:31 pm

I added 5% fuel across the board this morning and took another log- looks like it got rid of at least most of the knock. Now, if anything, it's just a blip here or there.

If subsequent logs show that the KR is staying at 0, should I lean it back out at all (with the goal of getting it to where it's as lean as it will get without knocking, and no leaner than the canned tune), or just leave it where it is? I would also assume that if I get consistent knock at one point that I would add some fuel in that range to get it back down just.

Thanks again Quick for the info.

Couple questions on some of the other parameters to double check my understanding of them:

Actual Spark Cyl 1: I assume this is when the spark plug in cylinder 1 is actually firing. Is the measurement on this degrees before TDC? (or after TDC if the value is negative)

Base Spark: Is this where the spark plug "should" be firing? i.e. what the timing would be if the spark wasn't retarded due to knocking? and I assume the measurement- degrees in relation to TDC is the same for this as for Actual Spark

Throttle Position Sensor %: I think this is measuring the position of the butterfly valve blade, not how far the pedal is pushed down. Is this accurate?

Quick · Post by **Quick** » Sat Oct 24, 2009 12:36 am

09Laramie wrote:I added 5% fuel across the board this morning and took another log- looks like it got rid of at least most of the knock. Now, if anything, it's just a blip here or there.

Looks great. You might want t try a bit more of a run with it. Like a standing start and WOT up into 3rd or through it if you can.

If subsequent logs show that the KR is staying at 0, should I lean it back out at all (with the goal of getting it to where it's as lean as it will get without knocking, and no leaner than the canned tune), or just leave it where it is? I would also assume that if I get consistent knock at one point that I would add some fuel in that range to get it back down just.

You could. That would be the process. Depends on how inspired you are to tinker with it

. Depends if your gas is consistent. The 5% you added is not a HUGE amount and you were seeing some significant/consistent knock retard before. You're probably very close to where you want to be. I'd run a couple more tanks of gas through it and maybe do a log or two each tank and see if you get similar results. Also you appear to be in ideal conditions with an IAT around 60*

Actual Spark Cyl 1: I assume this is when the spark plug in cylinder 1 is actually firing. Is the measurement on this degrees before TDC? (or after TDC if the value is negative)

Yes.

Base Spark: Is this where the spark plug "should" be firing? i.e. what the timing would be if the spark wasn't retarded due to knocking? and I assume the measurement- degrees in relation to TDC is the same for this as for Actual Spark

Yes. The PCM factors a number of parameters to modify from the Base spark. My understanding is that Base Spark is from the tables and then the PCM modifies that in response to dynamic inputs like maybe temps, load, torque, whatever and, obviously, knock detection.

Throttle Position Sensor %: I think this is measuring the position of the butterfly valve blade, not how far the pedal is pushed down. Is this accurate?

Depends on what you mean by accurate. Yes, I believe it is consistent. No, your throttle blade is not opening 127%. I think there is a Throttle Blade Position parameter and that's probably going to max out at 87% or something like that. That one they calibrate from idle where it's not completely closed or whatever. It's just the way those parameters are reported. Your throttle is calibrated and the throttle blade opens all the way up at WOT. I usually use Pedal Position in my logs. Good enough to see when you go WOT or not.

I guess they'd differ when you have your foot on the floor and the PCM modulates the throttle for traction control or maybe for shifts? or if it limits throttle in 1st like on the Jeep SRT8s.