2009 Challenger 5.7 6spd - some ST knock - thoughts?

[tractionlimited]

So, is the goal to get short term knock to zero at WOT, or is that just sort of unachievable? I've been messing with a tune for the last several days and no matter what I do, I can't take out all of the ST knock. The gas is solid 92 that I run in all my turbo cars for street tuning.

Here's a recent log (tonight) of a 93CAI tune +5% fuel (all three ranges) and -1 spark (all three again). It's close, but there's still some that pops in here or there. Thoughts? I've been as high as +15% fuel just trying to squelch it and it still gets a bit.

[ZMagnum]

Use the 91CAI tune with 92 octane fuel. Don't use the 93CAI tune unless you have 93 octane gas available.

[tractionlimited]

Use the 91CAI tune with 92 octane fuel. Don't use the 93CAI tune unless you have 93 octane gas available.

Thanks for the response, but the advice isn't helpful. I have used the 91CAI tune as a base as well and it's about the same.

My question, for the experts here, is whether the goal even should be shooting for no ST Knock at WOT or whether a certain amount is unavoidable.

[PlumCrazyDaytona]

I would not change a thing in your tune. You have so little knock that it is not affecting anything. You have zero LT and less than 3% of ST and that occurs at the shift so nothing to worry about!

Sure Zero ST would be nice but it is not going to happen without a catch can higher and the hemi does produce false knock so you should be very happy with your results. I would say you are as dialed in as you are going to get without a CMR tune

[ZMagnum]

Use the 91CAI tune with 92 octane fuel. Don't use the 93CAI tune unless you have 93 octane gas available.

Thanks for the response, but the advice isn't helpful. I have used the 91CAI tune as a base as well and it's about the same.

My question, for the experts here, is whether the goal even should be shooting for no ST Knock at WOT or whether a certain amount is unavoidable.

Anything under 3 or 4 is fine. If you are only seeing it at shifting then it's probably false knock.

If you have to add 15% more fuel you are way outside the norm. I've added up to 3% or 4%. Right now I'm set at +2%. Do what you want but it's been posted here and on LXForums that if you are running 92 octane you should use the 91 tunes not the 93.

You also may want to install a catch can (recommended numerous times by Diablosport) and use the Diablosport recommended brands of fuel.

[tractionlimited]

Thanks for the responses! To be clear, I do have a catch can (in my sig) and I'm not really worried about anything that happens on a shift or during wheelspin. Much of that log is long 3rd gear pulls across the whole range and that's what I'm optimizing for.

Forget the 15% fuel. I was just making the point that I've squelched it with fuel and still saw about the same ST knock behavior. I run at 5% across the board for now. And as for 92/93, I'm not too worried about it - thanks for the advice though!

So, what I'm hearing is that folks generally don't try to tune for 0* ST Knock. That's a relief because I really couldn't make it happen. I'm going to get a little more aggressive with the tune as I'm still not totally happy with the power and see where it goes from here.

[ywait]

Hello,
My Chally RT Auto is getting LT and ST KNK… I read what you guys did so I changed the tune to + 5 fuel / -1 WOT Spark ( MBT Spark unchanged). I use the 0-60 timer hack in the dash.. I’m having Headers and a camshaft installed over the next month and have an Oil Catch Can on its way. Please give or comments on this 0 to 60 run. There are only a few places where I get KNK and only during WOT…. So should I back off the fuel a little by running a little leaner than +5 fuel?
Thanks in advance….

[ywait]

I took a pic of the 0 to 60 Time of the run above.

[tractionlimited]

You have to change MBT Spark to be the same in each range.

For my comfort, that's still too much knock, especially since it ramps up during the pull. It looks to me like your fuel really can't support the 93CAI timing. I would try different fuel or start with the 91CAI as a base. With your mods, I wouldn't expect you'd need to add much fuel to the canned tune to get it right.

0-60 time is influenced by so many things that it's not useful for me to comment. With an auto, on a consistent level surface, with a consistent launch, you should be able to measure relative improvements, but that's a lot of if's.

[ywait]

I buy the from Valero 93 Octane... Crappy Gas ? Has to be.. But it's a company card so??? I'll change the MBT Spark to -1 to go alone with WOT Spark Right ? and buy some Octane booster.

93CAI Tune
WOT Fuel +5
WOT Spark -1
MBT Spark -1
Right ?????

Others settings
No MDS

[ywait]

Added GumOut Octane Booster to a Full take of 93 Octane from Valero. I'll log for KNK tonight.

Changed MBT Spark to -1

Thanks

[johan]

Valero is cheaper for a reason...
And as i might of mentioned before, catch can catch can catch can. You can try to dial things in until you are blue in the face if you have oil in your intake(which you probably do).
Get a catch can and throw some good fuel in there.
All the cars i dynoed here for development had catch cans and some had less than a 1000 miles and guess what was in the catch can already.

[ywait]

I beleive you.. The Catch Can is being shipped should be here in a few days. I have 10,000 miles on her now..
Is there a way to have the dealer clean the intake because of knk issues or should I clean it when I have the Cam put in..
What would you do???

[johan]

I would clean it when you put your cam in.

[ywait]

I would clean it when you put your cam in.

I thought so!!!
Thanks