Since so many guys are getting frustrated about getting a few degrees of KR with the DSP 93 tune, I figured I'd try to change things.
"Problem": DSP 93 tune leaves the Knock Threshold alone and removes 1-2 degrees of timing from 4k to redline.(Yes, 93tune has LESS WOT timing than stock)
Result: guys running stock PCM are getting a bit more knock with the 93 tune than Stock and getting pissed off.
"Solution:" After a bit of negotiation with DS, I think I have them convinced to "desensitize" the Knock sensor on the base 93tune for all PCMs This will change any stock PCM to basically the S1/S2 values. We all know the S1/S2 are proven reliable so no one freak out.(stage PCMs will effectively remain unchanged.) If all goes well it will availible on the next crom.
It seems that 90% of all "problems" SRT-4 users experience with the 93 Oct tune revolves around the perception that they have too much Knock Retard.
I think a very low risk improvement to the SRT-4 Predator 93 Octane tune would be to up the Knock sensor threshold to equal those of the Mopar stage PCMs.
Every MP stage PCM has the Knock sensor sensitivity "turned down" a little and has been proven over a few thousand vehicals and several years to be safe and reliable.
Many new SRT-4 Predator users experience up to 4-6 degrees of Knock retard with thier new "93 Octane tune" and are discouraged. Even though they are told 1.5-2 degrees of KR is acceptable, many insist the Knock must be 0 and can often wind up having a negative opinion of the DSP and its tune because they believe the must now pay for a custome tune.
I think this small change to the Knock tables would improve initial customer satisfaction with little to no risk to the customer's vehical reliability.
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"Just because someone goes fast doesn't mean you should do whatever you think they did.
This path assumes they knew what they were doing, which isn't necessarily the case"..........RB Racing
Last edited by duster360 : 08-16-2009 at 01:52 AM.
I asked around, and the reason we did not mess with the knock sensors is because we do not add any timing inthese tunes, in fact some have a bit of timing pulled, thus we did not think it would be necessary, especially on a stock car.
The idea was if you really wanted the sensors desensitized, you'd likely be running a custom tune anyhow, and you could have the tuner set your knock thresholds however you'd like.
Thanks
Mike
Quote:
Update for you guys, i took the srt4 and did a bunch of tests. I was getting 4 degrees pulled, so yanked 4 degrees more from the tables, still got the knock. So i up'd the thresholds for you guys and saw 1 count at 5500rpm. I yanked out 1 degree and still saw the knock however i went pretty aggressive on the thresholds. So i decided not to go any further. I took it out on the street and got 1 count beating on her repeatedly. And i hit the rev limiter when that count showed up, after which i didn't hit it anymore and saw nothing further........................
.............i even played around with the a/f mixtures and really saw no difference
yea i think its necessary and it will be on the next update. If you guys wanna give this one a try let me know, send me your ori ill send you a custom tune.
What i noticed even with the knock, power output was virtually uneffected. This car was an intake, catback, intercooler car with an adjustable waste gate (so i had no control in the tune) on the stock 15psi, which tapered off to 11 by redline,i saw peak power pretty low, around 5ish. The knock didn't appear on this car until 5557 and was spun to 5800. I also noticed the pcm was quick to recover from the knock, still at peak rpm it gave the engine what i commanded. But at 15psi, you are right on the verage of two different columns of a the timing table, the top table runs i believe 23 total advance, the one below it runs it up to 25. It further is a pain b/c boost tapers off quick and then the timing will jump to another part of the graph. Its based on pressure ratio to determine which row to use. I smoothed this out a bit to further help with any possible detonation that might occur. I also smoothed out the desired torque table since the factory had a smooth transition across the rpm, i mimiced that with higher outputs of coarse and you can see very clearly on the dyno graph there are less divots, its much smoother. Johan suggested adding some timing to the mid range since it was pretty wimpy looking, and it helped ALOT. it peaks higher EVERYWHERE. unforutnately since i had no control over boost, i only dynoed around 15rwhp higher then stock, it made 275hp. I think if that adjustable waste gate wasnt there i would have seen closer to 300. I know i could have just messed with his waste gate but I wasn't about to touch something like that on a car that doesnt belong to me. Plus i needed as close to stock as possible.
This is awesome. I hope that they get the update out quickly. I'm wanting to try it out. Even though I have a custom rage tune w/ 3bar sensors, I'm still getting overboost codes. I wish that they could fix that in the updates as well.
Good news,,,,,,,,,,,Don emailed me the tune and I installed it this afternoon. He upped the Knock threshold just a little bit more than the Stage PCMs.
Bad news,,,,,,,,,,,Unfortunately the Desired torque and wastegate tables inadvertantly were left "stock", and i just got home to recieve the fixed tune. So no real news.
I did load the lower boost tune earlier this evening just to check some other "special requested" changes and it seemed pretty peppy at only 15psi. No knock but thats not saying much because my tunes are so bad ass I was only getting 1 degree at 22psi anyway.
Last edited by duster360 : 08-18-2009 at 01:03 PM.
Thanks for doing the leg work on this, duster. Looks like some solid improvements.
While we were at it I asked for the same tune but with the Wastegate Duty cycle Adaptives turned on. Im going to see how well the PCM learning reacts with the higher wg dc of the 93tune.
I spoke with someone from DS months ago about this very issue, and agreed to keep my mouth shut about it. (for the most part) lol
They gave me permission to share, and post the information, but.. I didn't want to add to the rampant complaining that was going on at the time.
I told "them" that I would keep things quiet unless they felt the need to step in. I didn't want "them" being hammered by people bitching, .. or requesting different knock thresholds. (tunes,.. croms.. ect)
I'm not trying to take anything away from Duster,.. he's doing something that, well.. I refused to do. (share) Sorry guys..
Seeming that its in the open now,.. Duster, I would presume this would change your thoughts a tad on the whole "torquing of the sensor" ..?
While I would agree,.. a few cars may have issues with the sensor itself,.. I believe that most are threshold related. (knock retard)
Either that, or there isn't enough fuel.. or too much damn timing!! lol But,.. with a solid AFR on pump.. as long as the boost isn't crazy.. there should be little to no knock retard at all.
-Will.
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Stage 1 ECM (NOT stock), Diablosport Predator, 3 bar map and tip, Interceptor Scangauge, AEM wideband, 750's (no return-line), MPX BFMIC, Walbro 255, DCR top end modifier, AGP WGA, 3 in O2 housing, QTP 3in downpipe with E-cutout stock catback, Nitrous Oxide Systems 65 HP shot, motor mount inserts.
Best MPH to date on the bottle,119.04 --- Off the bottle 113.55. --- best ET 12.44. on borrowed DR's. Stock turbo, stock Mani.
Last edited by Nosfurato : 08-18-2009 at 01:19 AM.
Seeming that its in the open now,.. Duster, I would presume this would change your thoughts a tad on the whole "torquing of the sensor" ..?
-Will.
No not really. Changing the Knock threshold is just a cheap and easy "fix" for everyone. I would have never suggested anything unless there was substantial evidence that it was "safe". I figured if the Stage PCM can get away with adjusting for "less" knock and since they have a long and proven track record of reialbility, needing to incorporate this small change into the 93 tune was self-evident.
Changing the Torque on the Knock sensor slightly effectivly does the same thing, you just don't have to get your hands dirty and its a bit more predictable if you go through the PCM
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Knock "FIX" w/ 93 tune
Linear Mode
