SRT4 93tune Improvment request U7134

[duster360]

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

Yes I saw the few degrees of timing taken out from 4k up. The stage PCM adds a couple degrees along with the desensitized sensor.

For some guys its fine. But for others its not. May its an incorrectly torqued sensor maybe its crap gas, or something else.

I honestly don't think most of these guys are having real knock issues but its thier PERCEPTION that they are. Its sad when this perception spawns a negative opinion or worse they bail on the product(sologdog)

Wrong or right; justified or unjustifed, if the log says they're knocking 3,4,+5 degrees, they're freaking out.

Changing the knock tables to the S1/S2/S3 values (long track record, proven reliable) would be an EASY fix toward improving customer satisfaction.

[solodogg]

5 degrees of knock IMO can only be real. anything below 2 would have been great, and I would have never worried about it, but 5 degrees can't be an overly sensitive sensor. Especially when I could throw a stronger wastegate on the stock map, and have 0KR.

[slyder]

perceived/real fake knock/real knock The sensor is reading something correct. There has been lots of debate on if this is actual knock.

• Is there another tool to verify knock? I am not about to buy another $200 gauge to measure what this is supposed to.
  Why are so many people seeing such high counts then?
  What should the timing be at the higher RPM band, so we can see if we are in the correct range?

Yes I know every car is different and this is supposed to be a baseline. BUT I was Safer at S0 with FM wg than with this nearly $400 tool. Trying to learn!!! and not wreck my car.

-Slyder

ps Duster thanks for your patience w/us!

[duster360]

5 degrees of knock IMO can only be real. anything below 2 would have been great, and I would have never worried about it, but 5 degrees can't be an overly sensitive sensor. Especially when I could throw a stronger wastegate on the stock map, and have 0KR.

The sensor read out is just relative to its "Threshold" settings. If you had a S1 PCM you WOULD have had 1-2 degrees of KR, with the exact same DSP tune.

The engine would have performed the EXACT same. Th eonly difference would be the sensor would have reported sligtly less Knock.

[Quick]

5 degrees of knock IMO can only be real. anything below 2 would have been great, and I would have never worried about it, but 5 degrees can't be an overly sensitive sensor. Especially when I could throw a stronger wastegate on the stock map, and have 0KR.

The sensor read out is just relative to its "Threshold" settings. If you had a S1 PCM you WOULD have had 1-2 degrees of KR, with the exact same DSP tune.

To be precise the sensor read out is absolute. It's the PCM that maintains the threshold above which it will adjust to eliminate the detected knock. The second part is correct. The PCM would have needed to apply less knock retard (pull less timing) to bring the sensor read out down to the raised threshold.

The engine would have performed the EXACT same. Th eonly difference would be the sensor would have reported sligtly less Knock.

This is not true. The engine would have performed with more timing AND more knock.

[SCGt94]

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.

[SCGt94]

i even played around with the a/f mixtures and really saw no difference

[duster360]

The engine would have performed the EXACT same. Th eonly difference would be the sensor would have reported sligtly less Knock.

This is not true. The engine would have performed with more timing AND more knock.

Incorrect

(sigh,,,,,i didn't think I had to re-explain the whole thing)

the S1 would have had more timing except the DSP tune was used it will overwrite the timing back down below the stock level. Since the 93 tune doesn't touch the Knock tables, they would remain untouched at the S1 level which are less sensitive than stock.

So he would have been using the exact same timing but the PCM would have reported LESS knock.

[duster360]

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.

So Don do you concure that upping the SRT4 knock thresholds is worthwhile and we should see this change on the next Crom update?

[SCGt94]

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 kind of boost are you guys seeing on the 93 tune?

[Quick]

The engine would have performed the EXACT same. Th eonly difference would be the sensor would have reported sligtly less Knock.

This is not true. The engine would have performed with more timing AND more knock.

Incorrect

(sigh,,,,,i didn't think I had to re-explain the whole thing)

the S1 would have had more timing except the DSP tune was used it will overwrite the timing back down below the stock level. Since the 93 tune doesn't touch the Knock tables, they would remain untouched at the S1 level which are less sensitive than stock.

So he would have been using the exact same timing but the PCM would have reported LESS knock.

I understand what you're saying. (and this is just for the technical nit discussion)
The PCM would have reported less knock RETARD. The sensors report the same no matter what.

This part is more important. I was under the impression (given by mikel) that ALL ds tunes reduce/raise the threshold. So they would be writing to the knock tables.

Is this not true for the SRT4 tune?

[solodogg]

ah hell, go figure, this is finally gonna be fixed, and i dont have my predator anymore

Someone needs to do another group buy for 320 shipped haha

[solodogg]

I understand what you're saying. (and this is just for the technical nit discussion)
The PCM would have reported less knock RETARD. The sensors report the same no matter what.

This part is more important. I was under the impression (given by mikel) that ALL ds tunes reduce/raise the threshold. So they would be writing to the knock tables.

Is this not true for the SRT4 tune?

that's the way i've always understood it...that when you see 5KR, the PCM is pulling 5 degrees of timing to save itself from the knock it's seeing. When I saw 5.5KR, I could feel a difference in the car.

[SCGt94]

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.

[slyder]

If you need another tester I"m your man. Just let me know what you need from me and I can fire it off to you and run some pulls tomorrow and post the graphs

-Slyder