Finally made some headway on my Knock issue

[JPs2013GT500]

I've been chasing +knock readings for a while (see my earlier posts in this thread). I found/fixed a couple of small things over the past that I thought may have contributed to false knock, but nothing solved it. I of course tried different fuels, torco, etc.. Knock was still present. I figured my next step was to access the intercooler to check for oil contamination but put that off and just didn't drive the car much.

During the recent holiday sales I purchased a PMAS 120 intake kit just to test. I installed that along with an older monoblade throttle body I had sitting in storage that I hadn't tried yet. I replaced the dual 65mm throttle body and JLT 127mm Carbon Fiber air intake with the monoblade & PMAS parts. Contacted Lund for a tune revision & flashed it in.

I've run this setup for the past couple of weeks and NO KNOCK! It's actually adding timing now. I'm reading up to -3 on the knock sensors now! It idles so smoothly now that I caught myself checking the tach at stoplights to make sure the car hadn't cut off on me (it was somewhat rough before).

I'll definitely keep an eye on the data logs to see if it maintains this behavior as the warmer weather arrives....but man is it great to see the knock sensors adding timing for a change!

 

[RedVenom48]

If I were a betting man, Id say that JLT had something to do with it.

 

[merkyworks]

If I were a betting man, Id say that JLT had something to do with it.

Hypothetically if the JLT intake had something to do with the knock issue what is happening that would cause this?

 

[RedVenom48]

MAF transfer function. Basically the values assigned to a certain diameter intake are assuming that the tube diameter is, in fact, that advertised diameter. The tune is compensated for variation in air charge speed of the larger intake. Also, JLT intakes aren't very good at giving a clean MAF signal to the computer. As the MAF data is the PRIMARY source of data for the ECU to calculate fuel demand, if its off, everything else is off.

JLT intakes of all models are notorious for have inconsistencies in tube diameter. His car could have been dialed in for 127mm, but if the intake were 125mm or 129mm diameter, the calibration could have been very innacurate.

From my understanding, Lund Racing was charging a JLT tax on tuning JLTs because of the these inconsistencies.

Could have been a noisy TB assembly, but my guess is the JLT was off. I have systematically replaced JLT parts on my car with better quality parts. They aren't the worst, but they are not even close to being the best.

 

[RBB]

I'm not surprised. The normal MAF transfer function used for a JLT 127 had my fuel trims way off. Lund had to adjust the tune a couple times just because of that thing and I still had a little bit of knock after that. I've moved over to a PMAS now.

 

[RBB]

Double post****

 

[Cman01]

That's good to know, changing out those two items sorted out your knock issue.

I'm looking forward to installing my PMAS and SCJ monoblade also on my car.

Tony

 

[03terminat0r]

I've been chasing +knock readings for a while (see my earlier posts in this thread). I found/fixed a couple of small things over the past that I thought may have contributed to false knock, but nothing solved it. I of course tried different fuels, torco, etc.. Knock was still present. I figured my next step was to access the intercooler to check for oil contamination but put that off and just didn't drive the car much.

During the recent holiday sales I purchased a PMAS 120 intake kit just to test. I installed that along with an older monoblade throttle body I had sitting in storage that I hadn't tried yet. I replaced the dual 65mm throttle body and JLT 127mm Carbon Fiber air intake with the monoblade & PMAS parts. Contacted Lund for a tune revision & flashed it in.

I've run this setup for the past couple of weeks and NO KNOCK! It's actually adding timing now. I'm reading up to -3 on the knock sensors now! It idles so smoothly now that I caught myself checking the tach at stoplights to make sure the car hadn't cut off on me (it was somewhat rough before).

I'll definitely keep an eye on the data logs to see if it maintains this behavior as the warmer weather arrives....but man is it great to see the knock sensors adding timing for a change!

I just recently began sending Lund some datalogs and the knock sensors are pulling timing at WOT. After ruling out fuel quality by adding octane booster they believe it is false knock. So now I am on that search.

Do you mind sharing what parts you checked that would cause any mechanical vibrations or movements that would contribute to false knock?

List of mods on the car: JLT 123mm cai, 2.4 upper with idler, mrt o/r h-pipe, UPR LCA, UCA, eibach springs, strange struts, viking shocks, 3.73 gears, mgw shifter.

 

[50stangpower]

Crap, I'm chasing some false knock and have the same intake and TB as you.... I'm going to try my exhaust first but I now this has me wondering.

 

[JPs2013GT500]

Do you mind sharing what parts you checked that would cause any mechanical vibrations or movements that would contribute to false knock?
Sure, I adjusted the over axle exhaust pipes. The driver side was really close to the panhard bar support brace (still had knock after that). There was a long bolt (a/c support bracket if I remember correctly) that was super close to the headers. I trimmed the excess threads with a dremel tool (still had knock after that). I checked all the exhaust bolts to make sure they were pointing in the direction as to not contact with anything. Check exhaust heat shields to make sure they aren't loose and/or hitting anything. I re-torqued all the bolts on anything I had installed and/or could get to easily.

Knock only went away when I changed the throttle body and intake & installed new tune.

I was given two tunes when I installed the PMAS & monoblade. One for the monoblade & PMAS and one for the dual 65mm TB & PMAS (in case I had a temperamental monoblade). I installed the monoblade first, was happy with it and haven't tried the dual 65 + PMAS intake tune. I could swap TB's & tune to verify if it was the dual 65mm TB that was my knock issue if that would be helpful?

Also FWIW, I had a local shop dyno tune the car with the dual 65mm and JLT 127 intake. He said there was no signs of actual knock during the tuning session. However, whenever I data logged with his tune the knock sensors always read 0. Made me nervous that they were disabled/toned down and I wanted that layer of protection so I stopped using that tune.

 

[2011 gtcs]

I might switch over to a 120mm intake. I need to get my nGauge first.

 

[RedVenom48]

Are you planning to stick with the factory 2.3 TVS or upgrade to a bigger blower? 900 is about where ive seen the PMAS DD149 recommended.

 

[2011 gtcs]

Are you planning to stick with the factory 2.3 TVS or upgrade to a bigger blower? 900 is about where ive seen the PMAS DD149 recommended.

Stock TVS, I'm already at 730whp and 780wtq, I don't really want to make to much more power.

 

[RedVenom48]

PMAS 120 is perfect then

 

[JPs2013GT500]

Alright, this evening I data logged with the PMAS + monoblade. It added (-1.25) timing and then pulled (+0.75 knock). I drove it back home, swapped the monoblade out for the dual 65mm TB and loaded in the tune for that throttle body. Headed back out to data log that setup. Similarly it added (-1.75) timing and then pulled (+0.75).

So, fairly similar results between the two throttle bodies. Still a touch of knock (real or fake). When it did see knock it seems to mainly be detecting it when I'm nearing the end of 3rd and/or getting out of it.

 

[merkyworks]

The +0.75 definitely shows while coming off the throttle, I wouldn't be concerned with that. From what I have read its not uncommon to have +1.0 or less during initial WOT and then return to 0 so I would think the same logic applies when coming off WOT.

 

[2011 gtcs]

Alright, this evening I data logged with the PMAS + monoblade. It added (-1.25) timing and then pulled (+0.75 knock). I drove it back home, swapped the monoblade out for the dual 65mm TB and loaded in the tune for that throttle body. Headed back out to data log that setup. Similarly it added (-1.75) timing and then pulled (+0.75).

So, fairly similar results between the two throttle bodies. Still a touch of knock (real or fake). When it did see knock it seems to mainly be detecting it when I'm nearing the end of 3rd and/or getting out of it.
View attachment 1477766

Great info, so the PMAS intake helps out a lot with knock issues if you have them, or is at least a good starting point.

 

[VNMOUS1]

Just so I am clear, does someone wish to enlighten me as to what the mass air transfer function has to do with detonation?

Sent from my [device_name] using the svtperformance.com mobile app

 

[merkyworks]

 

[JPs2013GT500]

I have no clue. If that has nothing to do with it, then I wonder if that carbon fiber tube bumping against the coil cover could have been the problem? Seems like it wouldn't be the right frequency of tone for that, but it is located semi-close to the sensor itself.

I set it back up with the monoblade + PMAS combo, run it again and zero knock (attached). For whatever reason my car seems to prefer that configuration. I wish I knew the exact reason why.