2011 GT500 TVS tune analysis

[WileyCoyote520]

Hi all,

I am new to SVTP and excited to finally be a member. I have recently purchased a 2011 GT500 and have since added a '13 ported TVS with elbow and a 2.67" pulley. The car has a VMP twin 67mm TB, JLT 123mm CAI, 56lb. injectors, Brisk Racing GR12Ys plugs, an O/R X-pipe, and aggressive Roush mufflers.

I have attached the Data from my most recent 3rd gear pull and was curious if anyone wouldn't mind taking a look.

Outside temp during pull was 55 degrees and I am at 3,100ft elevation.

Thanks!

 

[Willie]

Welcome fellow Tucsonan!

Your timing can be advanced. Your load seems low also. What kind of boost are you making? Your AFR is good.

 

[WileyCoyote520]

Willie, thanks for taking a look! I am estimating boost to be anywhere from 14-15psi with my current setup.
From what I have read 17 degrees timing with a tvs 91 octane tune is the sweet spot.
As for the load, I was on pretty level road.
Are you going to Cars and Coffee at LA Encantada tomorrow?

 

[HillbillyHotRod]

wish I knew what all that means.

 

[sleek98]

Why is the pull only to 4,800? 17* is good for 91 at redline, but your logs only to 4,800 which is showing 15* of timing. Otherwise it looks good.

 

[WileyCoyote520]

I only went to 4,800 RPM because I had already put 2 carlengths on the corvette I was racing. I really just wanted to take a look at a mild pull before I head to redline.
Is anyone able to estimate power output based on this data? How is that done?
I really appreciate everyone taking a look!

 

[RedVenom48]

Youll want to do a few WOT pulls to redline. Unsure about estimated power from log data.

And welcome, btw! Nice to see another GT500 in AZ! Lived in Tucson for a number of years myself after high school.

 

[StrayBullitt]

Looks to me like you got some knock sensor action and then your timing dropped from 18* to 14.5. I think you're gonna need more octane even to maintain your current timing. Someone Correct me if I am wrong, but wouldn't 18 degrees timing be better suited for 93 Octane and around 16 for 91 ? In that range..

 

[WileyCoyote520]

Hey y'all,

I went ahead and did another log. This time I was able to go to redline! Please take a look and tell me what you think! Your analysis will be greatly appreciated as I am trying to learn about tuning these cars. Once again this 3rd gear pull was performed on 55 degree day @ 3,100ft. I was sitting for about 7 minutes before doing the pull, so it my have had some heat in it.

Could the knock sensor activity be a 'false' knock? The car has a 3" X-pipe with basically straight-thru Roush mufflers and it is raspy as a Mofo when I get on it. I will do my best to examine the undercarriage for parts which may be pinging against each other and exhaust leaks.

I'm currently at about 3/4 of a tank of 91 octane.....should I fill up the remaining 1/4 with 100 octane then do some data logging to see if more knock activity is observed? Would this be a good experiment?

I am pretty disgruntled by this knock sensor activity would appreciate any input

Thanks in advance!!!

 

[PaxtonShelby]

Don’t mess with knock. I suggest running the tank to zero miles to empty then running 5-10 gallons of 100 octane unleaded for 50 miles or so, driving it like you stole it. That will clean the combustion chamber of any deposits. Then with the 100 octane still in the tank, take another data log. Make sure your logs are comparable so you have an apples to apples comparison except for the quality of your gas. Your knock readings should be gone. If so, your original gas is no good. I had to go to 3 gas stations....GetGo, then Sunoco, and finally Sheetz before I found 93 octane that didn’t cause knock on my STOCK tune. My car is just a 2014 GT but the principle is the same.

If your knock is not gone, it may be false knock but could be your current tune.

Good luck!

 

[RedVenom48]

Its that JLT intake brother. Need to get rid of that thing stat. Some batches were poorly manufactured and caused a TON of tuning issues, including false knock. Essentially, the air coming in was being calculated wrong due to the diameter size of the tube not being as advertised. Lund Racing for a time was charging a "JLT Tax" because of the issues their intakes were causing.

Its not just as simple as the A/Fs telling the ECU to adjust the fuel trims for "unmetered" air or rich mixture because of the inaccurate MAF data calcs. The raw data is interpreted by the assumption that X volts indicates Y units flowing at a Z rate based on a theoretical calculation of area and volume of the advertised intake. This is adjusted by your tuner in the MAF transfer curve. Its a reference table for the ECU to know the actual volume of air entering the engine based on a simple Volt measurement.

If the data supplied by the intake manufacturer about flow is correct, but the physical dimension of their product is off, it sets off a whole set of issues that the ECU may not recognize as issues.

PMAS air intake is a machined unit at 120mm. Thats my choice and there are a few guys on here and in the 13-14 section that have switched from JLT to PMAS or a Whipple 123mm or Ford Racing unit with machined MAF housings and magically the false knock went away.

You MAY have some other issues that COULD be inducing a knock signal into your data, but Ive seen it on here enough that the JLT isnt a good option for performance. My opinion, based on a number of other owners posting up with issues traced to use of a JLT intake. I didnt want to mess with it and bought a PMAS 120mm last summer.

With your current tune, Id add a can of Torco Accelerator or VP Octanium and re-run your hit with data log. 100 octane obviously works too. The additives or race fuel will raise your octane beyond what the engine needs for that tune. IF you STILL have knock detected, its MOST likely the JLT.

 

[RBB]

Had knock activity with my JLT as well, and Lund had to revise the tune several times due to the inconsistency with it. Move on to the PMAS.

 

[VNMOUS1]

Help me understand how an intake can cause knock, false or otherwise. The JLT is plastic. You'd have to have a hose clamp hammering on a coil cover.

I've tuned a ton of JLT 123s and like anything plastic they will vary marginally with engine bay heat but well within fuel trim limits. Metal won't vary but it will introduce warmer than normal air past the sensor resulting in fueling inconsistencies.

The op is welcome to send me their log for review if they wish.

Bj

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

 

[WileyCoyote520]

Thanks very much for the information everybody! Every little bit helps me put the puzzle together.

I had some time to do a little more data logging today, this time I added 4.2 gallons of 100 octane to my 11.8 gallons of say 90.5 octane (which I feel is an accurate representation of a month's old 91 octane). This combination of these 2 octanes will net slightly >93 octane. I did notice there was less engine noise or rasp for the matter with this fuel combo.

Please take a look and let me know what you think! I have looked over the data, but don't want to bias anyone's opinion with my novice assumptions.

 

[MastaAce03]

Who’s tuning your car?

I’d run your tank empty and put 5 gallons of 100octane back in it. If it’s still showing the same knock, you know it’s false. Or put a can of Torco/VP Octanium in the current tank and re-log. If the knock is still there, that’s a great indication that it’s false. Check yours exhaust and make sure it’s not making contact anywhere and make sure you don’t have an exhaust leak. Unfortunately, you’re getting positive knock right where you’re car puts down max torque. Could be real knock.

I had a similar issue with my car, similar mods. I’m tuned by VMP. Back when BJ was there, him and his crew went through about 10-11 data logs of differing knock sensor activity. They determined the knock was false and with my current tune, have no positive knock sensor activity. Actually adds timing. Send BJ an email, he’ll help you out.





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[WileyCoyote520]

Hello Everybody,

So I took some of yall's advice and here are the most recent steps taken and the data log results:

1) Switched to a PMAS 120mm CAI
2) Got a revised tune from Joe @ VMP for 91 octane
3) Ran the car to 10 miles till empty, put 5.5 gallons of 100 in zee tank
4) Re-loaded the 91 tune at the 100 octane pump, then grabbed the attached data log, take a gander!

In the data log you will see 2 'baby' pulls then the real deal! I like to get it wet before going full beast mode!!!

Side Observations:
a) I used an endoscope to check out the cylinders/piston tops and everything looked great!
b) My intercooler doesn't have a spot of oil on it!
c) My IAT2s suck ass, when cruising in 60 degree weather will hardly ever drop below 120!
d) I don't know why I am using so many exclamation marks, oh well, here's a few more!!!!!!!

 

[merkyworks]

Full disclosure I'm not an expert on reading data logs.

Looked at the log and these are my thoughts

• IAT2 isn't that bad at 113-111*F
• FPDC is 0.43, not maxing out which indicates your pump is good.
  
• AF is 0.74-0.78, look good.
  
• Don't know how to interpret long and short trim fuel values so can't comment.
• With 100 octane your timing looks bad! Side note: 0 or (-) KR is good and (+) KR is bad.
• @3k-15.5* with 0*KR
• @4k-13.5* with 0*KR
  
• @4.9k-12.5* with +1.75*KR (really bad!)
  
• @5k-13* with +1.5*KR
  
• @5.9k-13.5* with +1.0*KR

Just for comparison I looked at my logs from my last tune session.

• 16-18 psi, 93 octane, elevation sea level to 80ft
• IAT2-113*F
• FPDC-0.44
• AF-0.76-0.78
• Timing
• @3k-17* with -0.5*KR
• @4k-17.5* with 0*KR
• @5k-18.5-19* with 0*KR
  
• @6k-18.5* with +1*KR
  
• @6.9k-19.5* with +0.25*KR

So something doesn't seem right with your tune but that's just my opinion and as stated I'm by no means an expert.

 

[WileyCoyote520]

Merkyworks,

I believe my issue is false knock. I agree the timing is low though, remember I am running a 91 octane tune with 100 octane fuel, to attempt to confirm my false knock theory.

I very much appreciate your input and stats, thanks again!

 

[fullboogie]

I've never heard of this JLT issue. Would like to know more details.

 

[WileyCoyote520]

Keep in mind that VMP writes their tunes a little more conservative compared to several years ago. My recent tune compared to my initial tune 5 years ago confirmed that.

So with their tune there should be zero knock, even with 91 octane in the tank and the current 91 octane tune loaded.

I can understand why they are taking a safer route.

Thanks for the info fullboogie!