2012 Silverado 5.3 with BTR Truck Norris and long tube headers. Overall, no issues idling. Just wanting to get more precise with the tune. No matter what changes I make, I?m not able to close the gap between throttle position and throttle desired position and the gap between MAF airflow and VE airflow. Could someone look this over and provide me with thoughts and guidance?
I have a 2012 5.3 bored to 5.7 with the Truck Norris cam.
Far from an expert at all, and I am still learning some stuff myself...but from my limited experience, here are the things I noticed.
You're asking for 675 rpm idle. I can force mine down to 650-700, but it is MUCH happier at 750-800. My tune runs 800 in park and 750 in gear.
Under the Idle tab, put your "min RPM Ref" back to stock. By setting it at 800 you're telling it that under 800 rpm disable adaptive idle for the most part. Leave this down at 525-550
Also, under Idle tab, put your "baro mult" back to stock. You have it at a constant value.....not great.
Your "throttle follower Torque" is WAYYYY too high. Asking for 96-106 ft pounds at idle?? As a matter of fact, the "airflow step up and down" needs to be back to stock. Not sure where you got those values.
I would set your "boundary" under "Fuel/General" to all 520. This is not tuned for our cam, but step in the right direction. The stock boundary was set to 360 deg on the top end for the VVT settings (I believe).
These are just a few things I saw that stuck out to me. Honestly, there is a lot more I have changed and would, but I'm not knowledgeable enough to be handing out advice that could possibly hurt someone's motor. The things I listed above are pretty basic, though, and will help for sure.
You're going to get told in this forum that changing less is more.....I started off changing EVERYTHING, thinking I was making things better. Now that I'm a year or so into tuning my truck, I have learned that what the experienced guys say is 100% correct.....Once you get your MAF and VVE, or in my case, VE dialed in......A TON of other stuff just falls into line without even being touched.
Thank you for taking the time to review and providing feedback. I made the adjustments based off what I have been taught from the classes I have taken over the past couple of years. Commanding P/N RPM at 700 and In Gear
at 675, my reasoning for requesting that low of RPM is just for preference. I like the low sound with a slow chop. With it starting up without issues, fuel trims being within 1%, RPM err being very minimum, hardly any idle adapt
advance, and dynamic airflow matching MAF airflow....I thought I had almost perfect idle other than TPS percentage. But.....I'm still learning and just wanted to share my thought process on what you are seeing in the tune. On
throttle follower torque, I was taught to set this table to what the VCM scanner logged delivered torque at each RPM. Is why it was only changed in the 600-1200 RPM range. I was also hoping that changes to this table would
change my TPS% reading.
Going to take your recommendations to the editor file, run a datalog, and see what I get.
This cam only has about 5 deg of overlap at 0.050", but that calculates to about 51 deg or so at 0.006". It is possible to get the idle down that low. Be sure to remember that with overlap, just because your O2 sensors say that your trims are within 1% doesn't mean they are at idle. Depending on your setup, you can get false lean readings due to umburnt fuel or air getting sucked through the overlap into the exhaust. For example with my setup, 10.6:1 comp, Long tubes to 3" y pipe, up to 3.5" straight back with flow through muffler, no cats, I get a false lean that in closed loop at idle will litterally richen the motor up so much it spits fuel out the downpipe behind the axle and leaves marks on my driveway haha.
The higher you get idle (to a reasonable amount), the less overlap has an effect on this. I found that at 750-800 trims showed richer somehow (still leaner than stoich) than at 700 rpm, however, my injector pulse width was smaller....meaning that it was obviously burning more effecient since the PW dropped.
Throttle torque, to my knowledge, should be somewhat close to what VCM shows....that being said, if your VCM is showing 100 delivered torque that's a whole different issue. You need to massage the VTT tables to get your idle torque down to about 30Nm or 22Ftlbs or so.
Look for idle torque posts from Ghuggins or hjturbo. Those guys have gone back and forth so much, helping guys get the VTT tables in order to fix idle. Basically, the ECM wants to see around a certain value to allow all the adaptives to operate correctly.
Once you get the VTT tables fixed then your VCM delivered torque will fall in line and you wont have such crazy values in the follower tables.
To give you an idea, my truck idles at about the following
30-32 ftlbs in park
800 rpm
8.5-9.0 g/s airflow
45-47 kpa Map
2.2-2.4 MS PW
0.160-0.170 Airmass
18 deg advance
100 percent agreed. My tune is very similar to this and i have managed to get here myself with the help of experts on this forum.Originally Posted by kertisallen1
If you get VVE and MAF dialed in you'll only need to touch the idle speeds and maybe 2 other tables in the whole idle tab. You'll have a rock steady idle that can recover if you let the clutch out too fast etc.. It will be robust.
I preach this over and over but it really never seem to catch on. Most idle issues are actually fueling issues.
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To clarify that I understand, when I begin a tune from a fresh build/install, I put it in MAF only mode and (using spark, airflow, and rpm) get it so that it idles on its own. Once it idles, I tune the MAF and VVE tables using narrow band at idle and part throttle.......and use wideband for WOT. After that is complete, the idle is basically solid and all that's left is dialing in the desired idle speed and the desired sound with over/under tables. Is this correct or kind of on the right track?
Yes and no. Everyone will have different outlooks on how to tune and in what order. Some guys will tell you to do both at the same time, which works well IF you are good at filtering data and don't have a heavy foot, or fast transitions.
I have a different approach/outlook. The way I see it is that you cannot ever truly FAIL VVE, but you can FAIL MAF.
Meaning that even in MAF only mode, VVE is present for transients/fast airflow changes. It is used in the background even when you have Dynamic Disable set to something low, like 100 rpm.
For this reason, I always fail the MAF and tune VVE/VE fully first. In my opinion, it makes tuning the MAF so much easier, ESPECIALLY at idle, because with our cam choice and the amount of RPM variation at idle, the ECM relies more on VVE than intended, like OEM.
But once you get both MAF/VVE dialed in (hot/cold starts stable, along with cruise and wot), then yes, you will find yourself changing a ton less to get it to cooperate.
One other thing I kinda figured out on my own...you mentioned "desired sound" of idle. So after MONTHS of messing around with tight vs loose ever/under spark tables, min airflow, throttle follower, coefficients, and a million other things.... I found idle was either "rolling" up and down a large smooth rpm range with loose spark (basically moved the table over 2 spots, leaving the first 3 values "0"), or extremely choppy with a tight table like OEM. I didn't like either because the rolling idle was a pain at low speed decel with my stall conv., and the choppy was annoying in low speed spots like stoplights or drive-throughs.
My current tune and the way I've had it for a few months now is what I consider perfect, haha. Basically, I loosened up the underspeed spark (moved 2 spots right from OEM so the first 3 rpms are "0") and then lightened up the overspeed spark and moved it over one spot. I also raised my min airflow 0.75 g/s once I had it perfect....so basically it is a tiny bit higher than needed airflow and it can pull spark as needed to drop it, but won't bounce back up, causing surging or bouncing. When in park, it has a perfect lope/chop about 75 rpm up and down, but in gear with AC on or off, it is as smooth as stock. I don't have any of the undershooting, overshooting surging I used to get when coming to a stop faster than normal, or any of the annoying skipping when the adaptive spark decides it randomly wants to go crazy.
Unless you have touched the VTT tables, I can almost guarantee that your airflow models are more off than you think....The reason I say that is that, is your Delivered Torque is so high at idle. That is causing all sorts of other issues behind the scenes. From changing spark, to messing with adaptive air, to changing trans shift and hold pressure....all of it.
Do you have cats and rear O2s still? If you do not, there are some options that have been removed from the current (and recent) versions of HPT that don't allow you to turn off rear O2 tests, and cat tests. If needed, I can either turn them off for you or walk you through how to do it yourself, but that messed with me for a while without me ever knowing what it was.
I appreciate you taking the time to share your feedback with me. Makes perfect since to fail MAF and start with VVE first. I haven't touched the VTT tables up to this point. Only set the throttle follower torque tables to what VCM was reading at idle. No rear O2 sensors or CATs. Just long tube headers with 50 series Flowmasters.
Yeah, that means you have both the tests constantly running. And they will do it over and over again. Mine did it multiple times per drive every single day, haha.
I will shoot you a message to help you get that part sorted out.
I encourage people to disable the MAF, tune VVE, then re-enable the MAF.
I'll argue that it is faster for most if not all to do it this way. By the time you set up all your formulas and filters you could have just done them independently. Which is the better way anyway.
To use the MAF to dial in VVE.. something that isn't good at transients to dial in something that needs to be good in transients just doesn't make sense. Especially because the parts of VVE that need to be spot on for good idle quality.. are the transient parts. The decel from a rev for instance.
Now personally I'll use MAF to do VVE stuff.. Sometimes.. but this has been my only job for 24 years now.. (F.. getting old) I can do that because I know what to filter out, I know what bad data looks like, I know how the car should be driven, etc.. I know what the VVE should look like cause I've seen so many.
The average new tuner is no where near ready for VVE from MAF tuning..
my 2 cents
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