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I'm in the process of having my motor rebuilt from ground up and I decided to change the cam (specs below). My overall question is ... What would the level of difficulty be for me to do the tune myself. Last year I asked for guidance on tuning my stock LS3 with 1-7/8" header and based on feedback I able to pull it off. I was pleased with the results and the car ran strong. My detail questions/process are below and I appreciate any feedback.
Car Setup:
- Drysump Manual LS3 in Grandsport
- Stock Airbox with Attack Blue Filter
- Stock Intake & Throttle Body
- Upgraded Cam (above specs)
- AFe 1-7/8" TRI-Y header with cats
- Stock NPP Exhaust
Questions:
1. Should I start with the factory GM tune, or build off my current bolt-on's tune?
2. What are the main tables that I will need to modify?
3. What are the best parameters to log during this process? Also what is the best refresh rate... 10Hz?
My current plan:
1. Decide which tune I want to start with.
2. Pull back about 3* of timing from high load situations to keep timing in the safe zone.
2. Set PE to 11.8 to ensure no lean conditions while working through the new setup.
3. Dial in the VE table
4. Dial in the MAF
5. Work on PE ( keep if rich for now )
6. Slowly add in timing.
7. Work on the transitional airflow characteristics: idle, coast down. WOT to nothing, etc.
Here are the dyno results from my bolt-on's setup.
You can go to the website/forum of the brand of tuning software that you have and look under your engine type. It will be full of detailed engine tuning routines.
That cam isn't that bad, but to do it right you should plan on some dyno time at a load bearing chassis dyno where you can hold the engine at a steady RPM against different laods (engine MAP) to collect all your correction data from the wideband. If you do that, you will end up with new coefficients in your virtual VE system that fix the background speed density airflow model and it goes a long way toward getting really smooth drive quality. We cover exactly this in our training videos, specifically the GM Tuning Advanced guide for the virtual VE tuning. It's not that difficult, but you have to follow the right procedure using the right tools.
Not knowing what's in your current calibration, I would just start from stock. I know that at least a stock file ran a stock car really well. You will be modifying either regardless, so I just prefer to start from a known good point.
That cam isn't that bad, but to do it right you should plan on some dyno time at a load bearing chassis dyno where you can hold the engine at a steady RPM against different laods (engine MAP) to collect all your correction data from the wideband. If you do that, you will end up with new coefficients in your virtual VE system that fix the background speed density airflow model and it goes a long way toward getting really smooth drive quality. We cover exactly this in our training videos, specifically the GM Tuning Advanced guide for the virtual VE tuning. It's not that difficult, but you have to follow the right procedure using the right tools.
Not knowing what's in your current calibration, I would just start from stock. I know that at least a stock file ran a stock car really well. You will be modifying either regardless, so I just prefer to start from a known good point.
Thanks for the response. I'll start with the stock file so I have known good VE coefficients. So before with my bolt-on's tune I didn't touch any of the idle airflow values, nor did I change any of the fuel injector values. My assumption is the idle airflow stuff will need to be changed, but I'm not sure about fuel injector stuff. Your thoughts?
Thanks for the response. I'll start with the stock file so I have known good VE coefficients. So before with my bolt-on's tune I didn't touch any of the idle airflow values, nor did I change any of the fuel injector values. My assumption is the idle airflow stuff will need to be changed, but I'm not sure about fuel injector stuff. Your thoughts?
You should ALWAYS start with known good data for whatever fuel injectors you're using. By definition, this limits which aftermarket injectors I will tolerate working with, since many of them do not have reliable data available despite what the sellers may claim. Any errors in the injector model WILL cause corresponding errors in your new airflow (both MAF and SD) calibrations. Beyond that, those same errors play into idle control, torque estimates and even transmission behavior, so it pays to make sure they're spot-on before you start.
You should ALWAYS start with known good data for whatever fuel injectors you're using. By definition, this limits which aftermarket injectors I will tolerate working with, since many of them do not have reliable data available despite what the sellers may claim. Any errors in the injector model WILL cause corresponding errors in your new airflow (both MAF and SD) calibrations. Beyond that, those same errors play into idle control, torque estimates and even transmission behavior, so it pays to make sure they're spot-on before you start.
My injectors are stock, so I'll do as I did before and left all of their settings alone.
05-22-2019, 03:21 PM
What's the difficulty level of tuning a mild CAM?
