98 Vette upgraded to stroked ls2 with ls3/Induction (6.6 liter) - Throttle Body 90mm
I had the tune very good with the LS1 heads and the stroked LS2 block. Now I am finishing the build with the LS3 induction. I'm curious what to change to account for the bigger throttle body since it is DBW. I understand the VE tables and idle tables. I am concerned that the idle will be really bad because the idle tables are based off of adding or removing air mass. Now the air mass will be significantly different for specific movement of the the throttle. I don't find any tables that correlate throttle movement or any tables that specify the anything related to the throttle body size. Anyone have any suggestions on where the start? Still in the middle of the build. It will be a few weeks before I have it running/tuning.
Morning Frank, I see no one has replied, so I will send my 2 cents: 98's are unique in wiring and PCM, so not sure if all applies. Also, my experience is coming from a 98 T/A and an 99 Camaro which I did generally the same combo. 98 I re-pinned harness to go with 99 and up settings/PCM
1. Are you changing injectors? If so, you will need to find and load your respective injector data. I used LS3 injectors, and the data was generally easy to find and swap in
2. I changed from LS1 to LS3/7 blade MAF with 92mm TB. Took me some time to tune, but was worth it. This is where you will be using closed loop vs open loop a lot to tune LTFT first then your VE tables
3. Get a wideband - makes life easier
4. Idle and start. When I built my tune, I took the time to turn off items in DTC/engine, figure out which ones you don't need -
5. Engine volume and basic settings, make sure you change these too.
6. VCM Setting for logging, these will help in areas of LTFT, engine knock etc... I used GoatRope Garage a lot on YouTube
My tune is available in many of my threads, feel free to plagiarizer as applicable, do a lot of compares - what I learned
Cazbah, Thanks for the notes.
1. I am familiar with changing the injector data. I did that with the last tune. I did go with a LS3 injector for these changes and have the data from the injector manufacturer. I think that is one of my easier hurdles.
2. I have been reading about using the LS3 MAF sensor. I think I would like to go that route. What I don't know is if I can since I changed to speed density with the last tune and eliminated the MAF sensor. The wiring is still there. Do you know if I can revert back to the MAF type tune without bricking the PCM?
3. Did you make any changes to the tables for the throttle control when you upped the TB? The software has warnings to basically not change them because of risk if incompatibility with calibration of the throttle controller. I am concerned that small pedal movements will equate to large power increases compared to the same pedal movement with the small TB. This is the same thought I have with how the idle control works. The table says you are 50 rpms off add x amount of air. That amount of are equates to so many degrees of throttle opening. (I am assuming that degrees movement equates to a air amount because I am running speed density and have no MAF.) But now that amount of throttle opening adds a lot more air then before. Am I over thinking this?
4. I understand how to use LTFT and STFT to adjust the VE tables. Having good Microsoft Excel skills makes that task easy. I used those tables to develop the tune. I have read some about the wide band. How did it make doing the tune easier? The fuel trims give the error adjustment data I needed to manipulate the VE table. Is the wide band a shortcut around that process?
I know what you mean about comparing tunes. I have done it myself. I appreciate you letting me know that it is available. I will take a look.
Again, thanks for helping and look forward to hearing form you.
Frank - Sounds like you have a strong understanding, so again this is my 02 cents, take it as you will.....
"2. I have been reading about using the LS3 MAF sensor. I think I would like to go that route. What I don't know is if I can since I changed to speed density with the last tune and eliminated the MAF sensor. The wiring is still there. Do you know if I can revert back to the MAF type tune without bricking the PCM?"
----- I don't see why not? I would think you just need to turn items on which allowed for Speed Density? I see this as simple tune updates or changes, but keep in mind, you have the 98 PCM which is a little different? (Note: I have a 98 PCM from my T/A if yours does brick - but, lets not get there). I used my 99 IAT (I think 98's are a little different but may be wrong on this) and just moved it forward. Always conversation on heat soak of these (like the GTO LS2 ones), so this is how I avoided it. Here is the harness is used: https://www.summitracing.com/parts/jms-jls1ls3ad . I then purchased a 4 inch tube and this: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 . I welded in the tube and purchased a ACdelco MAF - worked well.
Now in the tune what I did was use a LS3 Vet MAF AirFlow table as a base and then went and did some tuning. I used went closed loop using doing the following:
Fuel Tab
Oxygen Tab
LTFT - Disable
Long Term Fuel Trim
- 283 Scale all away across
Closed Loop Enabled
- ECT vs IAT - Set to 284
** Disable SFST
Fuel Tab
Open Loop / Base
- STFT Open Loop - Disabled
Fuel Tab
Temperature Control
- COT Disable - Note this is turned off already
Fuel Tab
Cutoff DFCO
Deceleration Cut Off
- Enable ECT Set to 280
- Stall Set to 12000
Dynamic Airflow
Steady State
- Hi/Lo RPM Thresh to 200
- Hi/Lo Map Thresh to 0
Exhaust
General
- Enabled - to disable
and used my VCM editor to capture LTFT's to map my MAF Calibration. I believe this more less answers to question three since this is focusing on the airflow. Do I think your overthinking it - no..... sounds like you are wrapping your head around it which is good...
Wideband was easier to capture the AFR at states of input in comparison with the MAP, so easier for me to pinpoint areas which needed to be addressed - I continuously learning and overthinking things myself.
One thing that helped me a lot was VCM editor and capturing my AFR, Knock Retard, and Mass Airflow Frequencies - This was huge for me, allowed me to understand more of the correlations of things occurring.
Cazbah,
I apologize, I wrote back to your last post and apparently didn't post it. I haven't been on for awhile. Been busy with building the engine. Thanks. I'm a week or so out before I start tuning. I will look at these closely at that time.
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