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Thread: Transmission Tuning Questions Jet DST

  1. #1
    Carb and Points!
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    Transmission Tuning Questions Jet DST

    Hello all. I was looking over some .cal files in JetDst, trying to understand what I will want to change on my car, and I had some questions come up and the information seems fuzzy. I just want to make sure I get as clear of a picture as I can. Some background information, the car I am hoping to eventually tune is a 1997 Pontiac Firebird Formula. It has a stock LT1, and 4l60E transmission. The calibration file I have been using was listed for a 1997 Camaro LT1 Auto. The only change made to the file is speed correction, to ensure that my tire size and gearing are represented. I have not saved the file with the updated information, I have just been using the file to understand what options I have. The program I am using to view the calibration files is Jet Dynamic Spectrum Tuner. My main interest is in transmission tuning. My first questions are regarding the shift tables. My first question comes from some reading I have been doing on the LS forums on transmission tuning. While I understand that a later GTO 4l60E is going to have different tables and options than a 97 F body, I keep seeing that the 4l60e needs to meet both an RPM target and a MPH target for shifting. The tables that I have only refer to MPH and TPS. I don't see any options that refer to RPM for shifting, other than for Kickdown Mode. Am I correct in thinking that kickdown mode just triggers the WOT shift points, and causes the tables to be ignored until you leave kickdown?My next question is about the transmission hot and cold modes. Are those triggered by coolant temp, or transmission temp? A related question, is there a factory way to read transmission temperatures? I am able to read a good deal of sensors on my Firebird with a Bluetooth adaptor and the TorquePro App, and do not recall seeing any transmission sensors available. Thank you for taking the time out to read and comment. If this was posted in the wrong area, I apologize.
    Last edited by Funnyontheinside; 02-22-2024 at 09:20 PM.
    1997 Firebird Formula LT1, Auto

  2. #2
    Fuel Injected!
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    All tables are mph vs tps, only WOT have some vs rpm threshols, but there is also another one that use mph so it is not clear which one is triggered first.

    Usually rpm is not good for changing gears, due to the nature of transmission slipping and torque converter slip rpm.[there is always a difference on input and output shaft, unless TCC is locked].

    Hot and cold modes are almost never used so you can just ignore them. If you have a wired temp sensor on trans, it can be logged, you need to know the pid number of trans temp and use a program that allows you to monitor it.

    What kind of cables you have for connecting to car.

  3. #3
    Carb and Points!
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    When I finally read and eventually flash my PCM, I will be using the JET DST cable via USB.

    For data logging, I am working on getting a new OBD2 Adaptor to connect to my computer. Will likely get OBD2 to USB for the cable, and I hope to log with GaryDoug's OBD2 program

    I currently used an OBD2 Bluetooth adapter with TorquePro on my phone.
    1997 Firebird Formula LT1, Auto

  4. #4
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    Quote Originally Posted by Funnyontheinside View Post
    Hello all. I was looking over some .cal files in JetDst, trying to understand what I will want to change on my car, and I had some questions come up and the information seems fuzzy. I just want to make sure I get as clear of a picture as I can. Some background information, the car I am hoping to eventually tune is a 1997 Pontiac Firebird Formula. It has a stock LT1, and 4l60E transmission. The calibration file I have been using was listed for a 1997 Camaro LT1 Auto. The only change made to the file is speed correction, to ensure that my tire size and gearing are represented. I have not saved the file with the updated information, I have just been using the file to understand what options I have. The program I am using to view the calibration files is Jet Dynamic Spectrum Tuner. My main interest is in transmission tuning. My first questions are regarding the shift tables. My first question comes from some reading I have been doing on the LS forums on transmission tuning. While I understand that a later GTO 4l60E is going to have different tables and options than a 97 F body, I keep seeing that the 4l60e needs to meet both an RPM target and a MPH target for shifting. The tables that I have only refer to MPH and TPS. I don't see any options that refer to RPM for shifting, other than for Kickdown Mode. Am I correct in thinking that kickdown mode just triggers the WOT shift points, and causes the tables to be ignored until you leave kickdown?My next question is about the transmission hot and cold modes. Are those triggered by coolant temp, or transmission temp? A related question, is there a factory way to read transmission temperatures? I am able to read a good deal of sensors on my Firebird with a Bluetooth adaptor and the TorquePro App, and do not recall seeing any transmission sensors available. Thank you for taking the time out to read and comment. If this was posted in the wrong area, I apologize.
    Kickdown mode shifting is activated by a TPS value and hyperstasis value. Usually at some point above ~90% TPS. The kickdown tables are usually a high and low value for each gear. If you have a kickdown set for say 65 mph for 3-2, above 65 mph it stays in 3rd, under 65 mph it drops to 2nd.

    Those MPH values are set a bit lower than GM expected the vehicle to reach at the RPM they wanted the engine to reach. The way GM calibrated the values, the RPM value is what actually starts the Upshift. I say starts because the RPM can continue to climb above the RPM programmed in that table.

    So lets say you have a vehicle that can reach ~40 mph at 5,500 rpm in 1st gear. Lets say you want the RPM to reach 5,500 rpm at its highest. GM would have the KIckdown 1-2 upshift MPH about 35 mph and the Kickdown RPM would be set at 5,100-5,300 rpm. Every vehicle is going to have some amount of lead time to account for especially at WOT. That lead time corresponds to both how quickly the transmission upshifts as well as how much the vehicle is accelerating during that time.

    Some 4L60Es were calibrated never to make a WOT 3-4 shift. Those will have the 3-4 MPH maxed out and the 3-4 RPM maxed out as well.
    Last edited by Fast355; 02-22-2024 at 11:45 PM.

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    LT1 specialist steveo's Avatar
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    its a bit odd to tune by MPH but you'll get the hang of it if you do a bit of tuning, then log and graph MPH, RPM, and selected gear. you will see exactly where you need to change the MPH points to achieve your RPM target

    i never practiced much tuning the LT1 ecm because all mine were manual transmissions

    everyone is different but lately i set a goal with automatic transmission tuning where below 25% throttle it shifts through the gears gently and generally wont downshift. then above 25% throttle i want the thing to be in its powerband all the time either by kickdown or shifting. due to gearing that's not always possible but i get it as close as i can.

    speaking of keeping in the powerband, i drove a porsche with a tuned CVT recently that thing had not a lot of horsepower, tiny engine, but had a huge power spike at like 6500-7000rpm. when you floored it the CVT slipped up to almost 7000rpm and held it there right at the rev limiter by changing the ratio. so even though it had a tiny engine, the transmission made it have maximum horsepower from zero to infinity. that should be the goal with transmission tuning. maximum possible time in peak power.

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