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Anyone have any tips or advice when steady state tuning an automatic turbo vehicle? I’m using 1-1 gear ratio 3rd gear in my case but I’m struggling to get into the lower load and rpm cells without the trans either downshifting or not being able to reach those parts of the map with load from the dyno. Can I use the lower gears? I’ve tried to and the Chassis dyno dosnt Seem to like it being the torque from the turbo car coming up on the front roller to hard. I wouldn’t be so concerned but on a road test I’m not happy with performance. Any help or advice would be awesome thanks guys
sometimes you need to do whatever it takes to hold it there this may include riding the brake just a short time
Ross, the problem seems to be the transmission kicking down under low rpm loading.
With some transmissions they use a cable or throttle switch to tell the transmission what the throttle load is and get it to kick down. You may be able to disconnect that if fitted and it should stay in the manually selected gear might only be 1st or 2nd, though, as it's been a long time and I can't recall if it will go into 3rd - but at least it will help.
it depends on what transmission you're using but if its OEM and anything from the last 15 years then the shift scheduling is controlled by the TCU and you'll need to access that to adjust the 3rd gear roll out point. You will also need to pay attention to the torque converter to make sure there's no slip and a lock up clutch is engaged as converter slip and the stator effect control the torque delivery. A higher stall speed converter might help as it will keep the engine out of the un-calibrated area. Typically with late model 8 and 9 speed transmissions the roll out point will be around 900/1400rpm depending on application and NVH/emissions requirements so this will be the lowest speed you can calibrate to. The long winded but best option to calibrate this area would be to take the engine out and put it on a test bed unless you can get access to calibrate the TCM
Thanks guys for the input, but yeah that’s the problem I am having the vehicle is 30 years old, kick down is fine I disconnected the mechanical cable and I can floor it anytime I’m in 3rd anywhere in the rpm but as soon as it gets to 2000rpm with little or no throttle input the trans downshifts eg on decell. I’ve tried the best I could in all areas but acceleration on the street in first gear is lean. Seems a little tricky may have to use a wideband on the street I’m thinking.