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Old 05-01-2024, 08:08 AM   #60 (permalink)
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Throttle response changes with heavier tires, the same for lighter wheels. If you drive 400 miles (example) non stop on the hiway then there may not be an impact but over a mixed tank where your starting/stopping it does impact mpg's.

one lb off an engine pulley was enough to see the throttle response change and enough for me to go after the remaining pulleys and driveshaft.

when I did the driveshaft I lost boost rpms, meaning it was starting to come off ambient pressure at approx 1400 rpms. After the DS install it was up to 1600+ rpms. Found out the areas in the tune where timing is key for boost (diesel) were no longer being hit. Changed the slope of the timing curve and got those 200 rpms back and once seeing the cause & effect, went after more boost down low. Ended up getting boost coming off ambient pressure all the way down to 800~900 rpms. Engine is always under boost now.

With all that and then some, got my truck up into the 22+ mpg's range with a peak at 25.0x & a couple of 24's. Had that for 2~3 years then needed new tires. Unfortunately they are stickier & heavier which impacted mpg's (now in the mid 20's :-( )

Weight matters...
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Ecky (05-01-2024)