jay_lt4
04-06-2007, 10:01 PM
hey, i just got a gps/nav unit and thought id try to tune my speedo a little closer than it is, here is what i came up with my current settings:
94 z28 auto 3.50 rear gear, p275/40zr17 tires(stock for camaro ss)
speedometer scalar=29
speedometer scaalar, fraction=1.057
35-45 mph speedo is 1 mph fast
50 mph speedo is correct
55-75 mph speedo is 2 mph slow
it is close and i can live with it but id like to have it right on, and if you enter my data into tunercat speed calibrator it comes up with scalar=28, fraction=.985 and the speedo is over 6mph off
is there a more exact formula than what tc uses for its calibrator
97WS6Pilot
04-06-2007, 10:19 PM
hey, i just got a gps/nav unit and thought id try to tune my speedo a little closer than it is, here is what i came up with my current settings:
94 z28 auto 3.50 rear gear, p275/40zr17 tires(stock for camaro ss)
speedometer scalar=29
speedometer scaalar, fraction=1.057
35-45 mph speedo is 1 mph fast
50 mph speedo is correct
55-75 mph speedo is 2 mph slow
it is close and i can live with it but id like to have it right on, and if you enter my data into tunercat speed calibrator it comes up with scalar=28, fraction=.985 and the speedo is over 6mph off
is there a more exact formula than what tc uses for its calibrator
The gps is probably not accurate enough for what your doing. I would check your speed against the mileage markers on the highway. 60 mph= 1 minute between markers. Our aviation gps's are right on when it comes to position but the groundspeed is usually off unless your moving really fast like 450 Knots. :)
jay_lt4
04-06-2007, 11:04 PM
maybe it isnt,,,, but i have 2- 2005 gm vehicles and on the same road the gps matches the speedo's exactly at the same speeds im testing the camaro and on the same road
97WS6Pilot
04-07-2007, 11:44 AM
maybe it isnt,,,, but i have 2- 2005 gm vehicles and on the same road the gps matches the speedo's exactly at the same speeds im testing the camaro and on the same road
I will have the same gears and tire combo so let me know what the final calibration works out to. I may want to use your calibration after I install my 9" with 3.50 gears. Thanks.:)
jay_lt4
04-07-2007, 12:27 PM
I will have the same gears and tire combo so let me know what the final calibration works out to. I may want to use your calibration after I install my 9" with 3.50 gears. Thanks.:)
right now i have:
speedometer scalar=29
speedometer scalar fraction=1.057
and it is real close only 2 mph slow at 60-75
we got another snow fall last night so testing is off till it warms back up, i will let you know what i end up with
anyone else running this combo 3.50 gear and a p275-40-17 tire??
Red on Red WS6
04-12-2007, 03:22 AM
The gps is probably not accurate enough for what your doing. I would check your speed against the mileage markers on the highway. 60 mph= 1 minute between markers. Our aviation gps's are right on when it comes to position but the groundspeed is usually off unless your moving really fast like 450 Knots. :)
Every hand held I have used is pretty darn accurate on the ground and in the air. I calibrated my speedometer using a hand held, just change the tire sizes until you get the right speed.
383TransAm
04-15-2007, 09:38 AM
I have a question on setting the Gear to Tire calibration on Tunner Cats.
I have a 93 TA with the OBD1 and a chip.
I just put a 9" with 4.10's and I need to rest my computer for the change.
I have a 275/40/17 tire with my 4.10's, can any one help?