HPtuner final drive ratio incorrect?
06-11-2016, 05:24 PM
#1
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HPtuner final drive ratio incorrect?
I got my HPtuner today and started having some fun with it.
I loaded my stock tune and started looking at all the numbers and I noticed that it said my final drive/gear ratio is 3.42. My car stock has 3.15 for the gears so I'm curious why it says that? I can upload my file if someone wants to look at it and see what I am talking about. As far as I know the gears are 3.15 but I am the third owner of this car and the last owner road raced it. I also noticed when I loaded up the DTC portion there were a lot of areas already disabled for dtc codes which I also found odd.
I loaded my stock tune and started looking at all the numbers and I noticed that it said my final drive/gear ratio is 3.42. My car stock has 3.15 for the gears so I'm curious why it says that? I can upload my file if someone wants to look at it and see what I am talking about. As far as I know the gears are 3.15 but I am the third owner of this car and the last owner road raced it. I also noticed when I loaded up the DTC portion there were a lot of areas already disabled for dtc codes which I also found odd.
06-11-2016, 10:00 PM
#2
Melting Slicks
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St. Jude Donor '15
mine says the same thing and it had 2.73 originally. the previous owner of my car was an autocross racer as well. he had transmission tables changed.
Last edited by mrr23; 06-11-2016 at 10:06 PM.
06-11-2016, 10:06 PM
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I was digging deeper and found that for some reason the software defaults to that regardless of gears installed as it reads it from the PCM supposedly. Leave it alone is what they are saying unless you do go up in ratio.
06-11-2016, 10:31 PM
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That makes sense, i do have an A4, tomorrow i have to edit my fans anyways. Is there anything else I should alter as well as the ratio? tire size as well i imagine since they are not the original run flats.
06-11-2016, 10:37 PM
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06-12-2016, 01:25 AM
#7
Le Mans Master
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St. Jude Donor '13-'14-'15
The correct rear diff ratio is not the 3.42 shown on the 1st page of the speedo file---All C5's show that same 3.42 ratio The actual ratio of your car is shown only when you look at the speedo correction tables-------
ALSO remember on a C5 you do NOT have to make a speedo correction when making a gear change---So these rear diff #''s don;t really matter----because on a C5 the speedo sensor is on the output side of the diff rather than the output side of the trans like on a Camaro there is no need for a speedo corretion based on rear gears----However a speedo correction is required when changing tire sizes ---You do have to make a "shift point correction" when changing gears or tire sizes---
ALSO remember on a C5 you do NOT have to make a speedo correction when making a gear change---So these rear diff #''s don;t really matter----because on a C5 the speedo sensor is on the output side of the diff rather than the output side of the trans like on a Camaro there is no need for a speedo corretion based on rear gears----However a speedo correction is required when changing tire sizes ---You do have to make a "shift point correction" when changing gears or tire sizes---