I have messed around an messed around trying to get the speedometer to calibrate out with zero luck it shows around 30mph @6moh an 110 @ 60. I now it has to be something in the calibration files being different because of the way a vette reads off the reluctor ring of the differential compared to the trans shaft an Ive tried everything I can thin of in comparison to a truck file an nothing works. Anyone got an answer for this.
Gear ratio and rear tire make/model/size?
Its not the gear ratio an tire size that's the issue a corvette reads of the reluctor gear of the ring gear that is about 8" in diameter compared to reading off the trans shaft that is about 1 1/4". No matter what numbers I put in the calibrations nothing changes theres something that has to be changed in the reading of it I'm sure. I know its an easy fix just gotta find someone whos ran into this before.
You want help but wont provide the required info. Assuming you have calculated the ppm correctly for a non-corvette vehicle which is what your likely currently doing, take that ppm and divide it buy your rear axle ratio. That will be your new ppm.Originally Posted by RIP1976
Here is the info 245/60r15 3.73 gear but what your not understanding is a c5 corvette does not calibrate the typical way were used to. I can write the tune of a truck in with the calibrations an it works fine. If you look at the speedometer calibrations of a vette you will clearly see the differences compared to any other gen 3 pcm.
I understand perfectly well, your the one not understanding. take your current ppm, divide by 3.73, put that number back into your tune file ppm value.
I have it don't change anything. That's why I'm looing for someone who has ran into this issue.
post your file
RIP1976 ... this is the first time that you have experienced working with a Corvette based control system in a conversion vehicle. However, this is nothing new to many people. Mecanicman is trying to help you ... whether you are able to see the "forest for the trees" or not.
When you purchased tuning software, and elected to do-it-yourself, then a certain amount of experimentation is necessary to gain experience and knowledge. Don't expect professional tuners to tell you the answers to everything that you may ask - that is how they make their living.
OK, that said ... Corvette base programming in the P01 / P59 PCMs is unique - because of their rear mounted transmission (or transaxle) setup. In very basic terms, the VSS pulse output is calculated AFTER the differential gear ratio (i.e. 3.73:1) with a Corvette program, but is calculated BEFORE the differential gear ratio with all other LSx V8 platforms.
Some of this is made a little more tricky by the speedometer "wizards" used by some tuning software. Some tuning software (like HPT or EFILive) will change how the wizard calculates, based on the presence of a Corvette VIN.
In a conversion vehicle you have a couple of straight forward options. You could change the VIN to something other than a Corvette (not really an option with HPT), and the wizard would then perform predictably. The other option is to configure the VSS output based on the percent error that you are experiencing - which is what Mecanicman is suggesting. From your description that 30 MPH = 6 MPH, which would be a magnitude of 5 - or that 110 MPH = 60 MPH, which would be a magnitude of 2.
Figured it out an as I suspected I did have to manipulate the file to get it to work properly.
Reply With Quote