Troubleshooting:
How the Three Sections are Linked:
The 'Vehicle', 'VehicleEngine' & 'VehicleEngineGranular' sections do not have to be next to each other (they usually are, just 'VehicleEngine' & 'VehicleEngineGranular' swapped around sometimes), but rather than their position/order in 'game.dat151.rel', the connections between the three sections are actually formed by the names & hashes directly under the 'Vehicle', 'VehicleEngine' & 'VehicleEngineGranular' lines.
Example:
<Item type="Vehicle" ntOffset="362535">
<Name>vigero</Name>
<Item type="VehicleEngine" ntOffset="362542">
<Name>hash_E03115BB</Name>
<Item type="VehicleEngineGranular" ntOffset="362556">
<Name>hash_33290B6F</Name>
Format of Three Main Names/Hashes:
They are in this format:
Example:
<Item type="Vehicle" ntOffset="362535">
<Name>vigero</Name> <!-- format = 'vehiclename' -->
<Item type="VehicleEngine" ntOffset="362542">
<Name>vigero_engine</Name> <!-- format = 'vehiclename_engine' -->
<Item type="VehicleEngineGranular" ntOffset="362556">
<Name>vigero_granular_engine</Name> <!-- format = 'vehiclename_granular_engine' -->
& from that (once you know the format of a value ('vehiclename_engine' &/or 'vehiclename_granular_engine' etc ), you can use OpenIV's Hash Generator ('OpenIV' > 'Tools' > 'Hash Generator') to confirm you are editing the right ones.
So, say we want to confirm we are editing the correct vigero sections, we would first:
find vigero in the 'game.dat151.rel.xml' file
then scroll down to find the next 'VehicleEngine' line:
<Item type="VehicleEngine" ntOffset="362542">
<Name>hash_E03115BB</Name>
make a note of the hash below it ('hash_E03115BB'. The 'E03115BB' part is the part you want)
then move to OpenIV's Hash Generator ('OpenIV' > 'Tools' tab > 'Hash Generator')
Input 'vigero_engine' in the left box
Change the 'Output format:' (bottom leftish) to 'Hex'
Then compare the generated hex hash on the top right, (in this case '0xE03115BB') with the one below the 'VehicleEngine' line we made a note of earlier.
As you can see they end with the same characters/digits ('E03115BB')
If the last 8 digits of the hashes do not match, you are editing the wrong section for that vehicle & would need to look at another 'VehicleEngine' section hash & check that in the same way.
You would use the same process to check the 'vigero_granular_engine' (aka 'hash_33290B6F') section name as well.