I have done vast research over 1000 km just test driving and setups on tdi cam timing or torsion value as it is said on vag tdi. I made a custom program that injects same amount of fuel 16mg/stroke all the time for full rev range on a 1.4TDI which is 3 cylinder diesel engine. So its not exactly same amount of fuel if rpm rise there is more fuel injected per hour, but still its constant amount per stroke. If you would have level road for testing you would get even better results, but you have to use what you have.
Test road was 6,3 km long full of uphills and downhills and I doubled that for fine tuning. Just by changing the timing, meaning adjustable cam you are able to get 5-10% improvements on a diesel engine at least. Problems arise when you change your drivebelt it often does not go exactly same place.
I moved adjustment from -2,2 torsio to 2,2 which was best setup for this car and the time went from 267 seconds to 243 seconds and to back direction from 278s to 253s. I started the test from 70 km/h speed and put the pedal to the floor. This way car would accerelerate and the small differences in start speed would not have so big impact to end result.
-2,2 =12600m/267s+278s=12600m/545s=23,1 m/s--> 83,1 km/h avg speed car needs about 8,5 hp for this avg speed
2,2=12600m/243s+253s=12600m/496s=25,4m/s-->91,4 km/h avg speed car needs about 10,5 hp
During the testing top speed got 10 km/h higher from 105->115 km/h and car was able to keep much higher speeds at uphills and steady sections as well.
https://ecomodder.com/forum/tool-aer...ToStep=40-65-1
As you can see there is big differences out there you just need to dig them out in testing.
All those values were inside VW tolerance +-3,0 degrees for diesel engines!!!
1.4TDI Audi A2 can now drive on 6th gear from 75 km/h and before any ecu modifications limit was aroung 90-95 km/h speed range. 100km/h is about 1750rpm. Now I am able to go 80 pretty easily if there is no big uphills.
I did same testing also on 1.9tdi and results were pretty much the same, there drive speeds got higher so avg speed wise it was not so big high speed difference but energy consumption was higher at higher speeds...
Best torsion values were not same for different cars so you need to find out which is best setup for your car. Cheap and easy method would be to make a stopper under gas pedal or hand throttle to have always same throttle position on petrol or diesel car.