mass-hole wrote:
Yeah, its hard to compare the two from a performance/mpg perspective, but I would guess that the GDE tunes are probably far more comprehensive than what most of the DIY tunes offer. They know what and where all the maps are in the tune and have the equipment to test/verify their changes have the intended effect. You can be certain that they are well tested and do what they say. Thats why they cost money.
Although we have a pretty good understanding of how the tunes are laid out and what each map does, there are still certain things that are outside of our understanding. Its easy to turn up the fueling, but things like turbo VNT control, injection timing, # of injection events and crap like that are still a bit unknown.
An example I am still trying to figure out is how exactly the tune uses the VNT control maps. There are 3 of them and there is no clear indication(to me) when each one is used and why. You can edit the boost map and request more boost, but if the VNT maps dont allow enough vane angle then you wont hit that boost. They work together, where basically the Boost map is the target and the VNT map is the upper limit of % duty cycle the ECU can apply to the VNT control system. If you exceed the boost target then the VNT vanes will back off and lower boost, but if you are below the boost target and the ECU is already applying the maximum duty cycle allowed for that RPM/Throttle, then it wont increase the vane angle to hit the boost. If I wanna increase boost at 3600 RPM, which VNT map do I change and if I change all 3, what are the side effects? I dont fully know. It may select the map based on coolant temp, air temp, ambient air pressure, etc etc etc.
I choose to go with a GDE tune even after the whole MPPS self tuning thing was discovered, and even though I am pretty proficient at tuning now, I still would buy a GDE tune if I had to do it all over again.
I was thinking of doing a byte comparison between the two but I don't have a GDE bin yet. Have you tried comparing your OEM bin and the GDE bin? Feel free to PM me to talk more about this and share any thoughts you may have.