I respectfully disagree, I got a base tune sent from from Steve at Fabspeed and even the base tune made a world of difference on my S4.
Since then, I've spent hundreds and hundreds of hours, tweaking Steve's original file and it's paid off. The car feels vastly different than it did from the factory.
I don't know what JHM does for their tune, in fact, I've been trying to find some logs which would allow me to see exactly what they did. Problem is, JHM won't say squat, which kinda makes me wonder if their tune is as great as they claim.
What I do know, is that there are some decent gains to be made by changing the factory cam timing calibrations. I've been devoting most of my time to this aspect of the tune and I now know how to successfully change the cam timing.
Interestingly enough, there is absolutely NO information online with respect to altering motronic cam timing. This leads me to believe that a) no one has taken the time to figure it out or b) those who have, are holding back that information.
I've been meaning to do a write-up on my findings and I'll hopefully get around to it in the next little bit.
In a nutshell though, here's what I found. Any sharp drop from full advance towards retard creates an instant increase in MAF numbers and torque. What I found odd was that the factory always has a zig-zag shape to their curves, dropping off from about 3000-4500 and then pulling back up towards advance and dropping again from 5000 to redline.
I initially tried to make one smooth curve from 3000-redline and found that while I got some good results, I lost some low end torque. When I looked back at my data, it occurred to me that the reason that the factory does it that way is because you basically run out of room if you only use one curve.
The best analogy I can think of is imagine jumping off a stationary tower with a glider, in order to maintain the your height relative to the ground below (analogous to the MAF readings jumping) you need to maintain a particular velocity relative to the lift you can create by pulling up. You could pull up early and spike your height early on, but then you run out of momentum and you drop early. You could drop early to pick up momentum and spike your height late, but then you sacrifice the height at the beginning, or you could try and find the best compromise between the two extremes.
Now, imagine that instead of trying to the jump in one go, you could ride back up to the top and jump off again and combine the two distances. That's why I believe the factory does it that way. I also think that they time the 2 curves to match the manifold switching positions.
Now, the mistake that I think a lot of people make is that they try to change the one main cam timing table (usually a 16x18 16 bit one), this does not work. In almost all ME 7.1.1 ECU's there are four 8x16 maps, two for warm-up and two for knocking combustion inlet. All 4 of those maps have to have the same shape as the changes made to the 16x18 main cam timing map. I believe that the 8x16 maps interpolate between their values and the main cam timing map.
In any event, use that as you may, it took me literally hundreds of hours of work/logging to find that little tidbit out.
Finally, tuning the throttle response and the KFMOIP/KFMIRL tables makes a world of difference as well. Yes, some may say that you can get the same effect by just pressing harder on the accelerator, but that's not true in reality.
The reality of driving is that you often have only a few tenths of a second to plan a move out in traffic. By the time your brain catches up with the soggy throttle response on the S4, it's already too late. The analogy I use is two fighters, equally matched. One has his fists up at the ready and the other is dangling his fists with his pants around his ankles, Guess which one is going to win...
Also, bear in mind that throttle response IS why people buy a N/A engine. If you think that people with even a K03 equipped S4 could give themselves instant throttle response, do you think that they'd pay for it? Absolutely they would. So I say that needs to be considered a benefit of a good tune.
Finally, for those with tiptronics, re scaling the KFMIRL/KFMOIP tables eliminates that annoying tendency of the car to require 2/3 throttle application to summon a downshift. As well, it keeps the revs up out of that 1500-2000 RPM zone where the TC is perpetually slipping and adding to the soggy stock throttle response.
So beleive what you will, but from somone who has dialed his S4 in right, a good tune is well worth the money.
PS, check out my V8 definition project in the DAMOS section, I've posted my findings if you want to try tweaking your own binary.Or, like I said, give Steve a shout at
Steve@Fabspeed.com (he's a member on Nefmoto as well).
Cheers