Rogue_Ant

In the interest of stopping mis-information and posterity...

The 951 AFM does not meter up to 375rwhp, not even close.
While you can pull 375rwhp through an AFM, that does not mean it is metering it.

Now, I'm not discounting what you saw, but it does need some explanation.

The AFM outputs 0-5 volts. This 0-5 volt range is mapped inside the DME software, corresponds to a specific airflow; 0 volts is the minimum airflow, while 5 volts is the max.
The volts vs flow curve looks similar to this:





With the AFM door fully closed, it will output near 0 volts. However, with the door fully open, it will only output about 4.6 volts... So, there is 0.4 volts (the 4.6 to 5.0 range) of unused voltages mapped inside the DME software. As can be seen on the graph above, this last bit of voltage has a large change in report airflow. (since the curve is non-linear)


After say 300rwhp, the AFM is wide-open and reporting the maximum voltage it can, 4.6 volts. What some piggyback tuners have done is use the piggyback to artificially report voltages higher than 4.6 volts to the DME. This tells the DME to use the higher airflow values, and inject more fuel (if possible).


So, whats the problem?

The problem is this: Once the AFM is maxed at 4.6 volts. Any increase in airflow is unmetered. So at that point piggyback fuel tuning is done blindly off of RPM. And while this can be done, the tune will only be correct for that one specific situation (boost pressure, temperature, baro, humidity, etc).

Take that 375rwhp car and turn the boost down 3psi, and now the tune will be overly rich. Likewise, take the same car and go up in altitude, and again the tune will be off. Or let the weather change 30-40° and see the tune drift...


There is a much better way to a robust DME engine management solution with these cars - a proper MAF conversion.

Eric_Oz_S2

Hmm, that graph looks familiar........

Works fine on a supercharged s2 though as airflow is constant with rpm on wot.

fast951

Assuming the MAF you purchased has the correct physical size for stealth setup (diameter 3"; length: 5"), all you need is an adapter to go between air box & MAF/hose. The MAF sensor sits in the same location as the AFM (airbox on the inlet side, J-pipe on the other side).

The MAF kit you purchased should have included the Vitesse chipboard. The chipboard contains the software which is configured for the injectors (size and brand).

MAF sensor, Chipboard, Injectors and more than likely a 3bar FPR all work as a system.

fast951

The AFM is not needed for the Stealth setup. Someone, as a personal project, modified the AFM and located the MAF inside of it. A unique setup, but not the standard Stealth configuration.

fast951

You don't need an AFM to modify. The restriction is the opening at the air box.
Notice the size of the opening (AFM side). Some Stealth owners did open it to a true 3" to match the diameter of the MAF. Look for a post from a few years back, someone posted pictures of what they did.

TheAllusionist

Thanks for the awesome information and insight, one of the reasons I love this site. I plan on having Evergreen build a KKK 27-8 for me, I have had discussions and waiting for when the time is right, can't spend all my money on parts all at once, my wife would leave me! LOL The KKK 27-8 just sounds like the best option as it has good power potential and less back pressure than the KKK 27-6 I believe. Charlie will build fast spooling high torque version for me and I will get the correct chips/set up for it. Of course if another awesome option falls in my lap.......

Joshua,
Thanks for the information, I had originally wanted to get an A-Tune (your reputation and that fact that you our creating new product for the 944 makes me want to support your business), but I kept looking for a good DME to have you convert and then you had things going on in your personal life and it sounded like getting product was difficult, I fully understand, and then the Vittise MAF opportunity fell into my lap. So it may be when I find a 944 Turbo S to really trick out I might try an M-Tune and help support you and LR.

John,
Thanks for your input, your reputation is legendary. Yes the Maf came new with the chip/circuit board, cone filter and bracket....... I figured when I knew exactly what my build would be I would contact you about paying for programming it and perhaps Fuel injectors if needed (I have 55 lb ones ready to install but it may be I need to upgrade that). I have been doing research and saw that boring out an AFM was only needed for a true stealth application, I just need an adapter to keep my stock air box and stock look that most people wouldn't know wasn't all stock. Thanks for pointing that out, I had contacted you before to see if you still sold stealth versions and was told you didn't so I was investigating the options necessary to pull off a stealth option or just peformance AFM options, now that I have one of your MAFs I will go stealth route. It could be that I have discusion with you on turbocharger when that time comes, I don't like to bother people before I am ready to purchase, I do know I want that part new and not mess with used ones, whether Charlie at Evergreen builds it or I buy a new one from you for example I am not being frugal on that part! Thanks for sharing your knowledge.

Thanks to everyone, I really appreciate how this community shares knowledge and participates in others threads, hopefully someday I have enough experience and knowledge to help others. For now I am fighting the tempation to go full out and just trying to make tasteful mods to my low mileage car. Maybe someday I will find an 'S' model that has seen some abuse, but solid to build to the gills!