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Dynamohum Dynamohum is offline
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Join Date: Jan 2008
Location: Midland Ontario Canada
Posts: 173
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Quote:
Originally Posted by Fast951 View Post
Interesting thread. I wonder why no one is going the MAF route? Why no one is getting a adjustable (fuel and ignition) to adjust over the Motronic to match the engine 100%?

The stock AFM is rated at around or less than 1000kg/hr flow, meaning it'll max out at relatively low HP. Under boost it'll generate 5V at lower RPM (regardless of position).

The AFM has a built-in Intake Air Temp (IAT). The IAT is used by the DME for calculations (fuel & ignition). This must be addressed and handled correctly when relocating the AFM to the pressure side (much hotter air).

I'm converting my 930 to EFI running a 3.2L Motronic with a blow-through MAF and Wasted Spark. The Motronic I'm using is enhanced to accept and interpret a MAP sensor to alter ignition based on boost. So the system wil have both MAF & MAP. If anyone interedted, I can document the conversion and share a few pictures as I progress.
I realize there are limitations within the stock Motronic system, I would love to use the most advanced fuel and ignition system available, but I need to justify the cost vs the gains. My wallet is bleeding in every direction right now so for me its a matter of doing it in stages.

I'm very interested in learning more about your system and what your doing, please tell us more.

I was wondering about the charge temp and IAT reference output. Do you have a wide band O2 / data log? It would be great to see the actual effects of the IAT on the F/R....
Yes agree the barn door will swing open at much lower rpm, I would think that this should help with mid range fuel demands as the boost builds.
The Wide open throttle position switch comes into play at 3/4 throttle when adjusted properly and the DME switches to a rich WOT fuel map disregarding the O2 sensor input.
http://www.911chips.com/ignition.htm

You can also alter the cylinder head temp sender output to alter the A/F ratios.

Also there are internal adjustments in the DME that you can tune with.
http://www.911chips.com/fuelsys.html

I find all this so intriguing and looking forward to testing it.

I'm using TBC thermal barrier coatings in my build, this will affect the propagation of the fuel front, combustion temp, thermal load, etc. This means that I will have to work out a few other variables that will come into play and to tune properly, I will have to buy a programmable system.
At this point I still have allot to learn and sort out, so I'm taking a conservative systematic approach. First step is a good foundation to build on, ARP hardware, fresh motor and run a low boost within the confines of Motronics.
This is so addicting, I'm already obsessed with learning all I can! The upgrades will come as I further hone my tuning skills.
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Thank You for your time, Paul. We do because we can.
87 911 3.2 (Turbo conversion, build in progress, Thermal Barrier Coatings, High Pressure Dry film coatings) Modified heads, boat-tailed case, ARP hardware, OBX Header, 930 clutch disk, G50 Trans
89 5.0 Mustang convertible (For Sale)
Old 02-07-2009, 05:17 AM
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