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Old 12-01-2008, 11:27 PM
duxthe1 duxthe1 is offline
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Join Date: Oct 2004
Posts: 3,277
Man, no sweat, I appreciate your input. The controller should very closely mimic an unaltered O2 sensor. The controller reads the O2 sensor digitally, decides to modify or not, and then outputs the new voltage through a MAX5354 DAC, once every repetition of the program. I havn't decided on maximum clock frequency yet, and have only simulated at ~125khz, but 8Mhz is theoreticly possible with the hardware I'm using. I'm going to determine clock frequncey once I can test it in operation.

I'm not too convinced that it'll need a wideband O2. Remember that I am getting a richer mixture by fooling the ECU leaner. Although I'll admit to not doing the math to figure out how much my 30% lambda ajustment will alter the mixture. FIgured it easier to measure it once I have it functional in the car. I'm lucky enough to have a gas analyzer at work. I know as an experienced mb tech that a car running at 20% lambda is pig rich. I'd expect peak power to have fallen off somewhere before 20%, though maybe not.

Don't forget that the controller is designed to lean out the mixture too. This idea was hatched back when gas was still near 4$ a gal. After a 14hr@4000RPM road trip last summer when gas won't cheap, I was really into the idea of being able to run lean on the long hauls.

Granted there are a lot of shortcomings compared to a stand alone EFI. My design goals were to keep it a simple interface that requires no other mods than to plug it in to the cig lighter and O2 sensor. Technicly, you won't even have to open the hood to use it. There's all sorts of tweaker gizmos for the EFI guys but almost nothing for us CIS-E tweakers. What I'm shooting for is a simple, easy to use interface that gives the CIS user control of the fuel mixture over most of the usable range of a/f mixture during closed loop.

Whether I pull it off or not remains to be seen but so far, so good.
90 300TE 4-M

Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197 intake cam w/20 advancer
4 ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff
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