nothing
04-30-2004, 12:32 AM
I installed my <a href="http://forums.audiworld.com/12v/msgs/24517.phtml">modified MAF</a> housing today with mixed results. First off, this radius:<img src="http://pictureposter.audiworld.com/70334/mafsensor.jpg"> is slightly smaller on the 4 wire sensor than the 3 wire sensor, thus when the 4 wire sensor is installed in the large bore housing, there is a half circle of plastic protruding into the sampling tube near the sensor wires. The wires are in the exact right spot, however. Unfortunately, I didn't have my camera with me when I was installing it, so I can't show you exactly what I mean. This has to be causing increased turbulence over the wires, perhaps an o-ring could smooth it out? Otherwise the installation went smoothly.
As far as results, well... before and after second gear 1000->6000 rpm timed runs were exactly the same. A likely explanation for why can be seen by watching the A/F meter: at WOT the mixture is now still dithering, continuing to oscillate all the way through the run. Before today's mod, WOT would cause the A/F meter to show steady rich, third led from the end. For some reason, my ECU seems to no longer go open loop. :( No CEL, no other indication of trouble. The car is running just as smooth as before. If I didn't have an air/fuel meter, I would have no idea anything was wrong, I would just be dissatisfied with the results.
So my question is: What triggers the MMS200 ECU to go open loop? I thought it was the throttle potentiometer on the throttle body, but tonight's experience suggests that the MAF sensor might have something to do with it. Might an o-ring in the sampling tube causing increased air velocity over the wires help to push the ECU into open loop? Or is the ECU going to figure this out and fix things on it's own? I have a velocity stack on order from Mance, so that will be thrown into the mix soon.
I don't think I'm in danger of getting too lean, the a/f oscillations at WOT are no further down the scale than when cruising on the freeway, which are the same as before the mod, but I didn't push it, going WOT only for a few timed runs. I'll drive on it like this for a while and see how the ECU adapts.
This is my 200th post. Yes, still but a pup. :)
As far as results, well... before and after second gear 1000->6000 rpm timed runs were exactly the same. A likely explanation for why can be seen by watching the A/F meter: at WOT the mixture is now still dithering, continuing to oscillate all the way through the run. Before today's mod, WOT would cause the A/F meter to show steady rich, third led from the end. For some reason, my ECU seems to no longer go open loop. :( No CEL, no other indication of trouble. The car is running just as smooth as before. If I didn't have an air/fuel meter, I would have no idea anything was wrong, I would just be dissatisfied with the results.
So my question is: What triggers the MMS200 ECU to go open loop? I thought it was the throttle potentiometer on the throttle body, but tonight's experience suggests that the MAF sensor might have something to do with it. Might an o-ring in the sampling tube causing increased air velocity over the wires help to push the ECU into open loop? Or is the ECU going to figure this out and fix things on it's own? I have a velocity stack on order from Mance, so that will be thrown into the mix soon.
I don't think I'm in danger of getting too lean, the a/f oscillations at WOT are no further down the scale than when cruising on the freeway, which are the same as before the mod, but I didn't push it, going WOT only for a few timed runs. I'll drive on it like this for a while and see how the ECU adapts.
This is my 200th post. Yes, still but a pup. :)