Several years ago I dyno'd with and without cooling fans on and found 1 h/p difference, so I have a toggle switch that only keeps the fans off when I choose, when the switch is in the off position, they work just like stock. Tracks like Miller, you just don't need cooling fans and when racing realy tight, you need every single horsey you can find!!! I tried another experiment, can't remember exactly what, but I think it was a K&N cone shaped air filter vs the stock box and got more with the stock box.

If the AFM is out of the loop at WOT, how does adjusting the AFM effect top end HP? This doesn't make any sense.

My understand was the same as TC's. The DME is closed loop at WOT so the chip is determining fuel, timing, etc.

Changing the AFM should help part throttle power but it should have no effect on WOT HP numbers.

944Racer72 wrote:


Ah, this is the big question. I've been doing some reading on Motronic 1.x vs. 3.1 and the early vs. late AFM. Tim, assessment is close, but not quite all there. I don't have the time to give a detailed response this morning, but I will soon.

Thanks,
-bj

Gents, I'm a SpecE30 racer. We learned the hard way a couple years ago to approach the idea of adjusting the AFM a few clicks too and fro with some caution. In this thread you guys seem to be pretty casual about it, but I submit that you aren't accounting for long term fuel trim which I think is very similar between our cars.

Bottom line up front....

1) You can't move the AFM dial a few clicks and then do an accurate dyno run because you haven't given long term fuel trim (LTFT) time to adjust.

2) Once it does adjust you might not be happy with the results.

See this thread.... spece30.com/forum/44-intake-and-exhaust/...girls-re-hi-rpm-miss

This post is an important one. spece30.com/forum/44-intake-and-exhaust/...0&start=20#61115

Thanks for posting. That is some very interesting info and jives with my understanding of how the DME works.

This is interesting, and I need to take some time to read the whole thread. One thing that might be different, though, is that the O2 meter is very much an emmisions only add on to the 944 ECM. Euro 944's had no O2 sensor at all. Our cars just revert to the baseline maps with the O2 sensor unplugged, and run fine (like a euro 944) that way. I don't think the O2 sensor affects the WOT throttle maps at all, and if you unplug the O2 sensor, there is no way for adaptation to happen. I am not an expert on this, so I'd love to have BJ and others chime in.