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Old 11-16-2012, 06:18 AM   #117
roger 04 rt OP
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Joined: Nov 2011
Location: Massachusetts
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I've been doing some further research on the Powercommander III for Oilheads and now have a much different view of how the PC and Motronic work together. My prior view that the PC didn't drive the Motronic's O2 sensor input was wrong and was due to a lack of documentation. But that said, here is an update for those interested:

I've heard from Dynoject and although I'd like some further clarifications, I don't think I'll hear more. The product was designed nearly 10 years ago and as you would expect the designers have moved on.
" the testing was done so long ago I may not be able to answer your question thoroughly."
The BMW Powercommander III USB Wideband is essentially a Wideband Commander coupled to a Powercommander III USB.

The essence of what I've heard fro Dynojet is:
"The connection to the stock ECU narrow band input is tied to our Wideband sensor. We are able to offset the narrowband signal based on our wideband input."
This is how the Innovate LC-1 works, although the LC-1 is a later, better performing design with data logging capability.

The BMW Powercommander and Motronic runs closed loop and develops Adaptation values everywhere the Motronic would on its own. That's because the Wideband signal, converted to narrowband format, is "Always connected". The shaded area on the PC fuel map (see photos several posts back) is just a guess on PC's part about where the Motronic is in closed loop.
"The highlighted area is what we have interpreted as the closed loop area of the stock ECU."
I have many measurements that show the closed loop area of the Motronic is up to 62.5% throttle and up to 6250 RPM. I think we should expect that it is closed loop everywhere below those numbers.

I did some digging and found letters from Dynoject to Harley forums where there was a clamor for this capability. Here is part of what the design manager wrote:
"Let us start with why the BMW uses a wide band O2 sensor as part of the unit. The bike already has a "closed loop" circuit as part of the OEM injection system. It does not "auto map" the entire rpm/throttle position range of the fuel map. Generally speaking, the closed loop system only adjusts the fuel curve below 40% throttle. Above that the system is "open loop". The new Wide Band BMW unit only controls the stock "closed loop" area. Outside of that the bike is mapped in the normal fashion, on the dyno.

We would actually prefer not to maintain the closed loop section. Due to the design of the OEM injection system it is not possible to bypass it as we do with other models. Closed Loop systems are not the "magic" that most people believe they are. There are a number of problems that keep it from being the best choice for high performance applications."
This all means that the PC III for USB works very differently on an Oilhead than on any other motorcycle most Dyno tuners work on. It also means that the WOT "pulls" aren't likely to provide an optimal tuning since most dyno tuners don't seem to understand the interaction with Closed Loop Adaptation Values. There's no reason that they should be familiar since this product works differently than most every other PC they would work with.

With this information, it is now pretty clear to me how the Powercommander and Motronic work together. My plan is to update the block and show a recommended fuel map for implementation. I am a lot more positive on the Powercommander as a tool now than before. It can be implemented on the majority of BMW Oilheads with NO Dyno tuning.

If anyone reading this would like to loan me a PC for a couple weeks I'd like to run some tests. In the meantime I'm going to try and buy one used. Then later I'll resell it, all set up for installation.
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