So the 1250 fuels nicely, from the factory. The only people that would need a Hilltop on a 1250 are those that change to aftermarket headers then. It’s a shame BMW don’t offer a map, similar to Ducati when they fit a full system.
There is no reason for BMW to offer an alternative map.
The ECU continuously monitor the combustion by means of feedback from the O2 sensors and adjusts the fueling to assure the engine gets the desired AFR. If you add/subtract factors that will require a leaner or richer fuel mixture, the ECU will readjust the adaptive map (also called long term trim in the none BMW world).
In the thread about HT posted for nearly a year ago, the HT guy finally entered and gave a brief explanation of what they do and don't do.
The HT procedure, as far as I understand it is a rewriting of the management part of the software, and not a remapping.
So, what does this management business mean? A bit of guess work on my part now, but generally when you build up a program that will do a job, you break down the different tasks in small sub-procedures. This could be a procedure for handling ignition timing, reading rpm, reading temperature etc. Then you build a management procedure that monitors the process by calling the sub procedures as needed. Most likely there is such a management procedure in the ECU already, and this procedure is fairly easy to find since it will be called in the startup process of the computer. If you want to do changes, you simply copy the management procedure, write in your changes, put it at a vacant spot in memory and simply change the management procedure address that is stored in the ECU to the address of the position of the rewritten management procedure. If you want a richer mixture you simply write in a change to the information received from the O2 sensors and voila, you get a richer mixture and keep all the benefits of ECU handling the timing, CAN-bus transmissions etc.
(I say "simply", but reverse engineering is always tedious and time consuming, and I do not in any way try to talk down what HT have done)
Even if the 1250 is reported to have a good fueling it must meet the emission requirements. This means probably an AFR around 14,7. I have yet to see an engine that will not benefit from a slightly richer mixture. So even if the 1250 is good, it is my humble prediction that slightly richer will improve even further. The catch is of course that if the engine already does a fairly decent job, the improvement will be difficult to notice and hardly anyone will se the point in paying for something that they will not notice.
This remains to be seen.
Yours truly will receive a 1250 in march, and my plans are to hook it up and see how it does and adapt my manipulator protype from my previous project (1200GSA) and check if a richening will be noticed. If I can not notice the difference by my ass-dyno I see no reason to mess about. Time will show..