I've been searching everywhere and I can't find a good explanation of how the allison ECM works. What I've found from playing around with the demo version of EFI live is this......

The code evidently uses the shift timing tables to look up the desired shift time for any given driving condition. Then attemps to shift in the time period requested. It does this by varying line pressure based on whether or not it made the shift in the time commanded. This routine is a part of the TAPS I assume? So by reseting the taps you are effectively erasing any learned line pressure tables and making the ECM start over from scratch....hopefully learning to up the line pressure to make the shift in the time you've requested.

Am I on the right path at all? I fully understand the allison is NOT like a conventional tranny that commands line pressure based on engine load. I'm just trying to find out how it's controlled. If I am on the right track it appears like the EFI live guys haven't fully hacked the ECM yet. It would be great to bypass the self learning and just program in the table that it is trying to create based on the taps system. This way you could lock in the line pressure and try to make the clutch to clutch 4-5 shift happen the same every time and eliminate any chance of a tie up.

Unfortunately I'm not currently tuning my D-max.....just trying to learn for when my warrantee runs out.

The little Ive read on it is that its sensitive and dont like to be messed with. All Im going to do with it is lock out 2nd every once and a while at the drag strip.

Here is some reading mabey this will help answer your questions. http://forum.efilive.com/forumdisplay.php?f=70

I've lurked over there off and on but I'm not really seeing a summary of how the alli works. A lot of those discussions would make a lot more sense if I know the general gist of things.

I've tuned on old school TPI and TBI systems for years and even got into reading source code. The biggest help was sitting down with the hac for a given ECM and just following the code through it's paces and seeing how it works. Unfortanetly those hacs for the newer ECM's are big money to EFI and HPtuners so they will never be released for general consumption. Then again those old ecm's would have 80-200 pages of code, so I couldn't imagine how complicated the new code would be.....probably thousands of pages.

I've been poking around the EFI software, I have the demo version, and I think I have a better idea of how things work....please someone correct me if I'm wrong.

The taps system is a way to adaptively vary the line pressure to achieve the desired shift times. When you reset the taps you go back to a preset pressure and then the system varies the line pressure from there depending on how much slip accurs. Does this sound right?

This is where the light bulb kicked on, everyone always says to drive it easy untill the tranny has a chance to "relearn" the tune. All they are doing is dealing with enadequate line pressure untill the taps system can up the pressure to the point where it won't slip the trans. EFI allows you to disable the learn function and vary the starting point of the taps system. Why can't we disable taps and then manually tune the taps preset tables to achieve the desired line pressure and set this thing up like an old school trans? This way the line pressure will be the same every time you are under a certain condition. My understanding the big problem is trying to time the shifts right on the clutch to clutch shifts and the biggest stumbling block is that the line pressure is always different so the shift times are inconsisten and lead to a tie up.....

I may be way in left field, but I can't seem to find any info explaining this better.

I think this is a good thread to ask this question in. I'm trying to learn about this like LMM Guy.

What are TAPS exactly? Are they mechanical or what? In other words when we reset the taps, are we just adjusting some parameters in the TCM, or is it resetting valves or something?

There are a couple of ways to do what you're asking, the safest would be to log actual shift time and make note of the the shift feel you like in the log. Then go back into the TCM tune and request that shift duration. Exporting the TAPs informaton, and disabling learning is another option, but likely less safe.

Nick

The reason I was thinking about this is basically the time it takes to relearn after a big change in ECM tunes.

Right now I use tow/haul for drag racing etc. I have the shift points and converter lockup changed for that, taps thinks I am going to hammer through the gears when I am in T/H.

Now when I actually want to tow something should I just load a new ECM tune, the stock TCM tune, reset taps and go on my way? Or not mess with the taps or TCM tune.

The problem is when I am done towing and now my T/H is good at pulling a 12,000lb trailer. Now I want to drag race the next day. Can I just reload the TCM tune and restore taps as they were, and sort of "forget" the towing episode ever happened?

How about towing with your transmission in the "normal" mode? Might want to adjust the TCC to lock sooner/longer. Leave the T/H for racing only. With the mods that you have listed you shouldn't have any troubles. If its a really heavy load use the manual selector & lock out 6th gear?
Just a couple ideas, works for me.