AE tuning with DBW

[434josh]

So I was out doing a little AE tuning tonight after watching some of the Evans Performance videos. After I was watching the logs as setup in their video and since I am DBW and it's giving all the idle air, the idle tps is 16-19% and cruising at hwy speeds is 32-36%. The typical AE tables give more fuel enrichment, clamp, etc at lower % and less as tps increases. So I was wondering if I should swap the tps axis for APS to gain that resolution back. Would that be fine to do? Any issues that I am not thinking of?

[cj]

Which table are you thinking of changing to APS? You cant change Accel load to APS. Generally you dont want to use APS as an axis for anything other than your TPS target table as it means any future changes to the TPS target table will affect some parts of the engine management but not others. 

eg (extreme example to get the point across): if you had ignition set to TPS, and fuel set to APS, and you change your TPS target table from say completely linear 0=0, 100=100, to something where the first 50% of APS movement only gives 10% TPS, then from 51-100 APS it ramps up the throttle very sharply. If you had tuned everything nicely to start with, after this change, having your APS at 40% would mean your fuelling would be at 40% load, but your ignition at about 8% load. Suddenly the 2 dont match up and you have to re-tune one or both of the tables.

Also, 16-19% TPS at idle is quite high. Are you running something like 0 deg timing at idle? Typical values would be 3-8, maybe 10% depending on ignition timing. (more timing means lower TPS angle for same RPM usually)

Are you having problems with throttle response when you jump on the accelerator? ie is there a problem you are trying to fix here with accel enrichment not working or is this just a theoretical question?

 

[434josh]

I get what you are saying now about the APS vs load, so I will certainly abandon that idea and focus on the tps load resolution on the AE tables. 

 

As far as tps% it's a GM LS7 throttle body that's around 90mm feeding a 363" v8. Idle advance is 23° btdc. The throttle body is supplying all of the idle airflow and generally the lowest I see is around 14% and when cold around 18% to. 

 

The VE table is pretty spot on and uses very little cll correction, usually less than 3% in basically all driving speeds/loads but yes in throttle transitions there are very brief lean spikes and while tuning for this is when I paid closer attention to the clamp and rate tables and noticed my driving tps% was at or beyond the default taper settings. I will just play with sliding the taper over a bit to see if that helps. The AE is doing exactly what the tables are telling them to do so I just need to adjust accordingly.