How much can the stock computer adjust rich/lean
Thread Starter
Junior Member
Joined: Oct 2003
Posts: 26
Likes: 0
How much can the stock computer adjust rich/lean
Say you are running real rich after adjusting your AFPR. Can't the stock ECU adjust accordingly to try to correct this?
If it can indeed correct this, how effective is it? Also......can it correct for both open loop and closed loop modes?
Thanks
If it can indeed correct this, how effective is it? Also......can it correct for both open loop and closed loop modes?
Thanks
yes it can. and it will hold the correction until the battery is disconnected. the issue is that the speed of the correction is slow. that is why one adjusts the VE table so the corrections are quicker. i would think it could be so far off the ecu cannot correct. after all there are limitations. that was my car. the stock ecu/ eprom data could not handle my mods so i had to learn to tune.
Member
Joined: Jan 2003
Posts: 363
Likes: 0
From: Sydney
The speed of the correction is actually very quick (seconds, not minutes), but the problem is that you may not operate in every Block Learn Multiplier (BLM or long term fuel trim) cell in a short period of time, because you might not hit the particular combination of MAP and RPM or the MAF equivalents (LV8 and RPM?). So this is what's behind Ronny's comment that "the speed of the correction is slow".
Another problem is that although the BLM correction can theoretically operate over a 0 to 255 unit range (a 128 BLM is stoichiometric), the BIN usually specifies a max and min BLM (about 102 to 160 on my BIN IIRC). That means you might have roughly a 15 to 20% rich or lean correction capability.
And in relation to your "can it correct for closed loop or open loop" question, that depends on your BIN again. IIRC, RBob has posted on this. For my BIN (for an '808), the BLM's lock under WOT conditions, and you don't apply any learnt corrections at WOT.
If your BIN corrects a lean condition under WOT, you don't need an AFPR, unless you need more than say 15% more fuel.
If you need more fuel than this, and you can't DIY PROM so you use an AFPR, you're unlikely to get adequate Block Learn corrections under non-WOT conditions, especially if you're running a bigger cam that already richens up the bottom end.
I'd say an AFPR is something that's likely to work better on a car that locks WOT BLMS and doesn't need more than 15% fuel correction to lean out at low rpm. Let's hear what others think.
There also may be an issue in the other important open loop condition- idle mode.
John
Another problem is that although the BLM correction can theoretically operate over a 0 to 255 unit range (a 128 BLM is stoichiometric), the BIN usually specifies a max and min BLM (about 102 to 160 on my BIN IIRC). That means you might have roughly a 15 to 20% rich or lean correction capability.
And in relation to your "can it correct for closed loop or open loop" question, that depends on your BIN again. IIRC, RBob has posted on this. For my BIN (for an '808), the BLM's lock under WOT conditions, and you don't apply any learnt corrections at WOT.
If your BIN corrects a lean condition under WOT, you don't need an AFPR, unless you need more than say 15% more fuel.
If you need more fuel than this, and you can't DIY PROM so you use an AFPR, you're unlikely to get adequate Block Learn corrections under non-WOT conditions, especially if you're running a bigger cam that already richens up the bottom end.
I'd say an AFPR is something that's likely to work better on a car that locks WOT BLMS and doesn't need more than 15% fuel correction to lean out at low rpm. Let's hear what others think.
There also may be an issue in the other important open loop condition- idle mode.
John
Thread
Thread Starter
Forum
Replies
Last Post