Why is Boost enrichment slow to respond?

[blacksi]

Having issues with mine. Initially I had an 02 sensor wire broken which put the computer in a not ready mode. I tuned the WOT PE anyways, once I fixed the wire the computer acts normal now and uses the BE table at whatever kpa I specify. Which makes it run rich whenever it comes into activation.

So the question is, if you tune the PE table and get it just right, what is the reason for the BE? Is it incase you didn't have a boost referenced FPR?

[WS6FirebirdTA00]

BE is so you can set up PE leaner if you wanted to, giving you a typical enrichment for lower engine load. BE would be there to come in under higher loads for extra fueling when and where needed.

[blacksi]

BE is so you can set up PE leaner if you wanted to, giving you a typical enrichment for lower engine load. BE would be there to come in under higher loads for extra fueling when and where needed.

I am pretty sure I understand what you mean. But, could you give an example of some numbers so I can understand how to use it.

Like tuning for 12.5 I guess and then under boost adding a percentage to bring it into the 11's?

Hmm, but if your boost consistantly hits at a certain rpm how does this help?

[WS6FirebirdTA00]

say up until 100 kPa (no boost) you wanted to run the AFR mid to high 12's but as boost came on, you wanted to bring that number closer to low 12's or even high 11's depending on how much boost you have. This way you can do that without causing an 11.8:1 AFR at 2000 RPM and no boost, or at 4000 RPM an no boost.

[5_Liter_Eater]

Thats how I have it set up. PE commands a normal ~13:1 and BE starts commanding more and more fuel linearly to ~11.5:1 at ~155 kPa (~8 PSI). So even at 2-3 PSI I'm only commanding in the 12's. It doesn't get really fat until the boost gets bigger.

[blacksi]

Got it, thanks guys.

[Frost]

Thats how I have it set up. PE commands a normal ~13:1 and BE starts commanding more and more fuel linearly to ~11.5:1 at ~155 kPa (~8 PSI). So even at 2-3 PSI I'm only commanding in the 12's. It doesn't get really fat until the boost gets bigger.

Try and match PE and BE to desired AFR against RPMs with your SC setup. That way, you won't get the initial lean hit that you can still get if commanding 13 in PE at, say, 4800 or more RPMs where you are just cruising and waiting and then you mash the throttle up there. You will get 13 for a brief moment before BE is active, but you will be in healthy boost right away. Maybe it varies by PCM/OS as well. Try it out and see, but be cautious. Set PE to like 11.6 or a few tenths higher than BE, just so you can see commanded change just after boost is present. If you know about it, and are prepared for it, this transition is no big deal.

[KySilverado]

I reported on this issue a long while back. Nice looking down at 8 psi of boost and still commanding the WRONG AFR.

http://www.hptuners.com/forum/showthread.php?t=9803

[sikhabib]

i was also having the same problem with my tt car
http://www.hptuners.com/forum/showthread.php?t=10553

i only use PE now as BE was just too unreliable. I hate having to command 11.xx afr at lower rpm and wot loads but its the only way to consistently have the right afr under boost.
if you want to lean out the off boost WOT areas ignore afr error and lean out the ve table until the wideband reads the afr you want, its not pretty but its the only safe way of doing it

[Ben Charles]

I know this thread is a few years old now, but I was wondering if the BE table was any better now a days??

I like 5 liter eaters idea, how is that working for you?

[5_Liter_Eater]

It rarely commands the PE. Pretty much by the time I'm in PE I'm already in boost so BE takes over.