RomRaider

What are you guys doing with Overrun initial injector enrichment?

On my 2011 STi, its set to 1.4 ms With 1000cc injectors on E85, it would pop a bit after hard acceleration but I didn't mind. Now I've upgraded to 1400's and even on light throttle lift, I can get some heavy after-firing and I see the AFRs go very rich. I'm certain its this 1.4 ms of fuel combined with 1400cc injectors that is doing it.

My question is, is there any value is scaling this down for 1400s and leaving some overrun active or should I just set it to zero to shut the behavior off? I plan to test both but wanted to get some input from others.

From what I understand the primary purpose is to spray some extra fuel in to cool off the catalytic converts, thus extending their life. As a result (intentional or not) this extra fuel causes the revs to "hang" a bit after you lift. This behavior took some getting used to coming from drive-by-cable Subarus but its normal to me now.

Curious to hear other people's thoughts on this.

Here's some info about the matter: http://www.learntotune.com/discussions/topic/thoughts-on-decel-cut/

To my experience the "Overrun initial injector enrichment" is also there for driveability reasons, it smoothens the on/off transition to coasting with fuel cutted off.
If you disable it, so that injectors cut off with no delay on throttle lift off -> With low gears you end up hitting your nose to steering wheel due to quick engine brake effect
About for cooling I don't really know how much it has effect.

personally, i LIKE the quick engine brake effect.

i intensely dislike the "dumbing down" of throttles...

This is what I'm getting at. I drive my wife's 02 WRX and for the first few minutes, I have to get used to lifting the throttle a little slower to avoid the jerkiness of no overrun. With my 2011, I'm using a lifting as quick as I want and the rpms hang a bit.

I think I'll scale it down and then reduce it a bit more until off-throttle is pretty smooth but the rev hang doesn't really happen.

So far I've only determined that 1.4 ms with 1400 cc injectors is enough to scare the crap out of other drivers even when slow shifting.

Let me ask another question - can someone explain how the fueling cut counter rpm threshold table works?

I don't under what the low - med - high exactly mean. Can someone provide a solid explanation of how this table works?

Hi td-d,
Will you please help with sharing the decel fueling addresses for A2WC522N? Thanks much!

Thanks so much! On the stock values with my new engine build, the car engine brakes HARD when I lift off throttle. I loaded up the defs and the initial enrichment is 0 ms for the stock value. I'm going to start with 1 ms and see how that improves things. Also, I get the impression that for the overrun fueling RPM, you'd want the injectors to resume at an RPM slightly higher than your idle RPM target at that ECT. Do you know how the RPM thresholds are used?

The table or the counters?

How they operate in practice.

Yeah - I get that, but which thresholds? The RPM resume table or the counters?

The RPM resume table is pretty straightforward - injectors will switch back on at the prescribed RPM. The counters less so - here's the definition straight out of the COBB manual:

"These are the RPM ranges that determine multiple counter thresholds which are used to determine when fuel cut will occur during overrun conditions."

I haven't examined the logic closely to understand exactly how the counters work.

At a quick glance at that section, there are a multitude of counters and switches that are used. Basically, the 3 RPM thresholds are assigned a number (0,1,2) and this is used to pick a specific counter (from an offset location) that is used in a long and convoluted routine to determine switch off. The switch off is also gear and vehicle speed dependent.

I noticed with the stock settings that at low speeds the fuel cut off is a lot more pronounced. I think just setting the initial enrichment with take care of things.
I couldn't find a thread for it, but could you share the address for the Front A/F sensor smoothing for A2WC522N?
Thanks so much for your help. These alpha tables are really helping to adjust for the major mechanical changes.

I'm looking for this tables for A8DK100P.
Can you verify whether I wrote true values.
Thank you.

<table name="Overrun Fueling RPM Resume Threshold" address="C7A24" type="2D" level="1" scaling="RPM">
<table name="X" address="C8C8C" type="X Axis" elements="16" scaling="DegreesF"/>
</table>

<table name="Overrun Enrich RPM Delta Activation" address="C7920" type="1D" level="1" scaling="rawecuvalue"/>

<table name="Overrun initial injector enrichment (pulsewidth)" address="C7924" type="1D" level="1" scaling="ms"/>

<table name="Overrun Fueling Cut Counter RPM Threshold" address="C796C" type="2D"
level="1" scaling="RPM">
<table name="RPM" type="Static X Axis" elements="3">
<data>Low</data>
<data>Med</data>
<data>High</data>
</table>
</table>

Your values are flipped for the 2D table, otherwise fine.

Thanks a lot, td-d
Will change to:

<table name="Overrun Fueling RPM Resume Threshold" address="C8C8C" type="2D" level="1" scaling="RPM">
<table name="X" address="C7A24" type="X Axis" elements="16" scaling="DegreesF"/>
</table>

<table name="Overrun Enrich RPM Delta Activation" address="C7920" type="1D" level="1" scaling="rawecuvalue"/>

<table name="Overrun initial injector enrichment (pulsewidth)" address="C7924" type="1D" level="1" scaling="ms"/>

<table name="Overrun Fueling Cut Counter RPM Threshold" address="C796C" type="2D"
level="1" scaling="RPM">
<table name="RPM" type="Static X Axis" elements="3">
<data>Low</data>
<data>Med</data>
<data>High</data>
</table>
</table>