I been tuning my part throttle operation via the MAF tables, to get BLMs right around 128. I have made some good progress, but have noticed something in my datalogs. Whenever i back off on the pedal, eg like to slow down for something on the road, the BLMs always drop to around 122. It doesnt really matter what speed/rpm I am going, the BLMs always drop. Now when that happens, my actual MAF readings go down as well, with the throttle closed. But it really isnt an idle condition, so I am not sure I want to touch the MAF tables.
I know there is this DECEL ENLEAN business in the bin, but I have not touched it all. 165 ECM, $6E-ARAP based bin.
Thanks.

 

Oddly enough after tuning for 5 hours yesterday and doing 7 datalog sessions, i noticed the same thing EXCEPT that in my case it went from around 120BLM at part throttle to 126BLM upon decelerating. I'm obviously running too rich but could the deceleration cause me to go leaner and you to go richer?

im also concerned that when i correct part throttle MAF tables to 128blm will this bring my BLMs too lean to say 134? id like to know if anyone has tried messing with deceleration stuff.

 

I am surprised not many comments. Seems like somebody would know something about this. I know in DFCO mode, after backing off the pedal, the injectors get turned off...so should go lean, yes? I know my WB goes way lean and usually pegs it lean, if I back off for long enough. So what is up with my BLMs going down? Maybe I am worried about nothing. The only other thing I saw maybe could affect it, was the Decel Enlean BPW factor, which was set to 1.00 of course. Maybe that could be adjusted.

 

Then if that is it's functionality then mine seems to be leaning it out "as it should" then. I'll play with it tonight and see if it changes some.

 

When you let off throttle the vac increases and the walls of intake are sheared clean of fuel wetness. Initially you see an enrichment(<BLM). Eventually it will level out. With 0% TPS I flip to open loop(locked 128BLM) which places the A/F about 14/1.

 

I was just reading another post before about DFCO (Deceleration Fuel Cut Off). There might be ways to tinker with this here?

 

There is a flag to uncheck to turn it off. Mine is active today. I started to tune and initially turned it off. Last year I placed in on and not had any advere results(stall on deacceleration).

 

I didnt see any flags to turn it off. But several constants to enable/disable. Why would you want to turn it off? I can accept what Ronny said above. I dont usually stay in this 0% tps mode very long, so maybe need more time for BLMs to recover. Also curious about going open loop at 0% tps. Did not see that parameter.

 

I run a different file definition(mask). Yours may not support OL at 0% tps. Yours may however support OL on < certain MPH? Or maybe some other table to flip OL? Dont know.

You may have than option in constantts. I think mine was flags. I may have been wrong. Again I cant remember where mine was. One more thought /comment. There must be a table to turn injector back on to m prevent stall with DE active when car comes to near stiop? I dont have laptop at office or I would take a look.

 

I think hes TPI I don't believe theres as big of an issue of fuel shearing or wall wetting like Tbi or carb, but sounds like MikeT should play with the decel enleanment settings.. problem with tbi doing to much enleanment to burn off the fuel in the intake is the inj pulse width can get to low and the engine can buck or surge so its really just trying to find a balance.

Dfco is another animal the injectors turn off so its not just lean but dead lean the engine keeps spinning because the driveline is still turning it also helps cool the motor down because theres no combustion.

 

Yea I run a 350 TPI setup. After I thought about it, it is a dry intake system, the fuel gets injected right down at the valves for each cylinder. I am running $6E tdf, with ARAP based bin. I dont see much of the OL settings that are mentioned above. But what I do have is several constants for DFCO(11) and Decel Enlean(6). It looks like DFCO is enabled, but I am not so sure about the DECEL ENLEAN. There are 2 constants that look high to me.
Decel Enlean Enable Delta TPS threshold, which is set to 94%.
and Decel Enlean Enable delta LV8 threshold, which is set to 245 LV8.

Those numbers seem high enough that NOT let DE mode to kick in. I need to look at some other bins and see what they are set to.
Keep the posts coming.
Mike

 

Right. My error.

If in fact in DE I would think BLM would lock and log would show 128.

Why would General allow DE to affect BLM? Maybe a rising BLM(adding fuel) will help the engine recover after DE event. That would be contrary to OP statement of falling BLM(pulling fuel).

Where is additional fuel coming from? VAFPR drops FP. No added fuel there.

 

Yea, somewhat agree that BLM should be locked 128 during DE. Have to look at some more scans. So what exactly is the difference between DFCO and DE? I know DFCO is Dxxxxxx Fuel Cut Off, which means 0.00 injector pulse width, but what is the D in DFCO? I checked my stock bin, and the settings for Decel Enlean are the same I mentioned above. My max LV8 in WOT is only 222, so I cannot even get a delta threshold of 245.
and yes, i have searched on DFCO, but not sure what the difference is with Decel Enlean. Please keep discussion going.
Mike