Decelerating air/fuel ratio

Black1987Stang · #1 (**permalink**) 11-07-08, 09:37 PM

With the Tweecer what setting do I change to adjust the decelerating AFR?

vristang · #2 (**permalink**) 11-09-08, 10:18 PM

Run through the DFSO (Decel Fuel Shut Off) Scalars...

What ecu?
What is the current AFR condition?

Black1987Stang · #3 (**permalink**) 11-10-08, 05:31 AM

It's an A9L and if I slowly let off the throttle the deceleration afr is 14 ish tops, it varies from 13-14 but if I bring the rpms up higher and back off the gas right away it will hang around the rich side more but it's still in the 13-14ish area..

vristang · #4 (**permalink**) 11-10-08, 06:32 AM

interesting.

If you want to mess with DFSO, then you can get started by copying all the settings for DFSO Scalars from the X3Z, over to your A9L.
Maybe even try loading up a X3Z.bin to your A9L?

Black1987Stang · #5 (**permalink**) 11-19-08, 07:58 PM

Quote:

Originally Posted by vristang

interesting.

If you want to mess with DFSO, then you can get started by copying all the settings for DFSO Scalars from the X3Z, over to your A9L.
Maybe even try loading up a X3Z.bin to your A9L?

What's the difference in the X3Z scalars from my A9L one? I guess it's just set to run leaner at decel....??

I looked through the scalars for my A9L, I didn't see anything that I thought would help me but I could be wrong. Which exact scalar would I change to lean it out under decel?

vristang · #6 (**permalink**) 11-20-08, 02:13 AM

What .bin editor are you using, as most programs use slightly different names?

Basically you are looking at all settings that have the term 'DFSO' in them.
Do a comparison between a stock A9L.bin and an X3Z.bin and all of these scalars will be easier to identify, as the A9L does not utilize DFSO. (iirc)

Black1987Stang · #7 (**permalink**) 11-26-08, 12:23 AM

I'm using Caledit, and now you got me confused with this. A9L has DSFO scalars but doesn't use them? I kinda assume youre saying it has the option but its just not enabled in the A9L's but it is in the X3Z? right?

vristang · #8 (**permalink**) 11-26-08, 01:36 PM

As far as I know, that is correct.

I have confirmed that the X3Z DFSO settings allow fuel shutoff, but I have not run an A9L myself to confirm.

Others have had to use the X3Z settings in order to get DFSO to function....

jason

EDIT:
CalEdit will give you headaches.... I suggest upgrading to BinaryEditor... it'll set you back a few bucks, but it is worth the ~ $55...

Black1987Stang · #9 (**permalink**) 12-08-08, 09:56 PM

Quote:

Originally Posted by vristang

As far as I know, that is correct.

I have confirmed that the X3Z DFSO settings allow fuel shutoff, but I have not run an A9L myself to confirm.

Others have had to use the X3Z settings in order to get DFSO to function....

jason

EDIT:
CalEdit will give you headaches.... I suggest upgrading to BinaryEditor... it'll set you back a few bucks, but it is worth the ~ $55...

I looked quick last time I was tuning and I didn't see a X3Z in that pull down menu....It's really sucking at cold start ups and coming to a stop so I'm thinking about putting on the stock maf and run it with that, I think it was you, or someone on here said the stock maf is much easier to get the tune going good first. If I still cant get it I'm going to put one tune back to stock and start from scratch since I messed with so many different things.

Black1987Stang · #10 (**permalink**) 12-19-08, 11:39 AM

Any comments about my last post?

Foxfan88 · #11 (**permalink**) 01-02-09, 10:31 AM

the way i see it, the EEC doesnt target a specific AFR while "decelerating" it operates the same during normal driving, goes off MAF flow and uses the injector slopes to calculate the PW to match the fuel trim. its up to your slopes to be accurate to deliver correctly under all the usable PWs you will see.

if your maf curve is accurate and if your getting lean or rich AFRs on closed throttle decel thats indicating low slope or injector offsets being off. reason being your lowest PWs are going to be under closed throttle decel, the higher rpm with low airflow means a smaller PW is used, since higher rpm means there are more injector firing events in a given time. so a smaller PW is needed. if you datalog and watch closely. while driving around at light throttle. the engine RPM will increase, but the airflow usually remains close the to same, so the PW will get smaller as RPMs rise (as long as airflow doesnt change too much)

so the error on decel is due to the low slope or offsets, since those have most affect of the short PWs

think of it this way. the smaller PWs are going to be during high rpm/low airflow conditions, and the longer PWs are going to happen under low rpm/high airflow scenarios.

i had a problem with going pretty rich on decel, into the 12s, CL would command a lean lambses (like 16-17) and once i tippied back in the throttle, since the lambses was leaner, i got a lean tip in, most of the time it wasnt so bad that it would hesitate but it did do it sometimes. but the CL was sluggish to correct this lean condition, so it would hang leaner for a few seconds.

i played around and got some different slope values to work. now my car accurate delivers fuel all the way down to around a 1ms PW then it starts shooting leaner, according FRPP injector specs 1.1ms PW is the smaller "repeatable" PW. so i contribute that leaner afr at the LOW pws to the injector being innaccurate.

also i am sure that the fact i am running 42lb injectors on a N/A 302 isnt the ideal combonation (going to use them for turbo project, so i am just using them at the moment) if i had smaller more "matched" injectors, i wouldnt be logging near as low as PWs.

but the lean at LOW pws doesnt bother me really, it takes a fairly high rpm closed throttle decel to get it to start getting leaner, and eve when it does, CL will command rich to compensate. then when i tip back in the throttle, if anything it has a slightly rich tip in, which i can live with, you cant feel it, plus CL is quick to correct the rich tip in i have found.

just play around with slopes and stuff. but honestly if its not so bad that you dont get bad tip ins or anything, you may not even mess with it.

also, get BE and EA

**millhouse** · #12 (**permalink**) 01-06-09, 03:42 PM

Keep in mind too that at a certain point during higher vacuum deceleration, the injector PW is completely cut causing a dead lean condition.

Foxfan88 · #13 (**permalink**) 01-09-09, 03:56 PM

the common 87-93 A9L and A9P eecs dont use a DFSO feature from the factory, it can be enabled though.

the XZ3 from the cobras and the CBAZA strategies use DFSO. and i am assuming all newer computers use it also.