Trying to understand Decel enleanment in $58:

Reply Subscribe

Thread Tools

Search this Thread

Jun 21, 2006 | 09:18 PM

novass

Thread Starter

TGO Supporter

iTrader: (1)

Joined: Nov 2002

Posts: 1,132

Likes: 1

From: Grand Island, NY

Car: 1990 Formula

Engine: 305 TPI

Transmission: WC T5

Trying to understand Decel enleanment in $58:

What I am trying to figure out is how to determine from a log if I am entering DE: (From what I am seeing I believe most of the time in DE I am going rich)

And How long am I in DE (how many scan entries)

From the info I have:
DETHROT component of DE is used if the rate of change (decreasing) is greater then a threshold.

I am not real clear on the threshold info:

THRESHOLD = Filtered throttle position if *KAFOPT3*, bit 4 = I = 12.5 mSec old throttle position if *KAFOPT3*, bit 4 = 0.

Then it is based on this formula:

DETHROT = *F36*( (THRESHOLD-TPS )*8)

Table F36 is:

0x04FB F36_TABLE DE Throttle Contribution vs Throttle Change
% 0 6.25 12.5 18.75 25
(%) 7.4 11.3 20.7 20.7 20.7

For map it is based on manifold pressure term where if it changes by a factor greater than KDEPMTH (Which is 1.9 KPA in my bin) is uses the table F35
0x04F5 F35_TABLE DE MAP Contribution vs MAP Change Above Thresh.
% 0 10 20 30 40
(%) 3.1 6.6 12.5 28.9 28.9

If looking at part of a scan, is this in DE? From the scan, how can I determine which of each factor is contributing to the DE. (I know that these two factors are added together and multipled by two other factors to get total DE, but I would like to know how to figure I am in DE so I can make educated changes to the DE terms)

Here is one where I go rich

Code:

TPS %	RPM	RunTm    KPA       AFR
9	2175	79	35.34	14.7
9	2125	79	35.34	14.7
9	2125	79	35.34	14.7
9	2125	79	35.34	14.4
9	2150	79	35.34	14.7
8	2125	79	35.34	14.7
8	2125	79	34.55	14.4
8	2125	80	34.55	14.7
8	2100	80	33.77	14.4
8	2100	80	32.99	14.2
7	2150	80	31.43	14.1
4	2150	80	27.53	14
2	2100	80	24.4	13.3
2	2150	80	22.06	13.1
1	2100	80	20.5	13.2
0	2150	80	20.5	13.8
0	2100	81	18.93	14.1
0	2100	81	18.93	14.4
0	2075	81	18.93	14.7

Here is one where its lean

Code:

TPS %	RPM	RunTm	KPA	AFR
25	4350	196	44.71	14.9
25	4350	196	43.93	14.9
24	4375	197	42.36	14.7
18	4375	197	34.55	15.5
3	4225	197	17.37	16.5
0	4025	197	14.25	17.9
0	3775	197	14.25	17.9

Thanks

Jun 21, 2006 | 11:31 PM

RednGold86Z

Supreme Member

iTrader: (1)

Joined: Mar 2000

Posts: 1,692

Likes: 1

From: Corona

Car: 92 Form, 91 Z28, 89 GTA, 86 Z28

Engine: BP383 vortech, BP383, 5.7 TPI, LG4

Transmission: 4L60e, 700R4, 700R4..

Axle/Gears: 3.27, 2.73

That's probably decel enlean (but at low MAPs, it's hard to tell what causes the A/F seen, because it's so dependant on so many things), but it becomes much more clear when you go from 80+ to <50 kPa. If decel enlean is disabled there, you'll see it reach 12's likely. If it's too much, you can feel the engine almost cutout and then comeback. Too much will cause a buck when lifting throttle (but not completely to 0), too little may be un-noticable, maybe will backfire out the exhaust if it's worst case and cutoff is entered.

Jun 22, 2006 | 05:36 AM

novass

Thread Starter

TGO Supporter

iTrader: (1)

Joined: Nov 2002

Posts: 1,132

Likes: 1

From: Grand Island, NY

Car: 1990 Formula

Engine: 305 TPI

Transmission: WC T5

As a note, I do have DFCO disabled.

One of the items that I am trying to get at is, In say the top log, I should be in DE because of the dropping tp%. How do I determine which cell in F36 I am using at a specific time and each log reading is how far apart?

So say these three entries from above:

Code:

7	2150	80	31.43	14.1
4	2150	80	27.53	14
2	2100	80	24.4	13.3

is there enough tp% change for DE?
If so is it using the 0% value of 7.4 for the tp enleanment term?
or is there not enough tp% over this given time in the log to enter the tp part of de.

Last edited by novass; Jun 22, 2006 at 05:51 AM.