Ok, I need help. Just starting out and I'm not sure what to do with what I'm looking at. I have a problem where the cat over temp keeps kicking in. Since I'm not running cats, I would like this disabled. Below is a $0E HAC, but I'm not sure what to do with what I'm looking at. I understand the first column is the memory location, not sure what FCB is. I'm assuming 3rd column is the value in that location, but how does that interpret to the phrase explanation after that. In other words, how do I get from "153" meaning 759c temp?

Is there an good explanations about cat over temp and how to get rid of it?



The Hac below, I'm assuming is close, as it seems very similar to what I have.



;==============================================
; CAT PROTECTION CALIBRATIONS
; BJDR, TYPE $0E ECM, 94 5.7l V8
;==============================================
L406D FCB 153 ; 759c CAT OVER TEMP UPPER 1ST HYST PR
L406E FCB 146 ; 738c CAT OVER TEMP LOWER 1ST HYST PR
; CAL = (Deg -300)/3
L406F FCB 194 ; 882c CAT OVER TEMP UPPER 2ND HYST PR
L4070 FCB 146 ; 738c CAT OVER TEMP LOWER 2ND HYST PR
; CAL = (Deg -300)/3
L4071 FCB 160 ; 80c Cool, IF G.T. 85 thresh, INIT CONV TEMP TO
; L4072, (Deg c + 40) * (256/192)
L4072 FCB 0 ; 300c CAT, HOT COOL CONV INIT TEMP
; CAL = (DEG -300)/3
L4073 FCB 210 ; 210 Sec, IF CONV TMR G.T. or E.Q. thresh USE AFR FM TBL L4088
L4074 FCB 30 ; 11.7% TPS, IF TPS G.T. thresh, CONV PROT CAN BE DISABLED
L4075 FCB 32 ; 800 RPM, IF RPM L.T. thresh, CONV PROT CAN BE DISABLED
L4076 FCB 15 ; 15 Sec's, DISABLE CONV PROT IH HI TPS & LO RPM
;-------------------------------------------------------------------------------------
; CAT CONVERTER TEMP FILT COEF vs AIR FLOW
; Dissassemby of BJDR
; USED W/LAG FILTER & TBL'S L4084, L408B
; TABLE = COEF *256
;-------------------------------------------------------------------------------------
ORG $4077 ; Coef AIR FLOW
----------------------------------------------------------------------------------------------
L4077 FCB 2 ; 0.78 0
L4078 FCB 3 ; 1.17 16
L4079 FCB 4 ; 1.56 32
L407A FCB 5 ; 1.95 48
L407B FCB 6 ; 2.34 64
L407C FCB 7 ; 2.73 80
L407D FCB 7 ; 2.73 96
L407E FCB 7 ; 2.73 112
L407F FCB 8 ; 3.13 128
L4080 FCB 8 ; 3.13 144
L4081 FCB 8 ; 3.13 160
L4082 FCB 9 ; 3.52 176
L4083 FCB 9 ; 3.52 192
L4084 FCB 9 ; 3.52 208
L4085 FCB 10 ; 3.91 224
L4086 FCB 10 ; 3.91 240
L4087 FCB 10 ; 3.91 256
;---------------------------------------------

 

Try setting these to the max temperature:

If that doesn't do the trick then will need to zero out some of the temperature tables. I'd have to look at which ones first.

RBob.

 

Easiest thing to do is turn off the Option Byte for Catalyst Overtem Protection. It can be toggled on and off with one click.

 

My apologies for being an idiot. The formula (DEG-300)/3 didn't sink in until I just read it again. Not sure why I wasn't reading that as a formula for calculating temp.


I do think setting the flag to disable might be better. Any idea where the flag is or how to find it in $0E?

 

L400F- Bit 4

 

Man this is great. Thanks a bunch. You don't even want to know how much money this should save me in fuel. This thing was tripping on every 5 minutes or so. I'd watch the pulse width jump .3 milliseconds anytime it tripped. I really appreciate how much effort those have gone before have put in to make this possible for us for the rest of us. I've not burned a chip yet, but this is all making sense and is seeming pretty simple. I'm really kind of surprised more people aren't doing it. There is still plenty I don't know, but I feel I'm getting over the hump.

 

You might save fuel, you might not. What I found with my Van, as heavy and tall geared as it is. My PE has to kick in really early (25% TPS), or else I am out of lockup and in 3rd gear, pushing 1,500 rpm more than the normal 1,800 to do 70. I increased my fuel economy by 3 mpg highway, the engine runs smoother, and I rocket up hills in OD with ease. So just because you take away fuel, does not necessarily mean better mpg. Now if it is tripping and not needing the fuel, that is another issue all togather.

The stock TPI throttle body on my van likes this.

Cruise TPS = 13-18%, Cruise vacuum 8-12 in/hg, 1,800 rpm @ 70 mph
As I accelerate up to 25% TPS, the vacuum slowly drops toward 0 in/hg. At about 25% TPS, the vacuum is reaching 0 in/hg, the same time the engine is no longer throttled by a pressure drop in the plenum, it is still being demanded for more TQ, that is when the PE should kick in. Once PE can no longer do anything, about 30% throttle in my case, I unlock the TCC. Around 50% I usually catch 3rd gear.

PS-The end result has gotten me several 90+ MPH speeding tickets in a fullsize van

 

I'm not really leaning anything out or effecting PE, just removing this CAT cool down that does not apply to my engine. It kicks on every 5 minutes to go through a "cool down" cycle and then turns off. O2 jumps to 900 mvolts for 1 minute and then back to normal toggling for another 5 minutes. When I tow the Jeep behind the motorhome, it will cycle on every 3 minutes. I'm guessing its probably hurting me by ~6 or 7%. When your only getting 8 mpg, 7% adds up pretty quick.

Incidently, so far I've been able to avoid speeding tickets in the motorhome, even though I've been known to cruise well above 80 mph. I've seen as high as 97 mph on the GPS and was still climing like crazy, just ran out of realestate. I didn't put this engine in it to cruise at 55.

 

Fast355, I tried disabling the bit, however this had no effect, its still will set the COT flag and go rich for a few minutes. Not sure why that had no effect.

 

Try setting L4074 to 0.0 %TPS, L4075 to 0 RPM, and turning off L400F Bit 4. That's the way it's set up in the BJYM bin (FED).

 

It looks like TPS and RPM were set to zero, but it still turned on. Curious if you know the formula for L4074 and L4075?

 

4074 = 0.390625 * X
4075 = 25.000000 * X

 

Thanks. Its nice to know when I comparing bins, what I'm actually seeing. It helps me decifer why, and gain some understanding.

I ended up slamming the temps up to 255, as the RPM was set fairly low anyway and the TPS was already set to zero. I just drove 4 hours and the COT never turned on, so I think I've got it. Thanks again.