Sponsored

Catless and the imfamous CEL

WildHorse

N/A or GO HOME
Joined
Jun 28, 2017
Threads
220
Messages
8,775
Reaction score
6,873
Location
Home World: CLASSIFIED
First Name
ⓇⒾⒸⓀⓎ ⓈⓅⒶⓃⒾⓈⒽ
Vehicle(s)
'17 S550
Vehicle Showcase
1
You said if it were lean it would hurt motors
I also said on FI engines.

So let's just say FAOSC is on and cats are missing, then fuel trims go high.
I've never seen that, unless it's going into cat protection

ok we're going into the weeds here. I gave my opinion which, to recap. Your fine with FAOSC on/off with a NA engine + feline delete. Take it, leave it. I ain't trying to sell a product.
 

junits15

Well-Known Member
Joined
Jul 7, 2022
Threads
13
Messages
700
Reaction score
764
Location
MA
First Name
Justin
Vehicle(s)
2019 Mustang GT
I also said on FI engines.


I've never seen that, unless it's going into cat protection

ok we're going into the weeds here. I gave my opinion which, to recap. Your fine with FAOSC on/off with a NA engine + feline delete. Take it, leave it. I ain't trying to sell a product.
If the car is running with an error in its o2 sensor feedback, it can be tuned out without realizing. You can adjust WOT lambda and the MAF curve to "fix" what it actually an error elsewhere.


I have a 21 year old BMW sedan that uses the downstream O2 sensors for fueling adjustments exactly the same way, that's how I learned about any of this at all. I spent nearly 2 years chasing a lean code that was caused by an exhaust leak around the downstream O2. They aren't just for cat monitoring.
 

K4fxd

Well-Known Member
Joined
Apr 2, 2020
Threads
104
Messages
10,737
Reaction score
8,989
Location
NKY
First Name
Dan
Vehicle(s)
2017 gt, 2002 FXDWG, 2008 C6,
I'll bet there is a way to tune the rears so they correct the fronts even with no cat involved. I'll dig through PCMtec and see if there are any tables. Maybe @Rolls can add them if not defined yet.
 

engineermike

Well-Known Member
Joined
Jul 15, 2018
Threads
16
Messages
4,288
Reaction score
3,731
Location
La
Vehicle(s)
2018 GTPP A10
So the conclusion is: if your fuel trims are good and you haven't mucked with the MAF curve then you can sleep easy.
That is assuming the trims were tuned down to zero with a properly functioning ego system.

The holy grail would be to find out how to alter the downstream O2 sensor biasing system to apply 0 offset in all scenarios. Then we can leave FAOSC on and be "ready".
As with most things tune-related, it may be more complicated than that. In PCMTec search the parameter list for FAOS, fore aft, and outer loop. The number of parameters piles up pretty quickly.
 

Sponsored

engineermike

Well-Known Member
Joined
Jul 15, 2018
Threads
16
Messages
4,288
Reaction score
3,731
Location
La
Vehicle(s)
2018 GTPP A10
I also said on FI engines.
That's what I was talking about as well. Ford (GT500, Ecoboost), Whipple, Roush, all allow them to run full load/boost at 1.0 lambda. Don't assume that going 15% lean is instant death.

I've never seen that, unless it's going into cat protection
I've seen it first-hand in before/after testing on the same car. And cat protect does not affect fuel trims.

Your fine with FAOSC on/off with a NA engine + feline delete...
If you're not worried about the accuracy of your A/F ratio, then ok I guess so. If you want an accurate A/F ratio then you'll run into problems.
 

WildHorse

N/A or GO HOME
Joined
Jun 28, 2017
Threads
220
Messages
8,775
Reaction score
6,873
Location
Home World: CLASSIFIED
First Name
ⓇⒾⒸⓀⓎ ⓈⓅⒶⓃⒾⓈⒽ
Vehicle(s)
'17 S550
Vehicle Showcase
1
If you're not worried about the accuracy of your A/F ratio, then ok I guess so. If you want an accurate A/F ratio then you'll run into problems.
Dunno what to tell yah. Wait.. I do. run an 5 Gas Analyzer then get back to us.
 

engineermike

Well-Known Member
Joined
Jul 15, 2018
Threads
16
Messages
4,288
Reaction score
3,731
Location
La
Vehicle(s)
2018 GTPP A10
Dunno what to tell yah. Wait.. I do. run an 5 Gas Analyzer then get back to us.
There are 140 logging parameters in PCMTec related to FAOS and countless technical articles explaining why it's done and how it works. My logging and experience confirms. You're saying it isn't important and doesn't affect anything even though you admitted that the exhaust smells different with FAOSC on vs off, which can only mean the mixture is different. The burden of proof is on you.
 
Last edited:

Chrizzle

Member
Joined
Sep 26, 2018
Threads
1
Messages
10
Reaction score
9
Location
South Dakota
First Name
Chris
Vehicle(s)
71 Torino GT, 17 MKZ 3.0T, 2020 GT PP1
There are 140 logging parameters in PCMTec related to FAOS and countless technical articles explaining why it's done and how it works. My logging and experience confirms. You're saying it isn't important and doesn't affect anything even though you admitted that the exhaust smells different with FAOSC on vs off, which can only mean the mixture is different. The burden of proof is on you.
Is there any detriment with FAOSC turned off and cats removed, does anything else need to be done?
 

engineermike

Well-Known Member
Joined
Jul 15, 2018
Threads
16
Messages
4,288
Reaction score
3,731
Location
La
Vehicle(s)
2018 GTPP A10
Is there any detriment with FAOSC turned off and cats removed, does anything else need to be done?
With cats removed and FAOSC off, the remaining concerns are the obd diagnostics will not reach “ready” status and there is some potential for air charge blow-through. I have direct experience with this on a supercharged car but not NA. My guess is it wouldn’t be an issue NA.
 
Last edited:

Sponsored

K4fxd

Well-Known Member
Joined
Apr 2, 2020
Threads
104
Messages
10,737
Reaction score
8,989
Location
NKY
First Name
Dan
Vehicle(s)
2017 gt, 2002 FXDWG, 2008 C6,
I have direct experience with this on a supercharged cat but not NA. My guess is it wouldn’t be an issue NA.
And there are parameters to tune for blow through. Although I doubt any pro tuners are doing this.
 

WildHorse

N/A or GO HOME
Joined
Jun 28, 2017
Threads
220
Messages
8,775
Reaction score
6,873
Location
Home World: CLASSIFIED
First Name
ⓇⒾⒸⓀⓎ ⓈⓅⒶⓃⒾⓈⒽ
Vehicle(s)
'17 S550
Vehicle Showcase
1
There are 140 logging parameters in PCMTec related to FAOS and countless technical articles explaining why it's done and how it works. My logging and experience confirms. You're saying it isn't important and doesn't affect anything even though you admitted that the exhaust smells different with FAOSC on vs off, which can only mean the mixture is different. The burden of proof is on you.
yah, when it goes into CAT protection. It stinks. I also checked my plugs.. old school. nothing indicates it running lean. by old school : do a 1/4 mile hit. Shut off the car, let it coast to a stop. Check the plugs.

Everybody knows you need more then one verification source. The analyzer will leave no doubt about what's actually going on. Or install a 3rd wideband with a standalone.
 
OP
OP
5.0_Lojos

5.0_Lojos

Well-Known Member
Joined
Feb 17, 2023
Threads
9
Messages
226
Reaction score
139
Location
Miami FL
First Name
Carlos
Vehicle(s)
2016 Mustang GT Premium
All I have to say is (Holy Shit) there's a ton of info here to grasp, oh yeah and Thanks to all for the info...... I'll stick to bodybuilding/Nutrition. If you need help building your body let me know 😅💪😆

Adding resonators on Thursday and will try and drive the car more often and report back.
 

engineermike

Well-Known Member
Joined
Jul 15, 2018
Threads
16
Messages
4,288
Reaction score
3,731
Location
La
Vehicle(s)
2018 GTPP A10
yah, when it goes into CAT protection. It stinks. I also checked my plugs.. old school.
Sorry, turning on FAOSC and/or the CEL does not affect CAT protection enabling or the triggers.

nothing indicates it running lean. by old school : do a 1/4 mile hit. Shut off the car, let it coast to a stop. Check the plugs.
Done that enough "back in the day" to know that calibrated Widebands are much more accurate.

Everybody knows you need more then one verification source. The analyzer will leave no doubt about what's actually going on. Or install a 3rd wideband with a standalone.
The rear O2's are the verification, which is why FAOSC works so well. If you want to prove all major automakers wrong about FAOSC by installing a gas analyzer, be my guest.
 
OP
OP
5.0_Lojos

5.0_Lojos

Well-Known Member
Joined
Feb 17, 2023
Threads
9
Messages
226
Reaction score
139
Location
Miami FL
First Name
Carlos
Vehicle(s)
2016 Mustang GT Premium
Along the subject, my shop custom made the 3" Cat delete for my setup which I see it's customary in the "Cat delete" scene. My question is, should there be any modifications done additionally or a custom H pipe 3" to match? I currently have the Steeda H PIPE which is not 3" does this matter.

A customer at the time of install made a comment about my exhaust from factory headers to catback was a "Bottle Neck" setup?

any insight on this?
Sponsored

 
 




Top