Catless and the imfamous CEL

[ZXMustang]

Right here, officer. This is the one you are looking for.

Jesus Christ, who is posting this shit nowadays...

lol

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[WildHorse]

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]

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]

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]

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.

 

[engineermike]

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]

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]

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.

 

[Chrizzle]

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]

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.

 

[K4fxd]

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]

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.

 

[5.0_Lojos]

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]

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.

 

[5.0_Lojos]

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?

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