Fuel Build-up in Catalytic Converter

[Havix00]

I wanted to ask how real of an issue is this for our trucks. I've heard of catalytic converters building up thin films of unused fuel over time, then slowly overheating, eventually combusting when enough has accumulated, or blocking exhaust back up into the engine.

I bring this up because some of us use tuners to add +% fuel to our WOT setting. I'm curious how real this situation could be. I don't have any crazy mods, but I do increase my WOT fuel % by 3/4/5. Wanted to ask if anyone else heard anything about this.

 

[Kelli25]

Im about to have my truck tuned on a dyno because i feel like its been running rich with my tune... interesting timing on seeing this post..[gulp]

 

[Talon_66]

I'm running pig rich.
I'm running catless but I can feel/hear popping in my exhaust from unspent fuel igniting after the exhaust

 

[Jerseymike]

I wanted to ask how real of an issue is this for our trucks. I've heard of catalytic converters building up thin films of unused fuel over time, then slowly overheating, eventually combusting when enough has accumulated, or blocking exhaust back up into the engine.

I bring this up because some of us use tuners to add +% fuel to our WOT setting. I'm curious how real this situation could be. I don't have any crazy mods, but I do increase my WOT fuel % by 3/4/5. Wanted to ask if anyone else heard anything about this.

Why are you adding fuel? The DS tune is already rich. By adding fuel you are going to lose power.

 

[Jerseymike]

I data logged the stock tune, DS tune and HF tune for A/F ratio. The stock tune was pig rich at 10, the DS tune was better at 11.5 and HF came in at 12.2(WOT). Most of the fastest N/A trucks are running around 12.6. More(fuel) is not always better. I pulled a little fuel from my HF tune and it was screaming until I blew the trans out. Also, no more black soot on my exhaust tips.

Make sure the dyno tuner isnt using a tailpipe sniffer for AF ratio if you still have cats on your truck.

 

[Havix00]

I data logged the stock tune, DS tune and HF tune for A/F ratio. The stock tune was pig rich at 10, the DS tune was better at 11.5 and HF came in at 12.2(WOT). Most of the fastest N/A trucks are running around 12.6. More(fuel) is not always better. I pulled a little fuel from my HF tune and it was screaming until I blew the trans out.

Hmm good tip. I didn't think that DS already added some fuel. I'll back mine off tomorrow and try that out. I'm just cautious about the opposite problem of running too lean and unnecessarily heating the chambers due to extra air.

 

[BlownGP]

Hmm good tip. I didn't think that DS already added some fuel. I'll back mine off tomorrow and try that out. I'm just cautious about the opposite problem of running too lean and unnecessarily heating the chambers due to extra air.

Well, if you start getting knock. Then you know you have gone to lean.

 

[Havix00]

Instead of leaving WOT fuel at 0/0/0, could one advance the WOT spark a degree or two, with +% 5/5/5? Or will that burn the same amount of fuel, just at a faster timing, leaving them at square one? (Essentially same amount of wasted fuel)

 

[TylerB]

Lean is mean!
FWIW, I run about 12.6-12.9 at WOT.


I suggest getting a wideband to tune a little more precisely instead of trying to do it by feel.

 

[Kelli25]

I data logged the stock tune, DS tune and HF tune for A/F ratio. The stock tune was pig rich at 10, the DS tune was better at 11.5 and HF came in at 12.2(WOT). Most of the fastest N/A trucks are running around 12.6. More(fuel) is not always better. I pulled a little fuel from my HF tune and it was screaming until I blew the trans out. Also, no more black soot on my exhaust tips.

Make sure the dyno tuner isnt using a tailpipe sniffer for AF ratio if you still have cats on your truck.

Thanks for the heads up. I will be there watching and doing my best to learn something. How should the tuner be logging the AF ratio if not by that? Somewhere in front of the cats? Is that where a wideband goes? Are those universal for the most part, or will i need to look into bringing my own when I take it in?

Sorry for the thread jack OP. Just tryin to learn somethin here. You definitely brought up a good subject it seems.

 

[TylerB]

Yes, ideally you want the wideband before the cats in its own ****, but with the stock configuration of cats your space is very limited. If you tried removing one of the stock pre-cat 02s to plug the wideband then it's going throw off how computer reads and adjust the air/fuel mixture. If you have longtubes already that's all a moot point as you would have plenty of space for a wideband ****.

Some shops will have a wideband on hand to use. You can also log with it downstream of the cats, but it can read up to a full point or more leaner because of them(not the most accurate).

 

[Kelli25]

Yes, ideally you want the wideband before the cats in its own ****, but with the stock configuration of cats your space is very limited. If you tried removing one of the stock pre-cat 02s to plug the wideband then it's going throw off how computer reads and adjust the air/fuel mixture. If you have longtubes already that's all a moot point as you would have plenty of space for a wideband ****.

Some shops will have a wideband on hand to use. You can also log with it downstream of the cats, but it can read up to a full point or more leaner because of them(not the most accurate).

Thanks man, Im calling the tuner to see if he has a wideband at the shop. I am running the LTs with the ''high flow'' cats currently, so as you said, i definitely have the room. Im wondering though, isn't part of the hemifever tune disabling those O2 sensors? If so, then i could just use the spot for tuning with the wideband and then reinstall after right? I could be way off there...

Again, sorry to be jacking this thread OP. Perhaps I should begin a thread with this subject in mind. I don't want to be rude here.

 

[TylerB]

Hemifever disables the post-cat O2 sensors, the pre-cat sensors(what I was referring to) are what the engine uses to determine proper air/fuel, so that's not what you want to do. You need a **** welded in before the cats solely for the wideband, you can then plug it after your tuning is done.

This is what you need.
http://www.ebay.com/itm/Stainless-S...Parts_Accessories&hash=item2ed187a908&vxp=mtr

 

[Kelli25]

Hemifever disables the post-cat O2 sensors, the pre-cat sensors(what I was referring to) are what the engine uses to determine proper air/fuel, so that's not what you want to do. You need a **** welded in before the cats solely for the wideband, you can then plug it after your tuning is done.

This is what you need.
Stainless Steel O2 Sensor **** and Plug Kit 02 Sensor 18 x 1 5 **** with Sholder | eBay

Ordered up. Thanks for the help dude.

 

[BlownGP]

Ordered up. Thanks for the help dude.

Make sure he welds that **** atleast at 15* angle or more.

If there's any moisture on sensor it will run off.
I run a AEM WB in my GTP and love it.

 

[Kelli25]

Make sure he welds that **** atleast at 15* angle or more.

If there's any moisture on sensor it will run off.
I run a AEM WB in my GTP and love it.

Thanks man. Is that the AEM Uego? Looks nice for sure.

As far as the angle goes... What is that in relationship to? The pipe is round, so I'm confused as to how i get to a 15 degree angle.. Im missing something i think..

 

[TylerB]

Just think about it like putting it between 10 and 2 on a clock.

 

[LoneStarHemi]

Tuner capabilities

Lean is mean, creates a hot combustion and heat = power. Until you go too far, lol. Interesting info on the AF ratio’s of the canned tunes so thank you for posting that Jerseymike. More questions about the available tuners now though. So with the DS tuner you can +/- the WOT fuel and also +/- the timing table? I guess that’s the whole table and not specific cells? Also you can datalog including knock counts and knock retard with the DS?
And to the OP, that minivan has to have other issues to go up in flames like that. Most tuning for factory PCM’s (IOW not a F.A.S.T. system or other) only affects WOT fuel. At part throttle the PCM always targets a stoichiometric 14.7 A/F ratio.

 

[BlownGP]

Thanks man. Is that the AEM Uego? Looks nice for sure.

As far as the angle goes... What is that in relationship to? The pipe is round, so I'm confused as to how i get to a 15 degree angle.. Im missing something i think..

Just think about it like putting it between 10 and 2 on a clock.

Thanks, yes thats the Uego

Yeah, what tyler said.. Mines barley at 10 o'clock since there's not much room under my car.
You do want sensor as close to the collector as possible for more accurate results.

 

[BlownGP]

Lean is mean, creates a hot combustion and heat = power. Until you go too far, lol. Interesting info on the AF ratio’s of the canned tunes so thank you for posting that Jerseymike. More questions about the available tuners now though. So with the DS tuner you can +/- the WOT fuel and also +/- the timing table? I guess that’s the whole table and not specific cells? Also you can datalog including knock counts and knock retard with the DS?
And to the OP, that minivan has to have other issues to go up in flames like that. Most tuning for factory PCM’s (IOW not a F.A.S.T. system or other) only affects WOT fuel. At part throttle the PCM always targets a stoichiometric 14.7 A/F ratio.

Yes it's only certain tables. It's not like HP tuners where you can adjust every cell block in the LTFTs and STFTs.

Yes the DS can data log ST and LT knock along with the usual parameters