TOPIC: 2006 Frontier 4.0 4x4 has been grooved!

Vernon wrote: The EFIE was on the front sensors. Not the rear. The reason the cat efficiency codes weren’t there I suspect is because it wasn’t running as rich with the EFIE connected. The EFIE affecting the front sensors isn’t making the computer think the cats are working/not working. These are cheaper aftermarket cats so they aren’t as powerful as the factory ones so higher temperature isn’t going to make them burn everything

You'll have to forgive me Vernon - I'm having a hard time keeping the story straight here because you're making changes faster than I can think them through for you.
I do recall you saying you bought "high flow" converters - If those catalytic converters have the proper catalysts (chemicals that encourage the desired chemical reaction) in them, any unburned Hydrogen from the hydrocarbon chains (fuel) will oxidize (burn) causing heat in the converter...if all the fuel is burning in the cylinders, there's nothing to react with the catalyst, and no heat will produced there, so you could get temperature errors on the downstream sensors.
I suspect you had the EFIE (somehow I was mistaken thinking you had it on the rear sensors...again, my apologies) tweaked just right, and the rear sensors weren't seeing temperatures they expected, so Ron's advice to insulate is 100% on target.

Yeah I called him and talked about the insulation idea. I had no idea that the rear sensors are also used to determine fuel mixture to! What a big screwball mess emissions are!

Well, big oil wants your money just as much as the big auto manufacturers. You're here (at least partially) to spit in both their eyes, I suspect.

Vernon, You might consider insulating the exhaust pipe from the manifolds, wrapping all the way to the downstream O2 sensor(s). If I read this thread right, the EFIE was reducing fuel, making the downstream O2 read out of range. Less hydrocarbons into a cat ought to make it run cooler, or be slow to "light off". That insulation that Ron called attention to and I used is pretty inexpensive.

Perhaps wrap the cat's as well as all pipe all the way to the downstream O2(s).

Just an idea...

Tracy G

Tracy Gallaway wrote: If I read this thread right, the EFIE was reducing fuel, making the downstream O2 read out of range. Less hydrocarbons into a cat ought to make it run cooler, or be slow to "light off".
Tracy G

That's my read on things too Tracy...and with 2 exhaust pipes, there's twice as much metal surface area to dissipate the heat of combustion leading up to the Converter...PLUS with a VERY efficient burn, there's little left over for the converter to sink it's teeth into, so the downstream o2s would be feeling any chill and telling the injectors to throw more logs on the fire.

Just a thought I had. Would it be possible to install the EFIE on the rear o2 sensors to make the computer think the cats are hotter than they are? Assuming the voltage goes up with heat. If it doesn’t, it probably won’t work

Ron, refresh my memory, did you say to put the steel wool on the front, rear, or both sensor spacers? I put some in the front and ordered spacers for the rear. But it now seems to run oddly. On cold startup, the rpms hunt a little bit and occasionally hesitates some. Idles fine when warm but it seems to have lost a little bit of low rev torque

The steel wool goes in between two spacers on the same sensor. Only on the REAR sensors!
The ECU monitors the SPEED of the response on the upstream, as the injector pulses alternate between wide and narrow pulses. When you added the steel wool there, you slowed the response time.

R.

Gotcha. Yeah it did have codes for slow response right at first but later just for cat efficiency

So Greg, and Vernon, does this vehicle have 2 exhaust pipes with a cat on each, or is it 2 pipes into one cat? I can imagine severa possible exhaust layouts.

I'm still learning, ya know? It seems to me, (I'm still a bit fuzzy here) there's two things going on w/ converters. A chemical reaction as the cat turns emissions into less toxic things, AND the resulting heat as byproduct of that catalysis.

Emissions result from unburned and partially burnt fuel. These HC's and CO are the feedstock "food" for the catalyitic converter. Less "food" equals less heat byproduct. And, cat's need to reach an operating temp. to work well. Again, the converter needs emissions input to heat up, and work well, and give output readings on the downstream O2(s) the ECU expects to see.

So--- if we do our mods in order to burn the fuel more completely IN the engine, then less "food" goes into the cat. The cat, logic says, could both run cooler, or take longer to heat up, causing the downstream O2 to go "out of range" more.

So, then, insulating the exhaust pipes (cat too?) can help keep the exhaust stream warmer and help that cat get and stay warmer more of the time.

So by wrapping the pipes and cat, while we aren't with this mod directly effecting the exhaust streams chemistry, we would help that cat (upstream or downstream) reach op. temp sooner, and maybe work more efficiently more of the time.

and therefore, help a downstream O2 sensor give readings more "in range" for the ECU.

Eh??

Tracy G

Yeah its a V engine. It has 2 upstream sensors and 2 downstream. It originally had 4 cats, but since the secondary cats were after the sensor and not being monitored, I removed them

Tracy Gallaway wrote: It seems to me, (I'm still a bit fuzzy here) there's two things going on w/ converters. A chemical reaction as the cat turns emissions into less toxic things, AND the resulting heat as byproduct of that catalysis.

Emissions result from unburned and partially burnt fuel. These HC's and CO are the feedstock "food" for the catalyitic converter. Less "food" equals less heat byproduct. And, cat's need to reach an operating temp. to work well. Again, the converter needs emissions input to heat up, and work well, and give output readings on the downstream O2(s) the ECU expects to see.

So--- if we do our mods in order to burn the fuel more completely IN the engine, then less "food" goes into the cat. The cat, logic says, could both run cooler, or take longer to heat up, causing the downstream O2 to go "out of range" more.

So, then, insulating the exhaust pipes (cat too?) can help keep the exhaust stream warmer and help that cat get and stay warmer more of the time.

So by wrapping the pipes and cat, while we aren't with this mod directly effecting the exhaust streams chemistry, we would help that cat (upstream or downstream) reach op. temp sooner, and maybe work more efficiently more of the time.

and therefore, help a downstream O2 sensor give readings more "in range" for the ECU.

Eh??

Tracy G

Thank you for paraphrasing, and yes, your interpretation is absolutely correct. Bullseye, bingo, that's right on the money, Tracy!

The video I linked to in my conversation/debate with Neil a page or two (or three!) back in this thread shows the heat output from a catalytic converter when it's fed with HHO...those components, (in our case unburned) HYDROcarbons (and the Oxygen they need to combust) hit the platinum and whatnot in the converter and turn into waste heat that's (partially) monitored by the rear o2 sensor(s) to balance the chemical reaction in the cylinder. (THIS IS WHY IGNITION IMPROVEMENTS HELP HORSEPOWER/TORQUE - you're getting power from more of the fuel in the air-fuel charge burning completely)
BUT If the temp coming out of the cats is low because we've tweaked the combustion event on the fire and air-fuel side, and the oxygen content is high (as it should be in a grooved engine), the computer might think it's not pumping enough fuel...not stoking the fires (in the cylinders) enough, in other words, based on the rear o2 sensor, the one nobody really thinks is important.
Clearly we have to do whatever it takes to keep that rear sensor happy too, or the computer won't trim back as much as it can...or stay as trimmed as it can year-round.
I say Insulate from downstream of the converter to just past the downstream o2 sensor(s)...especially important if there's a distance between them, and even more especially if you've opened up your exhaust pipe diameter (think heat density). Heck, I'd even wrap my exhaust manifolds to help push that heat to the back end past the converters and sensors from where it originates and is probably hottest.