Cat overtemp protection

[richardpalinkas]

What do most people set the cat overtemp stratedy at? Turn off or leave on as factory?

[FencePost]

It's best to leave the cat over temp protection ON. It models the heat flux through the exhaust system and will protect hardware like exhaust valves, turbo and the catalytic converter. If the engine has been working hard for some time then load limiting will kick in and protect the hardware. You will rarely see this kick in on public roads unless you're racing up Mt Hotham with a caravan on the back.

Don't be like most brotuners and turn it off

Edited March 30, 2018 by FencePost

[Andrew]

This was useful mate - thanks! It was one of the strange things in my tune that I thought was sus (thought my car was stock but turns out it wasn't).

Needless to say I've turned it back on.

[Roland@pcmtec]

You will find a lot of "strange" things in some tunes, eg turning off the torque module switch, disabling all of the knock and overtemp protection etc. No closed loop boost control.

All of these items can be made to work with a high power tune and they give you a safety margin if you have an overboost, overtemp or bad knock condition saving your motor. If the max commanded knock retard kicks in you will absolutely feel it and know something is wrong.

[BeerTurbo]

on a side note, i'm ruining a Innovative mtxl with the bosh 4.9 wide-band sensor, just before the cat and the sensor is apparently dead. 

 

looking up the tune in my car cat overtemp is still on and is set to std 873 deg C.

Looks like the 4.9 sensor max temp is 930 deg C

 

curious to know how often they would actually get to that temperature.

Have seen a few people place copper sheet around the 02 to sheild the body from heat, perhaps this is where the fault comes from...even so it says the body is raited to 500deg C

 

In one of the forums a poster said they dont like going from fuel to no fuel conditions.

 

perhaps a heat sheild and a little tickle to the fuel shutoffs are in order?

[Roland@pcmtec]

They are usually killed by water. If you turn the controller on (the heater circuit inside of it is the issue) when there is still moisture in the exhaust and it hits the tip it will kill it very quickly. The internal heating circuit will get the sensor to about 500c from memory, 500c + water = cracks.

The best way to run the wideband is to ensure it is not powered on until the engine is no longer spitting water out the exhaust. Mounting the sensor at 10-2 o clock will assist the moisture avoiding it, but it can still happen. Some controllers have excellent heating circuits with timers etc, you could also log the heater output from the actual PCM itself and use this as a gauge when the PCM turns the narrowband sensor on.

Heat will kill them also, but that is more a long term thing.

[BeerTurbo]

cheers Rolland.

The unit was new when i bought it, and had it roughly in the car 6 months before it played up. this was about 3-4 months ago now as i've been ignoring i due to having a kid. But its come time for a general service so i may as well fit a new sensor.

 

Its mounted facing 2 oclockish, so its fairly upward.

Its connected to the cars 12v - i did wonder if turning the key to ignition annoys it, as it does turn on for a sec, then off while cranking then back on again. Perhaps i might put a switch inline and just turn it on when i want to watch it, or only when cars at temp like you say, no longer spitting water. 

 

 

 

 

[Roland@pcmtec]

Some of the big workshops I know change their sensors every fortnight. Its cheap if you are using it daily.

[Roland@pcmtec]

4 minutes ago, BeerTurbo said:

Its connected to the cars 12v - i did wonder if turning the key to ignition annoys it, as it does turn on for a sec, then off while cranking then back on again. Perhaps i might put a switch inline and just turn it on when i want to watch it, or only when cars at temp like you say, no longer spitting water. 

An idea, put a relay off the narrowband heater circuit, then wire the power through this. The heater is PWMd but the relay should smooth that out and only trigger once its at full power.

[BeerTurbo]

6 minutes ago, Roland@pcmtec said:

An idea, put a relay off the narrowband heater circuit, then wire the power through this. The heater is PWMd but the relay should smooth that out and only trigger once its at full power.

you have peaked my interest.

Does the ecm 1) only run this with engine running 2) have a delayed start feature for moisture/whatever reason ?

[Roland@pcmtec]

1 hour ago, BeerTurbo said:

you have peaked my interest.

Does the ecm 1) only run this with engine running 2) have a delayed start feature for moisture/whatever reason ?

It estimates the exhaust/catalytic converter temperature and turns it on at 550°F I believe. It is configurable and uses PWM to control the heater circuit.

[BeerTurbo]

My second 02 is off and disabled, using details from another thread.

as im not using that plug for anything, does it still fire the pwm controlled heater circuit? as it may be a nicer way to get my wide-band ON

I guess i could do some testing.

[Roland@pcmtec]

3 minutes ago, BeerTurbo said:

My second 02 is off and disabled, using details from another thread.

as im not using that plug for anything, does it still fire the pwm controlled heater circuit? as it may be a nicer way to get my wide-band ON

I guess i could do some testing.

Not sure if you can turn off the trimming logic and still have the heater on. I think as soon as it detects a failure it turns it off. I don't see why you couldn't splice the primary narrowband though.

[Puffwagon]

The way I avoid cold shocking the wb sensor is to not let the sensor heater warm up before I start it. Just get in, let the fuel pump prime for a second and hit the starter.

I'm pretty sure I read that in a wb instructional manual.

[BeerTurbo]

15 hours ago, Puffwagon said:

The way I avoid cold shocking the wb sensor is to not let the sensor heater warm up before I start it. Just get in, let the fuel pump prime for a second and hit the starter.

I'm pretty sure I read that in a wb instructional manual.

just having a flick thro the manual now. two points caught my eye

 

* i think i used a shorter bung, may double check.

A 1” bung (provided in the kit) will best protect the sensor. When fully threaded, the sensor’s tip will sit flush with the inside of the exhaust piping, this does not adversely effect the readings. 

 

* as puff said :

Do not pre-warm the sensor before starting the engine, start the engine as you normal would. Allowing the sensor to pre-warm before starting the engine will increase the possibility of damaging the sensor from shock-cooling.

-

Im pretty sure having the wide-band controlled from the factory ford o2 will remove any possible shock loading