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Author: Subject: Lambda HEATER control necessary?
ElmrPhD

posted on 14/3/16 at 08:44 AM Reply With Quote
Lambda HEATER control necessary?

Hi,

I'm baffled.
Do aftermarket ECUs (Like my Omex 710) have a way to control the heater circuit of lambda sensors, somehow (that I'm not seeing) or do they just expect you to send 12V to the heater element (via relay) and let it cook the whole time the ignition is on? The Omex manual makes it look like the latter, whereas my Honda S2000/F20C manual shows the heater circuit to be controlled by the ECU, which makes sense to me. It seems like once everything is good-and-hot, you'd want to stop pumping heat into the lambda sensor, no?

Or does this depend on which Lambda sensor used? I.e. are some sensors designed to be constantly heated by 12V, but some (like the Honda's) intended to be shut down after the exhaust has gotten them hot enough?

Have asked Omex so many questions that I fear I'm gonna exceed my questions quotient.

Thanks!

Steve, in the NLs

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r1_pete

posted on 14/3/16 at 09:40 AM Reply With Quote
It is better for the sensor if it is only heated when the engine is running.

A convenient way to achieve that is to power the heater circuit from the fuel pump relay.

Once the engine is running the lambda tip temperature will be way above what the heater can get it to so leaving power on to the heater is not an issue.

[Edited on 14/3/16 by r1_pete]

[Edited on 14/3/16 by r1_pete]

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ElmrPhD

posted on 14/3/16 at 10:04 AM Reply With Quote
Well, I KNEW that...(the first part). Guess I wasn't clear.

OH, I did NOT know that (the last part). This helps alot!

This is a recurring theme in my build: my confusion and ignorance is usually solved by accepting that the sophistication of the original Honda system is just too much to mimic...

THANKS!!!

quote:
Originally posted by r1_pete
It is better for the sensor if it is only heated when the engine is running.

A convenient way to achieve that is to power the heater circuit from the fuel pump relay.

Once the engine is running the lambda tip temperature will be way above what the heater can get it to so leaving power on to the heater is not an issue.

[Edited on 14/3/16 by r1_pete]

[Edited on 14/3/16 by r1_pete]

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britishtrident

posted on 14/3/16 at 10:09 AM Reply With Quote
One thing to keep in mind is the heater takes anywhere between 0.8 and 3 amps depending on type so wire and fuse accordingly. These sensor heater elements are as tough as old boots any problems tend to be in the wiring which is exposed to vibration corrosion and heat.
I would use one of those relays with a built in blade fuse holder which are very cheap on eBay.
None of the Lambda sensor I have encountered shutdown on warm up in fact this would cause problems because the sensor would cool down on over-run when fuel is shut off.
One or two models have high output sensor heasters that are however pulse width modulated but I have never encountered one.





[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]

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britishtrident

posted on 14/3/16 at 10:14 AM Reply With Quote
The Honda PCM as on all modern tintop units will monitor the current flow to the heater so it can flag up a fault P-code if it fails. This is an OBD2 requirement because it effects emissions.

quote:
Originally posted by ElmrPhD
Well, I KNEW that...(the first part). Guess I wasn't clear.

OH, I did NOT know that (the last part). This helps alot!

This is a recurring theme in my build: my confusion and ignorance is usually solved by accepting that the sophistication of the original Honda system is just too much to mimic...

THANKS!!!

quote:
Originally posted by r1_pete
It is better for the sensor if it is only heated when the engine is running.

A convenient way to achieve that is to power the heater circuit from the fuel pump relay.

Once the engine is running the lambda tip temperature will be way above what the heater can get it to so leaving power on to the heater is not an issue.

[Edited on 14/3/16 by r1_pete]

[Edited on 14/3/16 by r1_pete]







[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]

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ElmrPhD

posted on 14/3/16 at 11:04 AM Reply With Quote
And my education continues...

THANK YOU!

This stuff helps more than you know.

I was already planning on using a normal (30 Amp) relay for that lambda heater circuit. Sharing that relay's output with the injection pump (7 amps, I think). Any problem with that?

Thanks, again.

Steve, in the NLs


quote:
Originally posted by britishtrident
One thing to keep in mind is the heater takes anywhere between 0.8 and 3 amps depending on type so wire and fuse accordingly. These sensor heater elements are as tough as old boots any problems tend to be in the wiring which is exposed to vibration corrosion and heat.
I would use one of those relays with a built in blade fuse holder which are very cheap on eBay.
None of the Lambda sensor I have encountered shutdown on warm up in fact this would cause problems because the sensor would cool down on over-run when fuel is shut off.
One or two models have high output sensor heasters that are however pulse width modulated but I have never encountered one.

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ElmrPhD

posted on 14/3/16 at 11:10 AM Reply With Quote
Very interesting (to me).
So, when Honda call it the "...oxygen sensor heater control", they really mean functionality monitor. Their manual's wording made me think that the pcm/ecu/ecm/whatever was turning the heater on and off with some strategy. Oh, well...
Thanks, again!
Steve, in the NLs


quote:
Originally posted by britishtrident
The Honda PCM as on all modern tintop units will monitor the current flow to the heater so it can flag up a fault P-code if it fails. This is an OBD2 requirement because it effects emissions.

quote:
Originally posted by ElmrPhD
Well, I KNEW that...(the first part). Guess I wasn't clear.

OH, I did NOT know that (the last part). This helps alot!

This is a recurring theme in my build: my confusion and ignorance is usually solved by accepting that the sophistication of the original Honda system is just too much to mimic...

THANKS!!!

quote:
Originally posted by r1_pete
It is better for the sensor if it is only heated when the engine is running.

A convenient way to achieve that is to power the heater circuit from the fuel pump relay.

Once the engine is running the lambda tip temperature will be way above what the heater can get it to so leaving power on to the heater is not an issue.

[Edited on 14/3/16 by r1_pete]

[Edited on 14/3/16 by r1_pete]



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big_wasa

posted on 14/3/16 at 11:49 AM Reply With Quote
Ford also switch the heater off.
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wylliezx9r

posted on 14/3/16 at 11:55 AM Reply With Quote
Do you need emissions control on your car ? If not ditch the lambda it's not required, I didn't use it on my build (on the advice of Omex).





I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
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ElmrPhD

posted on 14/3/16 at 12:38 PM Reply With Quote
Thought about that way out and inquired over the weekend. Verdict is, yeah, I have to pass Dutch emissions tests requiring a functioning lambda sensor.

Hence, bothering you guys with this subject...

Thanks, anyway,

Steve, in the NLs

quote:
Originally posted by wylliezx9r
Do you need emissions control on your car ? If not ditch the lambda it's not required, I didn't use it on my build (on the advice of Omex).

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MikeRJ

posted on 14/3/16 at 12:43 PM Reply With Quote
The heater in narrowband lambda sensors is self regulating, the resistance increases as they get hotter. This means the ECU doesn't control anything as such, it simply monitors the current to ensure it's within an acceptable range.

Wideband sensors are quite different, they need to have a proper temperature control loop and the sensor internal resistance is used to measure temperature.

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coyoteboy

posted on 14/3/16 at 12:52 PM Reply With Quote
As per MikeRJ - wideband controllers have their heater control built in and very tightly controlled. Narrowband is much more crude and just used to get the thing up to temperature faster and hold it there during over-run, light cruise events where it may cool enough to become less effective.





Report your local potholes, it actually works!

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obfripper

posted on 14/3/16 at 07:37 PM Reply With Quote
With the original s2000 pcm software, the lambda heater operated continually from start and while the engine was running.
Because of thermal shock issues due to bad sensor location, honda modified the pcm software, so the lambda heater is pulsed during warmup to stop cracking/failure of the sensor ceramic tip.

Honda service bulletin for lambda sensor failures

So long as you have the sensor at least 10 above horizontal in your manifold this will not be an issue, and you can power the sensor via the fuel pump relay with no issues.

Sensor positioning

Dave

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BaileyPerformance

posted on 14/3/16 at 08:19 PM Reply With Quote
Unless you are running a CAT no need for a lambda.

Factory narrow bands are next to useless for tuning, if you have the money fit an aftermarket wideband such as an innovate LC1

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ElmrPhD

posted on 14/3/16 at 10:19 PM Reply With Quote
Yeah, sadly, I gotta have a cat and a lambda therein....

Thanks for all the great info' guys - really helps a lot!

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Rob Allison

posted on 15/3/16 at 02:16 AM Reply With Quote
Caution running to many things off the ecu fuel pump output, dont overload it and keep everthing via relays all individually fused.
You could also just run the heater off an ignition live via a realy.

You can get away without a lambda sensor even with the cat. but its the fast idle test that really needs it to ensure your under the 0.3% CO (think thats correct).






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ElmrPhD

posted on 15/3/16 at 06:48 AM Reply With Quote
Thanks Rob,

But I never planned on using the ecu fuel pump output for anything except triggering the 30 amp relay that should easily handle both the lambda sensor and the fuel pump.

Don't worry, everything on my car is, indeed fused. I think everything except some LED lights are powered via relays, as well.

Thanks for the advice.

Steve, in the NLs


quote:
Originally posted by Rob Allison
Caution running to many things off the ecu fuel pump output, dont overload it and keep everthing via relays all individually fused.
You could also just run the heater off an ignition live via a realy.

You can get away without a lambda sensor even with the cat. but its the fast idle test that really needs it to ensure your under the 0.3% CO (think thats correct).

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