Removing the ugly heavy catalytic converter on a 312R. - MVAgusta.net
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post #1 of 58 (permalink) Old 04-25-2009, 07:42 PM Thread Starter
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Removing the ugly heavy catalytic converter on a 312R.

Hi all.
I have done a search of our archives and have found a few interesting posts on catalytic converters. My 312 has it's catalytic converter welded to the headers. From a previous post I think that's an indication that it's a "euro 3" spec bike. I can source the headers, no problem, but here is the issue you may be able to help me with.
There is a sensor that bolts into the link pipe just beyond the catalytic converter. I've attached some pictures.

I unplugged the sensor from the wiring loom and turned the ignition on. No worries. I then start the bike, warmed it up and it runs fine.
What is the sensor called and what is it sensing?
The reason I ask is that I'm going to remove the catalytic converter and replace it with a titanium link pipe. The titanium link pipe does not have provision for the sensor unless I have it altered. It's a round hole trying to get into a square peg.
Thanks,
Dave.
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post #2 of 58 (permalink) Old 04-25-2009, 08:10 PM
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Dave,

That's an O2 sensor which feeds the ECU info to regulate the A/F ratio. I don't know if it's required in your upgraded situation but if so the "bung" is threaded with an 18 mm hole and is a standard fitting readily available to be welded onto your Ti link pipe. Small potatoes this one.

I got mine. Boy do I ever got mine.
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post #3 of 58 (permalink) Old 04-25-2009, 08:31 PM
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As Lee says it's a Lambda or O2 sensor, with the standard ECU it is needed (or at least a connector that offers a duplicate signal).

With the 'Race ECU' I believe it becomes redundant and may be able to be eliminated, however this is not a bad sensor to leave in (depending on the ECU programming), so if you can I'd suggest the replacement exhaust system also includes a Lambda probe hole.

Most bikes only utilise the Lambda probe below about 5000 rpm and at constant partial throttle settings (i.e. when cruising). At full throttle and when revving hard the systems will revert to a pure mapped ECU setting. I don't know exactly when the Lambda prope operates on the MV though.

Andrew...
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post #4 of 58 (permalink) Old 04-25-2009, 08:56 PM Thread Starter
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Thanks guys. I appreciate the info.
Dave.
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post #5 of 58 (permalink) Old 04-26-2009, 05:33 AM
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Of course, you know you can't just weld the steel bung to the titanium midpipe like you would to a steel midpipe.
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post #6 of 58 (permalink) Old 04-26-2009, 08:33 AM
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Sorry Caggie but oh yes you can. I have a guy who does my critical welding and he does it all the time with his Tig. He also works for Usair in the engine shop and does repair to Ti engine components.

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post #7 of 58 (permalink) Old 04-26-2009, 11:58 AM
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Uh, no you can't. When he is welding titanium, he uses more than just the argon from the torch.

Either he:

1) puts the piece in a sealed container so the complete atmosphere is argon, or
2) he has some sort of device rigged up that injects argon gas to the back of the area he is welding.

Feel free to correct me again if I'm wrong.

Do I sound smug? My wife says I sound smug. I don't mean to sound smug.

Last edited by CAG; 04-26-2009 at 12:39 PM.
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post #8 of 58 (permalink) Old 04-26-2009, 12:05 PM
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You can't just plug in a resistor to trick the ECU with flat lambda signal either (that's why the DynoJet o2 eliminator won't work on Euro 3 Ducati and MV among others, so you can't use the PCIII).

The ECU looks for a varying signal (which is what it sees with proper working o2 sensor) and triggers a fault/fail safe mode if it doesn't see that. There are o2 sensor simulators available from the hot-rod tuners that send a sine wave signal to the ECU. I bought one to test, but got a race ECU before I got around to it. About $50.

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post #9 of 58 (permalink) Old 04-26-2009, 01:48 PM
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I have removed the CAt from my 312, but I did it diferently.
Here is a description of the procedure:
http://mvagusta.net/forum/showthread.php?t=14673
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post #10 of 58 (permalink) Old 04-26-2009, 05:08 PM
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Quote:
Originally Posted by CAG View Post
Feel free to correct me again if I'm wrong.

Do I sound smug? My wife says I sound smug. I don't mean to sound smug.
My wife and daughter do that all the time....

And yes, Caggimundo, you do sound smug. I'd be hesitant to challenge the old troll. He seems to know what he's talking about when it comes to arcane stuff like this......

after all, how does one challenge a guy that plays the bag pipes?

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Last edited by Randarosa; 04-26-2009 at 06:44 PM.
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