B3 800 Stock Exhaust "Cat" removed. Now poor fuel economy. - MVAgusta.net
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post #1 of 18 (permalink) Old 06-03-2016, 05:25 AM Thread Starter
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Angry B3 800 Stock Exhaust "Cat" removed. Now poor fuel economy.

My dealership removed the stock catalyst converter from my stock exhaust system. My fuel consumption has gone up significantly. Before removal of the Cat I got 200km's on a tank of fuel, now it's dropped down to 175km per tank. 16.5 liter tank. According to the dealership it was not needed to flash ECU as it will automatically adjust the fuel richness to what it should be. This does not seem normal, is it?

And I was like braap until the warning lights came on...
- Brutale 800 EAS
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post #2 of 18 (permalink) Old 06-03-2016, 05:45 AM
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Removing anything from an exhaust system could warrant a tune, sometimes you're lucky but in general it's best to retune, not just flash the ECU. Did you just remove the cat or did you do the muffler box too ?

In most cases the ECU can only adapt to a small percentage variation when picked up by the Lambda sensor.

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post #3 of 18 (permalink) Old 06-03-2016, 06:14 AM Thread Starter
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I tend to agree with you on the tuning, and I did ask the "approved" mv agusta technician whether or not it is necessary to tune it in again. He said the electronics of the bike does it automatically. Just the cat was removed, not the muffler box. According to them, removing the muffler box will void warranty. How would I go about tuning it in again?

And I was like braap until the warning lights came on...
- Brutale 800 EAS
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post #4 of 18 (permalink) Old 06-03-2016, 06:37 AM
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How did they remove the cat, isn't it part of the headers ?

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post #5 of 18 (permalink) Old 06-03-2016, 07:35 AM Thread Starter
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They removed the triple pipes from the header, they then proceeded to cut open the where the cat lies, literally scraped and cleaned the cat out, then welding it close again. Here is a link from a guy that did it, it was exactly the same method used. Click on the link, then scroll down to the bottom of the page, there he give a description with pictures on how it's done. http://blog.daviddemartini.com/archives/5004

And I was like braap until the warning lights came on...
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post #6 of 18 (permalink) Old 06-03-2016, 12:04 PM
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Fuel consumption is irrelevant - does it sound any better?
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post #7 of 18 (permalink) Old 06-03-2016, 02:34 PM
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So, cutting open the exhaust and gutting the cat doesn't void the warranty, but removing the box would? Balderdash!

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post #8 of 18 (permalink) Old 06-04-2016, 12:54 AM
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What other things have they done? Service? Map update?

The whole Lambda story is misunderstood by most people. They the think it measures exactly how rich/lean the engine is running. It doesn't because it's a narrow band sensor. In theory it could measure but in practice it's actually a binary sensor. Rich or lean, high or low, 1 or 0. Look for a picture of a narrow band Lambda sensors range and you'll see. (There are wide band sensors but not used in the industry from what i know)

There is a whole lot more about ECU's and the way they adjust mixture. Not enough time to write about it. I've been experimenting with them by hooking them up to a computer. I could then see when the Lambda sensor had an effect and when not. That allowed me to sift through the true and false stories on the Internet.

There might be a way for the ECU to adjust the mixture when running idle for a few minutes. It's just theory but it could adjust the CO trim. If the Lambda would say it's running rich/lean for a long period of time one could say it's running rich/lean and the CO trim could automatically be adjusted until the sensor would shuffle between lean/rich.
If your sensor was knocked about it could give a false reading and made your bike run rich. (In theory)

You should as has been told hook it up to a dyno. It will probably run rich as you think. Then a dealership should be able to adjust CO trim. It will make the bike run richer/leaner across the entire rev range.

But there is a chance that something else is going on if they did other things to the bike.
Good luck.
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post #9 of 18 (permalink) Old 06-05-2016, 12:30 AM
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Your ECU must be the smartest one ever fitted to a production bike.
I'd be looking for a new and not lazy technician.

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post #10 of 18 (permalink) Old 06-05-2016, 10:22 AM Thread Starter
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Quote:
Originally Posted by Jono View Post
Fuel consumption is irrelevant - does it sound any better?
Yes it sounds better, but I'd say it is not worth this trouble at all. And btw yes fuel consumption is relevant especially when it falls with 25km less on a tank.

And I was like braap until the warning lights came on...
- Brutale 800 EAS
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