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Discussion Starter #1
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?
 

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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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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?
 

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How did they remove the cat, isn't it part of the headers ?
 

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Discussion Starter #5
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
 

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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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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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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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Discussion Starter #10
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.
 

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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.
Thank you, You are basically confirming what I read up on and the research I have done so far. One would expect your dealership's technicians to be trained in this field. This is South-Africa for you! Nothing else was done except the removal of the cat. I'm having to take it in soon for it's 18000km service. In fact I'll go in to them tomorrow for this issue. Thank you for your insight and advice!
 

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Fuel consumption is completely relevant as it is indicative of how lean or rich the engine is running. Over-rich, or over-lean can cause their own brand of problems from fouled spark plugs and valve seats to overheating.

Get the bike's ECU tuned to the current exhaust configuration.
 

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Discussion Starter #13
So, cutting open the exhaust and gutting the cat doesn't void the warranty, but removing the box would? Balderdash!
Yes that is according to the dealership whom is a registered MV Agusta Dealership. In South-Africa we do not have to have cats. Thus removing it is legal and falls under warranty.
 

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^^^My general response to that would be skeptical at minimum.
 

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Discussion Starter #15
Fuel consumption is completely relevant as it is indicative of how lean or rich the engine is running. Over-rich, or over-lean can cause their own brand of problems from fouled spark plugs and valve seats to overheating.

Get the bike's ECU tuned to the current exhaust configuration.
I completely agree with you. Thank you I will have to go do this asap! They will have to pay for this as it was done for "free" to say sorry for all the hassles I have had on this piece of @#*&$.
 

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My 2c worth,
have seen this done on other bikes and the usual method is to replace the cat with a piece of pipe the same diameter as the tube that preceded it.

The method used on your bike has radically changed the resonant properties of the exhaust which depending on your style of riding, most used rev range & due to some reversion effect

you're probably unconsciously using more throttle in that rev band because the exhaust is now reducing power therefore more consumption.

Why remove it in the 1st place unless they have a habit of collapsing like the first gen 675 Triumphs or you still have leaded fuel in your country?

Has anyone done a before and after dyno run with that style of cat removal, if you want a better/louder exhaust note get a slip on.
 

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Discussion Starter #17
My 2c worth,
have seen this done on other bikes and the usual method is to replace the cat with a piece of pipe the same diameter as the tube that preceded it.

The method used on your bike has radically changed the resonant properties of the exhaust which depending on your style of riding, most used rev range & due to some reversion effect

you're probably unconsciously using more throttle in that rev band because the exhaust is now reducing power therefore more consumption.

Why remove it in the 1st place unless they have a habit of collapsing like the first gen 675 Triumphs or you still have leaded fuel in your country?

Has anyone done a before and after dyno run with that style of cat removal, if you want a better/louder exhaust note get a slip on.
Well in all honesty, yes the bike does sound a little better, therefore I will sometimes be heavier on the throttle. I mean let's be honest, we love that purr of the engine. But I do not ride like that all the time. We have Unleaded 95 in our country, and no, no dyno befor or after was done on the bike, that is why I am posting this, to hear the opinions of those that know more than what I do. Should they have done a dyno tune after they took the cat out, The Answer so far is yes, they should. Thank you, I do appreciate your 2cents input. Every bit of knowledge helps me.
 

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If you remove the cat that will change the speed at which the exhaust gas goes past the lambda sensor and I guess possibly the temperature. That will be relayed back to the ecu. What the ecu will do with that information I've no idea. I wish I knew more about stuff. Still if it sounds better.....
 
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