Brutale Backfire!? - MVAgusta.net
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post #1 of 18 (permalink) Old 08-01-2010, 07:51 PM Thread Starter
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Brutale Backfire!?

So I finally got around to installing the Arrow eprom I picked up last year along with a new BMC air filter. Now, I had already been running with an Arrow cat-eliminator midpipe, stock headers, stock cans, stock ecu and stock air filter. Ran well enough, with a couple minor issues. On-off throttle was a bit harsh, and it had a tendency to surge at low rpms (parking lot speeds).

Now, with the new eprom and filter, the idle is rock solid stable, throttle response is smoother and more precise, on-off transition is a little smoother, and the surging has nearly vanished. All in all, everything seems to have improved, with one exception. Now whenever I cut the throttle, for example coming in to a corner and relying on engine braking, I get a big, meaty backfire.

Any suggestions?

"...and as I shifted into 6th, the engine screaming ferociously beneath me, I stared into the face of god." - Johnny

'05 MV Agusta Brutale S 750 (Nero)
'05 Suzuki GSX-R 600
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post #2 of 18 (permalink) Old 08-01-2010, 08:27 PM
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I had the same issues but i had a custom map. I removed everything and went back to stock but I miss the look. Anyway I still backfire when I ride in the mountains. Mostly when the rpm's are high and I decel for a turn. It only happens a few times and most likely due the the higher elevation.

Does this happen at normal elevations ?


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post #3 of 18 (permalink) Old 08-02-2010, 08:20 PM
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I get backfiring too with the same setup. It's normal to a degree for a machine with high perfromance exhaust systems I was told. A little unburned fuel getting dumped into the exhaust. You don't want to run too lean as it can damage your engine.

By backfire, do you mean some aggressive popping on decel? or enourmous bangs? I get the former. I also get the same on my 1198 with termis and race ecu, and also the same on my 911 turbo with a full stainless steel system.

All 3 run much stronger after the exhaust changes and all 3 backfire on decel. I am thirilled with the performance improvements on my Brutale after changing the pipes and ecu. Much much better.

Hope this helps.
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post #4 of 18 (permalink) Old 08-02-2010, 09:23 PM
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Just to put the terminology correct....you are experiencing "After Fire" in the exhaust.....unburned fuel exploding.

"Back Fire" is through the intakes and is an altogether different condition with altogether different causes.

I used to be fast....now I just dream about it.
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post #5 of 18 (permalink) Old 08-03-2010, 08:06 AM
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you get extra speed from the afterburner effect i also have this happening,
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post #6 of 18 (permalink) Old 08-03-2010, 09:03 AM
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on performance vehicles it's normal to have "after burn" as ed said. I even get it on my star, little crackle and pops on the over run, sometimes a little more than that, but it sounds cool and is really doing no damage.

But when I was helping my neighbor restore his TR3 we were putting the engine back together, and we then started it, the backfire was so explosive that it blew out the muffler. Turns out the prior owner had been fiddling with something, I wasn't their when he figured out what happened, but basically it was dumping lots o' fuel in the exhaust, and when that heated up "BANG" muffler ruptured and ringing in the ears.

That explosive is bad, a little explosion is fine.

Adding power makes you faster on the straights, while subtracting weight makes you faster everywhere - Colin Chapman

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post #7 of 18 (permalink) Old 08-03-2010, 10:23 AM
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I had recently installed an Arrow thunder and BMC air filter and I am getting the after fire upon deceleration. I am also running a pcIII and have yet to get it tuned properly, so we will see it that calms it down at all. But, I must say I am enjoying the night rides with the after fire. Currently I am shooting little 4 to 6 inch blue flames and it looks awesome.

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post #8 of 18 (permalink) Old 08-08-2010, 03:18 PM Thread Starter
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Well apparently it's not uncommon. I know that race spec machines often have the same issues, but wasn't sure as to how damaging it may be in the long run. The only other thing I was curious about is whether the cans being stock are creating a bottleneck and allowing more pressure to build. I.e., if I put on less restrictive mufflers, the condition may be less noticable. I've only ridden once with the new setup, so I'll have to check it out again and re-evaluate how intense the explosions really are. I did notice that when the afterfire occurs, the engine seems to lose torque for a split second, which is mildly uncomfortable when leaned over.

@ '05Brut - Let me know if that PCIII works out for you. I was considering that as my next option, or possibly looking into a FBF custom chip.

"...and as I shifted into 6th, the engine screaming ferociously beneath me, I stared into the face of god." - Johnny

'05 MV Agusta Brutale S 750 (Nero)
'05 Suzuki GSX-R 600
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post #9 of 18 (permalink) Old 08-08-2010, 09:55 PM Thread Starter
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Update - Took it for another ride this afternoon, and for whatever reason, it seems to be much less noticable than before. I did re-evaluate the intensity, and most of the explosions are small, though it does depend on how much throttle I give it and how abruptly I let off. Not quite sure I understand why it's less severe than before, but I'll just have to keep riding and see if it improves or at least remains at an acceptable level.

"...and as I shifted into 6th, the engine screaming ferociously beneath me, I stared into the face of god." - Johnny

'05 MV Agusta Brutale S 750 (Nero)
'05 Suzuki GSX-R 600
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post #10 of 18 (permalink) Old 08-08-2010, 11:58 PM
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I have the same set up arrow eprom and full exhaust. I found some threads that say arrow eproms suck. I also found some info that says u need to set ur tps and get your co2 levels right by adjusting a screw under the tank. I have seen people say they get better results with other eproms. I am gonna try a fbf one. Getting new sprokets and chain and new rubber wensday. so stoked.
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