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Discussion Starter #1
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?
 

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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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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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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.
 

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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.
 

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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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Discussion Starter #8
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.
 

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Discussion Starter #9
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.
 

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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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Did you reset the TPS? My bike ran extremely rich and backfired a lot after the pipe change. TPS reset sorted it out completely. With the throttle closed, The ECU thought it was open 18%. Needless to say it ran like Shitte.
 

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@ '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.
I will be sure to let you know how it goes after I get her tuned properly.
 

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Discussion Starter #14
Did you reset the TPS? My bike ran extremely rich and backfired a lot after the pipe change. TPS reset sorted it out completely. With the throttle closed, The ECU thought it was open 18%. Needless to say it ran like Shitte.
How exactly do you reset the TPS? Is it a digital sensor or a positional (screw-adjust) component?

You say it ran 18% open at closed throttle, do you mean it revved to 18% without any throttle input or that it was fueled at idle with the same amount of fuel it would get at 18% open throttle position (i.e. really, really rich)? As I said, I seem to be running pretty smooth everywhere, idle is good, hasn't risen or anything, just a little excess fuel when I get on it and then chop.
 

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I don't know how they reset the TPS, my mechanic did it. The bike was running EXTREMELY rich. billowing black smoke when you revved the engine and not running smoothly. The engine was also surging and on the diagnostics it was running 18% rich. The rpm's were normal but you could smell gas and see the carbon. It would stutter low in the rpm range but smooth out as you revved it higher. It also backfired a lot.

I have to assume that means that when the throttle was closed. The bike thought throttle was open 18%, so was therefore dumping far too much fuel into the bike at all throttle positions. After the reset it ran like a champ. Took an hour or so to burn out all the execss carbon... I think if you changed the pipe and exu, the TPS reset is a must.
 

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Mine does the same popping on decel with the full Ti Corse exhaust and the Microtek ECU, may have to do with the emissions not being fully disconnected ala the charcoal filter in the tank. Just dont chop the throttle too hard mitigates some of it. Like a fire breathing dragon!
 

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Every bike I have ever had has done this when ridden aggressively. My brute does it a little mostly if I really wind up the rpms and then back off suddenly. It's very normal as fuel gets trapped from the deceleration.
 

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How exactly do you reset the TPS?.
Buy the VDSTS software. I personally think it's a "must" if you like tinkering. You can diagnose problems and change all sorts of parameters. TPS reset is a snap. The thing I most like about the software besides the TPS reset is the "Fuel Trimmer". You can richen or lean the mixture. I've found you can mostly dial out the popping, etc. Although, I think you'll always get a little with a full race exhaust.

You can get the "single bike app" for $229, which is well worth the money.

www.technoresearch.com
 
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