still popping on decel, after removing catalytic from exhaust
Have been reading a few posts on how to remove the decel popping. The problem started after removing the cat. conv. from the exhaust on my '10 DX, after believing that it'd be an slight improvement in running cooler and more responsive. The decel popping only occurs riding arround town etc. I did have it dyno'd again after the cat was removed, but no improvement.
I was told that " he is happy with the AFR line" and auto-tune? has been selected on my SEPST , and "hopefully it sort itself". It's been 4 weeks and NO better.
Topless, slip-ons ( with small baffles )
Any ideas that i should look at? Please be note that i've limited knowledge in tuning. Dyno results below
there is no auto-tune available for the SEPST. The problem will not fix it self.
IMO put the top back on your air intake and see if it helps out alittle on the deceal popping. ( probably won't fix all of it ).
Then find a shop who knows what the F they are doing!!!
__________________ 2011 Muscle :
SE Stage II cams
58mm Destroyer TB
6.37 g/s Fuel inj.
Vance & Hines Comp. Slip-Ons
K&N Cones - Topless
BOSS NOSS - Stealth system
Thats what I did on my PCIII no more Decel popping...0 Throttle Position up to 5K RPM add 20%...
I had the same problem after my dyno tune. It needs more fuel when the throttle is closed and you are decelerating.
With fuel injection on an engine that has open loop control. (an engine without oxygen sensors) the injectors go to an idle fuel position when you close the throttle. If you are still moving and in gear the fuel air mixture goes very lean! Way above 14 to 1 and the exhaust pops. On closed loop systems the oxygen sensors sense this condition and adjust the fuel automatically. On bikes without sensors you need to increase the fuel when the rpm is above idle (make it richer) and the problem is gone. Your dyno tune graph shows the reason it pops. To lean at low throttle positions. Just try and increase the throttle a little bit when decelerating and the problem will go away. This proves it needs more fuel.
Originally Posted by luxlamf
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Thanks for the ideas, when riding in the hills etc. the decel popping has gone. My guess is what you guys have been saying, add small amounts of fuel down low. I will go back to my original place to do the dyno...
Dyno runs just show what happens at max throtte, so I don't see what thy have to do with anything.
If you remove the cat there will be two results - very slightly better airflow, which means the bike runs very slightly leaner, so needs very slightly richening, ansd there is less restriction down the pipe so the sound of fuel burning in the pipe (AKA decel popping) will be more audible.
1) The change is very small, so the popping should be too. If it is loud enough to worry about then it is probably an air leak at the headers. Are they tight?
2) If the flow is better, maybe your tuner should be adding a bit of fuel to the map? Never mind the high end.
3) If you really want to tune out decel popping, you need to try adding (normally) or subtracting (less usually) fuel on the decel settings and the 0% throttle positions in the SEPST. However, I am surprised this is needed just for CAT removal. An air leak seems more likely to me.
Arnotts, D&D, SEPST, custom paint or all chrome according to mood, GRC seat, wave rotors, Muscle wheels, Burleigh bars, V-Gauge, assorted pretty bits.
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Thanks Louis, i have altered the baffles slightly. They did have a 20mm hole in the ends. I drilled them to 26mm and added two extra 11mm holes around the outside of the baffles. This, with removal of the cat has the bike just right, sound wise.
I'll have another look at the headers. Do you know what they need to be torqued to?
dropped the bike to Aldo at peter stevens and told him about the issues. Had it sorted in no time. Like you guys said, he added more fuel. No gains in removing the cat power wise, but i reckon bike runs a little cooler.
In your map you have a decel enleanment setting. Decrease the numbers in that chart by 10% at a time till the popping stops.
as an old calibrator, I can tell you it's better to add the fuel in the VE tables. Decel enleanment is "active" with every negitive delta throttle. So you would add "more" fuel every time you decrease throttle with decel enleanment. DE is just like AE it accounts for delta changes in throttle and the associated tranport lag times for scheduled fuel vs. actual throttle (manifold filling ) effect.
VE's will help the over run condidtions without hitting all those points under "normal" throttle operation.