Muffler delete equals Rich condition

cavemancan

I did some searching and I was not able to find a similar thread so here goes.

I went ahead and removed the muffler to save some weight and get some good noise. Ever since then I've been running extremely rich. I would say about 280 miles per tank of fuel (I used to average 310 to 340). So I did some research and I tried the "Idle Air Volume learning" procedure but to be honest I am sure I screwed it up:

2003-2011 Nissan 350Z - 370Z Idle Air Volume Learning Procedure | Nissanhelp.com

I can further prove this rich condition due to the fact that I had a dyno on the same day of the muffler delete and the shop tech told me I was running extremely rich.

Dyno:



Notice the TON of torque...I must have a v8 for like 1 whole second...LMAO!!



So my question is am I forced to get a tune? or is there another reset procedure I can run? Did I do the above mentioned procedure wrong? Etc?

EDIT: note that the pull showing the most power is with the filters removed.

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Mazda Rx8 MT Titanium - SOLD!
2009 370Z T-Sport MT Black - Takeda Intake, Swift springs, Rear Camber kit, SS B Lines, FI Exhaust, Z Speed CMAK Flywheel/Clutch Kit, Stillen Brake Cooling.

edub370

how can a muffler delete possibly cause a rich condition? it must be something else that has caused this. allowing air to more easily flow out of your cylinders cannot cause a rich condition.

someone else chime in if im missing something here

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cavemancan

I was confused about that one as well so let me add to the story:

When I originally picked up the car (used) I got a check engine light a few days later. Nissan (its still has factory warrantee) indicated that the car was "flashed tuned" by the previous owner. They went ahead and reflashed the ECU with the stock tune (so they say) and the check engine light went away.

I am not sure but could it be that after market tune is still hanging around causing some drama? The only thing is it was reflashed a long time ago. Why would it all of a sudden happen now after thousands of miles driven. In my opinion the exhaust is the most likely suspect.

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Mazda Rx8 MT Titanium - SOLD!
2009 370Z T-Sport MT Black - Takeda Intake, Swift springs, Rear Camber kit, SS B Lines, FI Exhaust, Z Speed CMAK Flywheel/Clutch Kit, Stillen Brake Cooling.

IDZRVIT

Muffler delete and air intake filter delete won't cause this. Bad O2 sensor sounds more probable or some other problem causing the fuel management system to dump more fuel through the injectors than is actually required.

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"America.... still builds rockets!"
Vette: 355 cid, 400 rwhp
'13 CTS-V Coupe: 6.2L LSA, 556HP

cavemancan

Right but a bad O2 censor would throw a code correct? Which in turn would trigger the CEL. Since Nissan reflashed the ECU I doubt I have a phantom flash so I am at a loss.

__________________
Mazda Rx8 MT Titanium - SOLD!
2009 370Z T-Sport MT Black - Takeda Intake, Swift springs, Rear Camber kit, SS B Lines, FI Exhaust, Z Speed CMAK Flywheel/Clutch Kit, Stillen Brake Cooling.

IDZRVIT

Yes, in an ideal world a code would be triggered. Welcome to reality.

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"America.... still builds rockets!"
Vette: 355 cid, 400 rwhp
'13 CTS-V Coupe: 6.2L LSA, 556HP

DR_

Why not put back on the exhaust and check your A/F again? Since you have a '09 it could be you have (had) a Cobb AP tune. You might want to see if you can pick one up used for cheap so you can check. It would also allow you to monitor your A/F. There are other devices that allow you to monitor the stock O2 sensors, I have a Dashhawk on my '09.

cavemancan

There was welding involved so I dont want any more invasive changes made. What I may end up doing is going to autozone and getting the codes checked. Either way I'll prob take it to Nissan on Friday.

__________________
Mazda Rx8 MT Titanium - SOLD!
2009 370Z T-Sport MT Black - Takeda Intake, Swift springs, Rear Camber kit, SS B Lines, FI Exhaust, Z Speed CMAK Flywheel/Clutch Kit, Stillen Brake Cooling.

SS_Firehawk

A bad O2 sensor doesn't throws a code. It took a long time before I figured out I had a bad sensor. Cipher helped me track it down. And yes, it ran pig rich.

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SS_Firehawk

Let me revise this and say it doesn't bluntly say your O2 sensor is messed up when you look it up. It was a ver common P0300 code and maybe something else that did nothing to help track it down. Data logging was the only way I saw it.

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cavemancan

After installing my FI exhaust my gas mileage went back to normal.

__________________
Mazda Rx8 MT Titanium - SOLD!
2009 370Z T-Sport MT Black - Takeda Intake, Swift springs, Rear Camber kit, SS B Lines, FI Exhaust, Z Speed CMAK Flywheel/Clutch Kit, Stillen Brake Cooling.

stewarts2008

so you fixed it? What was it?

If your muffler delete was rattling, then yes, the knock sensors could have picked up vibrations.

Im not sure how loud it was, but if you car was crazy loud, then the knock sensors can pick up on that in general.

any updates?

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2013 Mustang 5.0 | 650 rwhp (sold)
2011 Mustang V6 | 270 rwhp (sold)

cavemancan

Still running with stock gas mileage when I installed the FI exhaust. I honestly cannot give you a definitive answer as to why it ran rich with the muffler delete but perhaps the knock sensor theory has some merit? I don't think so but perhaps.

Shortly after the FI install I also installed the Takeda intake. The only change was a HP increase. Mileage while cruising on the highway is more or less the same. I have 15k + miles with both mods without any issues. So I consider the issue resolved.

__________________
Mazda Rx8 MT Titanium - SOLD!
2009 370Z T-Sport MT Black - Takeda Intake, Swift springs, Rear Camber kit, SS B Lines, FI Exhaust, Z Speed CMAK Flywheel/Clutch Kit, Stillen Brake Cooling.

370z-09

I also did a Cain and muffler delete and buddy was behind me o. Freeway. When I down shifted and matted it he said it puffed out black smoke (rich) makes me wonder.... what was hour end result???

Staples

Bad gas... pulls out timing and adds fuel when it determines ping. Put some Shell or BP in the tank, then go back on the Dyno.

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