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Anyone here installed Magnaflow

Old 06-11-2018, 06:00 PM
Andrew 07 XKR's Avatar
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Default Anyone here installed Magnaflow

Hi guys!

I have an '07 XKR with a Mina Gallery exhaust system and supercharger pulley. I am interested in swapping out the stock catalytic converters for the Magnaflow catalytic converters. I am hoping to get a more aggressive sound and maybe even a little bump in hp. I realize I am opening myself up for ridicule but I think I can handle it! LOL Any and all feedback is appreciated.

Thanks for your input!
Old 06-13-2018, 08:09 PM
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Magnaflow is a common upgrade for our Superchaged 4.2 engines.

Did you do a forum search on "Magnflow"? You should get several hits.

There are known issues with O2 sensor faults that can be remedied by installing a spacer to move the sensor out of the exhaust flow. (you can search for this too.)
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Old 07-04-2018, 07:22 AM
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Old 07-08-2018, 01:32 AM
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One thought to keep in mind, is that the 2nd O2 sensors are used to support the ECU in determining the fuel mixture. By using extenders, you are influencing the readings, and this can lead to some more enrichment under certain conditions.

I pulled one 2nd O2 sensor out t place a exhaust pressure meter, and let the unit bungle out in the air, and my fuel trim readings where all over the place for that bank. So I can confirm that even on the older AJ27 cars the 2nd o2 sensors are used for mixture control, however a good quality 200 cell cat will not trigger P0420/P0430 errors, so we are good here. On the later 4..2 engines the ECU is already more sensitive to Cat checks, but I have had good experience with one high quality cat that didn't throw P0420/P0430 errors, however after 20K it did. The later aluminium versions have a newer ECU again, which probably will throw P0420/P0430 errors, but here its probably easy to program out the catalyst checks so you don't need the extenders.

Best is to see if the catalyst converter checks can be disabled via a tune then to use O2 extenders.

Cambo has done some extensive research here, as he experienced the negative impact himself here as well. Here is just one of the threads where he posted about it:
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Old 07-08-2018, 10:30 AM
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Using O2 sensor spacers appears to be a common change for many cars. Here is a link with links to many different types for sale.

4-5 years ago when I was having random O2 sensor failures, I installed new down stream O2 sensors. Then I started getting continuous faults. I searched our forum and found the spacer Idea. I put in the spacers and haven't had a fault since.

Avos. Great input. Thanks.
Below is a good explanation of how typical systems work that I found on a Ford Ranger Forum.

O2 sensor voltage range is .10-.90volts, O2 sensors only read Oxygen levels not fuel levels
.10 means high oxygen levels, which is Lean for fuel
.90 means low oxygen levels, Rich with fuel
Upstream O2 sensor(s) get raw exhaust, so if fuel mix is correct they will be .30-.70v, sweet spot is .45v
Downstream O2 sensor is after the Catalytic converter so it "sees" cleaned exhaust, it should always show lower voltage, higher oxygen levels, than upstream O2 sensor
So your reading looks OK, under .2v

Lean/Rich codes come from fuel injector "dwell time", open time, "pulse width".
Computer gets the MAF(mass air flow) sensor data for the "weight" of the air coming into the engine.
Computer then calculates the 14.7:1/air:fuel ratio based on the weight of the air(this is a weight ratio, 14.7lbs of air to 1lb of fuel)
Computer then opens the fuel injectors(based on expected fuel pressure) for a length of time that will allow the calculated amount of fuel to flow into the intake to achieve the 14.7:1 ratio.
Computer then reads upstream O2 sensor data to see if the calculation is correct(downstream O2 is used to see if Cat is working, not fuel trims)
If O2 sensors shows voltage under .45v "lean" then computer opens fuel injectors longer.
If O2 sensor shows above .45v "rich" then computer reduces the open time for fuel injectors.

Engine never actually runs lean or rich.

Fuel Trims = open time for fuel injectors
0 fuel trim is the computers calculation based on MAF sensor, air temp, throttle position, and fuel pressure(this is a fixed number, computer has no way to "know" the fuel pressure)

+1 fuel trim means computer is opening fuel injectors longer that calculated based on O2 sensor voltage
-1 fuel trim means computer is reducing the open time for fuel injectors based on O2 sensor voltage.

If fuel trims get over +20 for any length of time the computer will set a Lean code,
If fuel trims get under -20 for any length of time then Rich code is set,
Again, the engine is never running Lean or Rich, computer is adding or reducing fuel to the mix.
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Old 07-08-2018, 11:55 AM
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Originally Posted by Tijoe View Post
engine is never running Lean or Rich, computer is adding or reducing fuel to the mix.
With non-wideband, it does. It cycles (a little) lean & (a little) rich to make the cats do their job. That's why you can see the upstream O2s switch.

(With wideband I'm not so sure. My car has them but I've not studied what the PCM does. I expect it cycles lean/rich for the same reason i.e. to make the cat effective.)

The downstreams should switch much less and as avos pointed out they fine-trim the fuel trims on many cars (as described in Jaguar docs if you look).

If you use downstream O2 spacers inevitably you'll force somewhat wrong fuelling.

Last edited by JagV8; 07-08-2018 at 11:59 AM.
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