2.5" exhaust

[BluMp3Turbo]

Yes the first pre cat can be removed and use the secong cat Im pretty sure that u wont thorw any CEL's

 

[1sty]

Will it in any way possible cuase knock becuase the car thinks its running to rich and pulls fuel back?

 

[Traveler]

Guys, if you eliminate the first cat and don't relocate the O2 sensors, I gaurantee you will throw a CEL. The 2nd O2 monitors cat efficiency as well as overall fuel mixture. If you put a voltmeter on the outputs of the 1st O2 sensor, you will see a reading that fluctuates up and down even while the car is idling. This indicates that the ECU is constantly adjusting the mixture for optimum mix. The second O2 will have a much steadier signal. The ECU watches BOTH of these O2 sensors and adjusts based on both of them. The 2nd one does monitor cat efficiency, but it also reports mixture to the ECU. You'll notice that the 2nd O2 also has 4 wires going to it. That's because it is heated and is a full range O2 just like the primary O2.

If you want to eliminate the primary cat, the best way to do it would be to put a longer harness to the each O2 and run one in the header collector, and the other just past the second cat. There are also O2 eliminators, but keep in mind that they will only give the ECU a fixed value. With the new OBDII monitoring, the ECU is using the data from the 2nd O2 to monitor overall system condition. If the value doesn't change in relation to the changes the ECU makes, it will generate a code for "O2 sensor slow or no response". Also, the ECU is looking for a heater resistance to check to make sure whether the heater is on or off. If it doesn't see the right signal, then it will set a code for "Heated O2 sensor faulty".

I'm going to try to enlarge the cat outlet for 2.5" pipe. I'll keep everyone posted.

 

[70]

I see you have the FM turbo. Do you like it so far? Install it yourself? I'm looking to get a qoute on an install. I see you haven't fullt optimized it yet. Having problems?

I love it. It works great. Its not "fully optimized" as of yet because FM still hasn't totally dealt with the timing issues that the MP3 presents. The advanced timing the MP3 has and forced induction don't totally mix well. They are, however, working on this very issue.

Other than that the "device" is working properly. And I'm only running ~5 - 5.5 psi, I would like eight. So once again, not "fully optimized." But they are working on that too.

I had FM do the install. I helped FM with the install. So I got kind of a deal on labor. I live just on the other side of the mountain from them, so it made it easy for me to go to the shop. Plus it was fun as heck to go.

 

[Keith@FP]

We pretty much have to lock Chris out of here.

Traveler's right on with the O2 sensor explanation. Basically, OBD-II is designed to monitor the effectiveness of the emissions controls. If you take the emissions controls out of the car, OBD-II will get upset. That's exactly what it's meant to do.

Keith

 

[1sty]

So if you yank out the first cat but give the first 02 sensor a place to go in the down pipe will there be any problems?

 

[Keith@FP]

Quite possibly. The ECU expects to see a cat between the two sensors. I'm not sure if the secondary cat wil behave the same way as the primary.

Keith

 

[blynzoo]

Listen all you really need is one cat and if anything a high flow cat... with that you can go up to 2.5 w/ no problem this way you can use a different downpipe which is better becuz of better flow. Meaning more whp!!!

agh!!!! no!!!!

 

[blynzoo]

Yes the first pre cat can be removed and use the secong cat Im pretty sure that u wont thorw any CEL's

agh!!!! no!!!!

 

[blynzoo]

Keith corrected.

BTW, "We pretty much have to lock Chris out of here."
Hilarious....

 

[BadDSM]

Quite possibly. The ECU expects to see a cat between the two sensors. I'm not sure if the secondary cat wil behave the same way as the primary.

Keith

How about producing a downpipe and test pipe in 2.5" for those who want CARB certified performance on the street and
true cat-less turbo back performance on the track or strip.

 

[BluMp3Turbo]

Well then Mr. blynzoo have you tried to remove the pre cat and see if it runs fine. Because from my understandings all you really need "(and I will repeat for those that have reading problems!)" is 1 cat it can be modified to be High flow cat! Some one that I know once did it like that on a different car and had NO I reapeat No problems you just have to know what you are doing.

 

[Keith@FP]

No. There's no NEED to go to a high flow cat if you only have one. The cats are in series and not in parallel.

Of course, you'll get more gains from a high-flow cat.

We are waiting for our downpipe/test pipe right now. I'm not sure what the OD is offhand.

Keith

 

[blynzoo]

Well then Mr. blynzoo have you tried to remove the pre cat and see if it runs fine. Because from my understandings all you really need "(and I will repeat for those that have reading problems!)" is 1 cat it can be modified to be High flow cat! Some one that I know once did it like that on a different car and had NO I reapeat No problems you just have to know what you are doing.

It is certainly possible to run with only one (secondary) cat. I just didnt want folks to think you could just throw a downpipe on there and not get a CEL. Our Mazdas (and most cars nowadays) are VERY smart. as traveler noted:

Guys, if you eliminate the first cat and don't relocate the O2 sensors, I gaurantee you will throw a CEL. The 2nd O2 monitors cat efficiency as well as overall fuel mixture. If you put a voltmeter on the outputs of the 1st O2 sensor, you will see a reading that fluctuates up and down even while the car is idling. This indicates that the ECU is constantly adjusting the mixture for optimum mix. The second O2 will have a much steadier signal. The ECU watches BOTH of these O2 sensors and adjusts based on both of them. The 2nd one does monitor cat efficiency, but it also reports mixture to the ECU. You'll notice that the 2nd O2 also has 4 wires going to it. That's because it is heated and is a full range O2 just like the primary O2.

If you want to eliminate the primary cat, the best way to do it would be to put a longer harness to the each O2 and run one in the header collector, and the other just past the second cat. There are also O2 eliminators, but keep in mind that they will only give the ECU a fixed value. With the new OBDII monitoring, the ECU is using the data from the 2nd O2 to monitor overall system condition. If the value doesn't change in relation to the changes the ECU makes, it will generate a code for "O2 sensor slow or no response". Also, the ECU is looking for a heater resistance to check to make sure whether the heater is on or off. If it doesn't see the right signal, then it will set a code for "Heated O2 sensor faulty".

Sorry, didnt mean to jump out like that. Just wanted folks to know that keeping that CEL quiet is hard sometimes. Each O2 sensor KNOWS what it is reading, knows where it is. You do have to "fool" the sensors into thinking that they are still where they are, otherwise you get a CEL. When you take out the first cat, the 2nd O2 sensor will notice the difference in emissions and EGT.

We may be agreeing. It is certainly possible to take the 1st cat out. Getting rid of the CEL is another thing.

 

[70]

We pretty much have to lock Chris out of here.

Keith

They don't realize I found the spare key under the mat!!