[JamesM3M5]

Originally Posted by MDORPHN

Not quite accurate. They detect degradation of the cats and, as the cats are become less effective, do affect fuel trim.

Neil

Affect in which direction - run the engine leaner or richer if cat degradation is detected? I would assume the ECU will lean out the bank with a failing cat, no?

And as a followup question - what is done about catless DP tuning for flash and piggyback to counteract this? Or is it such a small change that nothing is done in the aftermarket tune when running catless?

[MDORPHN]

Originally Posted by JamesM3M5

Affect in which direction - run the engine leaner or richer if cat degradation is detected? I would assume the ECU will lean out the bank with a failing cat, no?

And as a followup question - what is done about catless DP tuning for flash and piggyback to counteract this? Or is it such a small change that nothing is done in the aftermarket tune when running catless?

James -

You're asking me technical questions. Hah!

Certainly it is possible that the post-cat O2 sensors do little other than the monitor cats, but I've been told that they do adjust LTFT as the cats become less effective -- presumably leaning out the AFR.

For this reason, I'm told it's advisable for those using the DP fix to install it only when necessary to show readiness for inspections and not to leave it installed.

Neil

[awei130]

Only the catless downpipes work with the xi models.

[benzy89]

Originally Posted by Sered

Once again, you're providing misinformation.

[benzy89]

Originally Posted by JamesM3M5

Affect in which direction - run the engine leaner or richer if cat degradation is detected? I would assume the ECU will lean out the bank with a failing cat, no?

And as a followup question - what is done about catless DP tuning for flash and piggyback to counteract this? Or is it such a small change that nothing is done in the aftermarket tune when running catless?

A tune's serving a different purpose then an o2 Sim. Tune is increasing performance & just blocking out the SES/CEL thrown by emissions (thus blocking a OEM DME correction of AFRs). An o2 Sim alters your AFRs so you pass an OBD Scan when your car has the primary cats deleted; that's why there's a cool knob on the DP Fix to adjust how strong you need to go before the car is Ready & Passable.

[Sered]

Originally Posted by MDORPHN

Not quite accurate. They detect degradation of the cats and, as the cats are become less effective, do affect fuel trim.

Neil

So the DP fix is wired in to make the DME believe the cats are in tip-top shape whereas the Cobb Stage2 or JB4 clear the code, also making the DME believe the cats are in tip-top shape.

So no, for all intents and purposes it does not affect fuel trim.

Originally Posted by benzy89

Want to try again instead of taunting? You're probably the worst when it comes to misinforming people on this forum.

Originally Posted by benzy89

A tune's serving a different purpose then an o2 Sim. Tune is increasing performance & just blocking out the SES/CEL thrown by emissions (thus blocking a OEM DME correction of AFRs). An o2 Sim alters your AFRs so you pass an OBD Scan when your car has the primary cats deleted; that's why there's a cool knob on the DP Fix to adjust how strong you need to go before the car is Ready & Passable.

An O2 sim doesn't alter your AFRs, it alters what the sensor sees, big difference. If ithe sim actually altered the AFRs, then it would be adjusting fuel or timing or affecting the O2 sensors that actually measure AFR and not an AFR dropoff post-cat and it doesn't. And the primary O2 sensors in this DME are what is used for that purpose. The secondary O2s may be reactionary and cause the DME to alter the original tune in case of bad cats, etc; but as it stands, if the DME thinks the cats are A-OK, it does not affect AFR.

[MDORPHN]

The DP fix does not clear codes. Instead, it allows the DME to show readiness.

Neil

[benzy89]

You know what, how about you go drive around with an o2 Sim installed & take some logs. I can guarantee you that the logs won't be as pretty as when the o2 Sim is NOT on the car.


And if what you're suggesting is true (that the o2 Sim basically just fools the sensors), why aren't all the major tunes already incorporating it into their software & selling their own versions (instead only BMS has a corner on this market for the N54, N20 & S65 markets)? Why aren't Terry, Shiv & other major tuners running with o2 Sensors installed in their cars?

Explanation: It affects the tunes settings & should only be used (and installed) when getting an OBD scan. Otherwise, get rid of it cause it's going to negatively impact the cars performance settings.

[Quebequer]

There is a lot of misinformation here.
First, there are some options for catted downpipes for xi's. I have ultimate racing catted downpipes on my car. There is also AR's, and probably others.
Second, with my UR catted downpipes, I don't throw any cell without JB4 in. I always remove JB4 and meth kit before going in for warranty claim. I changed both turbos and my transfer case on warranty. A friend of mine has an Xi with the same downpipe as mine, and he's running JB+, which does not carry the downpipe fix option. Absolutely no cell, and car can go in for warranty with them installed.
I love my catted downpipes because there is no rasp. There is no place to put some resonators on xi's, so rasp is awful with an aftermarket exhaust. Also, I had catless ones before, and I really did not see downgrade in performance, buttdyno wise.

[Hellrot Sachin]

Since it seems that people here know a thing or two... Does anyone have any information on the change in emissions when you take the two rear cats out for downpipes.. not for a CEL or inspection, but for my own conscience.. I know, crazy thought. but I'm thinking of getting DP without cats, if someone tells me the emissions difference is negligible and the rears are really redundant.. anyone?

Thanks,

Sachin

[benzy89]

Originally Posted by Hellrot Sachin

Since it seems that people here know a thing or two... Does anyone have any information on the change in emissions when you take the two rear cats out for downpipes.. not for a CEL or inspection, but for my own conscience.. I know, crazy thought. but I'm thinking of getting DP without cats, if someone tells me the emissions difference is negligible and the rears are really redundant.. anyone?

Thanks,

Sachin

Concerned about a sniffer test? And there's two completely separate sets of cats in an N54 exhaust: 1st set are in the DPs, 2nd set are located further back in the midpipe section. Unless you replace the midpipes, the secondary cats are maintained (even if you change your axle-back exhaust).

[335ikiid]

Originally Posted by benzy89

^^^That'll interfere with the AFRs & could cause the car to unintentionally run rich/too lean

It's recommended that once you use the BMS DP Fix to pass an inspection test, that you remove it again before ripping on the car

really? learned something new today haha

[Hellrot Sachin]

Originally Posted by benzy89

Concerned about a sniffer test? And there's two completely separate sets of cats in an N54 exhaust: 1st set are in the DPs, 2nd set are located further back in the midpipe section. Unless you replace the midpipes, the secondary cats are maintained (even if you change your axle-back exhaust).

Ha.. not as concerned with a true sniffer test.. just wondering how much worse is it for emissions and the environment if I go catless DP..

HRS

[E90Company]

Originally Posted by Hellrot Sachin

Ha.. not as concerned with a true sniffer test.. just wondering how much worse is it for emissions and the environment if I go catless DP..

HRS

For the enviroment? Well the emissions will increase with catless DP's that's for sure, but like benzy said there are secondary cats still in place. Far less emissions than if you were fully catless, but a little bit more than fully catted. Once your car is warmed up, you can't smell the exhaust with only the secondaries in place, so there working

[benzy89]

Originally Posted by Hellrot Sachin

Ha.. not as concerned with a true sniffer test.. just wondering how much worse is it for emissions and the environment if I go catless DP..

HRS

Going completely catless, the most you'll notice is the smell at start up & in the cold (since you live in Chicago), you'll prob get smoke from the tailpipes until the engine & exhaust finally warm up

[TommyLights]

An O2 sim doesn't alter your AFRs, it alters what the sensor sees, big difference. If ithe sim actually altered the AFRs, then it would be adjusting fuel or timing or affecting the O2 sensors that actually measure AFR and not an AFR dropoff post-cat and it doesn't. And the primary O2 sensors in this DME are what is used for that purpose. The secondary O2s may be reactionary and cause the DME to alter the original tune in case of bad cats, etc; but as it stands, if the DME thinks the cats are A-OK, it does not affect AFR.[/QUOTE]

I dont think the first sentence is true. BMS states that the DP fix works by altering the signal the sensor is sending to the DME and replaces it with a fixed value.