question about catless DP

[baobao]

I would like to change the catless DP and did some search on the forum but still have questions. I am in Canada so don't need to worry about emission testing. Then the only question is CEL. Since I always have a CEL for the fail O2 sensor after I change the catless DP. Then I am curious if there's another problem which will also cause CEL (say really have some problems with the engine), will I be notified about that? I ask this because I never have a CEL before so I don't know how it works.

I read a lot on the forum about the BMS OBDII CAN which can delete the CEL for DP. But when I check their website, I didn't find this feature. Did they just delete this? (And why?) If so, is there any easy way to delete CEL for service purpose?

Also, if I just change the DP for sound, do I need to do tuning? IS there any negative impact if I don't do tuning? Since the improvement of tunning for Dp seems not that big, I may choose not to tune if no negative impact.

Thank you all!

[AlterZgo]

You can run DPs without tuning and will experience quicker turbo spool, louder exhaust, crappier smelling fumes. You would be wrong about lack of improvement in tuning. DPs will allow you to turn up boost more and run true stage II tunes that will push you up to 500 wheel hp without severely over taxing your turbos.

If you plan on not tuning your car, I wouldn’t bother with DPs. All you will do is pollute more, get marginally better performance and have to deal with CEL and crappy exhaust fumes.

[Lee808]

To be honest, if you keep secondary cats. One would be hard pressed to smell a difference. Either that or I am extremely nose blind.

[baobao]

Originally Posted by AlterZgo

You can run DPs without tuning and will experience quicker turbo spool, louder exhaust, crappier smelling fumes. You would be wrong about lack of improvement in tuning. DPs will allow you to turn up boost more and run true stage II tunes that will push you up to 500 wheel hp without severely over taxing your turbos.

If you plan on not tuning your car, I wouldn’t bother with DPs. All you will do is pollute more, get marginally better performance and have to deal with CEL and crappy exhaust fumes.

Thank you for correcting me. So the flash tune can give some good improvement on performance. Will piggyback do the same improvement, or it can just do a marginal improvement?

[baobao]

Originally Posted by Lee808

To be honest, if you keep secondary cats. One would be hard pressed to smell a difference. Either that or I am extremely nose blind.

Thats a good news for me since I didn't have a plan to change the middle pipe yet.

[AlterZgo]

Originally Posted by baobao

Thank you for correcting me. So the flash tune can give some good improvement on performance. Will piggyback do the same improvement, or it can just do a marginal improvement?

Flash and piggyback can both add noticeable power with DPs. At this stage in the game, I would personally go flash all the way. Some like piggybacks like BMS for logging and other features (remote control of exhaust valve, adjustment of lights, turning on-off active sound, etc. that the JB4 provides) but if you go with a JB4, I'd still get an MHD flash to unlock the most potential of the car.

If you don't care about those extra features, just get a BM3 and call it a day, or just don't bother tuning and keep your stock DPs.

[Jeff@TopGearSolutions]

Originally Posted by baobao

I would like to change the catless DP and did some search on the forum but still have questions. I am in Canada so don't need to worry about emission testing. Then the only question is CEL. Since I always have a CEL for the fail O2 sensor after I change the catless DP. Then I am curious if there's another problem which will also cause CEL (say really have some problems with the engine), will I be notified about that? I ask this because I never have a CEL before so I don't know how it works.

I read a lot on the forum about the BMS OBDII CAN which can delete the CEL for DP. But when I check their website, I didn't find this feature. Did they just delete this? (And why?) If so, is there any easy way to delete CEL for service purpose?

Also, if I just change the DP for sound, do I need to do tuning? IS there any negative impact if I don't do tuning? Since the improvement of tunning for Dp seems not that big, I may choose not to tune if no negative impact.

Thank you all!

In that past BMS was able to auto clear the check engine light for going catless. However, since late 2017 all new firmware eliminates the auto clear for that. As a result, you can manually clear the CEL but it will come back on. They never advertised these capabilities and don't intend to because they are trying to gain compliance with CARB.

You can do catless DP without tuning, understanding there will be a CEL.

All you need to ask yourself is why you want downpipes. If you want them for power then you should be getting a tune regardless as it's the biggest power adder.

If you just want them for sound and don't mind the CEL then don't get a tune.

[jafza412]

Originally Posted by Jeff@TopGearSolutions

In that past BMS was able to auto clear the check engine light for going catless. However, since late 2017 all new firmware eliminates the auto clear for that. As a result, you can manually clear the CEL but it will come back on. They never advertised these capabilities and don't intend to because they are trying to gain compliance with CARB.

Does Bootmod3 auto clear the CEL? Or can none of the tunes do that anymore?

[Schultz28]

Mini cats!

http://www.bigdaddiesgarage.com/mini...SABEgKn7_D_BwE

[gatorfast]

Originally Posted by jafza412

Does Bootmod3 auto clear the CEL? Or can none of the tunes do that anymore?

I believe all tunes except VF can clear the CEL.

[ObiChen]

It is funny that someone wants DPs but not tunes. DPs are performance mod not sound mod IMO. I got mine only because BM3 stage II recommends otherwise I'll never bother. If you don't care about performance, just get midpipes or catback exhaust, they are much better than DPs in terms of sound.

As of CEL, most tunes clear CEL for DPs and I believe keeping CEL off is necessary because in case some other parts go wrong, you need CEL to be noticed.

[gatorfast]

Originally Posted by ObiChen

It is funny that someone wants DPs but not tunes. DPs are performance mod not sound mod IMO. I got mine only because BM3 stage II recommends otherwise I'll never bother. If you don't care about performance, just get midpipes or catback exhaust, they are much better than DPs in terms of sound.

As of CEL, most tunes clear CEL for DPs and I believe keeping CEL off is necessary because in case some other parts go wrong, you need CEL to be noticed.

I disagree. DPs add a good amount of volume to an otherwise stock exhaust and make the sound more aggressive as well. Not to mention they are usually a fraction of the price of a midpipe or axel back setup. Plus they are direct bolt on with no cutting required.

[BMW9]

I had DPs on my M4. You feel the difference when you go back to stock. They did make a difference in improving throttle response and power. The power gain is minor and mostly noticed on the top end. You do get more volume of sound but be aware that the sound quality is very raspy and resonating. I could feel the vibrations as the revs climbed up. It is annoying if you compare it to a proper cat back exhaust. Now that I'm back to stock, I do miss the gains but, the car is much smoother.