[mike@x-ph.com]

Originally Posted by r33_RGSport

Was doing test on and for Evolution Racewerks.
Both CEL on and off doesn't make any difference.

I don't know what is happening here; it does not make much sense, but I can't disagree with the data.

You are replacing the downpipes with higher flow ones, but it's making less power, even with CEL not being on.

If it's not sensing anything wrong, why is the car making less power with higher flow downpipes?

[r33_RGSport]

This is my dyno test result on F15 X5 sDrive35i with and without DP.
Same everything but the dp. It shows gain.

[r33_RGSport]

Originally Posted by mike@x-ph.com

I don't know what is happening here; it does not make much sense, but I can't disagree with the data.

You are replacing the downpipes with higher flow ones, but it's making less power, even with CEL not being on.

If it's not sensing anything wrong, why is the car making less power with higher flow downpipes?

Exactly. The only thing that is very possible, is secondary O2 sensor data being used for AFR.

[mike@x-ph.com]

Originally Posted by r33_RGSport

This is my dyno test result on F15 X5 sDrive35i with and without DP.
Same everything but the dp. It shows gain.

This is consistent with everything i have been seeing for the last 15 years since downpipes were first introduced to BMW

Which is what makes the new chassis results even more baffling

[mike@x-ph.com]

Originally Posted by r33_RGSport

Exactly. The only thing that is very possible, is secondary O2 sensor data being used for AFR.

Do you think the active autowerke catted downpipes could fix this problem, given that it runs between the accepted parameters?

Or even an O2 spacer since it tricks the DME into thinking it's running between the correct parameters?

[mike@x-ph.com]

Originally Posted by M2siast

Doesn't JB4 trick the DME by clearing the fault code for the O2 sensor because of the cat? I'm not too familiar with how JB4 works, but I know it clears the CEL on the dash, not sure how influential that is for the DME.

The Jb4 does not automatically clear the codes, so if it's on map 0, its turned off, and the car is 100% running stock settings.

Originally Posted by M2siast

My assumption is, when the car senses the O2 sensor data is outside of factory parameters, car will not work "normally" to protect the engine. Hence, loss of power. Easy to observe in an N55, "going around the block" may not be enough, you have to drive the car a few miles, it usually popped for me getting on the highway. Any "tricks" (tunes, etc.) would mask that and make the car not lose power to protect the engine.

That is my observation of WHAT happens (my evidence) and assumption of HOW it does it (guess).

That's what I also thought, but RG is saying that he got the same results even with no CEL.

[r33_RGSport]

Originally Posted by mike@x-ph.com

Do you think the active autowerke catted downpipes could fix this problem, given that it runs between the accepted parameters?

Or even an O2 spacer since it tricks the DME into thinking it's running between the correct parameters?

Not so sure since downpipe game is pretty much dead in California.
All I do just helping out Evolution Racewerks, since I have the car and been friend with them.

[r33_RGSport]

Originally Posted by M2siast

Thanks, not familiar with JB4 at all.

Yes, about the S58 (which is this thread) that's an interesting spin. Losing power without a CEL is interesting to me.

r33_RGSport could it be that the car had "stored" the fault and the CEL had just disappeared?

I mean, technically very hard to reproduce, but the ideal condition to prove that it loses power WITHOUT a CEL is to have a stock car that had no codes running for a while stop, replace the cat, and the very first time you turn it on you run the dyno. That way you can see the car not trimming anything and observe when it happens. Almost impossible to reproduce.

I don't think so. Because even driving it every after fault reset feels the same.
Only when stock cat back-on, car feels alive again.

[aerobod]

BMW may have expanded the Lambda closed loop operation or perhaps eliminated open loop operation all together on the S58. The post-cat sensor is a narrow band one (deduced from the fact it is a 4-wire sensor), the pre-cat is a wide band (5-wire) sensor.

If closed loop Lambda operation incorporates both pre and post-cat sensors, then lack of a cat would cause the post-cat sensor under high engine loads to oscillate around stoichiometric output AFR at a higher input AFR than anticipated due to lack of oxidation of the exhaust stream that the cat would provide. Lambda feedback would then increase AFR at the pre-cat sensor too and likely either cause the knock sensor to pull timing or just revert to a lower timing on the ignition map due to a higher AFR for the load on the fuel map. The engine is probably then just operating at sub-optimal AFR and ignition values and producing less power.

[Squidget]

If it's knock sensor triggering, that would show up in ODB2 logs, right? OP may be able to test that theory.

[M2PDX]

I tried both Wagner and Fabspeed catted downpipes on my OG F87. Loved the Wagner, but it did throw codes occasionally. Switched to Fabspeed and it has been fantastic. Great sound, spools quicker, and zero codes in 2+ years.

Got it from Mike, at Xtreme Powerhouse.

More recently I added a Bootmod3 tune, and it is incredible, especially in Sport+.

HIGHLY recommend one.

[mike@x-ph.com]

Originally Posted by M2PDX

I tried both Wagner and Fabspeed catted downpipes on my OG F87. Loved the Wagner, but it did throw codes occasionally. Switched to Fabspeed and it has been fantastic. Great sound, spools quicker, and zero codes in 2+ years.

Got it from Mike, at Xtreme Powerhouse.

More recently I added a Bootmod3 tune, and it is incredible, especially in Sport+.

HIGHLY recommend one.

[mike@x-ph.com]

Originally Posted by M2siast

You got downpipes from a vendor that doesn't sell them, according to him? LOL

This thread is so confusing...

M2PDX is talking about catted downpipes; we sell catted downpipes

RG dyno was on stock vs. catless; we do not sell catless.

[M2PDX]

Originally Posted by M2siast

You got downpipes from a vendor that doesn't sell them, according to him? LOL

This thread is so confusing...

Not confusing at all. As Mike said, catted downpipes.

Why is that "lol"?

When you join the forum 3 months ago, and immediately start attacking both long time vendors and long time members, maybe it's time to take a step back and re-evaluate your approach.

[Dave07997S]

Originally Posted by Info@mad-us.com

You will need this https://mad-us.com/mad-bmw-s58-catte...-flex-section/

and this M18 X 1.5 Bung 32mm O2

Being Euro 5 will this keep a CEL from kicking off?

[M Division]

I have sport cats on my G87.

Get the occasional CEL. No performance impact or limp mode, car drives normally.

Clear the CEL to kill the dash light.

[mike@x-ph.com]

Originally Posted by M Division

I have sport cats on my G87.

Get the occasional CEL. No performance impact or limp mode, car drives normally.

Clear the CEL to kill the dash light.

[mike@x-ph.com]

Originally Posted by Dave07997S

Being Euro 5 will this keep a CEL from kicking off?

Euro 5 will still trigger the check engine light

[Info@mad-us.com]

Originally Posted by Dave07997S

Being Euro 5 will this keep a CEL from kicking off?

Technically it should but we have a customer in the g8x m3 threads with about 2 weeks and no cel. Keeping an eye on it.

[turnsignalslol]

Originally Posted by Info@mad-us.com

Technically it should but we have a customer in the g8x m3 threads with about 2 weeks and no cel. Keeping an eye on it.

Hello,

It's been three months since anyone last posted in this thread. Did the customer with your downpipes end up getting a check engine light? I'm potentially considering a sport cat + midpipe setup because I want to increase sound without causing a check engine light, but the dyno chart showing that using non-oem downpipes causing power loss is kind of making me apprehensive as I don't plan on tuning my car anytime soon.

Looking forward to your response, thanks!

[ToneM2]

Originally Posted by turnsignalslol

Hello,

It's been three months since anyone last posted in this thread. Did the customer with your downpipes end up getting a check engine light? I'm potentially considering a sport cat + midpipe setup because I want to increase sound without causing a check engine light, but the dyno chart showing that using non-oem downpipes causing power loss is kind of making me apprehensive as I don't plan on tuning my car anytime soon.

Looking forward to your response, thanks!

Was it the downpipes causing the loss of power or was it the o2 spacer? Apparently running a O2 spacer can cause these cars to run lean.

[mike@x-ph.com]

Originally Posted by ToneM2

Was it the downpipes causing the loss of power or was it the o2 spacer? Apparently running a O2 spacer can cause these cars to run lean.

O2 spacers have always been known to cause cars to run lean, not just this one.