[AlexFL]

Does anybody know the model and the specs of the stock catalytic converter in X3M? Trying to find out i) whether modding the car won’t melt the stock cat due to the hotter exhaust gases, and ii) if the high flow catted ER downpipes actually bring any performance advantage (aka less restriction) compared to stocks. Catless downpipes are out of question (baby at home).
Thanks in advance!

[two1bar]

Originally Posted by AlexFL

Does anybody know the model and the specs of the stock catalytic converter in X3M? Trying to find out i) whether modding the car won’t melt the stock cat due to the hotter exhaust gases, and ii) if the high flow catted ER downpipes actually bring any performance advantage (aka less restriction) compared to stocks. Catless downpipes are out of question (baby at home).
Thanks in advance!

IMO, I would go with the ER catless primary downpipes considering the secondary cats will still be in place. It will help with backpressure.

I just installed the ER catless downpipes on my X3MC earlier this week. Overall the sound has only changed under moderate to heavy throttle. Normal driving I have not noticed much change.

[redcrxsi]

Originally Posted by two1bar

IMO, I would go with the ER catless primary downpipes considering the secondary cats will still be in place. It will help with backpressure.

I just installed the ER catless downpipes on my X3MC earlier this week. Overall the sound has only changed under moderate to heavy throttle. Normal driving I have not noticed much change.

No cel lights with catless? Or are you running a tune as well?

[AlexFL]

Originally Posted by two1bar

IMO, I would go with the ER catless primary downpipes considering the secondary cats will still be in place. It will help with backpressure.

I just installed the ER catless downpipes on my X3MC earlier this week. Overall the sound has only changed under moderate to heavy throttle. Normal driving I have not noticed much change.

I’m planning on installing the Akra Evo link pipe set. My understanding is that it deletes the secondary cat.

[two1bar]

Originally Posted by redcrxsi

No cel lights with catless? Or are you running a tune as well?

Bootmod3 Stage 2 tune.

Originally Posted by AlexFL

I'm planning on installing the Akra Evo link pipe set. My understanding is that it deletes the secondary cat.

Ahh. That would change things. I myself would retain one set of cats.

[SuperSport]

I am curious how restrictive the secondary cats are. Not a lot of dyno data around.

[AlexFL]

Originally Posted by SuperSport

I am curious how restrictive the secondary cats are. Not a lot of dyno data around.

I know that on M4, the primary cats were way more restrictive. No idea about this car, hence this thread.

[smithf80]

Originally Posted by two1bar

IMO, I would go with the ER catless primary downpipes considering the secondary cats will still be in place. It will help with backpressure.

I just installed the ER catless downpipes on my X3MC earlier this week. Overall the sound has only changed under moderate to heavy throttle. Normal driving I have not noticed much change.

Really? Every car I've done downpipes on, it's made a major change. My F80, F32, etc, every one of them was a pretty nice volume increase. You're saying that isn't the case here? Any videos?

[two1bar]

Originally Posted by smithf80

Really? Every car I've done downpipes on, it's made a major change. My F80, F32, etc, every one of them was a pretty nice volume increase. You're saying that isn't the case here? Any videos?

Based on the dragy results, it hasn't impacted the performance like it has on other platforms. So far I've only seen .1 and 1mph in 1/4 mile which could easily be variance in weather conditions. We have 3 X3Ms with ER downpipes and all 3 have netted similar results.

[smithf80]

Originally Posted by two1bar

Based on the dragy results, it hasn't impacted the performance like it has on other platforms. So far I've only seen .1 and 1mph in 1/4 mile which could easily be variance in weather conditions. We have 3 X3Ms with ER downpipes and all 3 have netted similar results.

Honestly I don't care about the performance, I'd be doing it for sound, that's what I'm most interested in.

[two1bar]

Originally Posted by smithf80

Honestly I don't care about the performance, I'd be doing it for sound, that's what I'm most interested in.

The sound is a definite improvement. Normal cruising is for the most part negligible in sound. However under moderate to heavy throttle it is definitely a "good" louder sound.

[AlexFL]

Originally Posted by two1bar

Based on the dragy results, it hasn't impacted the performance like it has on other platforms. So far I've only seen .1 and 1mph in 1/4 mile which could easily be variance in weather conditions. We have 3 X3Ms with ER downpipes and all 3 have netted similar results.

Just to clarify, were you comparing stock X3Ms with vs without ER downpipe? Or were the cars BM3-flashed?

[onfireX5]

Originally Posted by two1bar

Based on the dragy results, it hasn't impacted the performance like it has on other platforms. So far I've only seen .1 and 1mph in 1/4 mile which could easily be variance in weather conditions. We have 3 X3Ms with ER downpipes and all 3 have netted similar results.

You are on the money as compared to what we've tested on other platforms. Z06 Corvette and Porsche Turbo S.

Factory cats have come a long way in flow.

[AlexFL]

Originally Posted by onfireX5

You are on the money as compared to what we've tested on other platforms. Z06 Corvette and Porsche Turbo S.

Factory cats have come a long way in flow.

Factory cats are non-restrictive in stock cars, but what happens when you add some performance? Don’t the factory cats become super restrictive compared to catless downpipes?

[ThumperMCS]

If you are melting cats due to tune.....you need a new tuner lol

[two1bar]

Originally Posted by AlexFL

Just to clarify, were you comparing stock X3Ms with vs without ER downpipe? Or were the cars BM3-flashed?

Sorry I should have clarified. My comparison is based on Bootmod3 tuned X3Ms where we went from Stage 1(stock exhaust) to Stage 2(catless primary downpipes) tuning.

[AlexFL]

Originally Posted by two1bar

Sorry I should have clarified. My comparison is based on Bootmod3 tuned X3Ms where we went from Stage 1(stock exhaust) to Stage 2(catless primary downpipes) tuning.

So this basically suggests that there is another restriction/bottleneck in the center pipes, correct?

[onfireX5]

Originally Posted by AlexFL

Factory cats are non-restrictive in stock cars, but what happens when you add some performance? Don’t the factory cats become super restrictive compared to catless downpipes?

Catless will always outflow a catted pipe on our flowbench. But, if a catted pipe flows enough to not restrict the power level you are at, taking it off puts you back into the +- 0.1 and 1mph level as mentioned above.

[AlexFL]

Originally Posted by onfireX5

Catless will always outflow a catted pipe on our flowbench. But, if a catted pipe flows enough to not restrict the power level you are at, taking it off puts you back into the +- 0.1 and 1mph level as mentioned above.

Or as an alternative interpretation; once the primary cat is removed, the secondary cat becomes the bottleneck. A nice comparison would be “catless downpipe” vs “fully catless”.

[Miko M]

I might do down pipes too
Need to think about it
Mine F90 M5 was brutally loud 126 decibel cold start
Driving kids around can be to annoying. Lol

[AlexFL]

Originally Posted by Miko M

I might do down pipes too
Need to think about it
Mine F90 M5 was brutally loud 126 decibel cold start
Driving kids around can be to annoying. Lol

Did you order the Eisenmann system with center pipes?

[Miko M]

Originally Posted by AlexFL

Did you order the Eisenmann system with center pipes?

Yes, getting installed on the 2nd
I hate waiting, I want those 100mm tips which are coming on the 2nd