[Butters]

Does anyone know if the exhaust flap needs to be or should be bypassed when tuned? it opens before it becomes restrictive at stock power levels, but if is rpm based and not load based could it be restrictive with increased low end power?

[enrita]

Originally Posted by Butters

Does anyone know if the exhaust flap needs to be or should be bypassed when tuned? it opens before it becomes restrictive at stock power levels, but if is rpm based and not load based could it be restrictive with increased low end power?

its never gonna be restrictive. is purely a sound measure.

[Fun w/N54]

I currently have a 08 135 with N54 and thinking about getting a 08-09 335xi with N54 before next winter. Assume the same AP can be used just grab the correct maps from Cobb site for the 335 ecu.

Thanks.

[enrita]

Originally Posted by benveds

I currently have a 08 135 with N54 and thinking about getting a 08-09 335xi with N54 before next winter. Assume the same AP can be used just grab the correct maps from Cobb site for the 335 ecu.

Thanks.

yes

[BlackBB6]

Originally Posted by benveds

I currently have a 08 135 with N54 and thinking about getting a 08-09 335xi with N54 before next winter. Assume the same AP can be used just grab the correct maps from Cobb site for the 335 ecu.

Thanks.

You can use the same one, after uninstalling it from the 135.

[Butters]

I agree the flap is used for sound tuning. However, a 3L engine at 2500rpm at 15psi pushes the same volume of exhaust as the same size engine running at 9psi does at about 3300 rpm.

[Jeef]

for stage 2+FMIC aggressive no need for exhaust correct? Also would i see any difference running 100 octane..?


oh by the way COBB i need a meth map for feb 25th inyokern! whens it coming?!

[JStang]

Originally Posted by Jeef

for stage 2+FMIC aggressive no need for exhaust correct? Also would i see any difference running 100 octane..?


oh by the way COBB i need a meth map for feb 25th inyokern! whens it coming?!

Exhaust is recommended but not required. You will be fine with the stock exhaust. You will not see any gains running 100 octane until the race maps are released which is hopefully soon.

[Brey335i]

Exhaust isn't necessary. Honestly, the secondary cats don't impede flow all that much. I gained a whopping 5 peak gain in hp and 6 tq from going catless. And it smells lol.

[Jeef]

well i hope they hurry before airstrip event at inyokern!

[MDORPHN]

Originally Posted by JStang

Exhaust is recommended but not required. You will be fine with the stock exhaust. You will not see any gains running 100 octane until the race maps are released which is hopefully soon.

I was under impression, apparently mistaken, that an aftermarket downpipe was required for Stage 2.

Neil

[mithiral67]

Originally Posted by MDORPHN

I was under impression, apparently mistaken, that an aftermarket downpipe was required for Stage 2.

Neil

On this site, exhaust and DPs are generally referred to as two separate things. Yes, the DPs are a part of the exhaust, but on this site, almost 95+% of the time that someone refers to the exhaust, they are only referring to the catback portion of the exhaust. Hence, when someone says an aftermarket exhaust isnt necessary for stage 2+, they mean the cat back portion only. You really should have catless DPs for stage 2+

Downpipes have the primary cats which are very restrictive at the turbos and need to be replaced for stage 2.

The secondary cats and the mufflers (referred to exhaust for the purposes here) are not very restrictive and dont limit you to run stage 2.

[MDORPHN]

Originally Posted by mithiral67

Exhaust and DPs are two different things.

Downpipes have the primary cats which are very restrictive at the turbos and need to be replaced for stage 2.

The secondary cats and the mufflers (referred to exhaust for the purposes here) are not very restrictive and dont limit you to run stage 2.

Makes sense. Thanks for clarification.

Neil

[AWD Addict]

Originally Posted by Brey335i

Exhaust isn't necessary. Honestly, the secondary cats don't impede flow all that much. I gained a whopping 5 peak gain in hp and 6 tq from going catless. And it smells lol.

Interesting. So our dual exhaust provides a lot of volume?

[Pseudo Nim]

Curious - what are the disadvantages of running Stg2+FMIC without an aftermarket FMIC? More potential to overheat (it's winter, though)? Timings/targets that are too agressive?

[mithiral67]

For intake temps, I am betting is safe for short bursts, but the fmic can heat soak pretty damn fast. I am not sure about the overall flow difference between oem and aftermarkets.

[Pseudo Nim]

Originally Posted by mithiral67

I am betting is safe for short bursts, but the fmic can heat soak pretty damn fast.

Ya that's what I figured. So for daily driving it makes no diff, but for track prob better to go down to the regular Stg2 map.

[Sleeper]

Haha, I love the different car forums' names for different parts. How are "DP's" different from an "exhaust"? DP's are part of the exhaust system from the turbo's back.

Downpipes, midpipes, catbacks, axlebacks... all exhaust parts.

Anyway, carry on.

ps. Cobb, still very much looking forward to ATR's release.

[rader1]

Originally Posted by Sleeper

Haha, I love the different car forums' names for different parts. How are "DP's" different from an "exhaust"? DP's are part of the exhaust system from the turbo's back.

Downpipes, midpipes, catbacks, axlebacks... all exhaust parts.

Anyway, carry on.

ps. Cobb, still very much looking forward to ATR's release.

You have a point. However, performance wise, DPs are a world apart from a catback.

[Sleeper]

^I wasn't talking about performance at all, just the weird nomenclature used on this forum for exhaust parts haha.

That said, I found that the significant weight difference between my OEM catback and my aftermarket catback definitely made my car 'feel' more powerful. Obviously that just a function of weight loss and not actually WHP increase, but it was still nice .

[AWD Addict]

Originally Posted by rader1

You have a point. However, performance wise, DPs are a world apart from a catback.

I think he's just talking about terminology, and the comments in this post.

Originally Posted by mithiral67

Exhaust and DPs are two different things.

Downpipes have the primary cats which are very restrictive at the turbos and need to be replaced for stage 2.

The secondary cats and the mufflers (referred to exhaust for the purposes here) are not very restrictive and dont limit you to run stage 2.

A Cat-Back is part of the exhaust system, as is anything else after the manifold (including the hot side of the turbo). What I think mithiral was saying is a Catback and DPs are two different things.

That said, there's certainly some conflicting information on that page. One person is saying the dp cats are so restrictive, they "need" to be replaced for the Cobb Stage 2 tune, and others (JStang & Brey 335) are saying an upgrade is relatively meaningless, as the stock setup has pretty favorable flow already.

[enrita]

Originally Posted by AWD Addict

I think he's just talking about terminology, and the comments in this post.



A Cat-Back is part of the exhaust system, as is anything else after the manifold (including the hot side of the turbo). What I think mithiral was saying is a Catback and DPs are two different things.

That said, there's certainly some conflicting information on that page. One person is saying the dp cats are so restrictive, they "need" to be replaced for the Cobb Stage 2 tune, and others (JStang & Brey 335) are saying an upgrade is relatively meaningless, as the stock setup has pretty favorable flow already.

dps are the bottleneck on the exhaust. Those are the first to be replaced. The stock exhaust after the dps is fine.