[Dazza335iC]

I'm going to be doing my VCG in a few days, and am tempted to delete the swirl flaps while I'm in there. What are the benefits/drawbacks of this? Obviously BMW put the swirl flaps in there to improve light load efficiency; has anyone who has done this seen a drop in fuel economy? Increase in power (dyno verified)? Or is this just a "I mod my engine because engines mods are cool bro" thing?

[dmanb2b]

Main benefit is eliminating possible sources of boost leak and two eliminate risk of broken swirl flap falling in intake

[BB_cuda]

Originally Posted by dmanb2b

Main benefit is eliminating possible sources of boost leak and two eliminate risk of broken swirl flap falling in intake

European market cars had instances of the small screws coming undone and intake inhaling them.

[Owen81]

My swirl flaps were leaking boost with oil residue underneath the intake manifold on that side of the engine.
I removed them and have noticed no ill effects. If it does affect mileage, it is not enough to notice regardless.

[Miko226]

No change in MPG.
Maybe a little more spool earlier ?

Do it.

[Thecastle]

Its a minor mod, and not many people have reported problems with the us swirl flaps. Its one of those things you might do if you have a problem or are already there. But I suspect there are other mods you could spend money on that have a better cost/benefit ratio.

[GodStang]

I did mine this weekend. My flaps were so gunked up with carbon that removing them and cleaning the ports the car drives like a whole new car. So much more pep. Now the gains were not just from the delete but from cleaning the ports also. Just getting in there to check everything out was worth the delete.

[Dazza335iC]

Yikes! Yes those are really bad. I already did my carbon cleaning about 25k ago, and with the EGR running on a modified program and a catch can in place, I'm happy to say that my intake is squeaky clean.

[GerryAttrick]

Waiting for my dealer to get the plugs in to seal the ports and then mine ar coming out. I have to have the car apart to replace 2 glow plugs so I am doing all of them and the Swirl Flaps at the same time.

[335stoner]

i want to see dyno results from a car with a clean intake with and with out swirl flaps..

The long runners (you see up top) are the main runners used all the time. Long runners help with power in the low RPM range.. The short runners help with power in the high RPM range. when the swirl flaps are removed it is easier for the motor to always use the short runners since that are closer and a little larger in size..

I wonder if it kills off some low end torque??

[335stoner]

Originally Posted by GerryAttrick

Waiting for my dealer to get the plugs in to seal the ports and then mine ar coming out.

why not just order them online? it will be cheaper and possible faster

[RL18]

Originally Posted by 335stoner

i want to see dyno results from a car with a clean intake with and with out swirl flaps..

The long runners (you see up top) are the main runners used all the time. Long runners help with power in the low RPM range.. The short runners help with power in the high RPM range. when the swirl flaps are removed it is easier for the motor to always use the short runners since that are closer and a little larger in size..

I wonder if it kills off some low end torque??

I could probably do that test! I still have my swirl flaps in. Dyno before and after. Also would like to do race pipe before and after

[Nadir Point]

Originally Posted by 335stoner

I wonder if it kills off some low end torque??

BMW had engineers sitting at CAD terminals doing mid-boggling math problems to come up with the exact size, shape and texture of the intake. Probably a couple other parts too. Were swirl flaps on the table at that point in time? That's the only place you're gonna answer that question, apart from a controlled before/after comparo. That would mean cleaning before in both cases.

[335stoner]

Originally Posted by Nadir Point

BMW had engineers sitting at CAD terminals doing mid-boggling math problems to come up with the exact size, shape and texture of the intake. Probably a couple other parts too. Were swirl flaps on the table at that point in time? That's the only place you're gonna answer that question, apart from a controlled before/after comparo. That would mean cleaning before in both cases.

hints why i said i want to see dyno with and without..

[robnitro]

I don't think it's so much to do with the runner length but the angle that the air comes to the valves to induce swirl at lower air flow (low rpm).

It's for emissions primarily but may affect low end torque but I didn't notice a difference in low end power or mpg when I deleted my flaps.

[jacks121]

Newly registered to the forum but have been lurking for a few months. I recently completed my CBU cleaning but did NOT do the swirl flap delete. I don't feel I understand the performance reason for doing this. I understand the mechanical concern with failure of these valves, but if anything according to the BMW technical manual, there is a LOSS of power at high RPMs with swirl flap closure:

"Effects of Swirl Flap Malfunctions:
If the swirl flaps stick in open position: Deterioration in exhaust gas
characteristics in lower speed ranges otherwise no effect.
If the swirl flaps stick in closed position: Power loss of approximately
10% at higher engine speeds."

I therefore fought the urge to "do something" to these valves (other than clean them) simply because I had the intake off.

[tryingtobebest]

Originally Posted by robnitro

I don't think it's so much to do with the runner length but the angle that the air comes to the valves to induce swirl at lower air flow (low rpm).

It's for emissions primarily but may affect low end torque but I didn't notice a difference in low end power or mpg when I deleted my flaps.

^Great thinking, i dont remember where i read this but it is to introduce swirl but NOT for emissions, its for cleaner and more efficient burn of fluid at lower engine speeds

Originally Posted by jacks121

Newly registered... I recently completed my CBU cleaning but did NOT do the swirl flap delete. I don't feel I understand the performance reason for doing this...

^I was STRONGLY determent to KEEP mine in and working, but they started leaking oil residue about a year after build up cleaning... I felt very bad and concerned when i was taking them out BUT dint felt any negative effect anywhere.

Once and for all BENEFITS of removing:
- Boost and oil leakage (turbos wont over spun from boost leak and might last longer, excessive example)
- Less obstruction on the path of air flow, even if they 100% alingend to each other, to control unit and open (Higher rpm scenario): theory here is if control unit open to the max it doesn't mean that flaps open to MAX air flow, they can be open to 105%, somewhat closed into the other direction past their max airflow point.
- Less possibility that part of them can get into combustion chamber (even tho ours/09+ are bullet proof, carbon can build up and then part into)
- If physically removed all components - weight reduction (joke)
- Less load on electrical system (alternator and swirl control unit might last longer) also a "joke"

DOWNSIDE:
- ENGINEER CALCULATED lower consumption OR/AND better emissions at lower rpm
- Maybe some other benefits other than above

[N52bigblock]

Originally Posted by robnitro

I don't think it's so much to do with the runner length but the angle that the air comes to the valves to induce swirl at lower air flow (low rpm).

It's for emissions primarily but may affect low end torque but I didn't notice a difference in low end power or mpg when I deleted my flaps.

Correct. The only reason they are there is for emissions. They close at idle and create a swirl in the combustion chamber which reduces NOx emissions.

[robnitro]

On another thread on xoutpost some who use dpf have seen more regens without flaps. One guy went back to using flaps and his regen happened less often. So besides nox, it helps create less soot.

[Nadir Point]

Originally Posted by neilj35

Correct. The only reason they are there is for emissions.

It helps to be bit more specific in this example. "emissions," in this context, refers to combustion efficiency - NOT NOX reduction or particulate control or any of the multiple gizmos and whackadoodle bits of kit they've plastered on to this fine piece of machinery.

We're talking about burning fuel here - not just emissions, whatever that means to you.

[robnitro]

It does reduce nox by making a more even mixture. Without good mixing you can have spots that are very lean and spots rich. But yeah emissions in general are improved at low load, which makes the flaps important for those who still use the dpf.

However, it doesn't seem to affect mpg to have it deleted, despite these benefits. I'm going by with what I see reported. The reports of a change in regen interval makes it look more to be a fine tuning for emissions.

[Nadir Point]

Originally Posted by robnitro

It does reduce nox by making a more even mixture.

Right - due SIMPLY to combustion efficiency. Nothing to do with the DEF system, yet still obviously contributing to the DPF system. Engineering that away 1 piece at a time is known as reverse engineering - typically done as a diagnostic process.

Take away the emissions nonsense and all you're left with is low speed combustion efficiency. Or not.