[robnitro]

I'm curious about comparing slow speed city driving mileage with the flaps in use vs wide open.

Anyone who deleted have a set that they would want to sell?

Unfortunately I deleted mine years ago.

Nowadays egr is not in use, so the carbon issues are not a problem to use the flaps.

[fearitself165]

I do have a set that I just removed.. not cleaned but I could do that im sure

[robnitro]

Originally Posted by fearitself165

I do have a set that I just removed.. not cleaned but I could do that im sure

Thanks. They weren't cut to get them out right?
Can you send pictures, I don't mind the dirt, but I remember my old ones were pretty worn on the shaft- that's why I tossed them.
Let me know what you want for em.
If you want to wait and hold onto them I can wait, no rush... It's just curiosity
I think they will all fit in a flat rate USPS priority mail shipping box.

[fearitself165]

No I unscrewed them lol. And yes I'm going home right now ill be able to send pictures.

[POBEP]

Originally Posted by robnitro

I'm curious about comparing slow speed city driving mileage with the flaps in use vs wide open.

Anyone who deleted have a set that they would want to sell?

Unfortunately I deleted mine years ago.

Nowadays egr is not in use, so the carbon issues are not a problem to use the flaps.

robnitro - IMO, this experiment would be waste of your time.

E70 is a heavy vehicle and magic device like swirl flaps will not be able to contribute enough to make noticeable difference on the city mileage.

The DPF delete does improve overall mileage as ECU no longer waste fuel for active re-gen.

IMO, the biggest E70 city mileage impact would be 6-to-8HP swap and/or xDelete

If city mileage is real concern - the best solution is EV

[robnitro]

Originally Posted by POBEP

robnitro - IMO, this experiment would be waste of your time.

E70 is a heavy vehicle and magic device like swirl flaps will not be able to contribute enough to make noticeable difference on the city mileage.

The DPF delete does improve overall mileage as ECU no longer waste fuel for active re-gen.

IMO, the biggest E70 city mileage impact would be 6-to-8HP swap and/or xDelete

If city mileage is real concern - the best solution is EV

Electric is a waste, in my area it costs a lot but I would have loved a parallel hybrid like the volt was!

You're right about the flaps! I realized they're only there for the egr gasses to mix evenly for combustion. Without the reduced airflow from egr/throttle plate function, there's no help.

Thanks for the help.

[Tambohamilton]

Originally Posted by robnitro

I realized they're only there for the egr gasses to mix evenly for combustion. Without the reduced airflow from egr/throttle plate function, there's no help.

This isn't true. The turbulence created by the swirl flaps helps combustion by promoting mixture of the (injected/ignited) diesel and air in the chamber. It really has nothing to do with egr. Also the inlet runners which the flaps force air into are longer, which flows better at low rpm and low manifold pressure.

[Nadir Point]

I've always been impressed by how little the 335D smokes. Even after removing the emissions controls, low speed smoke seems less than I would expect. -- SWIRL FLAPS --

[robnitro]

Originally Posted by Tambohamilton

This isn't true. The turbulence created by the swirl flaps helps combustion by promoting mixture of the (injected/ignited) diesel and air in the chamber. It really has nothing to do with egr. Also the inlet runners which the flaps force air into are longer, which flows better at low rpm and low manifold pressure.

I lost the link that explained the original idea but it goes this way:
Imaginary low load acceleration or cruising:
With egr, the afr is around 20:1
Parts of the combustion chamber are 10:1, others 30:1... It's not homogenous.
Swirl helps the mixture to be more uniform.

Without egr, afr is around 40:1, same parts are 20:1 and 60:1
Less issues with needing to mix, with excess oxygen available.

Keep in mind that beyond a certain throttle, the swirl flaps are wide open.

[robnitro]

Originally Posted by Nadir Point

I've always been impressed by how little the 335D smokes. Even after removing the emissions controls, low speed smoke seems less than I would expect. -- SWIRL FLAPS --

How about the mileage? No change in tuning or you did the flaps along with the tune?

[Tambohamilton]

Originally Posted by robnitro

I lost the link that explained the original idea but it goes this way:
Imaginary low load acceleration or cruising:
With egr, the afr is around 20:1
Parts of the combustion chamber are 10:1, others 30:1... It's not homogenous.
Swirl helps the mixture to be more uniform.

Without egr, afr is around 40:1, same parts are 20:1 and 60:1
Less issues with needing to mix, with excess oxygen available.

Keep in mind that beyond a certain throttle, the swirl flaps are wide open.

Well yes, but also no...

When diesel is injected into static air, the droplets can only react with the very limited volume of air immediately around them. And the rate of heat from combustion spreading through the chamber is slow (relatively). If there is high turbulence in the combustion chamber, the fuel is constantly being presented with fresh air to burn in so it burns better. The stirring also spreads heat from the pilot injection around the chamber faster, so subsequent doses ignite and burn faster. EGR or no, the flaps are important.

Also the flaps open with throttle and rpm, so at low rpm they are always fully closed and doing their job, regardless of throttle position.

[robnitro]

Understood. Do you have the flaps along with egr deleted? I'm curious if you could run some simple tests of idle in gear with accessories on, using the flaps, and with the flaps actuator unplugged, comparing fuel flow rate.

Or a drive cycle comparison perhaps?

Originally Posted by Tambohamilton

Well yes, but also no...

When diesel is injected into static air, the droplets can only react with the very limited volume of air immediately around them. And the rate of heat from combustion spreading through the chamber is slow (relatively). If there is high turbulence in the combustion chamber, the fuel is constantly being presented with fresh air to burn in so it burns better. The stirring also spreads heat from the pilot injection around the chamber faster, so subsequent doses ignite and burn faster. EGR or no, the flaps are important.

Also the flaps open with throttle and rpm, so at low rpm they are always fully closed and doing their job, regardless of throttle position.

[Tambohamilton]

Maybe one day... Don't hold your breath! I barely find enough time to do necessary maintenance on my car, let alone fun tinkering

[Owen81]

BMW's own documentation states the swirl flaps are for low speed cold engine emissions only, with "otherwise no effect" if they stick open.

Electric swirl flap control
Swirl flaps ensure better swirl of the air. The result is better emission levels.

The adjustable swirl flaps are located in the swirl ports of the intake system and are opened and closed according to the operating condition of the engine. With controllable swirl flaps, the swirl-flap actuator opens the swirl flaps as the speed increases. The swirl flaps are closed under the following preconditions:

at low engine speeds and low fuel injection rates (characteristic map-controlled)
The swirl flaps generally remain open when

the coolant temperature < 15 °C OR
the intake air temperature < 15 °C
Effects of faults
If the swirl flaps stick in open position: Deterioration in exhaust gas characteristics in lower engine speed ranges otherwise no effect.

If the swirl flaps stick in closed position: Power loss of approx. 10 % at higher speeds, in addition the intake plenum can overheat.

[Tambohamilton]

Can you link the entire document, please?

Note that it says the flaps remain open (ineffective) at cold temps, not the other way around.

[robnitro]

Originally Posted by Tambohamilton

Can you link the entire document, please?

Note that it says the flaps remain open (ineffective) at cold temps, not the other way around.

I'm not sure on the 35d, but on the VW TDI, egr was also closed at low temperatures to prevent combustion issues when cold.

If that's the case, swirl flaps work with egr, where the fresh air is limited, and at cold temperatures not used because there is no EGR being used and there's a huge excess of oxygen.

Just kind of makes me think it's to help reduce the low load nox which is highly dependent on having a very even mix of oxygen. Excess oxygen spots in combustion would create more nox.

[Tambohamilton]

Yeah, seems odd to me, hence why I'd like to read the whole thing

[robnitro]

Originally Posted by Tambohamilton

Yeah, seems odd to me, hence why I'd like to read the whole thing

A new tidbit from the conclusion of a study:
"Higher levels of in-cylinder swirl, the bulk rotation of the charge about the cylinder axis that is induced during induction, have been shown to reduce the emissions penalty traditionally associated with EGR. "

It reduces soot production which happens when using mid to high egr rates... Confirming my theory that these flaps are there for when egr is being used at low loads/low rpm operation. Better mixing to reduce particulates for the dpf life.

https://www.researchgate.net/publica..._Diesel_Engine

[TheBigSwede]

Originally Posted by robnitro

I'm curious about comparing slow speed city driving mileage with the flaps in use vs wide open.

I've pondered this very thing for a few years and finally did a country driving test last summer but forgot to post my results. The first weekend was a 460km round trip without swirl flaps. The second weekend was the exact same route with pristine swirl flaps installed. I did my best to replicate driving style, gross weight, fuel type (V-Power!), etc. The weather conditions were essentially identical +/- 2degrees C with similar humidity. I racked up 15 bonus kms with the flaps due to a detour... no matter. I witnessed a .1 L/100 "improvement" with flaps. Would love to see a stop n' go city test conducted where the flaps spend more time in the open position.

Without Flaps - Country Drive #1


With Flaps - Country Drive #2

[Edvinioks]

I have reinstalled the swirl flaps back to the car. The turbo spool now is way more responcive and faster. Without then itt felt like the small turbo isint working. Glad that ive did it