MAF screens removal

[Pingu]

I think that the main problem with this thread is that it is trying to target the wrong thing. It is targeting marginal gains when there is a much larger gain to be had by improving the airbox.

2cm H2O is a large amount of drag and should be quite easy to improve.

Hi, certainly very interesting shame you could not test with thinner side walls, did you remove the wire mesh from behind the front screen?

Andy

My MAF doesn't have a wire mesh.

I can render a drawing for a 0.25mm nozzled printer (standard nozzle is 0.6mm), so I've splashed the cash (£2.99) on a 0.25mm printer nozzle.

I'll have to wait until later in the week to see if the printer is up to the job of making thinner-walled screens.

 

[Pingu]

I think most of us would find that the results are of no surprise

It didn't surprise me, either, but not because Bosch (or BMW) did such a great job at designing the MAF.

The reason that it is hard to better is because trying to improve the air flow through the MAF is chasing very marginal gains.

Targeting the air box would be much more fruitful.

 

[5harp3y]

It didn't surprise me, either, but not because Bosch (or BMW) did such a great job at designing the MAF.

The reason that it is hard to better is because trying to improve the air flow through the MAF is chasing very marginal gains.

Targeting the air box would be much more fruitful.

Define much more?

What's the best you would see by optimising the airbox or the entire intake track, I reckon less than 5bhp .

Which makes it completely uneconomic to try .

That said.

More power to you as I enjoy the scientific approach to this

 

[t-tony]

Microscopic gains, we might not appreciate but then again ask F1 teams. This a manna to those guys.

Tony.

 

[Pingu]

Dear Sean,

What makes people carry out research? This is a question of fundamental importance.

Curiosity is an intrinsic characteristic of the human brain and a powerful drive in the exploration of man’s surrounding environment. To undertake research is to discover and understand the facts. By researching, conclusions may find for the original, this may be due to current limitations but does not detract from the legitimacy or the results of the research. Accordingly, curiosity for the known vs the unknown is a fundamental element in research.

Science sits on the implicit and unshakable belief that all events have cause. It can be argued nothing can occur or exist in an uncaused state. Research by design makes use of multiple techniques to examine various problems. Studying effectiveness of a technique, to apply to a cause or effect either known or unknown, is primarily responsible for results in any research.

As a result, research and the researcher are keenly interested in analysing existing techniques looking to improve and advance in them. Thus the refinement of techniques is another reason for conducting research.

Andy

Exactly. Some cavemen were happy to stay in the valley with some berries for food, others ventured into the next valley and found a lake full of fish and

Define much more?

What's the best you would see by optimising the airbox or the entire intake track, I reckon less than 5bhp .

Which makes it completely uneconomic to try .

That said.

More power to you as I enjoy the scientific approach to this

"Reckoning" is a good euphemism for "I don't have a clue, but I'll make a random guess". By taking a stab at a scientific look at the problem helps me to decide if a modification is worth keeping (I've binned more mods than I've kept).

Some measure improvement by using the seat of their pants, or hearing a different sound. I like to see real figures that prove betterment.

I think that cheap improvements to the S50 will be hard to come by, but improving air flow through the intake system is probably the best bet.

 

[Dalek]

Thanks for a really interesting thread....
I just wish I knew what the hell you are all talking about!!

 

[Jimmy Weston]

Firstly fair play for people trying to Gain an advantage out off a stock part so minimal,but it's there to create a linear even air flow over the Maf,which can even be disturbed bye having and induction kit fitted to close the Maf sensor sometimes,hence the mesh to even and balance the air air flow over the sensor.
Jimmy.

 

[Pingu]

Firstly fair play for people trying to Gain an advantage out off a stock part so minimal,but it's there to create a linear even air flow over the Maf,which can even be disturbed bye having and induction kit fitted to close the Maf sensor sometimes,hence the mesh to even and balance the air air flow over the sensor.
Jimmy.

I didn't know why the front screen was fitted. That's why I did the smoke tests. They were very good at showing that the air flow was straightened (and the obvious reason was as you describe).

What I then tried (and am still trying) to do is produce a shape that will straighten the flow by as much as standard, but have less resistance.

@windym 's suggestion of the honeycomb makes the most sense, as it has the most holes per unit area, yet with the minimum side wall area per unit area (I hope that makes sense), or the most straightening using the least plastic.

I have three problems doing these tests...

1. I can only suck on an 86mm bore at 4cm H2O. To replicate an engine I need to be sucking at around 2.5psi (175cm H2O), so I would need an industrial suction machine to get close.
2. My manometer is not accurate enough at the pressures that I am working at. I need to make another using smaller bore tube at a shallow incline. This is easy enough to do, but I'll wait for my digital manometer which should be here soon.
3. I've not been able to make the honeycomb patterned screen with thin side walls, as the nozzle on my printer is too big. I've just received a smaller nozzle and will make another attempt today.

 

[Ianmc]

I didn't know about "air straightening", so very interesting thread. You have much more patience than I, well done.

 

[windym]

Been looking at suitable honeycomb alternatives and found this, the plan is to fit this behind the air filter, before the MAF having the simota type this looks like it will fit in the filter itself.

It would appear the air is straightened around 3cm past the screen so this should give me the distance needed, before hitting the sensor.



Andy

 

[Pingu]

Looks good. How much?

What is stopping you swapping it with the OEM one?

What size is the honeycomb? What is the thickness of the side walls?

I've got one printing at the moment. I need to go to work and hope that it will be finished when I get back. It's only been printing for 11 hours so far .

 

[Sean d]

Dear Sean,

What makes people carry out research? This is a question of fundamental importance.

Curiosity is an intrinsic characteristic of the human brain and a powerful drive in the exploration of man’s surrounding environment. To undertake research is to discover and understand the facts. By researching, conclusions may find for the original, this may be due to current limitations but does not detract from the legitimacy or the results of the research. Accordingly, curiosity for the known vs the unknown is a fundamental element in research.

Science sits on the implicit and unshakable belief that all events have cause. It can be argued nothing can occur or exist in an uncaused state. Research by design makes use of multiple techniques to examine various problems. Studying effectiveness of a technique, to apply to a cause or effect either known or unknown, is primarily responsible for results in any research.

As a result, research and the researcher are keenly interested in analysing existing techniques looking to improve and advance in them. Thus the refinement of techniques is another reason for conducting research.

Andy

Dear Andy,
A plastic printer is not in any way going to compare to the millions of pounds that BMW invest in technology, no big words just plain and simple, the proof is in pudding,
kindest regards, Sean

 

[Sean d]

Exactly. Some cavemen were happy to stay in the valley with some berries for food, others ventured into the next valley and found a lake full of fish and


"Reckoning" is a good euphemism for "I don't have a clue, but I'll make a random guess". By taking a stab at a scientific look at the problem helps me to decide if a modification is worth keeping (I've binned more mods than I've kept).

Some measure improvement by using the seat of their pants, or hearing a different sound. I like to see real figures that prove betterment.

I think that cheap improvements to the S50 will be hard to come by, but improving air flow through the intake system is probably the best bet.

Oh dear, some cavemen had far to much time on their hands

 

[Sean d]

Dear Sean,

What makes people carry out research? This is a question of fundamental importance.

Curiosity is an intrinsic characteristic of the human brain and a powerful drive in the exploration of man’s surrounding environment. To undertake research is to discover and understand the facts. By researching, conclusions may find for the original, this may be due to current limitations but does not detract from the legitimacy or the results of the research. Accordingly, curiosity for the known vs the unknown is a fundamental element in research.

Science sits on the implicit and unshakable belief that all events have cause. It can be argued nothing can occur or exist in an uncaused state. Research by design makes use of multiple techniques to examine various problems. Studying effectiveness of a technique, to apply to a cause or effect either known or unknown, is primarily responsible for results in any research.

As a result, research and the researcher are keenly interested in analysing existing techniques looking to improve and advance in them. Thus the refinement of techniques is another reason for conducting research.

Andy

This post belongs on .net what a load of b*******s

 

[Pingu]

Oh dear, some cavemen had for to much time on their hands

Eat berries if you want, I'll eat fish.

I doubt very much that BMW spent millions on the MAF. They would have looked at the Bosch catalogue and picked the MAF that has a flow rate of more than 13,000 litres per minute at their acceptable Mach Number for air speed. The higher the Mach Number, the cheaper the component (due to it being smaller), but the less efficient (due to the air being more compressed).

The air velocity through the open MAF at 8000rpm is around 38 m/s (or Mach 0.12). Air starts to be noticeably compressed and change it's properties at Mach 0.1. (You want to be below 0.3 under ALL circumstances.)

Any obstruction in the MAF will increase the velocity, compress the air more and make it harder for the engine to "suck".

Hex_08 (5mm Hex, 0.5mm side wall)...

12 hours 24 minutes to print

I won't be able to fully test it, as the car's MOT is on Friday, and it needs its MAF fitted to pass the emissions test.

 

[Pingu]

This post belongs on .net what a load of b*******s

You are probably right. It takes a certain type of person to waste their time reading a thread that they have no interest in, and then commenting on it.

 

[windym]

This post belongs on .net what a load of b*******s

Oh dear bless poor boy, the paint fumes have finally got to her.

Andy

 

[windym]

Looks good. How much?

What is stopping you swapping it with the OEM one?

What size is the honeycomb? What is the thickness of the side walls?

I've got one printing at the moment. I need to go to work and hope that it will be finished when I get back. It's only been printing for 11 hours so far .

Ebay £7 will measure when it comes

 

[Redline]

Interesting stuff! (For some anyway )

A few things going on here that’s going to affect things I would think.
The first issue is I expect the air flow coming out of the filter is already turbulent and uneven.
Slowing that air and then speeding it up may help that.

The honeycombe structure is obviously the strongest, but, I suspect the depth will do little to straighten the airflow considering turbulence already within it, especially as that turbulence will change with different flow rates, especially if standing waves get set up.

The leading edges of the honeycombe is likely to create turbulence in the air as it passes over. A more aerodynamic leading edge will help air flow over it. Same with the trailing edge but to a lower degree.

I expect the airflow across the section is non linear too. Some channeling would help.

Something seemingly simple soon turns into a big exercise. I foresee lots of printer time and plastic being used.

 

[Pingu]

@Redline Interesting stuff! (For some anyway )

A few things going on here that’s going to affect things I would think....

The first issue is I expect the air flow coming out of the filter is already turbulent and uneven.

I think this is the reason for the front screen. I don't know the reason for the rear screen, other than to stop curious fingers touching the sensor.

Slowing that air and then speeding it up may help that.

This could be done, but it would need a lot of space as I would need to build a double-venturi system between the filter box and the MAF.

The honeycombe structure is obviously the strongest, but, I suspect the depth will do little to straighten the airflow considering turbulence already within it, especially as that turbulence will change with different flow rates, especially if standing waves get set up.

I don't agree about your comment on the depth not mattering. At one extreme there is a wire mesh, and at the other a very long honeycomb structure.
I haven't tested it, but I suspect that a wire mesh will just generate a lot of turbulence and do very little straightening. It is something that I will test, though. If it works, it would make things very simple.
A very long honeycomb would have many problems that would cause drag. Friction within the honeycomb being the main one, but (as you mentioned) standing waves would probably be a problem as well.

I think that this is a trade-off thing. The deeper the honeycomb, the straighter the flow, but the deeper the honeycomb, the more drag (especially, as you say if a standing wave gets set up). This is the thing that I am really testing for. I want to find a hole shape and depth that straightens as effectively as OEM, but has less drag. Personally, I see this as a marginal gain exercise compared to the much larger gains from a modified filter box, but "every little helps"!

I suspect that we wouldn't have to worry about standing waves, though, as they would only occur at a certain velocity and the velocity is constantly changing. But it is definitely a consideration.

The leading edges of the honeycombe is likely to create turbulence in the air as it passes over. A more aerodynamic leading edge will help air flow over it. Same with the trailing edge but to a lower degree.

True, there is turbulence created whenever you stick anything in an airstream, but there is no way that I would be able to fabricate something as intricate, and I think the gains would be in the 0.01%'s.

As the air hits the side walls of the mesh and is split, I need to be aware that the split air can collide with the split air from another side wall. This means that there is a minimum size for the holes. This minimum hole size gets bigger as the air velocity increases. BMW/Bosch have already decided that 4mm holes are adequate, but the bigger the hole, the less side wall interference there will be (I think). Using an aerodynamically shaped sidewall would allow an even bigger hole, but I don't think the gain would be worth the effort.

I expect the airflow across the section is non linear too. Some channeling would help.

I thought about this, but decided not to pursue it at the moment. The velocity through the centre of the MAF screen will be higher than the velocity at the outer edges due to drag (assuming clean, straight flow from the filter box [big assumption]).

It would be nice to see the actual airflow through the system in operation, but I think that I would need to cut up the system, add perspex windows and use tons of smoke and a fast frame-rate camera.

The best that I can do (and it is moderately successful) is to probe different parts of the system with a manometer tube. You can see the manometer level change as you move the tip of the tube around in an air stream. It's a very useful tool.

Something seemingly simple soon turns into a big exercise. I foresee lots of printer time and plastic being used.

You could be right