MAF screens removal

[Redline]

@Redline

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.

Haha. Designed and built a wind tunnel as a group project at school. Quite a challenge at 16. Creating non turbulent air flow was the hard bit and a problem that remained unresolved. Only had plate cameras then though

 

[gookah]

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

No need to hold back on our account, just say what you really think....

 

[windym]

So this is the plan, the 60deg honeycomb appears to, on paper at least, give the greater air flow. By fitting it into the filter outlet and removing the standard screen, I should in theory, have at the point the air makes contact with the MAF sensor, the least turbulent(straight) air.

Grammatically shocking; my apologies.

Andy

 

[windym]

Still waiting on the honeycomb so decided to remove the metal gauze behind the front screen. I can see no reason for this other than the car was driven without an airfilter, even then the gauze would do little good.

This can not have helped with the air flow or sensor reading the correct intake as this must have served to undo what the front screen had done. Will take it for a shakedown tomorrow see if there is any difference.

Andy

 

[Pingu]

You shouldn't run a car without an air filter unless yo plan to do a full engine rebuild every 1000 miles.

Vizard, the guru in these matters, tells the tale of running an engine without an air filter. If I recall an earlier tale that he told, the performance improvement lasted enough time for one race weekend - about six hours.

https://www.facebook.com/DavidVizardAuto/photos/so-many-drag-racers-are/406573572744469/

 

[Pingu]

I've made a flow bench and should be able to test some screens over the weekend.

I've made one using a very small nozzle. It looks quite promising.

 

[windym]

Just had the new honeycomb filter delivered today, took two images at the same magnification of both the pics are below.


This is the standard MAF screen

This is the new screen material

At this point it looks in favour of the new screen as the side walls are thinner and the holes are defiantly bigger.

The two combined

@Pingu can you ping your address over and I will post the screen for you to test.

Andy

 

[windym]

Both screens in-situ, will wait for the flow test from @Pingu to see if this is any good.

 

[Pingu]

Both screens in-situ, will wait for the flow test from @Pingu to see if this is any good.

View attachment 85743

View attachment 85744

Looking at them is a no-brainer as far as flow rate is concerned - hex will flow much better. The test that will determine if it's any good will be the smoke test to see if the hexagon straightens the flow as much as the square.

 

[windym]

Just taken the car out, feels smoother and the exhaust is raspier. Possible placebo will wait for Pingu's flow test, so far with the manifold conversion the simota and this, I can say huge improvement over the original. Although the honeycomb may still need work, I have the car booked in for a sport cat to be fitted, so a lot of little changes should net some significant hp gains.

Andy

 

[Pingu]

I've done some tests and they are VERY positive. The lower the number, the better

I have to do a test on the full system (air box + MAF), but...

Pressure drop across a 38mm hole (cut with a hole saw) = 20
OEM = 22.75
My best hex = 25
WindyM Hex = 18.75

How can it be better than a hole? It would seem that it has less drag than having an open hole. It does . How can I explain this?

I think that it is the same as adding a bellmouth to an orifice. Instead of air being made to do a right-angled turn to go into the hole, it is turned gently by the hex, in a similar way to how the air is turned by a bellmouth.

I have lots to do to my flow bench to make it better, including making a proper machined orifice - just a hole made with a hole saw won't do.

 

[windym]

Sounds like a start, how did it straighten the flow

 

[Pingu]

I haven't done the straightness test to compare it to the OEM yet. That's for tomorrow or Thursday.

It definitely straightens the flow - that's how it gets the flow to be so fast through the orifice. I just need to find out if the flow stays straight for as long as OEM.

 

[windym]

Thats great, so am I safe in assuming the difference I felt in the car was not a placebo then. Will work out the extra flow rate percentage after the straightness test.

Andy

 

[Pingu]

Here's a graph showing the STEADY STATE air velocity through each of the screens.

I used this rig to make the measurements

All the possible leakage edges were sealed with Plasticine. The yellow thing is an anemometer. The cardboard tube has 82.5mm ID.
The orifice at the base is 38mm. This is the best size that I found that allows the manometer readings to be in the range of the inclined manometer that you can see at the top of the image.

I used my vacuum cleaner to "suck" at a given depression (measured on a manometer that is inclined at 8.75°) and read the associated air velocity on the anemometer. The graph above shows the average readings for the four screens that I tested.

In steady state conditions, Windy's screen and my newest hexagon screen were both better (higher air velocity at a given depression) than the OEM screen, but (unsurprisingly) were not as good as having no screen.



but, I also did an acceleration test (which is NOT steady state). IC engines are not steady state engines.

I switched on the vacuum and, using a 50fps GoPro, read the manometer as the depression moved along the tube. Below are the results of the test (converted into seconds)...

Excluding the potentially corrupted data (Open Test 1 (27cm) and Test 3 (25cm)), the times for the depression to go from 1cm to 25cm were (fastest-to-slowest)

Hex_08 = 1.77 seconds
OEM = 1.81 seconds
Windy = 1.84 seconds
Open = 1.87 seconds


from 1cm to 26cm:

Hex_08 = 1.89 seconds
OEM = 1.94 seconds
Windy = 2.00 seconds
Open = 2.01 seconds


from 1cm to 27cm:

Hex_08 = 2.09 seconds
OEM = 2.16 seconds
Windy = 2.25 seconds
Open = 2.27 seconds

In non-steady state conditions, my newest hexagon screen allowed air to accelerate through it faster than the other screens.

I've got more tests to do, including a full air filter test and a test with the screens on the car.

 

[windym]

Hi, is it possible to make the initial tube from an old MAF. With the element in place as this must to some degree cause an interruption with flow.

Also just ordered some 45deg hex to test as well, maybe the smaller aperture of the 45 will create a faster flow

 

[Pingu]

I used the cardboard tube because it was easy to cut and install the anemometer, but it is very hard to calculate the area of the orifice. I've made a rough guess at 4500mm² to 4175mm².

Volumetric Flow Rate = Velocity x Area

The reason that I don't quote the flow rate is that the anemometer has its own area and affects the flow rate (this is what Schrodinger's Cat is all about). Ideally, the instrument that you use to measure something shouldn't affect the thing that you are measuring. It is VERY hard to achieve this.

I could have used any tube and there is no reason (other than cost) not to use an old MAF.

I'm not sure that I understand the relevance of removing the sensor. The system should be tested in the configuration that it will be used. Unless you are planning to replace the sensor with a different sensor, why would you remove it?

 

[Pingu]

More stuff...

I've tested the air filter and the MAF.

Here's the set up...

Here's the STEADY STATE graphs. They show that WindyM's hexagon is the best...

So, if the engine runs at constant speed, WindyM's hexagon screen is the one to have, but IC engines are not single speed engines.

I think that the better test is the acceleration test...

If we look at the time taken to accelerate to 25cm, the order (fastest first) is

1. Hex_08 (1.74 seconds)
2. WindyM (1.77 seconds)
3. OEM (1.78 seconds)
4. No Screen (1.82 seconds)

The next tests will be in the car

 

[Jack Ratt]

Very interesting tests and reports that may help us understand how air flow and restricted air flow affect the performance of an engine.
They may help us to understand how to make the engine more efficient but on conventional car engines we will never be able to straighten the flow enough to get any real gains.
Every bend in a duct or pipe will reduce air flow, (vena contracta effect) as will screens and filters and because of the compacted designs of the intake system, the duct lengths are not sufficient for the air flow to regain velocity before it is reduced again by another bend, and so on, and so on.
It needs a straight duct length of 4 to 6 diameters for static regain to the level before the previous bend.
What happens to the air flow after the MAF probably has more of an effect on engine efficiency as what happens before.

 

[Pingu]

I've been out doing some 20-70 tests and here's the results...

As you can see, none of the screens are much better than any of the others.

I did five runs with each screen and each of the lines is the average of the best three runs with each screen.