FREE Air-Intake Mod: Full Details on Page 6 of this thread

[jimmybell]

"When the volunteers have had the opportunity to test the mod, I will then disclose the full details of the mod on the forum for all and sundry to see and discuss.

i.e. lets not discuss the details, and leave that to exdos!

[Faheemo]

[carl]

Don't know how I missed this.

Does it involve irreparable changes to OEM parts, e.g. cutting bits off or drilling holes?

[exdos]

Does it involve irreparable changes to OEM parts, e.g. cutting bits off or drilling holes?

"completely reversible"

[carl]

"completely reversible"

There's reversible, and reversible as long as you buy new parts

[exdos]

"completely reversible"

There's reversible, and reversible as long as you buy new parts

"FREE Air-Intake Mod" + "completely reversible" = no cost to undo.

[carl]

Anyway, looking forward to seeing the results

[Adam D]

Watching with baited breath! /wonders if hunch is true

[billy_beemer]

Test faster

[mmm-five]

Test faster

I thought 140mph on the clock (8019rpm in 4th) was fast enough thank you

On an unrestricted autobahn/airfield of course.

Pity I corrupted my 'before' data of the same run - which means I'll have to undo the mod and re-run.

[exdos]

I said I would post the details of the "Eureka Air-Intake Mod" at the end of June, so here it is!


THE MOD

If you open your air-filter box, and look at the bottom of the box you will see a hole (9.8mm to be precise) in the rear corner, which is there for drainage of any water, which might find its way into the air-filter box. The mod is that you put a plug into that hole! It’s that SIMPLE! I've never previously seen anyone write up this mod before, so I'm claiming originating it!







I’m sure you’ll all be thinking that putting a plug into a drainage hole will be a bad idea, so I’d like you to read on and consider the situation in full. Many Z4Ms are weekend cars used in dry conditions almost exclusively, so in such cars, there really is no need for the drainage hole, but for those who use their Z4Ms in all weathers, this mod is easy to reverse.



THE THEORY OF THE MOD

The Z4M’s air-intake system is a “ram-air” intake and it is an exceptionally good design except for the existence of the hole in the air-filter box. The idea of a ram intake is that when the car travels head-on into air there is a build up of pressure at the front of the car, and if a sealed vessel (i.e. air intake system) has its mouth facing forwards, the vessel will fill with that air, which is at higher than ambient pressure. Since fuelling of the car is related to the quantity of air ingested as monitored by the Mass Air Flow (MAF) sensor, the more air that can be packed into the cylinders at each inlet stroke because the charge is at higher than ambient pressure (i.e. greater density), the more fuel that can be added to the charge in the optimum ratio, thus giving a bigger explosion within the cylinder which gives more power per stroke on the piston, which translates to more torque at the wheels.

From a performance point of view, if you go to all the trouble of creating an excellent ram-air intake, as BMW has done, why defeat the objective of creating a sealed container and then putting a hole in it, which will let air escape, thus reducing the pressure inside the vessel? As it is, it’s like trying to blow up a tyre with a puncture: the increase in pressure simply forces air out through the hole. Therefore, putting a plug in the hole in the OEM air-filter box allows the entire air-intake system to reach the highest internal pressure at all times.

OPENING THE AIR-FILTER BOX

If this is the first time you’ve opened the air-filter box, here are a few tips for you: Slacken the two jubilee clips on the duct that leaves the lid of the air-filter box and which also enters the plenum so that when the lid is unfastened you can more easily manoeuvre the lid once it’s open. You don’t need to completely remove the lid to do this mod.
You might find it easier to move the lid if you unfasten the plug for the MAF by squeezing the sides of the plug to depress the retaining clips and then simply pull the plug off the MAF connection.
There are five retaining clips that hold the lid in place; identify them all before opening and open the one with easiest access first, then refasten it, so that you become familiar with the mechanism for refitting the lid.
When refitting the lid, make sure that the air-filter is properly located in the air-filter box so that there is a proper seal.

IS A DRAINAGE HOLE IN THE AIR-FILTER BOX NECESSARY?

Since there is only one inlet into the air-filter box any water entering the box can only drain via this hole, whereas, if BMW had put a second air inlet into the air-filter box, as it has done with a similar intake of the E46 M3 and Z3M, drainage can be achieved via the bi-pass of having two inlets. In any event, in the case of the Z4M, BMW has placed the inlet into the intake at relatively high level of over 50cms above road level, thus water entering the intake as a consequence of the car driving into standing water of any depth is extremely unlikely, and if it did happen, I think that this would be the least of your worries!


Likewise, The mouth of the inlet is protected by a deflector (cup-like part in front of the radiator), which prevents any water spray during heavy rain, or from cleaning with a hosepipe, entering the intake. So all things considered, water entering the intake in any significant quantity, is highly unlikely. From my earlier experimentation with the air-intake of the Z3MC, which has an intake from the front brake duct at just 15cms above the road, I have paid particular attention to the possibility of water ingestion and therefore I have regularly checked inside the air-filter box for dampness/water, and although I’ve driven for long distances (i.e. from The Ring to Calais, Wales etc.) in driving rain in the spray of friends’ cars that I’ve followed and I’ve never seen any evidence of dampness inside the intake let alone any drops of water. Should spray enter, the high volume of rapid air flow through the system will atomise the water and will quickly evaporate any water droplets, should this occur: remember, water misting is a known technique with Superchargers, so this is not a problem.
I am deliberately labouring this point so that you can make up your own mind whether you feel happy to do this mod or not.


HOW TO PLUG THE HOLE

There are a host of different ways that you can temporarily plug the hole in the air-filter box using bits and pieces you readily might have, such as: Duct tape, silicone sealant, a nut and bolt, dowelling, rubber bungs etc. All these items can be inserted into the hole so that they plug the hole and will form a seal, but will not readily be displaced in ordinary use. The simplest and best method is to use the set silicone cone from a used silicone sealant gun. Silicone sealant can easily withstand the under-bonnet temperatures and it’s flexibility means that when the cone is inserted into the hole, it forms a seal and the plug won’t be displaced. If you leave the cone long enough, you can easily grab hold of it to remove it. Likewise, if you’ve got small enough hands, you can insert the silicone plug from outside the air-filter box without the need to open it.




If you want to make a reversible but semi-permanent and easy-access drain with a plug that can be removed, the simplest way is to get a small length of plastic or silicone hose (the sort used for windscreen washers) which can withstand under-bonnet temperatures, and seal one end of the tube in place in the air-filter box with silicone sealant, as shown in the photo below. You can then insert an appropriately sized bolt into the free end of the tube, which acts as a plug. The free end of the tube is then located in a position in the bonnet, which is easy to access; should the weather conditions require drainage, simply remove the bolt and position the end of the tube lower than the bottom of the air-filter box, and the box can then freely drain.




TESTING THE MOD

The pressure increase created by the ram-effect begins to have a significant, measurable performance effect at around 60mph and above. The best way to assess any performance gain that this mod might give is to drive your car at 60 - 70mph in steady state in 4th, 5th and 6th gears and then floor the accelerator to see if you notice any difference in pick-up in each of those gears compared to OEM state. So before you try this mod, it would be useful to take note of how your car performs doing this test in OEM state.
The other measure that is worth noting is your normal mpg return and comparing any difference when you drive with this mod.

This mod has been the foundation of all my other air-intake and exhaust mods for the Z4M, and without it, I found it impossible to make any progress due to the pressure loss with the open drainage hole.

[wattsie]

Well I wasn't expecting that! haha!

The theory looks sound, and you have obviously had good results, so well done and thanks for sharing!

Wattsie

[Beedub]

so pluggin that whole gave power increase???

honestly i genuinely cant see how it would make the blindest bit of different, fair enough however as i trust you, personally if it was Me and my stock car i wouldn't bother..... well done for the research your a huge asset to the community imo, i love you being here!!!

[Jembo]

I heard someone mention earlier that the 3.0 had a similar RAM air intake.


Is this correct & likely to benefit from a similar modification?

[exdos]

so pluggin that whole gave power increase???

honestly i genuinely cant see how it would make the blindest bit of different, fair enough however as i trust you, personally if it was Me and my stock car i wouldn't bother..... well done for the research your a huge asset to the community imo, i love you being here!!!

Have you ever tried to fill a bath when you've left the plug out?

I'm not claiming that this mod will give huge gains, but until I plugged this hole, I was unable to obtain any gains from doing other mods that had previously produced gains on other cars. The ram-effect is all about pressure in the intake system relative to what it would be if it was not an otherwise sealed design.

I've recently obtained a published scientific paper in one of the most well-respected automotive engineering journals, which states: "At high RPM, gains were considerable; up to 31% in power and torque" and these guys are doing something very similar to me but in a totally different way. I honestly wouldn't have wasted all the time and effort I've put into R&Ding air-intakes over the past 8 years if I hadn't been able to obtain significant and measurable gains along the way.