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      07-19-2023, 08:50 AM   #1
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Another revised inlet a take on Mr.5

A few words and pictures on my version of what is known as the Mr.5 airbox modification for N54 engines as in the 35i/35is.

A bit of history for those not au fait with this matter…Mr.5 was a member of a US based E90 forum who proposed an alternative option for addressing the issue of limited airflow when a N54 engine is tuned.

Many folks went down the route of two dual cone intakes, each one sitting on the end of the disconnected turbo pipe inkers after the stock airbox was removed. The counter arguments to this are the much poorer filtration of the DCIs and the induction noise they create…In addition there were arguments about heat fade caused by sucking in hot air in the engine bay.

Mr.5 suggested retaining the stock airbox and filter but adding an additional air inlet post filters to the interior plenum chamber. Subsequently he and many others came up with various interpretations of this design.

Here’s my version made out of 50mm waste pipe fittings plus a Pipercross Viper aftermarket generic inlet / filter kit.

I’ve done a blended intake on the inside of the plenum chamber, most designs I’ve seen just terminate in a hold in the side of the plenum chamber.

In the end the flexible pipe and lovely aluminium inlet were redundant as there was not enough space to add those..

This is fitted to a RHD 35is..not sure if it would work on a LHD.

Off to the dyno next week to see what impacts it has.

Previous experiments on E89 air boxes showed a small improvement in power and torque ..on a N20..4 BHP in 300…on a N54 6 BHP in 400 and 10 BHP in 500 by removing the airbox lid and / or filter parts..never tried DCIs but the dyno guys rated the impact broadly similar to an unrestricted airbox ..ie no lid ..

One of the great unknowns with all these things is not just how restricted or not certain parts of the system are but how these things interact as a function of rpm and load..an area known as fluid dynamics..for mere mortals the only way is to suck it and see..I’ll report back on the dyno results…
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      07-26-2023, 11:06 AM   #2
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So we did some runs on the same tune with air filter no air filter in the standard box and Mr.5 mod…on a 500 BHP car the Mr.5 mod is worth 50 BHP over the stock arrangement..
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      07-26-2023, 11:12 AM   #3
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So with more boost the Mr.5 mod sings..out upto 546bhp on 22.5 BHP boost tapering to 20 on 98 Ron fuel
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      08-10-2023, 05:47 PM   #4
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Interesting results and a big thank you for sharing!

So I did a similar test back in 2017 on my Z4 35i with Stock airbox vs DCI on a hot summers day in South Africa. (if I recall, I was running MHD Stage 1+ on the 91oct 95ron map. So a very mild map, not allot of boost at all and it was with stock turbos)

I did real world tests, i.e back to back logs with airbox on vs DCI and the results were staggering. A dyno would show differently as it is a very controlled environment.

So the first thing I noticed is that the Waste gate duty cycle never improved with the DCI. This would point to the stock airbox not being a restriction, any restriction in the system would immediately show in the WGDC as the waste gates would have to stay closed for longer to produce the same boost as a "less restrictive" setup like the DCI.

The next thing I found was intake temps...Intake temps went through the roof with the DCI very quickly, as soon as I would come to a stop at a traffic light after doing a log, that engine compartment would start heat soaking so fast and after the 3rd log the car just felt sluggish and the intake temps were ridiculously high. I can't remember the exact figures but they were enough to make me throw those things in the bin afterwards.

Now you can add a bigger intercooler and Water methanol to mitigate the heat soak but the logs don't lie. if the wgdc isn't higher with the stock airbox compared to the DCI then all you are actually gaining is the intake sounds, definitely not power.

BUT and there is a but.

On your setup, running hybrid turbos with a 500bhp car, Then the Mr 5 mod would then more than likely be beneficial, as we can see on your Dyno results. I did do this mod at some point but on my setup at the time which was stock turbos etc it made no difference, not in real world logging and not on the dyno, so I took it off in favour of a cleaner looking engine bay.

On the N54 platform the stock airbox is not restrictive unless you start pushing much higher than stock power like you have done, however in no shape or form would I ever recommend the DCI setup unless you run plumbing through to the large cavity in the front bumper separating it from that engine as the N54 engine produces a monumental amount of heat.

That's just my 2c
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      08-11-2023, 04:00 AM   #5
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I would agree that at up to around 400 BHP there is no significant restriction on the airbox…I didn’t post it here but the same car on the same dyno with MHD V10 stage 2+ on 98 RON fuel did 399.1 BHP stock box and with the lid of ie no restriction it did 308.4 BHP on the same dyno same day..

So about 2% impact…earlier on a N20 heavily tuned E89 we found about a 4 BHP impact on a 300 BHP N20.

In Bonny Scotland we don;t have such high ambient temperatures but as I think I said I don’t like the DCI sound and the poor filtration performance doesn’t fill me with confidence for a ‘keeper’ car..
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      08-11-2023, 04:11 AM   #6
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Old dyno runs
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      08-11-2023, 05:05 AM   #7
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From where does this poor filtration claim come from?
BMS DCI uses S&B Filters... S&B are built to pass or exceed ISO 5011 standards.

From S&B website:
https://sbfilters.com/pages/iso-testing

Quote:
S&B tests to the internationally accepted ISO 5011 Standard when testing for airflow, efficiency and capacity. This is the same protocol used by most of the large automakers.
I did not bother reading the whole ISO standard, but had ChatGPT make a summary of it:

Quote:
ISO 5011 outlines specific testing procedures and requirements that air filters need to meet in order to pass the standard. The following are some key aspects that air filters need to meet to pass ISO 5011:

Filtration Efficiency: The filter needs to demonstrate a certain level of efficiency in removing particulates and contaminants from the air. This efficiency is usually measured in terms of the filter's ability to capture particles of various sizes. The filter's efficiency at different particle sizes is assessed.

Dust Holding Capacity: The filter should be able to hold a certain amount of dust without a significant drop in airflow or efficiency. This is important because as a filter captures particles, it shouldn't become clogged too quickly, leading to reduced performance.

Initial Restriction: This refers to the pressure drop across the filter when the air is flowing through it at a specified rate. The filter should not create an excessively high resistance to airflow initially, as this can affect the engine's performance.

Dust Arrestance Test: This test involves subjecting the air filter to a controlled amount of fine dust over a certain period of time. The filter's efficiency and pressure drop are monitored throughout the test.

Cyclic Test: The filter may need to undergo a cyclic test that simulates real-world conditions, including variations in airflow and dust load. This test helps assess the filter's performance over time and under different operating conditions.

Filter Design and Construction: The filter's design, materials used, and construction play a role in determining its effectiveness and durability. The filter should be designed to maintain its structural integrity and filtration efficiency throughout its operational life.

Documentation and Reporting: To comply with the standard, manufacturers need to provide detailed documentation about the filter's specifications, materials, construction, and performance test results. This helps ensure transparency and allows consumers and regulators to verify compliance.
So it cant be that bad??

Also S&B makes a drop in filter from same material for the OEM airbox.

Of course not maintaining those filters is a big issue... people slap them on and forget about them, they dont clean them or replace them... thats the issue imho.
Also there are knockoff DCI-s out there that arent as good as say BMS DCI. I have seen a video of a 335i that had some other brand filters put on and the material had started coming apart. inlet was full of small pieces of filter material. Dont remember the brand though.... so not all DCI-s are the same. It is a really simple product to replicate after all.

Also when i first installed mine... i noticed it did help with the spooling up a bit. Maybe my OE filter was in need of replacement anyway. This is from my butt dyno though and i dont really have any testing data. Maybe it was a placebo. Tbh i got them just to try them out. Ended up liking the noises. So i kept them.

Also on the heatsoak part... intake air gets heated up by the turbos anyway. A good intercooler is here what is needed to cool it down... so this is more important part to concentrate on... not which intake, filter you are using?
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      08-11-2023, 05:37 AM   #8
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Quote:
Originally Posted by KennyP View Post
From where does this poor filtration claim come from?
BMS DCI uses S&B Filters... S&B are built to pass or exceed ISO 5011 standards.

From S&B website:
https://sbfilters.com/pages/iso-testing



I did not bother reading the whole ISO standard, but had ChatGPT make a summary of it:



So it cant be that bad??

Also S&B makes a drop in filter from same material for the OEM airbox.

Of course not maintaining those filters is a big issue... people slap them on and forget about them, they dont clean them or replace them... thats the issue imho.
Also there are knockoff DCI-s out there that arent as good as say BMS DCI. I have seen a video of a 335i that had some other brand filters put on and the material had started coming apart. inlet was full of small pieces of filter material. Dont remember the brand though.... so not all DCI-s are the same. It is a really simple product to replicate after all.

Also when i first installed mine... i noticed it did help with the spooling up a bit. Maybe my OE filter was in need of replacement anyway. This is from my butt dyno though and i dont really have any testing data. Maybe it was a placebo. Tbh i got them just to try them out. Ended up liking the noises. So i kept them.

Also on the heatsoak part... intake air gets heated up by the turbos anyway. A good intercooler is here what is needed to cool it down... so this is more important part to concentrate on... not which intake, filter you are using?


There have many tests on K+N aka cotton gauze filters vs 'standard' filters..the Jeep guys discussed this extensively from the contamination perpspective..the K=Ns were the worst be a long long way...see picture

There are several videos also showing the poor performance generically of cotton gauze filter elements.

As a long time user of K=N I was shocked..I thew my brand new K=N of of Jeep TJ and put a stock airbox on with a factory filter.

Its your call but if your car is a keeper then it doesn't make sense, IMHO, to say change oil regularly but then use cotton gauze filters..

As far as DCIs vs stock vs cold air intake..

Its true that the amount of temperature increase from ingesting air from the engine bay, when compared to the adiabatic increase in temperature caused by a turbo running significant boost is much smaller it does all contribute to penalties in the net performance of a turbo charged engine..

The worse case situation is stop /start, slow crawling traffic or idling prior to say a 1/4 mile dash.

In all these cases there is a double whammy..the intercooler itself is being heated by ambient increases in the engine bay, radiant heat from the adjacent radiator is heating the intercooler up and there is no or little air flowing over the intercooler to cool it.

Then in addition the air in and around the DCIs is heated considerably..

On application of throttle all that hot air get sucked into a warm intercooler that is not doing much cooling as its pretty warm and the amount of air cooling it is still low.

Of course, as speeds builds up cooling improves and the hot air in the engine bay is both consumed and displaced by colder air forcing its way in..although of course a lt has passed through the radiator and is therefore still warmer than ambient.

Does it matter?

Well it all depends on..

Ambient temperature
Speed of vehicle
Duty cycle between idling and rolling
How much throttle
Gear selected
State of tune
Fuel used

You can see that as you demand more from the engine the greater the proportional impact of these variables.

Many tuners have noted how their perception of how sweetly the car is running improves at night when colder, damper air is prevalent.

They also note that their perceptions are matched with how the N54 engine is adjusting ignition timimg ie corrections..

The more highly tuned, the more corrections, the colder the air the less the corrections.

Hope that helps..
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      08-11-2023, 07:58 AM   #9
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Well.. I get what you are saying about K&N filters. have even read about those issues myself. K&N is very performance oriented filter so they skip on filtration performance quite a lot. Some filters are almost see through.

But.. ALL filter companies arent the same... BMC, AEM etc filters do alot better on filtration tests than K&N. Picture below.. And they use that cotton filter material aswell. Difference comes from simply adding more layers and some use felt like material in some layers.





S&B is similar. Said to be similar to AEM filters construction. Regarded to be more filtration performance orientated than K&N.

While K&N filters use 4-6 layers in their Highflow filters, S&B is said to use 8 layers.
https://www.motortrend.com/how-to/06...a&test=control
They aim for higher than 99% results in filtration efficiency tests, Often being 99.3 -99.5 %. There are some ISO5011 testing results as pdf-s out there if you google enough.


Also i get why you wouldnt want to use a K&N filter in offroad vehicles that probably face dusty rural conditions alot more than say a low sportscar that cant even go on many traillike roads without bottoming out. So its not that bad if you use your car on paved roads say 99.8% of the time.

Also according to the picture above we should all use old already gunked up filters as they provide the best filtration

Just joking.

Im sure we are just splitting hairs at this point.
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      08-11-2023, 10:02 AM   #10
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I saw that chaps video when I was pondering a cold air intake AFE style

I think we can agree that K+Ns are not good at filtration.. a stock Mahle filter is pretty good (i've been use Mahle filters on all our cars for the lasy 7 years)..everything else is in between.

I've created an unknown with a Mr.5 mod as we have no idea how much air flows though the stock airbox and its filter and the Mr.5 inlet with its Pipercross foam filter.

It will vary at which throttle / rpm seting you are at..

However it will be filtering better than a pair of K+N DCIs..

I'm now going to start doing regular engine oil sampling..that will give an indication of how much dirt i getting into the engine..
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      08-11-2023, 05:57 PM   #11
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Quote:
Originally Posted by KennyP View Post
Also on the heatsoak part... intake air gets heated up by the turbos anyway. A good intercooler is here what is needed to cool it down... so this is more important part to concentrate on... not which intake, filter you are using?
I am not going to comment on the filtration part of it as that is like arguing about oil makes, it's a very long deep discussion for another day lol.

However on the heat soak side of things, I have tested this as I stated above and I used logs to gather the data to do accurate comparisons. On a single run it's is fine, but after the 2nd 3rd, 4th 5th and so on the difference in intake temps are quite literally staggering and I would go so far as to say that you are actually hurting the motor by running a DCI setup in an N54 with the standard placement of the filters.

Many will argue this point and that's fine, we are all entitled to our opinions, but log's don't lie! Dyno results don't count as it's a very controlled environment and in no way shape or form depicts what happens on the road. In a very cold country the differences might not be so bad but in countries closer to the equator like south Africa etc during the summer months you are just putting tons of performance on the table and quite literally hurting the motor. Not only do intake temps go up, oil temps go up and coolant temps go up, dct oil temps go up etc, heat Soak smashes performance because it is a knock on effect on the motor. Slapping a big intercooler to mitigate this is silly in my opinion, rather run a better setup where you run plumbing to the cavity inside the front bumper and run the DCI in there, That way you actually get a true cold air intake. This is quite a popular mod on the M4's it's a bit harder on the Z4 but it can be done.

One thing you need to also take into account is that road driving is extremely variable and unpredictable in nature, you can put foot and do a little traffic light to traffic light run against another car, then get stuck at a big intersecion or get stuck in traffic for some time, in that time that motor is now heat soaking a ton, After that it takes quite a bit of time driving in some free air to get temps down and even then you might not get them down enough before the next intersection etc and if that's on a very hot day it's just compounding the issue and once everything is heat soaked it's done, the car becomes a sluggish thing and pushing it in that state is hurting the motor in my opinion and destroying the oil much faster as well.

With my car personally I did everything to get my intake temps low, I fitted hybrid turbos(This is obviously not for cooling, I just wanted bigger turbos) , charge pipe with duel nozzle water/methanol as well as direct port water methanol, so 8 x water/methanol nozzles in total as well as a 7.5" stepped intercooler. All this with the stock airbox and a K&N drop in filter (Think it's K&N but might be BMC, I have since forgotten and must check lol) for the stock airbox. with MHD stage 2+ I saw no gain in performance with DCI on a dyno vs the stock airbox and I would equate that to the water/methanol cooling the intake temps so much that the air density would increase substantially. There are many variables involved here. No methanol + high boost = hot intake temps, means much less dense air so then no lid on the air box or DCI or Mr 5 Mod on the dyno will definitely help as every little bit of extra air will help, but it simply can't be compared to actual cold air going into the motor from a water/methanol setup. You can also easily see the differences in your logs by looking at timing corrections, as the car heat soaks with DCI etc you will notice the car pulling more and more timing after each consecutive run (hence why I say you are actually physically hurting the motor and the motor is in turn trying its best to protect itself). This was also why I ran water methanol, there are almost zero timing corrections in my logs no matter what time of day it is or how many hard pulls I have done in 3rd or 4th gear etc, the water/methanol + 7.5" intercooler simply overcome the hot air easily.

There is allot to consider when trying to up boost and make more power but make no mistake DCI causes heat soak on a hot day and especially in slow moving traffic etc. you are being fooled by placebo due to the intake sounds.

Last edited by Sachak; 08-11-2023 at 06:09 PM..
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      08-12-2023, 05:09 AM   #12
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Guess ill do some testing when the intercooler from B21 arrives. I think it should be in Estonian customs today. So ill maybe have it on monday or tuesday... I still have OEM airbox in storage so ill swap them back and forth and see how it feels... Maybe even do some logs or acceleration testing.

The argument for slow stop and go traffic say a traffic jam doesnt bother me at all... you cant do strong accelerations, use power in a traffic jam anyway

i do get the argument for a dragstrip idling before a run where milliseconds matter. That is a valid point imo.

For my use case..
1) driving around the town ( town that only has 3-4 traffic lights so i rarely have to stop)
2) highway runs
3) winding backroad runs
i dont really see a problem.

Also if its such a big issue, then why doesnt anyone apart from DINAN offer a closed cold air intake? we have alot of dualcones AFE, BMS, VRSF, ARM, Magnum etc... but nobody offers an intake with piping to the front grilles..
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      08-12-2023, 07:22 PM   #13
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Quote:
Originally Posted by KennyP View Post
Guess ill do some testing when the intercooler from B21 arrives. I think it should be in Estonian customs today. So ill maybe have it on monday or tuesday... I still have OEM airbox in storage so ill swap them back and forth and see how it feels... Maybe even do some logs or acceleration testing.

The argument for slow stop and go traffic say a traffic jam doesnt bother me at all... you cant do strong accelerations, use power in a traffic jam anyway

i do get the argument for a dragstrip idling before a run where milliseconds matter. That is a valid point imo.

For my use case..
1) driving around the town ( town that only has 3-4 traffic lights so i rarely have to stop)
2) highway runs
3) winding backroad runs
i dont really see a problem.

Also if its such a big issue, then why doesnt anyone apart from DINAN offer a closed cold air intake? we have alot of dualcones AFE, BMS, VRSF, ARM, Magnum etc... but nobody offers an intake with piping to the front grilles..
Saying idling around in traffic argument doesn't stand but the one about idling before a drag strip does is ridiculous to be perfectly honest. Just because a certain situation doesn't bother you because you may live in a quite little town means nothing to the rest of the modding community. The fact is that sticking two cone filters in the middle of a hot engine bay with zero shielding yields very hot temps and over a relatively short time heat soaks the entire engine. Weather it bothers you or not is irrelevant, the argument is that it does happen. I am not trying to attack your car or your situation or you and I am certainly not making it personal, I am just stating facts as I literally tested this with logs on a hot day to prove a point.

The facts are as follows:
  • WGDC DOES NOT GO UP...THUS the stock airbox is not a restriction under a certain power level...Once you fit bigger turbos and reach certain power levels then obviously it will become a restriction but there are other variables involved, I.e. High flow silicon inlets vs stock inlets. I ran inlets with the stock box and found the WGDC to stay the same vs DCI with inlets...proving once again that the stock airbox wasn't a restriction for me....But I will reiterate again that I was running water methanol and a ton of it too! so air density would thus obviously increase. All of this is simple physics.
  • IAT's go through the flipping roof after the 3rd run and onwards from there THUS power is lost, You can easily see this in the timing corrections the car starts to make as the intake temps get hotter and hotter because a detonation event starts getting closer and closer to happening, the engine thus protects itself by pulling the timing back...The physics behind this are unfortunately real...The hotter the air is the less dense it is, and the more likely you can get knock/detonation.
    The less dense the air is going into your engine the less power you make, Just like when we flight plan before going on a flight we check ambient air temps and humidity as this effects aircraft performance and heavily effects take off and climbing performance.

You can't argue these points because it doesn't affect you personally in a very specific situation or say that you can't do hard pulls in a traffic jam anyways, there are far too many variables you aren't taking into account here. To give just a small example, you goto a midnight racing event with DCI, you run a car maybe once or twice, then go line up to race again, while waiting in the queue to race again which is moving your car is heat soaking like you can't believe, If you have the stock airbox this doesn't happen, not to the same extent at all. Once you get to the start line and you try race, your car now ingests a monumental amount of hot air which obviously negatively affects performance, and after that race your car is now further heat soaked to the point where if you had to do another race and check your logs you would then realize how badly that setup affects performance by the sheer amount of timing corrections you will see and how hot the intake temps are. That's just one example!

And to answer your last point about why all these companies make DCI options instead of plumbing through the front of the engine bay to get a pair of DCI into the bumper cavity....Well that is infinitely easy to answer, none of these companies want to or care to cut into the front bumper support assembly to get pipes through there. I said it can be done, I never said it would be simple. Unfortunately on the E89 it is anything but easy to get a pipe into there from the engine bay. It would require a substantial amount of planning and a fair bit of cutting through metal and plastics as well as building a custom set of intakes!

I didn't come here to argue and have forum wars, just to state my findings, that is all and to help other people to make informed decisions.
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      08-24-2023, 04:23 PM   #14
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Here’s the update on a new version of a tune plus some runs using DCIs..


For those not following the other thread on airbox discussions here’s the abridged version..

All on an E89 35is running TTE500 turbos on 99 RON fuel..

So here’s the answer to ‘well how does it compare to DCIs?’…

Today’s dyno runs..

The chart with 3 lines is tune V17 (iteration 19) which has been tweaked to reduce timing corrections and improve spool..peak power is slightly down on the earlier v13+..torque up..two versions one with the Mr.5 mod and one using DCIs…compared to v13+ with the Mr.5 mod…

The chart with 5 lines is version 6 of the tune ..revisited twice..once with a Mr.5 mod and one with DCIs
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      08-24-2023, 05:43 PM   #15
Hejnfelt
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I can chime in here with a lot of experience from motorcycle racing and tuning over the past 20 years.

Engines running K&N Cotton Gauze filters get wrecked fast. Particularly it's the cylinder liner that gets shredded and both liner, piston rings and piston lifetime is compromised. This is especially true in countries like Estonia where 5 months of the year every car drives on studded tires creating a serious amount of very rough and sharp road dust that accumulates in the snow and ice which then settles in crevises of the streets where it doesn't clear out until well into June after springtime rains.

In the N54 that's notorious for blow-by just imagine how much debris ends up in your oil and eventually coating every surface in the engine. Obviously these engines are pretty tough and you're unlikely to see much day to day difference, but reliability of the troublesome components like Vanos or PCV Valves will be more likely to fail. Particularly the Vanos system should be of concern as debris in that system can rapidly lead to oil leaks between the steel cut O-rings inside the cam phaser system and that's a common and expensive repair.

Cotton Gauze filters have their place but in the majority of road cars they cause much more harm than good, especially if you're chasing performance as most of us want performance in combination with reliability but with cotten gauze DCIs your reliability is shortened significantly.

It's a shame that filter technology isn't progressing in the regular market and is really only concentrated at the higher end of cars. What UFI is doing with the Porsche tubular filter system is pretty cool and I would love to put such a setup in the Z4.
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      08-25-2023, 04:30 AM   #16
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Quote:
Originally Posted by Hejnfelt View Post
I can chime in here with a lot of experience from motorcycle racing and tuning over the past 20 years.

Engines running K&N Cotton Gauze filters get wrecked fast. Particularly it's the cylinder liner that gets shredded and both liner, piston rings and piston lifetime is compromised. This is especially true in countries like Estonia where 5 months of the year every car drives on studded tires creating a serious amount of very rough and sharp road dust that accumulates in the snow and ice which then settles in crevises of the streets where it doesn't clear out until well into June after springtime rains.

In the N54 that's notorious for blow-by just imagine how much debris ends up in your oil and eventually coating every surface in the engine. Obviously these engines are pretty tough and you're unlikely to see much day to day difference, but reliability of the troublesome components like Vanos or PCV Valves will be more likely to fail. Particularly the Vanos system should be of concern as debris in that system can rapidly lead to oil leaks between the steel cut O-rings inside the cam phaser system and that's a common and expensive repair.

Cotton Gauze filters have their place but in the majority of road cars they cause much more harm than good, especially if you're chasing performance as most of us want performance in combination with reliability but with cotten gauze DCIs your reliability is shortened significantly.

It's a shame that filter technology isn't progressing in the regular market and is really only concentrated at the higher end of cars. What UFI is doing with the Porsche tubular filter system is pretty cool and I would love to put such a setup in the Z4.
Like you I used K+N filters on my bikes for many years..I never wracked that many miles on them so wear was not obvious.

I intend to keep my 35is for a very long time so longevity of the engine is a concern..hence why I went down trying to avoid any modifications to the very good stock air inlet system..hopefully my Mr.5 version will still offer pretty good filtration…

I drove back yesterday some 2 hours and 70 miles with the VSRF DCIs fitted and it confirmed my prejudice against DCIs based on inlet noise as well..

So Mr.5 being refitted this morning.
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      08-25-2023, 05:03 AM   #17
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I've seen all kinds of racing, from 70cc tuned mopeds to superbike road racing. I think when it became most apparent for me that K&N and other low layer count cotton gauze filters like Sprint filters wreck engines was when I raced the Aprilia SXV550 supermoto bike. Amazing bike, crappy head design and that thing blew head gaskets constantly leading to all kinds of issues. What really struck me as odd was when re-doing the cylinder head gasket once, 500km after having totally redone the engine after a crank case seal leak and I'd put in new liners and pistons and the cylinder walls looked like they came out of a clapped out MX bike with no filter. It should not have looked like this.

In Tallinn, my friend has the most advanced dyno place for bikes and also builds some of northern Europes most high end race bikes and many bikes have been run through there to test the differences of stock, sprint, BMC and other filters. The stock filters run maybe 1-3hp behind the cotton gauze filters on the top end when the engine is brand new. But after a season, the bikes are on par with each other.

The cotton gauze filter engines all display the same symptoms on visual inspection which is cylinder walls looking much more scuffed up than bikes running stock filters. The issue seems related to the size of the debris that can enter the combustion chamber and all those bikes also have sand in the airbox.

Our theory is that the scratching induced on the cylinder walls by the debris becomes a passageway for gasses to escape during compression, combustion and exhaust stroke which robs the engine of power over time.

Foam filters in our experience is a better alternative than cotton gauze filters however the very best solution for an engine you want a lot of power out of while keeping longeivity is to stick with stock filters and do some kind of airbox modification.

That's also why I liked the MR5 airbox mod although my plan is to probably 3D print a miniature stock airbox which fits some OEM stock filter which essentially just increases the airbox volume and filter surface area allowed the engine to breathe better.

... Winter project
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      08-25-2023, 09:28 AM   #18
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Look forward to the ‘better than a Mr.5’ auxiliary air box..please bear in mind you will have a RHD customer !-
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      08-26-2023, 05:07 AM   #19
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Better is relative and it may need exactly the same ducting into the original airbox, but what it can do differently is the box mechanism and we can do some CFD on the airbox and ducting to ensure it's smooth.

I've been wanting to do a complex ducting project for a while and this seems like it might be it. Would combine it with printing in carbon fiber reinforced high temperature nylon which is good to 200C and with very high tensile strength which should survive any kind of vibration thrown at it.
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      08-26-2023, 07:00 AM   #20
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Quote:
Originally Posted by Hejnfelt View Post
Better is relative and it may need exactly the same ducting into the original airbox, but what it can do differently is the box mechanism and we can do some CFD on the airbox and ducting to ensure it's smooth.

I've been wanting to do a complex ducting project for a while and this seems like it might be it. Would combine it with printing in carbon fiber reinforced high temperature nylon which is good to 200C and with very high tensile strength which should survive any kind of vibration thrown at it.
Well crack on
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      09-07-2023, 05:46 PM   #21
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Interesting - It seems like the DCI is the best option here, judging by the whole power curve. Massive gains over the stock airbox.

Does the car have turbo inlet and outlets?
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      09-08-2023, 04:04 AM   #22
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Quote:
Originally Posted by AmuroRay View Post
Interesting - It seems like the DCI is the best option here, judging by the whole power curve. Massive gains over the stock airbox.

Does the car have turbo inlet and outlets?
I wouldn’t describe a peak torque increase of 11nm in 730nm or 6 BHP in 530 BHP as massive..ie 1.5%…hardly in the 10%-15% claimed for various air box upgrades..

As discussed peak torque is now excessive so any gain there is not useable as we’ve gone past traction limits..

Of course the heat soak and filtration and noise aspects were the other factors..

VSRF 2” turbo inlets and VTT turbo outlets fitted..
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