pilchardthecat's MAF screen mod
- Thread starter pilchardthecat
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pilchardthecat
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exdos said:pilchardthecat said:
You could've just cut away all the plastic beneath the CF skin and left a margin to bond the CF skin to the plastic lid. In essence you've used the sonorous properties of CF to get an induction noise in the same way that the front of a violin is made of quarter-sawn spruce for its sonorous quality, whilst the back is made from maple for its sound-reflective quality.
You should manufacture the part.
My intention was to cut the whole section away yes, but my saw gave out and so I resorted to drilling big holes. This one was only supposed to be a temporary experiment to see if making a complete cf airbox would be worthwhile so it was a bit of a hack job - I never expected it to stay on the car really, but it worked so well I left it
I used just a couple of layers of cf and 3 of resin so it is very very light and thin, lots of nice noises get out
pilchardthecat said:exdos said:pilchardthecat said:
You could've just cut away all the plastic beneath the CF skin and left a margin to bond the CF skin to the plastic lid. In essence you've used the sonorous properties of CF to get an induction noise in the same way that the front of a violin is made of quarter-sawn spruce for its sonorous quality, whilst the back is made from maple for its sound-reflective quality.
You should manufacture the part.
My intention was to cut the whole section away yes, but my saw gave out and so I resorted to drilling big holes. This one was only supposed to be a temporary experiment to see if making a complete cf airbox would be worthwhile so it was a bit of a hack job - I never expected it to stay on the car really, but it worked so well I left it
I used just a couple of layers of cf and 3 of resin so it is very very light and thin, lots of nice noises get out
Really interesting mod, does it still seal as per the original for the ram effect? More noise must mean less pressure?
Where did you get the cf sheets from?
Liverpool
pilchardthecat
Active member
Yes, it's completely air tight and sealed - easy to check, just push it under a sink full of water and check for bubbles ;-)
pilchardthecat
Active member
As exdos said, the airbox is pressurised by the ram air system, and overall it is very well designed - you do not want to leave holes as this will reduce the pressure. There are some things you can do to increase the pressure and/or retain more of it/reduce losses - this is what exdos and myself have been messing about withAlienZed said:
Also, it's not a good idea to remove the mesh from the maf screen and just leave the plastic air straightener - the plastic alone does a poor job of inducing laminar flow (there is a reason they stuck the mesh on there). You need both, or something that fulfills both functions as per my mod. You might not have noticed it, but there will be points in the rev/speed range where you will have turbulence around the maf, and the mix will be off
Thanks for the info guys starting to understand wot your both aiming to achieve, your tech knowledge is great.
Well done.
Just off for a blast round the peak dist then put Zeddy to bed for 10 days.
Off to Salou on tues so i'll start again when we get back.
Cheers Moz
Sent from my GT-I9300 using Tapatalk 2
Well done.
Just off for a blast round the peak dist then put Zeddy to bed for 10 days.
Off to Salou on tues so i'll start again when we get back.
Cheers Moz
Sent from my GT-I9300 using Tapatalk 2
daz05 said:
Many engines and intake systems rely upon "resonant effects" for optimal performance and high volumetric efficiencies. As I understand, all of BMW's ///M cars with the S54 engine incorporate such resonant effects, particularly with the runner lengths inside the plenum, immediately in front of the throttle bodies.
There appears to be a strange phenomenon specific to the Z4M, related to the recorded powerband, which shows a drop in power at around 7200rpm followed by a rebound around 7600rpm, as shown in a typical dyno plot, as below. This doesn't seem to occur in the E46 M3, and so I wonder whether this phenomenon is caused by resonant effects which are related to the Z4M's unique air intake system upstream of the plenum? Since pilchardthecat's CF air-filter box mod will have different resonant characteristics to OEM, it would be interesting to know, what changes to performance, if any, this mod has?
From datalogging in "real world" driving conditions, this drop in power at around 7200rpm is clearly shown by a reduction in air-flow rate through the MAF coupled with a slight deceleration of engine rpm, followed by a surge in airflow and an increase in engine rpm acceleration, as if the engine has taken a sudden gulp in air for a "second wind".
pilchardthecat
Active member
Changing the material wont have any effect on the resonant effects you are talking about, as long as the replacement material has the same rigidity - the phenomenon you are referring to are caused by pressure waves bouncing around inside the system - when these waves are in phase with the opening/closing of the valves, there is a beneficial effect. The same is true on the exhaust side, hence the position of bends etc in manifolds
As long as the dimensions and the rigidity of the materials are unchanged, nothing should change in the shape and size of the internal pressure waves.
Of course the downside of using this approach in the design, is that for any given dimensions, certain parts of the rev range will be in the opposing phase, and there will be a negative effect. This is probably the cause of the flat spot you are talking about
On the intake side there will probably only be significant wave characteristics inside the plenum, and possibly between the plenum bend and the maf screen. I doubt that anything as far from the valves as the airbox itself will have much of an impact
As long as the dimensions and the rigidity of the materials are unchanged, nothing should change in the shape and size of the internal pressure waves.
Of course the downside of using this approach in the design, is that for any given dimensions, certain parts of the rev range will be in the opposing phase, and there will be a negative effect. This is probably the cause of the flat spot you are talking about
On the intake side there will probably only be significant wave characteristics inside the plenum, and possibly between the plenum bend and the maf screen. I doubt that anything as far from the valves as the airbox itself will have much of an impact
pilchardthecat said:Changing the material wont have any effect on the resonant effects you are talking about, as long as the replacement material has the same rigidity - the phenomenon you are referring to are caused by pressure waves bouncing around inside the system - when these waves are in phase with the opening/closing of the valves, there is a beneficial effect. The same is true on the exhaust side, hence the position of bends etc in manifolds
As long as the dimensions and the rigidity of the materials are unchanged, nothing should change in the shape and size of the internal pressure waves.
Of course the downside of using this approach in the design, is that for any given dimensions, certain parts of the rev range will be in the opposing phase, and there will be a negative effect. This is probably the cause of the flat spot you are talking about
My point is: the E46 M3 and the Z4M both share the same engine and plenum, where the resonant effects you've described are beneficial to cylinder filling in both platforms, but there is a loss in performance in the Z4M at around 7200 rpm which doesn't occur in the E46 M3. So what's different in the Z4M which is causing this to happen? Is it intake/exhaust/ECU differences?
pilchardthecat said:
If, as you say, your CF airbox lid mod has changed/increased the induction sound, then surely the resonance of the entire air intake has changed? Surely the sound characteristics of the intake as a whole, from inlet to throttle plate, is because it acts like one large sound chamber? Whether or not the difference has any impact on performance neither of us knows.
pilchardthecat
Active member
Resonance and sound are not the same thing - resonance is specifically the relationship between the frequency of pressure waves and the dimensions of the space they occupy. Neither of these things have changed.
Sound is more general, and is effected by timbre, amplitude, reverberation, etc. You can change the external sound without having any effect on internal resonance
Sound is more general, and is effected by timbre, amplitude, reverberation, etc. You can change the external sound without having any effect on internal resonance
pilchardthecat said:
I would think that you've changed the rigidity of the air box significantly with this mod. More than that, what once was an airbox with walls of equal reflectivity to pressure waves (at least with respect to material properties although not in shape), is now a hybrid which will deform and reflect differently in the carbon fibre sections from elsewhere. I suppose it is conceivable that the filter will serve to "damp" the of effects of the carbon fibre section since you've only altered the airbox before the filter. It's interesting to speculate on the effects of your mod, but I'd love to hear it in person and see data logged before and after your modification
pilchardthecat
Active member
Gutting the bends from the exhaust back boxes will have a much bigger impact, as this is changing the internal dimensions significantly. I doubt there is much difference in reflective/rigidity characteristics on pressure waves between plastic and CF. And of course the pipe between the plenum and the airbox/maf is rubber, and will deform, as well as changing is deformation properties with age, temperature, etc
pilchardthecat said:
I know that reducing the exhaust length and making it more free-flowing by gutting the silencers does have a measurable and significant impact on performance, but it hasn't changed the fact that there is still a dip in performance at 7200rpm with a rebound at 7600rpm. Therefore, I'm simply attempting to explore the possible reasons why the Z4M has a different torque/power curve to the E46 M3, with the same engine/plenum, and if modifying the exhaust doesn't give the answer, then it seems logical to me that the answer must lie in either the ECU mapping or the air-intake upstream of the plenum.
From reading postings of other Z4M owners elsewhere, this dip in power is still a feature after having various remaps by different tuning companies. Likewise, I've not seen the dip in performance in dynoplots of supercharged Z4Ms, which eliminates the OEM air-intake system and mapping. So, it seems logical to me that the Z4M's OEM air-intake, which is significantly different to that of the E46 M3 looks like the most likely cause. I still observe this dip in power with my own air-intake mods (which are all different to yours) so I'm wondering if your CF mod might shed some light on this?
pilchardthecat
Active member
I am much more interested in what happens when you improve the maf screen (no maf on supercharged cars either....) this really is a huge restriction. The top end "dip" you refer to is noticeable when driving the car, but since i changed the screen it feels much more free revving at the very top.
I would be very very surprised if the CF makes any difference at all other than to the external noise.
Very much looking forward to your datalogging.
I would be very very surprised if the CF makes any difference at all other than to the external noise.
Very much looking forward to your datalogging.