Carbon plenum 3D printed Snorkel

[Justino]

The standard CSL set up has multiple other ways air can enter the airbox, not just the snorkel, so whilst having it sealed seems a good idea, I wonder if it would feed enough air? Having it partly open would create the effect of sucking air in to the open section as the air rushing in from the grille creates a negative pressure effect.

Yes, I am aware. Without going into which way is best, fully closed off certainly provides "enough" air. There is a car in the forum that has a Goke Z4M specific airbox and it has very healthy dyno figures - I believed it's cammed too so the limit is not at the intake.

You are fundamentally correct, but the M3 has a fresh air feed where the open section of the snorkel would be, the Z4M does not. Therefore, one could argue you'd now be sucking in hot (post radiator) air instead of cool rammed air. The easiest way to tell what is best and what drives lower IATs is to datalog both solutions and do back-to-back dynos.

A Z4M with a 4.1 final drive is borderline too fast for fast road driving (my use case), the extra power that comes with a CSL intake is a bonus to me, I just want the sound... which would most likely drive me towards an open snorkel similar to the above. I just so happen to be a mechanical design engineer in a powertrain department, so god knows what I'll come up with after some advice from work colleagues.

I'm not knocking what you are doing, I probably would have bought one from you had I gone the OE style inlet with trimmed snorkel as I agree the trimmed version is a compromise and could restric air flow as it no longer gets air from the snorkel part as I think that jams up against the inner wing once cut, not dangling in free air as on an M3. I wonder why BMW created the original CSL intake with open air ingress feed into the bottom of the airbox post snorkel from the front bumper inlet if the front input is sufficient? Karbonius boxes no longer have this lower feed.

I think the air feed temperature is a red herring as once moving the air that is coming in will be cooler, its the heat soak of the plenum that is the issue, not the air temp in my opinion, and that doesn't change whether sealed or open.

I was very happy how the Race Karbonius inlet aligns to the opening on the back of the grille area once the original air box feed is removed from the 'socket'. The gap between the 2 is probably 10mm at most, so the air flowing in doesn't have much chance to go anywhere else other than into the inlet.

I have logged IAT temps, and they do rise when in traffic etc, but soon drop back down once you speed up.

My winter job is to replace both throttle sensors as I have an intermittent limp mode and Severn Tuning said the throttle voltage didn't look clean. Unfortunately it involves removing the inlet again to access the lower sensor. Its a time consuming job as the oe trumpet clips are fiddly.

 

[lucasxdiniz]

Unfortunately it involves removing the inlet again to access the lower sensor. Its a time consuming job as the oe trumpet clips are fiddly.

You probably have the right tool, but I have bought this CV Boot Clamp Plier and it made removing, and installing the OE clamps really easy. Works so well that it removed the clamps with no damage, I could even re-use them.

 

[Justino]

Unfortunately it involves removing the inlet again to access the lower sensor. Its a time consuming job as the oe trumpet clips are fiddly.

You probably have the right tool, but I have bought this CV Boot Clamp Plier and it made removing, and installing the OE clamps really easy. Works so well that it removed the clamps with no damage, I could even re-use them.

I have something similar, but when fitting I had to get new clips as the diameter is different on the new inlet, but this time I will be reusing.

 

[RedUn]

The standard CSL set up has multiple other ways air can enter the airbox, not just the snorkel, so whilst having it sealed seems a good idea, I wonder if it would feed enough air? Having it partly open would create the effect of sucking air in to the open section as the air rushing in from the grille creates a negative pressure effect.

Yes, I am aware. Without going into which way is best, fully closed off certainly provides "enough" air. There is a car in the forum that has a Goke Z4M specific airbox and it has very healthy dyno figures - I believed it's cammed too so the limit is not at the intake.

You are fundamentally correct, but the M3 has a fresh air feed where the open section of the snorkel would be, the Z4M does not. Therefore, one could argue you'd now be sucking in hot (post radiator) air instead of cool rammed air. The easiest way to tell what is best and what drives lower IATs is to datalog both solutions and do back-to-back dynos.

A Z4M with a 4.1 final drive is borderline too fast for fast road driving (my use case), the extra power that comes with a CSL intake is a bonus to me, I just want the sound... which would most likely drive me towards an open snorkel similar to the above. I just so happen to be a mechanical design engineer in a powertrain department, so god knows what I'll come up with after some advice from work colleagues.

I'm not knocking what you are doing, I probably would have bought one from you had I gone the OE style inlet with trimmed snorkel as I agree the trimmed version is a compromise and could restric air flow as it no longer gets air from the snorkel part as I think that jams up against the inner wing once cut, not dangling in free air as on an M3. I wonder why BMW created the original CSL intake with open air ingress feed into the bottom of the airbox post snorkel from the front bumper inlet if the front input is sufficient? Karbonius boxes no longer have this lower feed.

I think the air feed temperature is a red herring as once moving the air that is coming in will be cooler, its the heat soak of the plenum that is the issue, not the air temp in my opinion, and that doesn't change whether sealed or open.

I was very happy how the Race Karbonius inlet aligns to the opening on the back of the grille area once the original air box feed is removed from the 'socket'. The gap between the 2 is probably 10mm at most, so the air flowing in doesn't have much chance to go anywhere else other than into the inlet.

I have logged IAT temps, and they do rise when in traffic etc, but soon drop back down once you speed up.

My winter job is to replace both throttle sensors as I have an intermittent limp mode and Severn Tuning said the throttle voltage didn't look clean. Unfortunately it involves removing the inlet again to access the lower sensor. Its a time consuming job as the oe trumpet clips are fiddly.

Do the knock sensors while your at it. My rear one had a spurious reading when I swapped it. Well worth doing all the sensors at the same time

 

[D.Bryce]

So after reading all the posts on here, I went back and done some redesigning. I have now taken the intake end to the same size as the opening and made it flush with the rubber seal on the slam panel.

I have printed it in carbon fibre reinforced petg and after a track day I can confirm there has been zero issue with iats or heat soak.

 

[maupineda]

I followed a different approach, but will very likely redesign it. I am not a fan of the elephant trunk shape when installed.