How far can you go with a stock or maybe modified Z4 35is N54 airbox?

[ShocknAwe]

I'd be looking at the slinky air entry but the front radiator support.

How about circle saw cutting out the stock inlet attachments and putting large 3" flanges in there matched with couplers to larger inlets.

Then bore a hole in the wall divider inside the box for a small cone filter placed on the prefilter side leading to the post filter side, and then use the Z4 lid. Bunch more filter area and more graduated decrease in pipe radius for inlets for less turbulence. Could probably even find some 3" velocity stacks for the flanges inside the box.

Then pair all this to the standard forward feed neck with a circle saw hole next to it feeding a CAI down to an open pipe behind the bumper should be plenty of air supply to the now increased filter area.

I'd say keep the fins inside the box, helps collect and organize the airflow.

 

[fmorelli]

@ShocknAwe nothing an LS swap can't fix.

 

[ShocknAwe]

@ShocknAwe nothing an LS swap can't fix.

Stop encouraging me Filippo, 2-3 more years and the mutt will get a supercharged V8 transplanted. Whether it's a LS3 or a S65 based setup is yet to be seen.

 

[CantSitStill]

I thought I would chime in here for a quick comment. I have run Dci's on 2 335i's now and it always annoyed me the amount of heat they must pick up when around town. I live in the city and only WOT the car in between driving in traffic so heat soak can be measured very clearly and it takes about 5-10 mins of open road to cool the engine bay down again after being in traffic. Yes I'm sure dci's work better on the open road but I'm not sure in most practical circumstances. I also wonder how much of the hype around them is down to marketing for a few big companies...

Anyway what I wanted to say is that I just changed back to the stock airbox (stock filter and using 2inch inlets) with the mr5 mod where I have one of the dci's behind the left side head light. It fits perfectly. The car is running about 550-600hp and I have yet to do any WOT testing but will report back. The main thing I notice is it sounds WAY better. Its lost all those snorkel noises that everyone thinks sound amazing - for me they sounded hellish. Now I can still hear spool and the dump vavle is clearer/crisper. Engine bay also looks better without the dci's. I painted the bmw logo white as well on the box :-O

Will see how the setup copes with full power soon.

 

[Darke Peak]

I thought I would chime in here for a quick comment. I have run Dci's on 2 335i's now and it always annoyed me the amount of heat they must pick up when around town. I live in the city and only WOT the car in between driving in traffic so heat soak can be measured very clearly and it takes about 5-10 mins of open road to cool the engine bay down again after being in traffic. Yes I'm sure dci's work better on the open road but I'm not sure in most practical circumstances. I also wonder how much of the hype around them is down to marketing for a few big companies...

Anyway what I wanted to say is that I just changed back to the stock airbox (stock filter and using 2inch inlets) with the mr5 mod where I have one of the dci's behind the left side head light. It fits perfectly. The car is running about 550-600hp and I have yet to do any WOT testing but will report back. The main thing I notice is it sounds WAY better. Its lost all those snorkel noises that everyone thinks sound amazing - for me they sounded hellish. Now I can still hear spool and the dump vavle is clearer/crisper. Engine bay also looks better without the dci's. I painted the bmw logo white as well on the box :-O

Will see how the setup copes with full power soon.

This is the second time I saw mention of a “modified MR5 airbox”. The first time I thought it was a typo and went searching for “MX5 airbox for N54” thinking that it had something to do with a Mazda MX5. Now after some searching for mr5 I found the thread created by “Mr. 5” who modded his airbox like I was planning to do. I’ll be using an enclosed cold air intake and drawing the air from outside the engine bay, but it will be a 2” line where he used 3”.

 

[CantSitStill]

This is the second time I saw mention of a “modified MR5 airbox”. The first time I thought it was a typo and went searching for “MX5 airbox for N54” thinking that it had something to do with a Mazda MX5. Now after some searching for mr5 I found the thread created by “Mr. 5” who modded his airbox like I was planning to do. I’ll be using an enclosed cold air intake and drawing the air from outside the engine bay, but it will be a 2” line where he used 3”.

Haha yes it confused me. It was some time ago before the days if the DCI being that common. The 3 inch pipe is hard to fit anywhere I found. I had to squeeze a 2.25 inch duct past a support bar to get behind the headlight.

 

[Darke Peak]

Update: the extra cold air intake is installed. Just need to paint the alloy tubes matte black and wrap the carbon fibre pod in matte black vinyl. It’s currently drawing air from the left front scoop near the horns. I might need to drill out some of the fake holes in the grille.

 

[pbondar]

Lovely piece of work…any details on the c/f can and it’s filter mount?

 

[CantSitStill]

Nice! I went for more cheep looking solution. Yours looks like it's supposed to be there! I can say I tested mine at 22psi to the red line and wgdc was under 55 on 19T's, from looking at logs with the Dci's and the same boost I can't tell any difference in the wgdc but obviously it moves around so hard to say with certainty. I can honestly say however it sounds waaaay better at all RPM's. All the turbo noises (spool, blowoff, full boost) sound much more like you would expect them to sound. With the DCI's it sounded like hellish (sounds like you have a leak when it's boosting, blowoff making strange slicing noises and snrokle nosies under spool).

 

[Darke Peak]

Lovely piece of work…any details on the c/f can and it’s filter mount?

It’s a cheap Saas unit. Product code SF1003. I shortened the carbon fibre pod by 35mm, and shortened the flanges at each end by 15mm each. I didn’t use any of the accessories/fittings that came with it except the 3” clamps.

Carbon Cold Air Box Filter Kit 76mm Inlet/Outlet | SAAS Automotive

Buy SAAS SF1003 Carbon Cold Air Box Filter Kit 76mm Inlet/Outlet | SAAS Automotive

www.shopsaas.com

The other parts used:
2 x Saas 75mm-50mm silicone reducer (shortened slightly)
1 x 50mm 60 degree mandrel bend pipe
1 x 50mm 90 degree mandrel bend pipe
1 x 50mm rubber toilet seal (connection to airbox)
Plus some hose clamps.

 

[studio54]

Very clean and well realised ! Looking forward reading your new times with it. Do you already have any impression ?

 

[pbondar]

Its the lovely mandrel bent pipe now..any ideas? Domestic waste plumbing connections? Not really suiting the C/F enclosure?

 

[pbondar]

Wonder what the dilution ratio of air from the 'proper filter' vs the after market as various levels of 'suck'?

 

[Darke Peak]

Its the lovely mandrel bent pipe now..any ideas? Domestic waste plumbing connections? Not really suiting the C/F enclosure?

I’m not sure what you mean by “ideas on the mandrel bent pipe”?

I didn’t actually want a CF airbox, and although it is genuine CF it is flimsy and the filter looks real cheap. I considered using stormwater PVC pipe to make my own, and wrap it in matte vinyl - which I might still do so I can use a better quality filter. Even with a better cotton filter I would prefer that the engine only uses air from this source at high RPM and WOT, but that would require a solenoid operated flapper valve on the inlet to that pipe, perhaps operated automatically by the Reflex+ that I will likely install. There’s another project….

Wonder what the dilution ratio of air from the 'proper filter' vs the after market as various levels of 'suck'?

I’m not sure.

Presuming the filter material offered relatively equal resistance on both paths, and there was negligible additional turbulence (which is not true but hard to know the extent), then the cross section size, length and shape of the delivery lines would be the defining factor. The lengths are similar and the shape of the paths is similar (ie, several 90deg bends). Therefore…

Cross section size at smallest point:
Stock: 54cm2 (74% of the flow)
New intake: 19cm2 (26% of the flow, a 35% flow increase over stock).

After turbulence is considered I’d like to think that it is increasing the capacity of the stock system by 15-20%.

In hindsight I probably could have got away with 2.5” (62mm) alloy pipe through the choke point behind the LF headlight. But they don’t make $3 rubber toilet flanges in 2.5” so I would have needed a different mount to the airbox.

 

[Darke Peak]

Very clean and well realised ! Looking forward reading your new times with it. Do you already have any impression ?

I took it for a quick drive and did a couple of third gear pulls (40-120kmh) but they were uphill so I didn’t bother recording the Dragy times. My butt says it isn’t any different, but that’s what I expected. I did the modification in preparation for 17T hybrid turbos.

However, the VRSF silicone inlet has been coming off the rear turbo lately. I am suspicious if I’ve reached the limit of the stock airbox filter and maybe there is significant vacuum in that inlet at high RPM and WOT causing it to deform at the turbo (where it doesn’t have internal wire support) and pop off.

 

[studio54]

I took it for a quick drive and did a couple of third gear pulls (40-120kmh) but they were uphill so I didn’t bother recording the Dragy times. My butt says it isn’t any different, but that’s what I expected. I did the modification in preparation for 17T hybrid turbos.

However, the VRSF silicone inlet has been coming off the rear turbo lately. I am suspicious if I’ve reached the limit of the stock airbox filter and maybe there is significant vacuum in that inlet at high RPM and WOT causing it to deform at the turbo (where it doesn’t have internal wire support) and pop off.

Curious about the difference in sound too ?

I am not sure if you installed silicone inlet recently or long time ago and if you planned to do this, but it could be great to compare times of the new intake with the exact same setup that you used for stock filter/k&n filter & DCI in previous posts (before your new turbos).

I plan to do the same install, but very interested to see if there are real benefits with stock turbos.

 

[Darke Peak]

Curious about the difference in sound too ?

I am not sure if you installed silicone inlet recently or long time ago and if you planned to do this, but it could be great to compare times of the new intake with the exact same setup that you used for stock filter/k&n filter & DCI in previous posts (before your new turbos).

I plan to do the same install, but very interested to see if there are real benefits with stock turbos.

Sound: same as stock airbox. But I must be partly deaf because I don’t think the DCI sound much different to the stock airbox.

Further testing on stock turbos: yes, the inlets were done before I started logging results so I will know (and report) if this modification provides any benefit with stock turbos

 

[CantSitStill]

I took it for a quick drive and did a couple of third gear pulls (40-120kmh) but they were uphill so I didn’t bother recording the Dragy times. My butt says it isn’t any different, but that’s what I expected. I did the modification in preparation for 17T hybrid turbos.

However, the VRSF silicone inlet has been coming off the rear turbo lately. I am suspicious if I’ve reached the limit of the stock airbox filter and maybe there is significant vacuum in that inlet at high RPM and WOT causing it to deform at the turbo (where it doesn’t have internal wire support) and pop off.

Have your inlets got the wire reinforcement at the rear turbo where it bends to join the turbo? Its common for those without the reinforcement to collapse from what I have read. It's also common for them to pop off the stock turbos because there is not much to clamp on to. 17t's should have a longer inlet to clamp on to and solve the problem. If they are 2inch inlets going on to the stock turbo it's made worse. FYI all the China aliexpress inlets are 2inch (required for 17'ts I think) now (well the 2 I tested were) and had the reinforcements. You can get them for about 100-120 USD.

 

[Darke Peak]

Have your inlets got the wire reinforcement at the rear turbo where it bends to join the turbo? Its common for those without the reinforcement to collapse from what I have read. It's also common for them to pop off the stock turbos because there is not much to clamp on to. 17t's should have a longer inlet to clamp on to and solve the problem. If they are 2inch inlets going on to the stock turbo it's made worse. FYI all the China aliexpress inlets are 2inch (required for 17'ts I think) now (well the 2 I tested were) and had the reinforcements. You can get them for about 100-120 USD.

Yes, they have wire insert on the bend but not for the last 1-2” before connecting to the turbo. I’m hoping the RB Two Plus have longer snouts and a bead to heal them stay on.

 

[Dumaurier7]

I took it for a quick drive and did a couple of third gear pulls (40-120kmh) but they were uphill so I didn’t bother recording the Dragy times. My butt says it isn’t any different, but that’s what I expected. I did the modification in preparation for 17T hybrid turbos.

However, the VRSF silicone inlet has been coming off the rear turbo lately. I am suspicious if I’ve reached the limit of the stock airbox filter and maybe there is significant vacuum in that inlet at high RPM and WOT causing it to deform at the turbo (where it doesn’t have internal wire support) and pop off.

Too much suction will not only starve the turbo and reduce performance it will also create excessive loading and wear on the (turbos') thrust bearing which will eventually cause premature failure.