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

[CantSitStill]

I would be very surprised if you have any inlet vaccume issues on that setup. With the mod your going to be flowing as much air as a DCI setup, maybe a bit less with the smaller filter in that induction kit. The rear inlets can pop off because the inlets rubs up and down on the firewall/bulkhead when the engine moves. They are crazy tight and I recall when fitting them thinking there is no way they would fit. You might need to reposition them maybe and push them down more so they fit right on the turbo without the clamp in place. Anyway the new turbos will come with a longer snouts and you can get it perfect when fitting them. Good luck with that. I did mine on jack stands and took me about 50 hours.

 

[Darke Peak]

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.

100% agree. And it’s not a load they are designed to sustain. My turbos have started making the “siren” sounds and I have wondered if this is the cause. At low rpm and low loads I can make small adjustments to the throttle to change the pitch - it truly sounds like a distant police siren inside the cabin.

 

[Darke Peak]

I would be very surprised if you have any inlet vaccume issues on that setup. With the mod your going to be flowing as much air as a DCI setup, maybe a bit less with the smaller filter in that induction kit. The rear inlets can pop off because the inlets rubs up and down on the firewall/bulkhead when the engine moves. They are crazy tight and I recall when fitting them thinking there is no way they would fit. You might need to reposition them maybe and push them down more so they fit right on the turbo without the clamp in place. Anyway the new turbos will come with a longer snouts and you can get it perfect when fitting them. Good luck with that. I did mine on jack stands and took me about 50 hours.

Before the mod, using the stock airbox only, it probably was creating too much vacuum. I have a Z4 and they have a lot more room than the 135/335 so the inlet doesn’t really rub on the firewall. I have attached it to various points of the engine and inlet manifold to make sure it moves with the engine.

 

[CantSitStill]

Before the mod, using the stock airbox only, it probably was creating too much vacuum. I have a Z4 and they have a lot more room than the 135/335 so the inlet doesn’t really rub on the firewall. I have attached it to various points of the engine and inlet manifold to make sure it moves with the engine.

Would the same not happen on the front turbo if it was too much vacuum? Do your turbos smoke at all? When I inspected mine after I removed them the front turbo was leaking oil and had loads of in out play (had no up and down play). Mine was smoking after it had sat for 8 hours or so and when started and left idling for 5 mins would start smoking. Went away after a few mins driving. The wastegates were ready to fall off. That was at 95k miles on the clock. I was running them at 24psi though with sports cats! They sounded pretty normal right enough so not sure what causes the siren noise

 

[studio54]

My turbos make the siren noise aswell for 1 year & half now (my inlet are stock & stock airbox). Only at low RPM (1500-2500 rpm). No smoke, boost on target, checked for popped off inlet.

I often read people having the siren noise, especially after running very high boost (at least for OEM) for extended periods.

I am not sure about the origin of it, my turbos (mitsu OEM) were only 1 year old, and it started to exhibit after running more that 17-18psi. I was mostly running MHD V7 for a long time in the past, with previous turbos for 2 years and new turbos for 1 year with no siren noise, and ran V9 a bit & V10 (18-20psi) for a month (can't remember exactly, but tons of WOT) and the siren noise, coincendly or not, appeared and became more & more louder. At first days, it was quiet, barely audible when hot, now it's really loud when engine is cold, and fairly audible when engine is warmed up. The intensity of the sound seems to have reach its max (some times running V10, sometimes running my custom tune that target 20 psi) and has not evoluted these last months, it does not sound very healthy TBH, but got used to it.

Not sure but a siren noise can probably have other causes, like a small damage on a blade, a oopped off inlet ??
The way it sound on mine make me think it's a bearing noise.

I recorded it when it was barely audible : https://voca.ro/13rQ5kaxDs2x

Now it's much louder.

 

[Darke Peak]

@CantSitStill - front turbo inlet hasn’t popped off but maybe the wire support is better. I think the rear inlet is a bit longer and smaller diameter so vacuum would also be more intense. No, my turbos don’t smoke.

@studio54 - my story is almost the same. Stock original turbos; the first 50,000k (30,000mi) was by the elderly previous owner without any tune. Then I’ve added another 5,000km in a tuned state, mostly MHD 2+. Mine got progressively worse very quickly and has stabilised. Wastegates are still very good. The pitch varies with throttle position and therefore turbo speed. But not sure if it’s bearing or bent/damaged vane. New turbos are on order: RB Twos Plus. Maybe I’ll be able to identify the source of the noise when I remove and inspect them.

 

[CantSitStill]

@CantSitStill - front turbo inlet hasn’t popped off but maybe the wire support is better. I think the rear inlet is a bit longer and smaller diameter so vacuum would also be more intense. No, my turbos don’t smoke.

@studio54 - my story is almost the same. Stock original turbos; the first 50,000k (30,000mi) was by the elderly previous owner without any tune. Then I’ve added another 5,000km in a tuned state, mostly MHD 2+. Mine got progressively worse very quickly and has stabilised. Wastegates are still very good. The pitch varies with throttle position and therefore turbo speed. But not sure if it’s bearing or bent/damaged vane. New turbos are on order: RB Twos Plus. Maybe I’ll be able to identify the source of the noise when I remove and inspect them.

On both my old and current 335i's (n54) they started making more of a spool whistle noise but it was pretty normal from reading. That was at higher mileage so 75k+ miles. Did it more before it was warm. On inspection my current old turbos had perfect shaft play so I would say the siren noise is as below where the turbine is starting to ever so slightly touch the casing. Really bad if that's the case.

Quote from Tony at Vargas:
Turbos should not I repeat not make that noise, a whistle is 100% normal and with less restrictive exhaust you will hear it more. With a siren or as its called turbo howl your turbos are well on there way to going out. The noise is caused by excessive play in the center section, either in the journal bearings radial play or in the thrust axial play, usually its a combo of both. This allows defelction under boost as the exhaust imparts force on the turbine wheel, the excessive play allows the compressor wheel to actually slightly contact the compressor housing causing metal to metal contact and this noise. Once this occurs it actually starts to machine away the blades of the compressor wheel a little at a time and it will eventually throw itself out of balance, take out the piston rings and everything else with it, and you will start smoking badly. Another thing I have seen with stock turbos is, the turbine side piston ring allowed excessive oil to escape past, which gets under the heat shield and from the extreme heat turns into carbon and as this builds up under the heat shield it pushes the back of the heat shield into the back of the turbine wheel, this can also cause this noise with the same results. Bottom line, turbos are on the way out, next thing in the time line is smoke. Hope this helps.

 

[studio54]

On both my old and current 335i's (n54) they started making more of a spool whistle noise but it was pretty normal from reading. That was at higher mileage so 75k+ miles. Did it more before it was warm. On inspection my current old turbos had perfect shaft play so I would say the siren noise is as below where the turbine is starting to ever so slightly touch the casing. Really bad if that's the case.

Quote from Tony at Vargas:
Turbos should not I repeat not make that noise, a whistle is 100% normal and with less restrictive exhaust you will hear it more. With a siren or as its called turbo howl your turbos are well on there way to going out. The noise is caused by excessive play in the center section, either in the journal bearings radial play or in the thrust axial play, usually its a combo of both. This allows defelction under boost as the exhaust imparts force on the turbine wheel, the excessive play allows the compressor wheel to actually slightly contact the compressor housing causing metal to metal contact and this noise. Once this occurs it actually starts to machine away the blades of the compressor wheel a little at a time and it will eventually throw itself out of balance, take out the piston rings and everything else with it, and you will start smoking badly. Another thing I have seen with stock turbos is, the turbine side piston ring allowed excessive oil to escape past, which gets under the heat shield and from the extreme heat turns into carbon and as this builds up under the heat shield it pushes the back of the heat shield into the back of the turbine wheel, this can also cause this noise with the same results. Bottom line, turbos are on the way out, next thing in the time line is smoke. Hope this helps.

Yes, the whistle and the siren are totally different noises. I remember reading this on a thread (on another forum) about the siren/howl. I will be careful and watch for smoke. I am running cat less downpipe & catted midpipe (MOT ) for now, but ran for 1 year without cat at all while whining and no smoke.

 

[Hydra Performance]

This, in conjunction with my special sauce Carbon rear inlet, constitute what I believe to be the best overall solution for minimizing both pre-compressor pressure drop and IATs on our cars

 

[pbondar]

This, in conjunction with my special sauce Carbon rear inlet, constitute what I believe to be the best overall solution for minimizing both pre-compressor pressure drop and IATs on our cars

Do you have more details on the rest of the parts pls? What does the C/F airbox do that the OE plastic one doesn't do? What filter(s) are in there?

 

[Hydra Performance]

Do you have more details on the rest of the parts pls? What does the C/F airbox do that the OE plastic one doesn't do? What filter(s) are in there?

The airbox in question is a custom straight-through design, unlike the stocker in which airflow is forced to take a convoluted path. Keep in mind that I only use the airbox to feed the rear turbo, thereby doubling its effective flow. The straight-through design also increases induction noise which is always welcome in my book.

 

[RTA]

Is the front fed by an open filter?

 

[derekgates]

ha, reminds me of a couple years when we brought this topic up:

Restrictive air intake

What's a good way to measure if an air intake is too restrictive for the turbos? Thanks in advance.

www.spoolstreet.com

BuraQ did some extensive testing on an aFe intake which eventually became https://afepower.com/afe-power-54-76306-momentum-gt-pro-5r-cold-air-intake-system

He shows the modifications he did and the results compared to stock

https://www.e90post.com/forums/showpost.php?p=11735900&postcount=1

A followup thread: https://www.e90post.com/forums/showthread.php?t=1245659 with FAR more detail


If you feel like the stock is restricted, consider the Mr.5 Intake:

• Updated Mr. 5 Intake - Mr.5 enlarges holes for the side intake to 3"
• 'Mr. 5 Intake'... Zasquatch style - Custom CNC flange and CAI filter in lower bumper
• DIY - SyndicateGT's Custom Intake
• Custom Cold Air Intake with K&N Apollo supplemental airbox - PPK (like 335is) PS relocation, K&N Apollo CAI fed from lower bumper, PS reservoir relocated to fit Apollo behind fan relay for PPK

If you are 'room limited' like my 335is consider extra airflow with a Z4 35is lid like I did on my car:
View attachment 35539View attachment 35540View attachment 35541View attachment 35542

I went this route after being recommended by BuraQ (BQ Tuning) as it ensures the maximum airflow is being delivered to the inlets on the stock box. You can see the massive reduction in the stock box of the 335i/s compared to the Z4 35is...

I didn't want to suck in hot air from engine bay and also wanted the noise under control. My car uses the ram air system and maximizes flow now.


Otherwise without dyno, not sure how to test? Someone else will have to chime in...

I've been running the Z4 lid for quite some time. I attempted the Mr.5 Intake but can't snake a hose down from the intake due to radiator fan bracket and coolers on drivers side. I still have the lower box with hole, hoses and the velocity K&N filter... The engine bay is TIGHT.


@Hydra Performance what intake tube are you using for that front turbo? Do you have any photos of the airbox and are you considering offering them for sale?

 

[Dumaurier7]

I have been looking at this thread and waiting on a more definite response so that I can decide what I'm going to do with my Z4, I was considering the AFE intake below then this thread was started, not sure now!

 

[RTA]

I have been looking at this thread and waiting on a more definite response so that I can decide what I'm going to do with my Z4, I was considering the AFE intake below then this thread was started, not sure now!

View attachment 77070

Even with wider piping around my engine and some bigger turbo's, these filters can flow enough. I do think that the routing in this thread is even better. On the other hand, my setup with these AFE's are not causing issues the last 100k miles and neither on the track. To keep temps at the track under control it's probably most easiest to spray water.

 

[Torgus]

To keep temps at the track under control it's probably most easiest to spray water.

This. 100%. Spray water in the intake track for basically free or throw in a bit of meth in the water for more AKI. The water will cool more than moving filters around in your engine bay by far. At the end of the day the coolest air the filters can absorb is ambient air. The water or water/meth will cool the intake charge by a large degree and increase AKI.

 

[Dumaurier7]

I have been looking at this thread and waiting on a more definite response so that I can decide what I'm going to do with my Z4, I was considering the AFE intake below then this thread was started, not sure now!

View attachment 77070

Decision made! Picked this up on eBay for $320! Missing the rubber seal but that’s minor.

 

[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.

Just a quick update here, the car was dyno'd on a dynapack at 600whp WGDC 70% at full power:

datazap.me | Stuie1982 | V10 on dyno meth on

datazap.me

These turbos (UK upgraded china 19t's) are rated for 24-25psi so this was them being pushed as far as sensible. WGDC does not indicate any sudden incline so suggests the mr5 mod can support these power levels for anyone interested in it. I will never go back to DCI's

 

[pbondar]

Useful to know..do you have any piccies of your Mr 5 mod..

In May my TTE500s are being fitted with 2” pipes , Evo 3 FMIC, VTT outlet pipes..

We will tune it with the stock airbox and then on dyno day we’ll see what it does with the lid on and then off..

With a MHD V10 stage 2+ tune it did 399 BHP with lid on and 405 BHP with lid off..

Recent data log posted here on that configuration shows everything healthy apart from a bit of elevated IAT on a stage 1 EVO FMIC..

 

[CantSitStill]

Interesting to hear about the lid off dyno. Did you do multiple runs with it off/on because 6 bhp is within the dyno error margin. Most people will agree though 400bhp is about the limit of the stock airbox.

This is the only pic i have right now, my intake pipe is not as big as some go on the mr5 mod, some keep the cone in the engine bay but i wanted it in the bumper to get it out the way where it cant make much noise and gets cooler air. I have a m3 style bumper about to arrive and i will take some more pictures when i fit that. Hopefully, the cone still fits OK under the new bumper!!