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

[pbondar]

No one on any setup is remotely making or missing 50HP from an intake or filter. Add scoops to the stock intake and call it done if you already have inlets.

ECS intake isn't much better than DCI because the box isn't sealed. If anyone really thinks they need one, I have both the ECS intake and AFE SI Elite sitting in boxes for years that I'd be glad to sell lol

Well when the tune is almost completed I’ll put it on my trusty dyno tuner and we can what it will do with OE box n filter and we’ll pop the filter and lid off to see what that gives..

I must be getting old as I can’t find that many places I can let 400 BHP do it’s work for more than a few seconds

 

[RSL]

Well when the tune is almost completed I’ll put it on my trusty dyno tuner and we can what it will do with OE box n filter and we’ll pop the filter and lid off to see what that gives..

I must be getting old as I can’t find that many places I can let 400 BHP do it’s work for more than a few seconds

Dyno really won't tell you anything realistic for intakes unless it's in a wind tunnel. Just popping the lid (or using DCI) effectively shortens the intake and reduces pressure loss, which directly effects pressure ratio. Scoops on a sealed intake do the same without also reducing mass density, but the car has to be moving. Shop fans and blowers aren't able to duplicate frontal air flow at even 40mph, let alone 100+.

I'm all for dynos, but you'd want to duplicate the tests on pavement, no matter what the dyno says, to see how it really translates. If you magically see double-digit whp gain on the dyno with the lid open, would be an obvious difference in actual performance measures if the gains aren't just circumstance.

 

[pbondar]

I agree however I’ve not yet mastered consistent road based performance testing…

For me using the same dyno for several years at least gives me a good pointer…

Unless the dyno shows a mega change with the lid / filter off I’ll live with whatever reduction the lid and filter creates….

 

[RSL]

I doubt it will be mega, but any gain will kind of be a false positive anwway. At some point I might actually measure the pressure diff between intakes/scoops, but if I haven't done it yet, maybe not lol

I've tested a lot of things and at ~480-500whp/23-25psi range on the road, stock airbox/paper filter are just not any kind of limitation (with scoops and inlets).

I don't have the roads to do that kind of stuff where I am now either or I'd be out running numbers on intakes right now.

Looking forward to the dyno results.

 

[wheela]

For what it's worth, i've seen a prominant n55 guy on a different forum compare the stock air box against a cone-style under-hood inlet like the DCI's on quarter miles, and was consistently faster on the stock air box. I agree that what you see on the dyno may not translate to the road, but nonetheless i'm excited to see your dyno results! Thanks in advance for offering to do that

 

[wheela]

I doubt it will be mega, but any gain will kind of be a false positive anwway. At some point I might actually measure the pressure diff between intakes/scoops, but if I haven't done it yet, maybe not lol

I've tested a lot of things and at ~480-500whp/23-25psi range on the road, stock airbox/paper filter are just not any kind of limitation (with scoops and inlets).

I don't have the roads to do that kind of stuff where I am now either or I'd be out running numbers on intakes right now.

Looking forward to the dyno results.

I'd love to see some delta P results like you're talking about, please post about it if you do!

 

[RSL]

Will do, I've been curious about it for years.

 

[ShocknAwe]

I still think the best high flow requirement compromise is a huge relocated front inlet and a closed box for the rear in stock location. I was working on trying to make the stock box work for this but eventually gave up and went back to my modified aFe Momentum GT/Apexi setup.

 

[Darke Peak]

I have another theory about the poor performance of the K&N panel filter: the cleats run perpendicular to the factory panel filter. The bottom side of the airbox is convex and basically touches the filter. This means one of the K&N cleats acts like a wall to block off access for the incoming air to half the filter. On the factory filter the air can go do between the cleats to access the full area of the filter. Hope that makes sense but take a look at the depth of the middle section of your airbox some time and it should be clear what I mean. The same issue applies to the 135/335 since the base section of their airbox is the same as the Z4, only the lid changes. Very poor design by K&N and a significant oversight.

 

[studio54]

View attachment 74405
I have another theory about the poor performance of the K&N panel filter: the cleats run perpendicular to the factory panel filter. The bottom side of the airbox is convex and basically touches the filter. This means one of the K&N cleats acts like a wall to block off access for the incoming air to half the filter. On the factory filter the air can go do between the cleats to access the full area of the filter. Hope that makes sense but take a look at the depth of the middle section of your airbox some time and it should be clear what I mean. The same issue applies to the 135/335 since the base section of their airbox is the same as the Z4, only the lid changes. Very poor design by K&N and a significant oversight.

Interesting, the BMC drop in I have is the other way. (pic attached, not mine)

I need to do some testing, but sadly I haven't a Dragy device, so I plan to tick only speed on MHD logging to have a good/fluid refresh rate and measure a fixed speed range without gear change multiple times on the exact same road the exact same night (letting cooling while driving for a few minutes between each shots), I thought about for example 5 times WOTing from 80 to 170 kph , and catch 100 to 160 kph from that in 4th gear with the BMC, and 5 times with the paper (Mann-filter). I should have time to do that in two weeks.

 

[Torgus]

I still think the best high flow requirement compromise is a huge relocated front inlet and a closed box for the rear in stock location. I was working on trying to make the stock box work for this but eventually gave up and went back to my modified aFe Momentum GT/Apexi setup.

Front turbo throw as large a cone filter as you can fit up by the headlight w/ 2'' pipe, rear turbo 2'' silicone inlet to stock box. Should be about the best of both worlds. Ideally both would be solid pipes but the rear makes fitting a 2'' pipe impossible.

 

[ShocknAwe]

Front turbo throw as large a cone filter as you can fit up by the headlight w/ 2'' pipe, rear turbo 2'' silicone inlet to stock box. Should be about the best of both worlds. Ideally both would be solid pipes but the rear makes fitting a 2'' pipe impossible.

Or 3" whatever!

 

[Darke Peak]

Front turbo throw as large a cone filter as you can fit up by the headlight w/ 2'' pipe, rear turbo 2'' silicone inlet to stock box. Should be about the best of both worlds. Ideally both would be solid pipes but the rear makes fitting a 2'' pipe impossible.

That would require relocating the coolant bottle (a lot of work) and it would still be sucking hot air (especially being the turbo and exhaust manifold side of engine bay).

 

[Darke Peak]

Here’s my plan. Add an extra cold air intake to the existing airbox. Photos were taken with the items roughly sitting in place. I haven’t modified anything yet. It will use a 50mm/2” pipe to go behind the left front headlight, past the horn, to the semi closed scoop on the bottom left corner of the bumper.

 

[fmorelli]

@NoQuarter .... ahem.... ^^^^^

 

[Darke Peak]

I think I have all the necessary parts. I’ll shorten the aluminium pipes - just keeping the bends.

 

[ShocknAwe]

Still gonna heatsoak that whole assembly.

Also recall that as air expands it cools and compacts it heats. Especially if low reaistance. One of the reasons the hot side front inlet works if you use a big enough filter and pipe.

If I redid my whole system I'd go this route, if you want it closed stick with something close to OE.

BQ Tuning 740i style N54 intake

BQ Tuning N54 Intake Conversion Build Prelude

BQ Tuning N54 Intake Conversion Build Prelude

www.e90post.com

 

[NoQuarter]

@NoQuarter .... ahem.... ^^^^^

Agh yes.... we have seem this plan before!

 

[NoQuarter]

 

[Darke Peak]

View attachment 74516

Unless I’m missing something that is completely different. It is just adding another intake BEFORE the stock panel filter.

My idea is to add an external cold air intake (including filter) and dump the filtered air into the stock airbox AFTER the stock panel filter. 2 intake sources (red arrows). 2 filters. 2 filtered air outputs (blue arrows).