Airflow tested the 50i air inlet box

[onfireX5]

Completely stock 50i airbox with the better flowing X5M air filters.

Placed the pressure drop inside the filter to test the entire inlet system..this tests the entire restriction from the plastic inlet curve to the box inlet and the filter itself.

1. Zero PD as expected on all part throttle accel.

2. Around 70mph part throttle the box actually starts receiving positive pressure. Around 1" h20. Around 1.5" positive at 80mph. That is VERY LITTLE pressure but it does show the inlet is well positioned. Most systems I have tested show 0

3. Standing start WOT 6700rpm shifts show a pressure drop of 3" h20 in first gear dropping to 1.5" h20 drop at 80mph wot. That measurement make sense due to the positive airflow at speed overcoming some of the inlet restriction.

4. The airbox design is great.

5. Interms of horsepower loss:

Atmospheric pressure is roughly 402" h20 depending on elevation, baro,temp,etc.

So use the worst drop at the top of 1st gear at 3"

3"/402" X 450 engine hp = 3.36 hp loss due to the restriction. This reduces to 1.68 hp loss at 80mph.

Considering packaging constraints, etc. the Germans hit a home run with this airbox design and the X5M filters as a drop in replacement.

Also tested the exhaust back pressure on the stock 50 muffler. Going to retest tomorrow to confirm, but that big old muffler flows....too quiet...but flows....

[bjcarls]

Love it

Now could you cut open your 50i exhaust, seal over the perforated pipes and see if we can get some sound out of it. Or will anyone sell me there exhaust for cheap so I can do it.

[chrisfc923]

how does it compare to stock 50i filters?

[onfireX5]

I did not test the pd on the stock filters. BMW claims these filters flow 14% more per filter and they do have 14% more filter area than the stock filter.

For $60 bucks and BMW quality they are a no brainer upgrade when it's time to replace the factory filter. Drop right into the factory 50i airbox.

[buckeyewalt]

Something tells me that if this is such a good option, then why didn't they just put it across the board for both the M and non-M 50i? Less part numbers, less inventory, better flow, less restrictive, there's just has to be a reason. I know that you put some work into this, and don't want to burst a bubble, just thinking out loud I guess.

[bjcarls]

Originally Posted by buckeyewalt

Something tells me that if this is such a good option, then why didn't they just put it across the board for both the M and non-M 50i? Less part numbers, less inventory, better flow, less restrictive, there's just has to be a reason. I know that you put some work into this, and don't want to burst a bubble, just thinking out loud I guess.

Beaucracy-silos-politics

[onfireX5]

Yep. Plus the 50 was designed first. The X5M needed more flow to keep the pd down at the higher HP. On a mass purchase scale, the 50 filters should be cheaper for BMW.

[X5Jouster]

Originally Posted by bjcarls

Love it

Now could you cut open your 50i exhaust, seal over the perforated pipes and see if we can get some sound out of it. Or will anyone sell me there exhaust for cheap so I can do it.

yes? i can do cheap.....let me know get pictures to you and you can send over an offer.

[onfireX5]

Originally Posted by X5Jouster

yes? i can do cheap.....let me know get pictures to you and you can send over an offer.

Be interesting if your stock muffler looked like this older photo. Large internal pipes like this flow very well.

Cut it and post it up !!!

[buckeyewalt]

Originally Posted by onfireX5

Yep. Plus the 50 was designed first. The X5M needed more flow to keep the pd down at the higher HP. On a mass purchase scale, the 50 filters should be cheaper for BMW.

Great job!! I'll give it a shot

[cit1991]

First off, nice work.

+1.5" at 80 MPH is impressive. Total dynamic head of air at 80 MPH (standard conditions) is about 3" so if they're getting half of that all the way in past the filters, that is very very good.

On the resulting HP calcs, my only comment would be... The engine has forced induction and is controlling to a manifold absolute pressure. So, technically the turbos would spool up a bit more to make up for intake losses. Therefore, the intake losses would result in higher turbo speed and slightly higher backpressure at the turbine inlets, slightly more-closed wastegates. It would impact HP, but not as much as an NA engine, the way you calculated.

[onfireX5]

Totally agree if it was a typical boost target ECM. These new DME's are a strange load based target and will react somewhat like NA at small load deltas.

Logged boost factory curve is not a curve. It bounces +- 4psi based on Maf load calcs. Strange deal.

[bjcarls]

Originally Posted by onfireX5

Be interesting if your stock muffler looked like this older photo. Large internal pipes like this flow very well.

Cut it and post it up !!!

Holy bird nest! Where would you even start - is this from an e70? The M3 exhaust was much simpler!
It appears the left and right side have different tracks.
Left looks more direct and open, the right side appears to be very closed off...

Are you saying you would ship from FL? I'm relatively cheap ��