air funnel kit - BMW S1000RR Forums: BMW Sportbike Forum
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post #1 of 31 (permalink) Old 09-01-2017, 11:37 AM Thread Starter
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air funnel kit

Any benefit with Alpha air funnel kit with stock engine? I picked up a used set at a good price so I was going to try them.
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post #2 of 31 (permalink) Old 09-01-2017, 11:50 AM
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What's the purpose of this mod?
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post #3 of 31 (permalink) Old 09-01-2017, 12:30 PM Thread Starter
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No real purpose. I seen them, bought them don't know what to do with them. For $190 why not I have wasted a lot more than this before.
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post #4 of 31 (permalink) Old 09-01-2017, 05:14 PM
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From the Alpha site, it sounds like this mod would require re-tuning, and should only be used in conjunction with camshaft and/or piston mods. That means the engine wouldn't be "stock"...so why do this?
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post #5 of 31 (permalink) Old 09-01-2017, 06:20 PM
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Any air flow change should get a tune.
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post #6 of 31 (permalink) Old 09-01-2017, 07:24 PM
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The engine is only going to inhale a certain volume of air through filter, air box, and into the engine. The cylinder is only so big.
I dont think it will do much without supporting parts.

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post #7 of 31 (permalink) Old 09-01-2017, 08:56 PM
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Quote:
Originally Posted by sro View Post
Any air flow change should get a tune.
Of course. Should have thought about that for a minute before posting. Any fuel change would do the same...

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post #8 of 31 (permalink) Old 09-01-2017, 09:45 PM
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What's the purpose of this mod?
As soon as I can actually type because this forum sucks so bad...

These shorten the intake runner distance, which effectively shifts your power-band upwards, resulting in a power gain because volumetric efficiency improves with RPM. In order to take full advantage of these you'd need to raise the rev ceiling to 15 or so.

These also result in less restriction on the intake path, though that result is minimal compared to the resonant tuning mentioned above.

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Any air flow change should get a tune.
Not at all, in fact the ECU can adjust for a wide range of airflow perfectly fine for our uses. Now for the guy wanting every last horsepower, then there is some to be had. But really tuning doesn't adjust for changes in airflow, tuning adjusts fueling/timing for all airflow values. For example Bren gains their measly power numbers by leaning the motor out some, and advancing timing some. Both of these decrease safety margin for bad fuel and other problematic conditions, but that's something a lot of us can live with as BMW leaves quite the margin to cover their bases.

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The engine is only going to inhale a certain volume of air through filter, air box, and into the engine. The cylinder is only so big.
I dont think it will do much without supporting parts.
You're absolutely incorrect, that's why we make 200hp out of a 1 liter while a Honda makes just 150hp out of the same size engine. This is because, quite simply, our volumetric efficiency is significantly better. VE is the amount of air introduced into an engine versus the volume of the engine. So 100% VE means we would injest 1 liter of air for every 2 engine revolutions. It is generally accepted that 100% VE is approximately 100hp/L. So the BMW S54, S65, and S85 all run at approximately 100% VE. This is quite remarkable considering the relatively large size of the engines, and that they need to be street tuned. But compared to smaller sportbike motors, it's crap. Now by this formula we pull in 2 liters of air, effectively running at 14.7psi of "boost", in NA form. This formula is obviously a wildly inaccurate approximation, I don't for a second believe we get in double our engine volume. But the point is, our motors are substantially higher than 100% VE.

However, you're right about this not doing much without supporting parts. This is because these really only add power if the rev ceiling is raised, and we need supporting parts to raise that because the factory parts are all tuned for 14,000.

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Any fuel change would do the same...

Not quite, in fact without touching the electronics or the pressure regulator, you really can't change fueling at all. Bigger fuel pump, bigger injectors, bigger fuel line, none of it will do anything

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post #9 of 31 (permalink) Old 09-01-2017, 10:38 PM
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As soon as I can actually type because this forum sucks so bad...



)

The forum you leveraged to raise money sucks so bad?
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post #10 of 31 (permalink) Old 09-01-2017, 11:11 PM
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As @Dragor pointed out in the ECU thread, there are many factors at play in how the engine manages power. In particular upto 8000 rpm it tries to decrease volume to increase velocity by not opening the throttle as much as the rider asks until the revs can handle it.
BMW put the DISA servo on the S1000RR that adjusts the length of the intake manifold (stacks) under ECU control.

I think to get optimum use out of a change like intake manifold length you would need dyno testing, fuel and spark changes and probably adjustments to the DISA control graph (which is not in RCK2/3 so it custom ECU code for that one).

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