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Originally Posted by lux.sh
Alot of you say intake for E90 will cause in loss of horsepower.
Does anyone have proof of this or any read-worthy technical data regarding this?
Cause really, and usually. Free-er flow intake supposed to give you more
horsepower. Unless BMW design is completely advanced that the intake
tubing is absoutely tuned to the max, which I doubt it. Because if it really is,
it wouldn't be so quiet.
btw, that does look pretty ghetto, but cool idea and kudos to you for brave attempt. 
Its just "proto-type" so I'll let go of the design. You had the right idea though.  |
Youīll need to spend some time in the auto industry (especially with quality german automakers) to understand how foolish the assumption is that you could better something like the stock intake on an E90 with some home made thing. Development on such a seemingly simple thing as an intake can easily occupy 3 full time engineers for at least a month. And thatīs only finetuning for a particular engine/model. No wonder developing a new model can easily cost several billion dollars.
In detail: The design of an intake will typically be done by a team of engineers and prototyping will incorporate such technics as finite element analysis, wind-tunnel-testing and rapid 3d prototyping.
Sure the set of parameters the engineers will try to optimize is different from what the home-cooker (or even an aftermarket tuner) is interested in. First priority for the automotive engineers is to protect the engine and the MAF with proper air filtering even under extreme conditions, second priority is to keep the intake noise down. But then next on the list is horsepower, torque and fuel efficiency.
The aftermarkete intake builder on the other hand only cares about power and sound. But his resources are limited.
Sure, in theory, by negating filtering and noise priorities you can build an intake that should be more free flowing and hence offer a very slight power advantage. (Hence, in motor racing the stock intake and filter is often the first thing to go. But then, racecars donīt run on dusty/sandy streets or in winter with salt and snow, and the engines have a far shorter lifespan). But with a trial and error approach you often arrive at a solution that offers no power increase (or even a loss in power) and still offers the engine (and mostly the MAF that reacts really badly to unclean air) less protection.
Youīll often find that such mods are argue for with things like "it feels a lot faster" and "it sounds great". Psychology 101 will tell you that anyone who has taken an effort will unconsciously lie to himself to justify the effort. And the butt dyno is so ridculously inacurate, anyone who refers to it immediately disqualifies himself. Besides, a different, louder or even more agressive engine sound will allways make a car feel a lot faster. On of the problems the E90 faced during introduction was that E46 owners felt it to be slower on a test drive, while it actually is (at least a bit) faster. Problem is, the E90 is quieter. A Merc 600 will equal the acceleration Performance of many Ferrari, but the Ferrari will allways feel a lot more rapid.
Even dyno testing suffers from the old Psch101 syndrome. Dyno testing has so many parameters that numbers are hard to reproduce. Even small differences in test setup can lead to differences in output of single digit percantages. The only way for dyno test of performace mods to be scientifically significant would be to take a batch of at least 10 cars and have them all dyno tested (5 with the mod and 5 without) on the same dyno by someone who doesnīt know which is modded. And so itīs a double blind test, the driver taking the car to the test may not know which is modded either. Then repeat with the 5moded cars turned back to stock and the 5stocks modded. Only then could the results of such a test become relevant. Not exactly the kind of resource that the aftermarket has...
As for the intake pictured here, there are at least two errors that would probably make it cause a drop in horsepower. One is the fact that it draws air from close to the engine. And the N52 engine runs extremely hot, so itīll be sucking far hotter air than the stock intake. Also the Aluminium or steel tubing will heat up and thereby transfer engine heat to the air flowing in the engine. Warmer air equals less power.
But even the airflow itself, Iīm not sure if itīll really be better than in the stock intake. Aerodynamics can be incredibly complex. What looks more free-flowing to the eye may not be. Visiually, less obstruction would seem like less drag, but well lead air can go through quite some obstacles with very little drag while an open area can have turbulences that actually cause a lot of drag. The stock intake takes cool air from in front of the radiator (Which is cool despite the radiator thanks to the very high air flow in this area by being directly in the airstream of the moving vehicle. It actually is even slightly compressed by the vehicles forward moevment (a very slight ram-air effect) and is then lead smothly and gently toward a very big square airfilter that it flows through unidirectionally (contrary to the aftermarket solution shown here which is circular and where the air has to flow from all sides just to collide with eachother on the way further to the MAF) and then on in a clean stream to the engine. All parts are made of plastic which isolates the air better from the engine heat than metal.
Also, the N52 in 330 version has a three stage intake manifold that optimizes clyinder filling by changing the length of the intake pipes depending on load and rev. It uses resonance effects of the air to maximize the filling. The "intake" is part of the total intake pipes and calculated into the ecuīs switching points for the variable intake. Changing the "intake" can play havoc with the desired resonances of the variable intake and therby cause overall or least partial loss of torque and thereby power.
And thatīs just the obvious Iīm stating here. There may be other effects that I donīt know about or havenīt thought about. But somme of the above may be of little relevances as well. Point is, I donīt know and I donīt think the guys with the hacksaw know either. Theyīre out to be different at any cost
In short, I donīt think modding the intake of a N52 engine is a worthwhile engagement. You may get lucky and get a very insignificant power gain, but allways at the cost of engine life through less perfect air filtering. In most cases, youīll only get a different sound and no power gains or even a loss in power. In any case you will void your warranty unless youīre as immoral as to change back to the stock intake when problems occur that might be intake related and go on and offload your ignorance at the cost of the manufacturer (and thereby all BMW enthousiasts since warranty costs are calculated into the price of the product).
So to anyone who has to hacksaw around at his fine Bavarian, thatīs fine with me. Just donīt tell me you got any power gains unless you can prove them in a manner stated above, or Iīll simply ignore it. But most importantly, do so at your own risk. If the MAF starts to show trouble, buy a new one out of your own pocket and we can still be friends.
Btw. my preaching does not mean Iīm free from temptation. There were times when I myself was in search of more power on a budget. Some of the sermon up there is based on my own bad experience. Some of the others on insight into the complexities of automotive engineering, which is sometimes far more trivial than one might expect and then again sometimes incredibly more complex.