Quote:
Originally Posted by tjoy
I'm open to being wrong.
It just seems pretty logical:
1. the filter is a source of drag, aftermarket filters supposedly work by helping air flow better, but when the filter is removed, there is no appreciable gain
The more controversial bit:
1. When part of the exhaust is removed, and exhaust can supposedly flow freely, there is no gain. I'm open to misinterpreting the results.
I do however think I won't be buying an aftermarket filter for the stock airbox based on his results.
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20 years ago we as a car buying public could go and buy a metal intake tube and and filter and it would legitimately improve the ability of the engine to ingest air at and given load by simply reducing restrictions. Nowadays a drop in filter probably doesn't gain 9/10 times. They still serve a purpose, I prefer them if for no other reason than I like the idea of reusing one part instead of throwing them out yearly.
But as far as airboxes and actual intake setups go, its not snake oil. They do really make power.
Today most factory intake systems are much better designed even on an inexpensive car. They have to be because manufacturers are constantly increasing efficiency while needing to still make competitive power figures. Then add to that sensors that are extremely accurate at determining how much air is being ingested and a fuel management solution that tries very strongly to keep the engine being efficient and you have engines that have fairly unrestricted intakes and don't respond to brute force 'pipe and cone' intakes that aren't truly engineered, but just made to fit properly.
What does that mean for us? It means the gains we get from an intake are not just a result of simply being less restricted. A lot of clever engineering goes into not only flowing a bit more air but in how the MAF is allowed to interpret the incoming air. Take a look at a few intakes and you will see they all move the MAF. This combined with resizing the size of the tube (MAF calculates its value based on stock tube diameter. Change the diameter and you change the calculations.) This is done as a sort of hack to trick the car into running a bit more aggressively with the optimally designed intake setups. These air boxes etc are all going to be less restricted than stock but the power comes from the MAF trickery.
On the exhaust side, I don't know as much about how they make power beyond just more airflow (I do know that acoustic tuning in the primaries and secondaries of the header is an art and a science and can make power) Personally I would think that removing the muffler it is just too far down the path of airflow to have much of an impact at the stock exhaust flow levels. The exhaust back there looks pretty free flowing.
However, Upstream near the over pipe area there is no doubt restrictions that can be removed and once the car is making more power (say, with forced induction or a few boltons and a tune) it very well may start flowing enough air that the mufflers do become a restriction.
There is probably also methods to extract power even that far down the exhaust with acoustic tuning, but they're beyond my knowledge.