The "Poor" Man's (or Woman's) high flow air intake

From what I've been able to gather, there's a trade-off between slightly increased power (cold-air intakes) and slightly increased mpg (grill blocking, etc.) but either way, the effects seem to be relatively minor.

It seems like this would be an interesting thing to try, but there's a problem - tree rats. When I bought my Prius, one of the first things I did was to change the air filter, and sure enough, under the filter was a pile of acorns. I screwed some stainless steel mesh onto the very front of the intake (and cleaned out the acorns) - problem solved. But - if I try this mod, how can I keep the damn squirrels out?

 

Your speculation is known to be very good, sir.

 

At least they covered everything up!! The Gen3'ers have to buy all the covers....

 

My resonator got broken by a snow bank, is off 2009 prius, do I have to get a new one? Getting better milage... reading looks like it only protects from getting water in the engin..engine... any thought?

 

A good introduction to the reasons for a Helmholtz resonator in the air intake can be found here (though that page specifically is a motorcycle site).

The resonator is open to the side of the air path; the main air stream flows past it, not through it. (Picture somebody playing a flute.) It is not a source of air resistance on the flow path.

It has a function similar to that of a capacitor in an electronic circuit.

The engine's intake valves open and close, and draw air in pulses. Without the resonator, when the valves open, the intake pressure drops, which then has to accelerate the stream of air in toward the manifold. When the valves close, the continued airflow into the manifold raises the pressure there, until the flow is reversed and sent back outward. This is a source of resistance to cylinder charging, and also causes the escape of energy from the intake snorkel in the form of pulsation noise.

When the resonator is present, and at the RPMs where it is tuned to have the best effect, it absorbs those pressure highs when valves close, and returns the air stream toward the intake when the next valves open. This reduces the effective impedance of the air path, leading to more complete cylinder charging.

As a side effect, there is less pulsation at the intake snorkel; the air flow there is more continuous, and less energy escapes in the form of noise. So yes, it does reduce noise too; that's one way you can tell it is working.

 

I've noticed that claims of increased power or torque or "throttle response" from dubious easy modifications are never accompanied by even the most rudimentary objective data to back up the claims.

Besides attenuating sound energy, the intake plumbing is designed to reduce risk of water intake during heavy rain, and the amount of airborne dirt reaching the filter.

 

Yeah, looks like a hamster run. I put rodent mesh over the engine air intake.

 

I chopped up my bumper cover and routed my intake there just over two years ago (~30,000 miles) now:

Yes, these threads about "high flow" intakes always seem to be devoid of any measurement. I haven't measured pressure drop/flow restriction because I was only interested in seeing the effect on intake temperature (which is indeed lower now with the bumper intake; it rarely goes more than a couple F degrees over outside air temperature). But I might measure the flow restriction one of these days just to see.

As far as water intrusion, I have found that you really only need to worry about standing water. I've driven through all sorts of weather--pouring rain, snow, and everything in between--with no issues (in fact, I drove through a thunderstorm in South Dakota last month that was so heavy I had to pull over because I couldn't see anything for several minutes). The airbox and filter are designed for this; the filter sits at the top of the box, with the engine air flowing up through it. This works because the effect of gravity on air flows is negligible while the effect of gravity on water is not negligible. There's a drain hole on the bottom of the airbox to let out any water that does manage to make it in.

My 1991 pickup has a similar intake, stock. Engine air is pulled from a "bucket" around the driver side headlight, exposed to rain and precipitation. The short intake tube runs to the airbox where, just like in the Prius, air is routed up through the filter opposite a drain hole at the bottom. And before I modified the Prius, I also looked at similar intake designs on the Dodge Challenger and Charger, which have a short, open tube next to the headlight, completely exposed to rain, that runs to an airbox with the filter at the top and a drain hole at the bottom. I would bet if I open the airbox on just about any car today I would find...the filter at the top and a drain hole at the bottom.

 

Just get a INJEN, Got mine from the Prius Chat store here.

 

Looks Awesome !!!! There really wasn't a lot of performance stuff for the 3rd Gen's back in 11, Injen was the only one we could find.