anyone try a open air filter

You know, I should have guessed that from the 't'/'th' replacements, since most European languages don't have the 'th' sound. Sorry about that, sometimes younger people here like to use the 'leet speak' or variations from that, so I wasn't sure of your reason.

I've heard of the turbo Prius, and I guess in that scenario an open air filter might be needed. I'll let more knowledgeable people speak on the air filter for a standard Prius, but like they've said, there are other things that can be modified on the Prius for better mpg (or l/100km). It's good that you know how engines work, but trying to carry over your experience from the Subaru directly to the Prius may not be the most effective. You might enjoy Hobbit's web pages or darrelld, etc. (Sorry, I don't have the links right now, but look for one of their posts, the link is usually at the bottom.)

 

Again, those two concepts work together when you talk about engines... You are getting better response with less throttle use because you are getting more horsepower with less engine strain...

more air equals more horsepower.. thus, less throttle to get what you want... It all depends on your foot... if you are heavy on throttle you will see no mpg improvements... if you are light on throttle you may see improvement.

 

Hi lIon,

I think you have a misunderstanding. If you get more air into the engine, the control will make it use more gas.

The efficiency improvement of a better induction system is that it takes less energy out of the crank shaft to pull the air into the cylinders.

You do not directly control the throttle opening on the Prius. The accelerator peddle tells the computer what you want to do. And the computer opens the thottle.

In fact, the best efficienciencies in gasoline engines occurs when the throttle is more open, rather than less open.

The question is will the Prius take advantange of the better intake flow, and up the transmission ratio, in response to the better torque available from a better induction system? Its possible, as the Prius has a mass flow guage. But maybe not, too.

 

I modified the air box on the '05 Prius using a K&N filter . I removed the secondary filter , opened the baffle in the lid , removed the vanes in the area around the intake throat . The snorkel now runs straight to the grille . Engine noise is not much more the a stock airbox.

The car has more Punch from a light , when passing , even running 80+ on the interstate , tops at 105 . It will walk way from any stock Prius .

Running at a steady 70 MPH it will average 52 mpg , this is done from Punta Gorda exit to exit 98 in Lakeland FL , about 125 miles .

Vehicle will Average 48-50 mpg in the city , 42-44 mpg hywy running 80-90 mph . Upgraded tires and brakes help with the handling and stopping . This is my wifes car , I personally don't like it , but it's fun to play with .

 

llon, you are forgetting one point about an "open air filter":

Unless the throttle body is nearly wide open, the biggest air restriction is the throttle body! In other words, the air filter will have no effect on fuel economy until you make the air filter the restriction instead of the throttle body.

This means that in general, only high RPM and high throttle positions will improve.

JohnP65: Your fuel mileage is exactly the same as my bone stock Prius and many others. So I doubt that your intake mod is affecting mileage by any significant amount, but I could see it improving power output at WOT.

 

No,
With the peddle depressed less, the air/fuel ratio is still the same. Air/Fuel ratio is not supposed to change with RPM, and that is the ECU's job. But the amount of air flowing into the engine at lower RPM's, per second (or per mile at the same speed as previously), is less. This only improves mileage if the car can run a smaller ratio between the engine RPM and the wheel RPM. To run at a smaller ratio, the engine must have more torque, or it will lugg and/or stall.

The question still remains, will the Prius control units take advantage of increased torque? It appears not based on JohnP65's post. It seems he is getting the same mileage.

 

It certainly will, but again, realize that an open air filter will only benefit torque at high engine loads where the engine is moving a lot of air (and fuel).

Essentially, you are not going to see a mileage benefit in normal driving unless you use a lot of wide (or near wide) open throttle and even then, it will likely be offset by the increased amount of air/fuel you are pushing through the engine.

Now, if we were talking about reducing exhaust restriction, that is one place where if you are able to reduce restriction under normal loads you are more likely to net mileage benefits.

But again, I strongly suspect that on the Prius the stock exhaust is not a restriction until you are moving a lot of air/fuel through the engine.

 

The engine on the Prius makes a whopping 78 hp. It simply does not move much air.

My Subaru WRX makes 222 hp and it's air filter is correspondingly about 2-3 times larger. No, the intake/stock filter is not a significant restriction on the WRX, either (and yes, it has been measured).

 

The Prius engine style simply does not require much airflow so it is very doubtful you will see any MPG gain by swapping to an open faced air element. HP does not increase an appreciable amount either as I have tested this in the 1/4mile. Now if you are comparing a dirty paper filter to a brand new open element filter then you may see a gain but that is not apples to apples.

I have tons of experience racing cars and trucks (and I sell air intake kits/performance parts) but I do not see a need to change the intake system on the Prius. It's just a totally different beast.

 

There is no magic here, more power means more fuel.
If your theory is true, all car manufacturers should install the open air filter.
Do you know why they don't?

Ken@Japan

 

What country you are from?

 

The noise from an open filter gives the impression of more power but the reality is that car manufacturers are careful to use air cleaner designs that match the air required by the engine.

The reason paper filters are almost universally used by manufacturers is they provide the best filter medium and are the most reliable. If an aftermarket filter falls apart and wrecks your engine the manufacturer will only replace the filter, for engine repairs you are on your own.

Personally I'll stick with a paper element, if you want more airflow find a bigger paper element. The surface area of the stock element is bigger than it looks due to pleating.