really? how many test have you done? many things have you read about stock air box mods vs. CAI? lemme gess, you haven't done any of that... i completely understand that most of us do not have the equipment or time to go out and do our own testing, but you could at least do some reading.

and the air directly above the pavement isnt? please... the air directly above tarmac thats been roasting in the sun all day is pretty damn close in temperature to the air where the stock airbox sits. just because its called a CAI doesn't mean it makes the air any colder... so here, read it and weep. http://forums.vwvortex.com/zerothread?id=666711 3-5hp > CAI using a modded stock air box. total flow was better too. obviously, you will see different results on different cars, and this is only 1 example, but there are others if you feel like going out of your way and doing some fact checking before jumping to conclusions.

so if anyone else wants to try to prove me wrong, please provide some backup info, because honestly, this is getting old. i've backed up all my claims with documented research. i realize that they are not hardcore scientific tests done in control environments, but you must realize that they are all consistent repeatable results.


to the guy that started this thread: i'm just trying to provide helpful information. i apologize for mucking your thread up.

 

I'll start out by saying I have no empirical evidence to back this up, just experience and my "seat of the pants dyno". If you think about this in gradual phases, the first phase would be to replace the stock paper filter with something like a K&N gauze or Uni foam filter, keeping the stock airbox lid on. I certainly don't see anything wrong with doing this, and in the long run, this mod would save you money because the K&N and Uni filters are re-usable. The Uni filters are about half the price of a K&N, so the breakeven points on these filters, compared to the prices on a stock paper filter, could be anywhere from 1 - 3 stock filter changes.

Next, if you drop in one of these filters, and remove the airbox lid, no doubt you'd be flowing more air, but the air will be the hot air from inside the engine compartment. So I'm not sure if the added volume, albeit it at engine compartment temp, would give you any more hp. It'll definitely sound better, but not sure of the hp increase. Could do more harm than good, because in a lot of applications, the MAF sensor has to be jury-rigged somehow, since they are attached to the airbox lid. Another version of this upgrade would be to keep the airbox lid in place, keeping the MAF sensor in its stock location, and just cut out the top (swiss-cheese it, use a hole saw, or just one big cut out). I did this mod on a motorcycle I used to have, and it did make the intake louder, but felt like I lost some low-end hp and torque. Seemed to gain a few more hp and torque in the mid to upper ranges though...

The next phase would be some kind of short-ram with a K&N or similar filter on the end. Again, the good part would be the more free-flowing filter at the end, similar to the drop-in filter in the stock airbox. But the downside is you'd still be drawing in the hotter air from the engine compartment.

Next phase would be a "CAI", which by definition should be drawing in air from outside the engine compartment, which s/b colder than the engine compartment. Depending on where the filter/intake is located on this setup (fenderwell, lower part of the engine compartment, hood scoop, front grill, etc), you may or may not wind up with a true "CAI".

The setup that I'm using is a Uni dual-stage filter fitted right behind the left corner of the middle grill. I have some flexible aluminum ducting running bewteen the filter and the stock airbox inlet. I removed the stock air filter, and put some black window screen mesh between the air box halves. If I could figure out a way to deal with the MAF sensor, I'd get rid of the airbox entirely, and run a hose from the Uni filter directly into the intake system. It's been working great for the last 10K miles, so I see no reason to change it...

What's obvious is everyone has opinions of some degree on this subject. Yes, hard evidence can trump BS, but there are lots of folks out there who have experience using these products, and their comments/advice should be considered as well.

 

I'm going to agree with SOCALXB on this one. A CAI will help lower intake temperature and as cooler air is denser, that is a good thing. I have an '05 xB BCP and it's got 5100 miles on it. I am a tinkerer, anything that I can mess with i will. I began looking under my hood and realized that there are much better places that the engine could be drawing air from instead of 2-3 inches away from the hood by the battery. I left the airbox stock except for removing 5-6 inch tube that goes directly before the MAF sensor( does anybody know waht that does?). I took the stock air intake pipe away because it is dreadfully small and ill shaped. I went to Autozone, got some plastic air intake tubing for $20. You could use the material of your choice but this works for me. I went to Home Depot and got a rubber PVC pipe connector 2 inch to 2 inch and put this connector and the inlet hole into the airbox. The rubber stretches to about 2.5 inches and needs a 3 inch hose clamp to make sure it doesn't come off for the saftey of the plastic fan blades. I slid the plastic air tubing onto this connector and viola!! 3 inch tube that I can route almost wherever I want it. It is currently drawing air from the drivers side fenderwell right behind the foglight opening. I also bought a very cheap automotive thermometer that has a wired remote sensor. The sensor is about 4 inches inside the plasic air tubing giving me the temp of the air going to the engine. My setup works as a CAI because when moving, the engine gets air that is the same temp as the air outside the car. Unless you could somehow cool the intake air(naturally aspirated w/o an intercooler) below ambient you can't do any better than that. The seat of the pants dyno confirms that the car is much happier passing on the highway and taking of from idle, and I have yet to confirm but I believe my gas mileage has gone up. All for about 30 bucks and 2-3 hours labour. I live in florida and it is darn hot not matter what you do, I just can't wait for winter...

 

any pictures of this thing? i've never personally seen the inside of an xB airbox. but if its what i think it is, and one end of that tube is flared out, its a velocity stack.


this is the kind of airbox modding i'm talking about. have you looked at the inside of the airbox? does it have a bunch of big plastic ridges all over? if so, you can take a dremel and some sand paper to smooth it out and likely see more gains.

 

you should be able to unhook the box from the maf, and hook your tube directly to the maf. but then, you'll end up losing your low end torque like you do with a CAI. the design/shape of the stock air box helps down low, but is a little restrictive up top.

 

aychse7en...you are on the right path. however dont be fooled by dyno tests on intakes. Its really hard to replicate the air flow that is picked up on the road when you are on the dyno. there are numerous other factors that change things. I have done numerous dyno tests with different stuff. CAI almost always lose power on dynos. This is mostly due to piping length, multiple bends, and pressure differences. If you ever have the ability to data log while driving you will see. Also include an a/f data log, intake temperature, and pressure. CAI intakes are pretty notorious for good midrange gains.....they suck for throttle responce though.

 

only time i've seen dyno results really differ is if you're looking at a ram air setup or anything intercooled. but i agree that data logging while driving will give you the most accurate results.

i'm not denying any gains from a CAI, especially from 3k rpm and up. but you can most definately see a difference down low; i've never heard of a CAI that doesn't rob low end torque. this is where stock airbox design comes into play. i don't know all the math and reasoning off hand, but it has something to do with how engines take in air in pulses and the volumetric dimentions of stock box etc. i've seen a few cars wth variable length intake runners to combat the restrictions air boxes have at high rpm.

honestly, i've had CAIs on other cars and have always switched back to stock box after a few months because the cars felt really slow off the line with the CAI. i figure 99% of my driving is done below 4k RPM, so i want the most power in the lower RPM band. plus, considering that most CAIs are made of metal, they're not helping the whole hot air situation by conducting engine heat. the thick plastic ones stay pretty cool, but i dont know of they make one of those for the Scions.

i really feel that a modded air box using a large piece of flexible tubing routed to the front the car in place of the stock snorkel type setup is the best of both worlds; you get your fresh, cold air, you can route the tube yourself to possible avoid sharp bends, there is less heat transfer from the engine bay, and you save a bit of money.

but, really its all about what makes you happy. some people really just like the noise it makes with a CAI. and some people don't wanna go ghetto style and hack up their air box and have this hideous tubing running through their engine bay.