How do you guys justify using an open element filter?

I mean, if you're not running an Aquamist system or something of that sort, wouldn't you just be adding more variables to detonation due to it sucking hot engine bay air? I see a TON of people using the Apex'i intake -- I just want to see why you would use it over something like the RB Intake Duct, PFS Airbox, or M2 Airbox?

 

man, right now, i don't even have a filter on... still waiting for my greddy... also, those of us with singles, and big intercoolers don't have room for an air box

 

Well, it flows better. Some people will build an airbox around the open elements and single turbo guys have no choice.

 

The stock airbox sucks in warm air too, since the IC just so happens to be in its intake track. The idea of an aftermarket intake is to provide more air, not cooler air, than the stock system.

That being said, many people have fabricated ducting and heat shields to go along with an aftermarket intake that provide cool air and shield it from engine bay heat.

 

I´m agree with Walien.

How hotter is the stock air box than an open element filter?

The open element gives more power but is not reliable and a closed air box gives less power but is very reliable. That´s the point, what do you want?

If you use a huge FMI the use of an open element filter is ok but for stock mount IC -not including M2 IC- i don´t think it is a good idea.

Somebody has intake air temp measures from differents intakes types?

Another fact is the money, an open element -$100,$200- is less expensive than an air box -$400, $500- but is less reliable too.

My personal opinion is that i don´t sacrifise reliability for power, it is not agood deal. I preffer to save and wait for some money and buy reliable & powerful mods and not to wait to save money to rebuild my engine.

RT.

 

if you got a big enough intercooler surely it shouldnt matter?

 

The stock air box can be modified to flow like the expensive cold air intakes (M2...etc).

I designed a sheild to keep hot air out, and cut a hole in the box. It works great. I sell them for $70. Here's some info:

https://www.rx7club.com/showthread.p...hreadid=121491

 

The "hot air" you're sucking in from the engine bay is probably cooler than the compressed air that leaves your turbo. That's where your intercooler comes in.

Anyhow, warm air flows faster than cool air, so a certain amount of hot air upstream (obviously thre is a point of diminishing returns) of the turbo is actually beneficial.

Of course, if your intercooler isn't up to the task then BOOM!

 

wingsfan is right, and the people with the mentality that cold air intake is going to matter on a turbo, the effects are negligible

if you want to prove me wrong, install some temp sensors on intake, before intercooler, and after intercooler

i gurantee you'll see that the size of the intercooler determines it all

 

Of course the compressed air from the turbos is hotter, but is no reason to avoid a cold air intake.

How about this:

The human body has a temp around 36,5 °C.

1.- If you breath cold air -like 10 °C-, how will be the air that comes out of you? It will be warm but never reaches 36,5 °C.


2.- If you breath hot air -like 40 °C- , how will be the air that comes out of you. Surely it will be hot, more than 36,5 °, i mean hot.

So, the same works for the turbos, that´s why people like M2, PFS, RB take time research, design and builds cold air intakes.

Anyway we need numbers to compare temps.

RT.

 

This is true but how large of a IC does it take to remove heat from warm engine air compared to say 60 or even 70 deg F air?
Besides how large of a IC do you really want on the car?
You only have a certain amount of area on the front of your car, which intern only allows a certain volume of air in which to cool the IC, why make the system work harder than it has to, get that cold air in there.


True again but what happens to warm air when compressed? It gets warmer still.
So if you where to compress just hot engine bay air it will be even hotter than the engine bay, yes!

 

Compressing cool air = hot air
Compressing warm air= hotter air

 

my thoughts on open air intake:
1. this time of year, an open intake will out perform a box, b/c it can suck in more air, and the air is going to be cold as long as you are moving.
2. even when its hot outside, an open intake is not sucking in that much hot air when moving. when you are moving, air is constantly moving past the engine and throughout the engine bay. thats what that fancy little piece of black plastic does thats under your car.
3. if you are that worried about intake temps, buy a vented hood. it will look good, and help keep the intake temps down, and engine bay cooler.
4. imo boxes are ugly. you have a stock box, why pay $400-$500 for 1 with a slightly larger opening.
5. open intakes can be made cold air with a heat shield.
i have an open air intake if you havent already guessed

 

Here's a great post to the old "list" (archived at www.scuderiaciriani.com) regarding a few intake boxes. The M2 in this comparison was their original aluminum box, not the current c/f one, which should run cooler.
___________
Here is how the tests were performed. The car was driven through two areas. The first area was a rural highway where the air temperature was 75 degrees F. The second area was a cool valley area where the air temperature was 68 degrees F. Data was taken in both areas at 60 mph. Additionally, upon finishing the road tests, the car was allowed to sit at idle until the temperature readings stabilized. This was done to see the effect of the airbox while sitting in traffic.

The car was brought up to operating temperature and then shut off for several minutes before leaving for measurements. This was done to allow everything in the engine compartment to heat soak so that it would be nice and warm and the effect of fresh incoming air could be seen. I used a thermistor placed about one inch away from the filter element for temperature readings. On the aftermarket intakes, the sensor was placed between the dual cone filters (above one and below the other).

I did my best to drive the car in a similar fashion in all three runs trying the same speeds/throttle usage at the same points on the roads.

Here is a table of my findings, with comments below:

Temperatures are in degrees F.

STOCK M2 PETTIT
IDLE 147.4 137.5 162.3
HIGHWAY 97.7 112.5 124.2
VALLEY 90.8 104.2 122.9

As you can see, the stock airbox performs best with regards to intake temperature with exception of idle temps. I believe the thick plastic of the stock box heat soaks pretty badly.

The Pettit intake's temperature did not drop much when going from the highway to valley area. This tells me that most of its air is being sucked from the engine bay. Also, any speed above 30 mph didn't cause significant changes in the temperature. It got really hot when the car wasn't moving.

The M2 intake's temp did drop when going from the highway to valley area, which would indicate that it is getting fresh air (though not as fresh as the stock box). I could also tell a difference in intake air temp based on speed. The faster I went, the cooler the intake air (dropped by about 5 degrees from 60mpg to 80mph, went back up 5 degrees from 80mph to 60mph). Also, the temperatures in the M2 box dropped/stabilized very quickly at idle and when the car was shut off. I didn't take readings of how long it took the temp to stabilize, but it seems to bleed off heat much better that either the stock or Pettit units.

Bear in mind that I paid no attention to the amount or velocity of the air entering the intake systems. I am sure that the aftermarket units allow more air in more quickly that the stock box. The intake ducting for the stock box is restrictive and the stock systems contains at least three ninety degree turns.

So, here's my opinion.

If you are worried about intake temps, keep the stock airbox and put a K&N element in it.

If you want more air to get to the turbos and are willing to put up with slightly higher intake air temps, go with an enclosed box like the M2 or Rx7Fashion. The sealed boxes force the air to be drawn from the crack between the radiator and frame rail. While this isn't really a great source of ram air, at least it isn't engine compartment air. Oh, the M2 box isn't actually sealed. It has an opening in the front/side area (probably to make it easier to install). This opening is mostly blocked off when the unit is installed, but I suspect it may take advantage of any fresh air that leaks in around the headlight/hood seams. I believe the Rx7Fashion unit is completely sealed (except, of course, the hole in the bottom where it gets air).

Do not go with an open type system such as the Pettit/N-Tech. There is no way in hell that it will draw in fresh air. They will draw air from the engine compartment. They will not magically only use the air that flows up from under the nose of the car. Also, this air from under the nose of the car would be ok, except that they are depending on ram air. You just won't get much ram air from there. It can't come from below because of the engine under cover. It has to come from the nose of the car, make a left hand turn at the radiator and squeeze between the crack between the radiator and the frame rail.

Let me reiterate. Don't buy the Pettit/N-Tech systems if you want fresh air. They should not be calling them Fresh/Cold Air Intakes. If they had ever tested the intake temps they would know better. I'm sure these units are great for getting more/less restrictive air, but they should be calling them something else. Even the manufacturers of the sealed boxes (M2/Rx7Fashion) should probably change the name, as they bring in warmer air than stock.

 

what about putting a hose from the blank on the left of the big opening to the filter or box (whichever you opt to go with.)...that would provide a more direct route to the bottom of an airbox/open element...right?

 

That would only work on Base/Touring models, as the R1 has an extra oil cooler in that duct. Also, that would be somewhat ineffective unless the car is at speed.

 

There was no way to justify it, so to speak. I couldn't really used a closed intake with my Greddy FMIC.

 

I made my own heat shield today based on your design. Great idea, thanks!

 

Glad you liked it. You owe me $5 in royalties... hahaha

 

Somtimes the biggest driver is packaging. I HAVE to use the GReddy Airinx with the GReddy Type 24 V-spec FMIC, and Koyo radiator. There's just no room to do a cold air intake. As for the hot air sucking, the FMIC's core size is so huge, hot intake air gets cooled very quickly with the better efficiency of a large FMIC core. FD owners with the stock, or smaller core SMICs need to worry about cooling the intake air before the IC core LOL

 

Ideal gas law:

pressure * volume = molar mass * ideal gas constant * temp

Any turbo system is designed to pressurize the intake air by a certain amount. The pressure and volume of the intake after the turbo remain the same for a given boost level so the only things that can change are the molar mass (number of molecules) or temperature. The hotter the air is after the turbo the less dense it will be. If you lower the temperature of the air before the turbo you increase its molar mass and that means that to reach the given pressure and volume the temperature will have to be increased by a smaller factor. So in theory at least, starting with cooler air being sucked into the turbo will make it more efficient. However in practice, intake temps at the throttle body are so dependant on intercooler efficiency that what kind of intake you run becomes a bit less important. Given an ideal intercooler though you would make more power from cooler air being taken in by the turbo. But then again since it's such a great intercooler, having hotter air sucked in would still produce good results.

 

Excellent post below! To reiterate--no one is arguing that having cool intake air BEFORE the turbo is a bad thing...on the contrary it's a good thing (especially for those with small IC cores). The point is, that the IC core's cooling efficiency (larger is more efficient) will ultimately dictate what the charge air intake temperature into the combustion chamber will be.

Merry Christmas!