What's better: Modified Stock intake or open element intake?
 

About a year ago, I did Adam C's cheap bastard intake mod and was very pleased with the outcome. I'm installing a Power FC tomorrow and was advised by Chris @ RX7.com that I'd get more horsepower by installing and open element filter system. As far as looks goes, I like the latest unit from Fighter's Garage at:

http://www.fighters-garage.com/rx7.html

What is the consensus regarding this topic? Should I stick with my modified box or go with one of the open air units? The $200 or so is not an issue...I'm happy to spend it if their's a performance gain. If not, I'd rather not.

Thanks for your input,

Ian

You might notice a difference on the dyno, but on the street? Doubtful. Obviously if you want to go with a bigger IC, you'll have to ditch the stock box.

Thanks Tyler....I don't plan on going with anything any bigger than the Greddy SMIC. So for now, I'll probably just stick with the stock box, unless anyone else has something to chime in with :)

You should consider what Chris's job is: To sell you parts!!!

It is unlikely that you would see any gain with an open intake. Most likely, you would lose some power, and have spent $200 (or more) to do it.

Thats been my experience, intake temps go up sucking hot engine bay air and power goes down even though restriction is reduced. Air density is key to power.

Yep. And, with a properly modified stock air box, there is very little restriction. In addition, the stock airbox accomodates a huge filter. With a K&N in there, you can't do better.

Agreed. Air density--cold air is where it's at.

I used both an adam_C style modified stock air box and the ebay style open element intakes. Didn't notice a big difference other than the open intake made a lot more noise and the air pump moo was annoying.

and with adams mod you fly under the smog radar.. big help if your in Cali..

Jeff

I agree with all that, but isn't that what the intercooler is for? To cool the air, no?

I mean, how hot does the air coming out of the turbos get? If, let's say, the turbos heat the air from the intake up to 300 degrees (totally arbitrary number), wouldn't that temperature stay the same regardless of wether it brought in 80 degree air or 90 degree air? I mean the turbos create such intense heat that the diference of a little more ambient air temperature shouldn't make much of a difference, right?

Take a look at this link:

http://www.stealth316.com/2-turbotemp.htm

Once you enter the ambient temperature, it will calculate the turbo's output temperature. Then you can enter the output temperature below that to calculate the temperature of the air coming out of the intercooler.

Basically, what I'm saying is that if you try a few different calculations, you find that a difference of 10 degrees or so will only output a difference of 2 or 3 degrees into the motor. So wouldn't it be better to have a free-er flowing open intake with a little more heat than a more restrictive closed-off intake with slightly cooler air? Also, doesn't the stock airbox hold a lot of heat in the plastic?

Excuse my ignorance, but I just wanted to shine a new light on the topic (not saying that no one's ever brought it up before).

-Ian

I have the Fighters kit FWIW

Plastic holds temperature less than metal I think everyone is in agreement with that.
Before, I had a K&N kit with the Damian-Style heatsheild and a Pettit Coolcharge II only on days where it was 30+C outside in traffic would I see some of the 60c intake temps. That is why I decided to go with the same setup again as usually my intake temps would be like +10-15c over ambient which I think is pretty good.

Personally, I am gonna try making a cold air style box from the Fighters kit making the use of a stop sign (Hey gov't you been f#$%ing me over with taxes for awhile). If you want to be updated send me a PM and I will get back to you.

The only restriction with the stock intake to my knowledge is that is draws air from the intercooler. The reason why the M2/SR Style boxes are so good is because they draw air from the bottom.

I think the top of the top would be to have a closed box drawing air from the front of the car, I think the highest wind velocities would be there and you would be getting the most cold air.

Sorry for my rambling non sensical gargon but on a side note last night I was cleaning out styrofoam from my recently purchased intercooler with a ShopVac and for kicks I put the exhaust of the shop vac (which just happens to be 2.75in) on the turbo side of the IC.
Suffice to say the air going into it was HOT but the air comming out was like that of an air conditioner.

Yes an no. In the general sense, colder air is always better. For NA motors, its a LOT more important as there is nothing before the motor to cool it. For FI, it's not quite as important which I've mentioned in a lot posts about this subject.

You don't see the single turbo guys going all out trying to make sure they are using/building CAI's. ;) Heck no. Most of them slap a filter on the inlet of the turbo and call it done (I'm not going to get into ram air intakes).

*IF* you are after every tiny little bit of performance like race teams go after, then you might want that extra 4-5 degrees out of the intake temps (granted you are getting the same amount of air between the open air intake and the CAI). However, for 99% of the people on this forum, it won't make a difference. It just comes down to what do you like to see under your hood.

My new setup is changed from using the HKS filters to the M2 CAI. I didn't do it for performance reasons, I just liked the look of the M2 box.

Ian,

Differences in intake temps will normally be a lot more than 10 degrees when comparing hot & cold air intake systems. As an extreme example, when a car with a hot air intake is stopped, the air it is taking in can be 100 degrees hotter than a stopped car with a cold air intake.

The temperature of the box isn't that important when talking about perfromance. Under hard acceleration, air passes thru the box so quickly that the box doesn't have time to heat it up.