dial8

iTrader: (4)

You don't completely lose low end, its just not there as much as before, and the "feel" of the top end is better. I've stood and watched over the shoulders of an ex co-worker who did this, and after wards he claimed his top end got a lot better, but in the passenger seat all I could feel was loss of low end.

Or try this. Take the entire air box, intake tube, all that crap off all the way to the TB and then drive the car around the block.

Your definition of ram air is correct but you left out two crucial points. 1.) the intake tube needs to be as straight as possible to channel air into the TB. 2.) second the shorter the tube the smaller the amount of torque the engine will out put. ITBs are smaller in size but greater in volume, thats why you don't lose torque. The IM on an FC is right below the Tii hood scoop, and off center a few inches. How long can you make the tube and still keep it straight? Not very, which why you wont have a lot of torque. ITBs are also more efficient, as they are more precise. The only problem I see with an individual set up is the cost, as they are all custom made.

ericgrau

iTrader: (1)

Numbers! Sweetness. Okay, time to go to work.
11.5" water / ((12 inches per foot) * (2.31 feet per psi)) = 0.41psi lost

As a side note for comparision, I recently calculated <.05psi lost through the stock intake pipe. That's at WOT and high revs.

Air density is proportional to absolute pressure: 0.41psi/14.7psi (atmospheric pressure) = 2.8% drop in pressure, or a 2.8% drop in air density. That means 4HP on an s4. So, assuming a cone intake still has a little restriction, it probably nets 3HP to gain.

Of course, since a CAI gives 6-7 HP compared to hot air, you better have that cold air box. Assuming the stock intake is already cold air, you're losing 3HP with a cone intake. Assuming stock intake isn't 100% cold air, you could gain a little by converting it to cold air.

EDIT: That's the extra power from getting denser air into your engine. Kinda like having 0.41psi of boost. I also calculated another 0.5HP from not fighting against the restriction. But for 0.5HP, I'm not gonna go through the calcs here. Just figure out how to use power = pressure * flow if you're curious.

kontakt

^^ that's what I was referring to. I don't know why I said ram air. I meant "short ram" which is still wrong, but is often used to describe what I'm talking about. Essentially just a cone sitting in the engine bay. This will guaranteed lose you power.

If you can make an intake that truly gets 100% cold air, and absolute minimum restriction, then you make out. Most people I've seen failed on one or both of these issues. I have almost never seen an insulated intake pipe either, so heatsoak is still generally worse.

I never said it was impossible to gain power, just that tons and tons of systems out there fail to, and that it really is more work than most think to do this right.

RotaMan99

I can never argue with your math I think there was one thread I saw that there was a 17 inch H20 restriction in the intake system, but im not sure if that was with the manifold or not.

Although, I lost you when you starting talking about loosing 3hp with a cone filter, you must mean with the filter in the bay without heatshielding right?

One thing I always wondered, is how much restriction a K&N filter drop in has compaired to your standard K&N cone filter. The surface area must be smaller unless you get a large cone filter.

Assuming thats what you were talking about, be a little more specific next time

Since we are on the same page about installing a cone filter on the AFM and leaving it in the engine bay to suck in hot air, I agree. Personally, I don't see why people convert to a cone filter in the bay without heat shielding, mainly its the new guys, which is ok since they are learning, but it really needs to be said more often to members wanting to build or buy a so called...cold air intake.

RotaMan99

It would be fairly substantial. Arn't most ITB's around 50mm each? So the runners in the manifolds must also be larger, not 50mm but larger then stock intakes which would only hurt the low end.

Straighter the better, as we all know bends add resistance but not by much, so having the ram air tube in a high pressure air flow path, even if you had easy bends, you could still get the effect from it. Now how much you would actually gain is beyond me, I have never seen anyone do any official testing with a ram air intake.

This is true for AFTER the throttle body as I understand it.

dial8

iTrader: (4)

Not as much as you think. 50mm and 55mm are th most common, but any size velocity stack can be used, and you can get them tapered, etc. The best thing about them is the COLLECTIVE intake effect, two heads> one. But don't think about just the intake side of the equation. More throttle bodies=more air=more fuel=great response+great power(when tuned right). Think of the 5 valve system Toyota applied to the 4AGE(?). 3 intake 2 exhaust. The three can cove more are collectively than the 2 on the standard engine making them more efficient and more powerful. That jump in intake design alone took those engines from 120(?)hp to 160(?)hp. Sorry for the question marks, I'm not a big Toyota fan and my knowledge is limited, but...ITBs remain the best in my opinion. I refuse to run anything but, and will until I can come up with something better or something just as good that costs less.

dial8

iTrader: (4)

I forgot that. Short answer...No. Do the test I suggested to any car. ANY car.

Not to be a dick, I'm just curious, do you actually roll Rotas?

black_88

so how whould a cold air intake keep your engine cool? that is what the Radiator is for

SayNoToPistons

Why are people so obsessed with "Cold air intakezz"? WHy can't you stick with the stock box and duct since there's very little if any increase in efficiency (correct me if i'm wrong) with those "cold air intakez"? Mad koo filter in yo face, yo?

RotaMan99

If you asking if I have a rx7, yes I have had one for 6 years now.

Well if this is true, then getting rid of the AFM and airbox would make you loose torque. considering there is fractions of a difference between leaving the tube on and leaving the tube off considering the amount of CFM an engine on sotck ports can consume.

RotaMan99

btw thanks for the info

dial8

iTrader: (4)

Any time . When I can afford it and I'm at the stage where I need to change my intake, ITBs are the only I will consider.

By Rotas, I meant the knock off brand wheel. I'm not a copyright ****, but I think making an unoriginal product, and making it cheaply is ******' dumb. Though not as dumb as the people who buy them and swear they're getting a good product.

RotaMan99

Ah, nope, never did. Just a name I came up with.

freemanrx7

I have put a few k&n filter charger kits on my rx7's

I loved the way the car wanted to go to the redline. Thats my kind of driving. I live in a small town 1st and 2nd gear felt much better


I noticed the loss of some low end torque. Flooring the gas in 5th gear felt sluggish.


I'm very happy with my CAI ( if you can call it that)

dial8

iTrader: (4)

Cool

Macrophobic

I like the z3 idea because it keeps the hoses short and relatively straight minimizing power loss, as long as you can build a decent enclosure for the filter, but would those vents provide enough air flow? also i live in vegas where its like 115 so i dont really think a CIA is such a good idea so im keeping mine stock and saving for a kickass exhaust system

dial8

iTrader: (4)

^Smart Man

Project88Turbo

iTrader: (22)

I had a cold air box on my car, but it wouldn't fit with my new TID. Before I took it off it did make a nice difference :-). Here's a picture of the box:



Installed pic (not my car):



I've got it for sale : https://www.rx7club.com/showthread.php?t=679393

Vince

Circuit Theory

iTrader: (52)

AHHHHH!!!!

Why why why...

clokker

iTrader: (2)

These sentences seem to describe two different cars.
How can 1st and 2nd gear "feel much better" with less low end torque?
If it "wants" to go to redline more easily, why would accel in 5th feel sluggish?

You can call your intake anything you want ("CAI"?) but unless it's winter where you live I doubt there's anything "cold" about your intake air.

Where does the K&N kit pull air from?

racerlinkfc

hey natey can you tell me how to build one like yours it looked pretty clean let me know please!

freemanrx7

The K&N pulls air from under the hood. I live on the coast and it doesn't ever get over 80 deg.

What I was saying about 1st and 2nd gear was that The 7 pulled much harder to the redline. Engine could breathe much better.

While driving in 5th around 2800 rpm flooring the gas it felt sluggish. Meaning it didn't want to rev to the redline so fast. JUST my experience vs STOCK

This mod prob doesn't add any HP! It does change the CHARACTER of the car and that is my point.

If you ever get a chance go look at a stock S2000 intake. That might be the right way to go. Kinda combines both types of intake

Roen

iTrader: (2)

Or just look at clokker's intake posted in this section of the forum. Not too bad of a job.