After reading all the arguments back and forth about ambient air intakes (particularly in a non-modded N/A), I took my K&N out and put the stock Mazda box back in, with a new drop in filter. Car now idles smoother and pulls just as strong throughout the power band and even up to red line. I agree with those who have said that in a N/A the difference is not noticeable. I had fabbed an insulated box around the K&N, but hadn't given it a source of outside air to breathe.

 

One of my biggest regrets with my NA (when it was still NA) was that I paid money and put on a cone. I gained some throttle reponse, that's about it, but it really wasn't worth it.

You made a good choice lad.

 

I have hks intake and can tell no power gain. Actually i think its hurt gas milage I thinking about going back to stock

 

lol mine's 87 tii and i still have the stock box with k&n panel filter. I don't know but i really like that look with the shiny mazda sticker haha

 

yea i bought a cone filter, but its making the idle quite disturbing... i think i'm gonna change it back to the stock box soon too.

 

you all see the LIGHT!

 

I bought my TII with a cone filter, and I don't have a problem, what are you guys doing wrong? :P

 

for this thread both intakes are good..if you have a t2 and start down the mod path i would recoment a cone but if fairly stock stick to the stock mazda airbox. it was designed well and our cars the "air" isnt the big restriction it is the exhaust. so intake on rx7s will be fairly diff from pistons.

 

Rotating the AFM when installing a cone intake will cause a rough idle, loss of mpg and loss of power. The rotated AFM flapper stays open a hair more to make the car think it's getting more air than it is. The ECU responds with extra fuel and you run richer than normal.

A cone intake may be good for up to 2-3HP. But if it's not breathing 100% outside air you'll lose 5-6HP. So net loss of ~3HP w/o cold air box, net gain of 2-3HP if you use a cold air box. My car's dumb P.O. put in a cone intake. I'm thinking of putting a box around it and getting a stock intake snorkle from someone to deliver cool outside air. I already rotated the AFM back the way it should be and my idle greatly improved.

Oh yeah, one more thing. Re-usable cotton filters (cone filters, lifetime filters) don't filter as well as disposable paper. That means more dust in your engine, oil and oil filter.

Come to think of it, everything the P.O. added to my car has turned out bad except the clutch and spark plugs. I just hope my clutch doesn't break and my spark plugs don't seize.

 

Oh lord...butt dyno strikes again!


-Ted

 

WHY???

naw man, no reason to be scared (unless you're a noob that hates searching), I just say what's in my head. Both on eh webz and in real life. Some ppl don't take criticism well while others (like me) like it in order to improve. Others take my sense of humor and get all pissy.

Edit: I expect to hear from a mod soon. *flinstones quitting time horn*

 

phoenix7 your alot like me i dont care if pps dont like the way i tell it to them strait.
and the rest of you guys get the sand outta your vaginas or use some vagisil if need be
the stock air box is definatly adequit until about 250 hp. i put cone in and extended it to infront of the rad for a more simple look. not hp gain

 

Bullshit.
Too bad most of your non-turbo FC's don't even come close to 250hp...
har har

I tell you what...
I'll put up a challenge.
Stock airbox versus K&N cone filter...
K&N cone filter needs to be at least 6" long and at least 6" in diameter at the base.
Do a back-to-back-to-back run on a dyno and see what makes more power?
I'll *PAY* for your dyno runs if the stock airbox makes more power than the K&N cone.
If you lose, you pay for you own dyno runs.

Power difference needs to be at least 1hp between runs to be considered significant.

Put up or shut up.


-Ted

 

I put in a cone filter with the intentions of helping my car warm up faster...(it gets a little chilly up here this time of year) and to get the idle down more quickly.
Unfortunately and not suprisingly, there was no difference in any way....

 

The cone argument is a reality, unless you have a source of cold air it's a worthless mod. However i found one thing that helped. I put in a k&n drop in filter and cut the top of the air box so that it had a large hole in it, then covered the hole with a screen so nothing could get in there. I know it gave me more power. But i had to clean the filter ALOT more often. How good for the oil/engine I dont want to know but hey it was a better gain than the cone filter.

 

for cars with AFM's, many people have had prblems with just a cone intake. The afm doesnt get good readings. Happens with almost any car with a afm

 

I guess im the only one that seen the humour in this?

 

and what on earth made you think removing the stock airbox would make this work?

and an aftermarket intake makes a much bigger difference on a turbo II.

 

I've tried the car with a standard box intake with a K&N drop in. A ebay cone filter and a K&N cone filter. There was absolutely no difference between each.

I would definitely agree that the cone air filter isn't getting cold air at all rendering it an almost worthless mod for a N/A. But then again, I wouldn't say that the stock airbox gets any better air either.

The stock duct does absolutely nothing. There is no air in the area where the duct entrance is. The car is designed to have the front bumper pull air from under the car up. Unless you reroute the whole intake system you're not gonna get cold air either way.

The idle problem IS annoying though. It scares me sometimes. I'm going to make a surround for my intake soon and maybe direct some air from the front bumper using flexible tubing or something. Will keep you guys updated.

 

where was this thread last july when i dumped my cash into an intake that just killed my idle an mpg for no noticable gain

 

all you had to do was search. We've had this argument for years.

 

whats so wrong with having throttle response?

 

On an S4, moving to a cone filter from the stock airbox saw an increase in volumetric efficiency on a ported N/A engine with full exhaust and a standalone. Throttle response also improved, idle quality did not change. Cone filter was not fed fresh air. Car required slight retuning to achieve equal AFR's after the cone was installed. Removing the AFM and moving to straight pipe saw next to no change on the same engine. Accelerometer logged improvement after the stock airbox was removed.
Home-built flowbench mated to full S4 intake manifold, throttle body, AFM, and airbox saw noticable improvement by changing the stock airbox for a cone filter. Changing the AFM to a piece of straight pipe did not show a significant gain.

Anyone claiming that the stock airbox is not a restriction on an N/A engine had better have done some testing other than just using their ***, because an accelerometer, flowbench, and EMS all say otherwise.

 

I'm with scathcart and reted on this.

In addition to all of the things that scathcart pointed out...

https://www.rx7club.com/showthread.p...ter+fenderwell

I have done a side by side test with a digital thermocouple thermometer on S4 N/A intake setups: stock box VS cone in engine bay VS cone fenderwell CAI

Hottest: stock intake box, terrible heat soak that did not go away
Cooler: cone in engine bay, significantly cooler intake air than box, but heat soaked a small amount as well. heatsoak dissipated with light airflow.
Ambient air temps: fenderwell CAI <--- best setup, IMO

Your butt dyno is officially pwned.

 

I'll have to look back at the logs to see if there was a difference in intake temperatures, measured just before the throttle body. I recall there being a slight advantage in moving to the cone filter, but not enough for me to consider substantial. My on-car tests were mostly 3rd and fourth gear WOT pulls on a highway.

One test beats a million speculations. But, hey, ignorance is bliss.