asherwood

I can't bear to pay $55+ for a paper filter when I can get a K/N drop in for about $80, also from the posts that I have read the gains from a cone filter even with a cold air box are only about 1-2HP.

I probably won't be doing a terrible lot of mods to this car, maybe a better exhaust so which is it? And will I really notice the difference?

tmak26b

I had a K&N generic cone setup, and a K&N drop in setup (www.geocities.com/tmak26b/airbox.jpg) with the stock box cut open. I felt the drop in setup was faster because the air is cooler. If you want, i have a RB replaceable performance air filter brand new for 20 bucks shipped

NZConvertible

It would have been exactly the same, because the open airbox would be sucking the same hot air as a pod filter would be. The stock snorkel only works if the box is sealed.

NZConvertible

While K&N will show you data proving their panel flows more air than a stock one, what they don't mention is that it's been proven the actual filter causes only a tiny fraction of the restriction in an intake system. So a drop-in replacement filter will make no measureable difference and are a waste of money. There's more info on this in this thread.

Evil Aviator

Drop-In: Because it is easier to install, and your street-driven NA isn't going to pull enough air to make the stock scoop a significant obstacle to the airflow.

Cone: Because it is less expensive for your Series 5, and it looks cool. Oh yeah, and it gives you an excuse to spend a lot of time making a cold air duct so that everyone thinks your car is faster.

It's all up to you.

Yes, the performane increase on your NA will be about 1-3 hp. The increase will be larger for more powerful engines. Anybody who has put their car on a dyno knows that the K&N flows better than ANY paper element, so go ahead and try it yourself if you don't believe it. No, you will probably not notice the difference on your NA. Even if you don't care about the performance, the K&N, which lasts 10 years / 100,000 miles, is less expensive if you do the math, as well as less maintenance, and better for the environment.

tmak26b

actually no. my cone was right in the smack of the engine bay where the stock box is pretty close to the hood. So the chances/area of getting hot air is a lot less thant he cone. Like i said, I 've used both. I dont really see any difference ebtweent he cone and a cut K&N stock box. I do feel the difference between stock and cutting the airbox

NZConvertible

Under the bonnet is under the bonnet. Stick a temp probe in those two locations, you'll see the temp is pretty much the same.

gotorx7

Replacing the Stock Airbox with a K&N Cone on my '88 Vert Turbo was worth doing just for the noises I can hear now !!

I can hear the air intake, the Turbo spooling up, the Blowoff Valve, and the Turbo Flutter when I back off..
None of which were audible before....

asherwood

From what I've been reading here the gains are minimal for either set-up unless some work is done to increase the available cold air to the filter.

The cold airbox/K&N cone filter combo with out changing out the stock snorkel supplying it would still be restricted by the stock supply tubes.

The stock air box with a K&N drop-in and the stock supply tubes would probably have the same maximum flow potential as the above combo.

I've seen the NACA vent cut into the passanger headlight cover to supply air to the after market cold air box, seems to me that you could fabricate a cover for the stock air box that could receive air in the same way that the cone filter does

I'm not sure how much surface area the cone has but I'm pretty sure that the drop-in and cone are comparable and there is enough filter area in the drop-in filter to feed the engine all of the air it needs

What do you guys think? Oh yeah, the cost locally for a K&N cone is $79 and the drop in $85 hence the idea!

Josepi

Has anyone done the TID mod using the stock airbox ever?

kllntyme

I just installed a K&N complete kit in my 87 N/A. It's oval cone is large enough that I have to play with it a bit to get it to not rub the upper radiator hose or the side of the radiator. The cone sits as far forward as the stock airbox, and gives me a great whoosh sound abouve 4000 on the tach. I would say that I got very little as far as horsepower, but the car now pulls better through the entire tach. This was the first of a fleet of mods coming in the next two months.

vosko

iTrader: (4)

if your gonna custom make a tid why bother using stock airbox ? all that effort might as well throw a cone filter on the end

ACTION RT

So if i go and buy the k&n filter right now, it comes with the bracket?? so it will mount right up? or what?

thanks

Action

PlayinW/Wankel

Will someone please answer ACTION RT's question, I am wondering the same thing, because I will be getting a K&N Cone filter soon. Thanks

selanne8

for the 91's, i don't think you need an adapter thingy. from what i'm told the cone filter will fit on the air sensor...i think all you'd need is a clamp thingy to keep it from falling off.

i don't have a cone filter, so don't take my word for it.

out of curiosity, since i have an s-afc on my car, could i use that to measure the airflow if i were to do a comparison between cone, drop-in and open top drop in? i'm sure the measurement wouldn't be exact, but it might be enough to eyeball what's giving the engine more air.

john

Gefunk

OK so say if you made a small slanted peice of material (who cares???) that were to sit right above say a cold air box. Since air moves in waves like sound, than it can be bounced around, the air comming in through the snorkel would head toward the blocade and fly down into the cone. Not ram air mind you but you would get more function out of the snorkel than before.

PlayinW/Wankel

How would I hook up a K&N cone filter on my 88 na. I know I need an adapter, but where can I get one. I read that K2RD.com had them but I checked there site and couldnt find them. Someone help please

NZConvertible

The actual difference in flow rare would be so tiny you would need to test each filter under identical conditions. This would be difficult on a dyno, let alone on the road. If you want to know how to measure the difference in performance, the best way is to measure pressure drop through the filter. Read this article to learn how.

NZConvertible

The short answer is no. Airflow is just so much more complicated than that.

Evil Aviator

OK, lets see (prices in Canadian dollars):

$80 K&N filter + $15 K&N filter service kit = $95 for 120 months or 1,000,000 miles

$55 paper filter @ 1 filter per 30 months / 30,000 miles (per Mazda FSM) = $220 for 120 months or $1,883 for 1,000,000 miles

Who is wasting money?

What bracket? If you mean a hose clamp, I think they come with one, but if not then you can get one for about $1 at any auto or marine supply store. If you mean an adapter for a Series 4 RX-7, then you will need to make your own, or order one from RP, HKS, Aircraft Spruce, etc. It looks like K2RD is sold out. The S4 adapter is the silver piece shown in the pic below, which allows the circular filter to mount to the square S4 AFM. This is not required for the S5 RX-7 because it has a round AFM. BTW, the smaller "crankcase" filter and other hardware shown in the pic are for the air pump, and are a good idea if you decide to retain the air pump on your car.
http://www.rx7.com/pics/fc-bonez-intake5.jpg

My own opinion on "cold air" intakes is that they tend to incur a pressure drop, which ends up counteracting the temperature difference. This is why you don't see much of a difference on the dyno. Note that the longer your intake tubing, the less low-end torque you will have (generally speaking). This is not to say that a well-designed cold air intake wouldn't work, but you would probably get the same performance from a less-elaborate deflection system.

Also, I think that the effect of underhood temperatures is overstated. Yes, there is a large temperature increase when the car is stopped, but I have seen real-time EMS data which shows that the intake air temperature on a cone filter is nearly that of ambient once the car gets up to about 30 mph. This may make a lot of difference at the drag strip, but for a street car or road race car I don't think it makes much difference at all. BTW, yes, it does make a difference where you put the intake, because the hot air from the radiator and oil cooler will take a certain path through your engine bay while the car is moving, and you don't want to suck in this air if possible. An intake air temperature gauge (standard on most aftermarket EMS units) will help you choose a good location.

Evil Aviator

Air doesn't move in waves like sound, it has a fluid motion like water. Yes, deflectors would work at speed, but they wouldn't work very well when the car is sitting at the light. Yes, it is complicated. You can learn more about aerodynamics at this link:
http://www.allstar.fiu.edu/

NZConvertible

OK, when I said “waste of money” I was talking in a performance sense. But your million mile comparison is pretty pointless because nobody here is going to get even close to one million miles out of their car, let alone their filter! If you drive the car 10,000 miles a year and keep it for 5 years, the price drops to only $94. And if you think you’re going to get one million miles out of a K&N service kit, you’re mistaken. Most people here are not using a sealed system, so there is no pressure drop. Even is it is sealed, if it’s properly sized the effect is negligible. A dyno is the worst place to test this theory because the airflow around the car is nothing like real-world conditions. The intake temp display measuring the temp at my pod filter (no heat shield yet) says you are very, very wrong. Even at 100km/h, the temp at the filter can be 20ºC above ambient.

Read this article, it shows the real-world positive effects of a decent sealed cold air intake. It would be difficult to replicate this in an FC, but it proves my point.