Air filter box removal/ replace w/ cone filter
 

Hey folks, in the next week or so i have to replace the alternator in my 83 944, all of the forums I've found on how to do this says to remove the air filter box. for the past year I've been thinking about replacing the box with a cone filter, much like a K&N filter, one to free up some space under the hood and two, I've broken 3 of the screws that hold the lid on the first time I replaced the air filter.

I know the good and bad of putting a filter like that close to the hot engine but i was curious if anyone has already done this and had any other problems with sensors or the car not starting right? would this effect the Mass Air Flow sensor? since these cars are so bipolar to begin with I'd like to know of any possible problems before i commit.

Also, are there any kits available for this? any tips?

P.S.
any tips or advice for changing the alternator would be much appreciated :)
Thanks in advance!

1) these cars don't come with a Mass Airflow sensor
2) K&N filters are garbage
3) there is no performance benefit from running anything other than the factory airbox/stock-type paper filter on an NA...dyno tested by both me and the guy who developed the available aftermarket MAF conversion.

you can get replacement screws for the airbox at any hardware store, I found some at Lowes one time, they are M5 (5mm thread) screws.

alternator...the lower bolt that holds the alternator to the bracket is kind of a pain to reach...I have found that if you remove the two bolts that the AC compressor hangs from (both 17mm heads, one front and one back, can be reached from the driver side wheel well next to the sway bar drop link) and drop the compressor a little bit (support it on a brick or something to keep strain off hoses) then you can reach the alternator bolt easily.

I love my k&n filter set up on my 951, a lot of room has been freed up under my hood. I knew my air box was toast from the original owner, you know with and without the k&n set up I don't really notice any difference. Keep it cleaned and properly oiled and you should be ok......

a cone filter CAN produce more power, but it has to have more surface area than stock, be isolated from engine heat, and have a short, direct and non-turbulent path of colder intake air. failure to do any of those will result in power loss.

K&N filters are the BEST filters on the market. you just have to use them and maintain them correctly. most people don't. ignore the argument about "dirt getting past the filter". this is an urban myth, when they are properly maintained

you can prove all of this easily with a manometer. you will not necessarily see the gains on a dyno, unless you test it as it would be on the road, with an 80mph 4' diameter fan, and most importantly, the hood closed. most dyno shops don't have any of that, and most of them want the hood open. the one i use does things correctly. also, you can't use a standard dynojet for stuff like this. you have to use an eddy current dyno.

i have yet to see a car not gain by a PROPERLY DESIGNED cold air intake. i have tested dozens of different model cars, and without exception, gains were there.

to date, i have not seen anybody do this right, hence the mixed reviews. i never mass produced one, only because there was no market for one, and as soon as it was out there, every broke-assed 944 kid in the world would be knocking it off, rather than buying mine. i know for sure that it can be done though. i did it once, and then the owner destroyed the car in a race, and never went back to the 944. the design died with the car.

you can also look into the 944 NA Tune MAF and put a K&N on it. Pricey but from my friends experience on his 87 944, he said it is loads better then the factory choke box.

I bought the car with one on it from PO and they just swap the stock one out and put this one in I bought mines none running so don't know how it performs but I bought a stock air box to replace it anyway

http://forums.pelicanparts.com/uploa...1483545976.jpg

I recently did this to my 924S autocross project. I love not having the OE air box as there's much more room now to work in the engine compartment. I initially went to Lindsey Racing but all they offered was the intake adapter for 951. Dave steered me to MSDS Inc.

MSDS Inc. -Â* HIGH QUALITY HIGH PERFORMANCE ACCESSORIES

who does have the cone filter adapter for NA 944/924S. You'll also need a bracket to support the MAF which is supported by the OE air box. That bracket and the cone filter comes with the adapter. I actually found a used MSDS adapter at a buddy's and rigged my own bracket directly to the AC delete bracket. Then I purchase a large 3" x 6" cone filter through a speed shop.

Performance gains are debatable and because it's an autocross car, engine compartment heat isn't that big a deal (a quick lap and the cool down). I did it more for convenience and access.

http://i1336.photobucket.com/albums/...psty5jqutd.jpg

I run a K&N in the stock air boxes on both of my 944s. The stock box is a true cold air induction and the stock filter has way more surface area than the cone shaped ones the kids love these days. Any air flow that might be smoothed out by the cone filters is going to get AFU'ed again once it passes through the AFM anyway.

it isn't always easy to get the right size filter in there AND isolate it from heat AND have a smooth path for the air AND have it be serviceable. it's no simple feat in the 944 either, but it can be done, if you are willing to make the changes necessary, and spend some money. you definitely won't see gains by just sticking a filter on there.

the other issue is that as a rule you will only see a 5% gain. that isn't a lot of power when you talk about a 150hp motor. it can also bring with it cold start issues, because it is exposed to colder air. the older the car (with its inherently older controls) the more this is the case. on a race car, this is not an issue, and every little bit counts, but on a daily driver, it may be more headache than it's worth

the K&N can help, even if in the stock airbox. as an example, on the 968, by merely opening up the airbox to direct cold air, and installing an OEM K&N replacement, we saw almost 12hp on the dyno. it took some pretty serious manometer testing to figure out just what to do, but in the end it worked extremely well

Not 100% on the early cars, but on the later cars you can change the brushes on the alternator without removing it from the car. Usually it is just the brushes that wear out, and they are much cheaper to replace than the whole unit.

I'm not concerned about adding power with K&N this and K&N that, i just want to free up space under the hood and make changing the air filter easier.

I've noticed a few people here say the surface area on the filter must be at least the same as the surface area on the stock filter, if not more.... can someone explain to me why exactly? I don't know what diameter the intake is but for easy math lets call it 4'', now that's just over 12.5'' of surface area, so if a filter with 24'' of surface area is feeding a hole with 12'' of surface area, isnt that a little over kill? can someone help explain in more detail?

it's all about fluid dynamics. all other things being equal, it takes a certain amount of surface area of filter to pass a particular volume of air at a specific rate. the engine is drawing in the air. it is not being fed into the filter and pushed into the motor. it needs a certain amount of area at normal density to provide that volume of air. the filter itself will present restriction, dictating more area than what it is feeding. part of why a K&N works better is that the restriction per square inch is less than with a paper filter. so, to see gains, you have to have at least the same surface area as the paper filter. additionally, OEM filters are generally less than optimal from a flow standpoint, so as to provide for enriched starts. hence, having a filter with more surface area AND freer flowing, naturally allows more air into the engine. as long as you don't increase the intake temps, you can see gains. for example, you could gain about 5hp on a 944 with a free flowing filter the same size as stock, but then lose it if the intake temps go up 50 degrees. that's why we use manometers and temp sensors in our intake designs.

Buy mine:
http://forums.pelicanparts.com/porsche-924-944-968-used-parts-sale-wanted/933747-k-n-cone-air-filter-w-custom-bracket.html

Here's a question that puzzles me, for the pod-filter fans.

If they are performance-enhancing, safe, have no negative effect on engine behaviour or wear, and use less space, why is it that not one single car manufacturer in the world uses them from the factory?

that one is simple. they are over 5 times more expensive, AND they require a lot more frequent service, and more importantly the kind of service that most car buyers are not willing to do. you can't let a K&N sit in there for a year of driving and not service it. if you had to pay somebody to service it, you would be looking at over $100. most car buyers won't pay that, or even want to deal with it.

It's all about induction noise abatement. Most of you guys are too young to know the sounds of a large cubic inch muscle car engines sucking in huge amounts of air. It was thru exposed paper air filters under lovely chrome tops with stickers boasting the displacement and horsepower. The induction moan was much louder than the exhaust note and music to a High School gearhead. My 396 would moan like a lonely ghost. Yamaha 250 and 305 two stroke twins of the mid 60's had un-silenced intakes and would make quite the intake moan when riding in groups as the sound carried. My own hopped up RZ350 makes a nice moan thru it's Swiss cheesed air box. In it's case the plenum of the air box plays a important part in performance.

it is true that germany has the strictest noise regulations of any country, and any car made there has to comply with them. that does factor into the airbox design. it really doesn't affect the filter material itself though it can certainly affect the design shape. more flow means more noise. pretty basic physics there.

of course most of us like a little more growl, so this is a good thing

flash968. Do you have specific recommendations and or pictures of how to properly mount a K&N in a NA engine bay? I'm also interested in finding a source for the correct sized (diameter and length) tubes from the cone to the housing. Thanks for any help.

you can use the formulas on the K&N website for sizing the filter.

unfortunately i do not have pictures or anything on the airbox design. this was way back before digital cameras. i stopped playing with 944s over 20 years ago. i'm sure i could do it again, but then we would be right back to how much it would cost, since there would be almost no chance of selling it. the time and materials involved for me to do it would be ridiculous, given that the gains might be 5hp. you would be much better off installing my 968 centrifugal supercharger kit, retuning for the 944, and then going away with an extra 75-100hp and a whole lot more torque.

Cone it bro! Just cone it!http://forums.pelicanparts.com/uploa...1483980864.jpg;)

Alright, so I've got an update on my car........

my belt tensioner strut was snapped, but wedged up against the A/C compressor enough to keep the belt tight, but loose enough to cause some problems with my head lights and cooling fans and so on.... had the alternator tested and it checked out with flying colors. so I've just finished replacing the tensioner with a new belt along with new spark plugs, no issues with having all my electronics turned on at the same time.... I'm happy about that, I'm not happy with my dash light, the battery light to specific, it still stays on unless i rev the engine to about to 1,200 rpms then it fads out and stays out.... is this common?

I've decided not to go with a cone filter however my the filter box is still out of the car because the gasket between the box and the air "do dad" (the correct name escapes me right now) was broken so I'm waiting on a new gasket to show up in the mail..... I strongly doubt it, however, would that cause an issue with that light in any way?

If your battery light is on something is not right. Check the following with a digital volt meter or using the dash gauge:

1. battery voltage engine off should be 12.7 volts if the batter is fully charged, a little less (12.3-12.5) if the batt is partially charged or old.

2. Battery voltage with the engine idling and accessories off (lights/ A/C, etc) should jump up to around 13.5 or so.

3. With the accessories turned on and engine idling the voltage should hold steady at 13.5 or so.

Let us know what you find. Use a digital volt meter if you have one, as it is more accurate than the dash gauge.

So heres what I found with my digital volt meter....

engine off with no accessories on, battery 12.85 (less than 6 months old)
engine idling but with battery light still lit with accessories off 11.8
engine idling but with battery light turned off (i tapped the gas a little for it to fad out then let it idle again).... 13.9
engine idling with A/C, head lights, fog lights, interior fan, rear defroster and 4 ways all turned on, 13.25

the car was stone cold by the way, its been sitting in a garage all week at about 20 degrees. i did not warm up the engine what so ever before I took these readings.

not sure if it helps any but the car idles around 850 to 900 rpms when cold, when warm idles around 1,100 rpms.

If the belt is tight and the connections are correct and tight then the alternator is not working properly.

on the voltage issue, i'm guessing voltage regulator. they wear out.

it should not idle higher when warm. in fact, if anything it should idle higher when cold. that's a whole different issue you have going on there

I am not sure about the 944 but I have had a similar battery light issue on other cars. From what I recall the battery light is in the exciter line to the alternator. The input to the bulb is 12v so that when the alternator is not running you get 12v across the bulb and it lights. When the alternator starts (the 12v on this line is required for this) it puts out 12v (or so) and the light goes out since there is no voltage drop across the bulb. I found that a coroded connection to the alternator from this line caused this issue. If it gets really bad the alternator will not work. I hope that this helps.

on the early 944 they don't have a "cold fast idle" so they do vary the speed based on temperature...simple bimetallic spring in the auxiliary air valve to bypass the throttle plate, not even controlled by the ECU.

typically cold they run at 700-800 and warm 900-1000 depending where it is set to.

If the tensioner rod snapped, check both AC mounting bolts. Mine snapped because the back mounting bolt had snapped and that let the AC unit twist enough to snap the tensioner. I went through 2 tensioner rods before I figured it out.

every engine on every car legally brought into the US since about 1978 has a cold fast idle. it's due to emissions. if it doesn't idle faster cold than warm, then something is wrong or modified.

last year I over heated my car pretty good, i blew out my oil cooler seals in the process.... ever since then the car had a hunting idle issue once it warmed up. it did idle high BEFORE it over heated. after chasing down one thing after another trying one thing after another I got fed up with it. I found that by adjusting the small screw next to the throttle cable a few turns lessened the hunting idle, so I just kept adjusting it down until the hunting idle stopped. I know that isn't the correct thing to do but its been running just fine, it does start hard sometimes when its hot but nothing serious. whatever caused the hunting idle hasn't been fixed i'm sure of that, adjusting that screw just masked the problem for the time being. so that explains the cars lack of a high idle when cold....

hunting idle and high idle tell me vacuum leak

I thought it was a vacuum leak too but 30 minutes and a can of parts cleaner later i couldn't find any. I let the engine idle and spray the parts cleaner around all the vacuum lines and it never revved up or effected the running of the engine.

use a guage. could be at a valve, head gasket, yada yada. you should get a solid reading of not less than 17 inches at idle (per workshop manual of 900 +/- 50)

I've never had a lot of luck with that approach on these cars. I've had most luck finding leaks with a half inch plastic tube held to my ear whilst probing around with the other end. Remember to probe around the intake gaskets.

just use a gauge. that is really the only way to definitively determine if you have a leak, and what kind. every backyard mechanic should have one. it's the single best tool for diagnostics.

Today I took the Electric Air Valve (small valve in the vacuum line that mounts behind the air box) i took that out and cleaned it. cleaned the connections on my Auxiliary Air Regulator (idle Control Valve under intake manifold), cleaned the connections on my radiator temp sensor and the DME coolant sensor, put a little grease on all the terminals. if i back out the screw next to throttle body a few turns i still have the hunting idle issue... a few forums I've found talking about this issue is to spray parts cleaner or carb cleaner into the J-boot while the engine is running to trying and clean out the ICV.... which i gave that a try and no luck.... now the Electric Air Valve (behind the air box) does work, i touched a 9 volt battery to it while out of the car and blow air through it with the battery on it... however with the car running from cold to hot enough the fans kit on the leads that plug into it don't put out any power....

I can't think of any way to get to the ICV with removing the intake manifold, i would like to take it out and clean but really really don't want to remove the intake manifold just do so... is there a way? anyone have and solve this problem before?

IMO removing the intake manifold is probably the most satisfying and productive jobs you can do on these cars, plus it's really cheap to fix a lot of stuff wyit and so easy to do.

Buy some LR silicone vacuum hose, new AOS seals and new intake gaskets before you start. Some good quality stainless hose clamps in various sizes would also be handy and some small brushes, solvent and rags for cleaning under there. It should take you no longer than half a day and take plenty of pics with your phone as you take things apart.

You will feel much happier knowing everything is in good shape under there. GL

not sure it it's the same or not, but on the 968 the ICV is underneath the intake manifold, held in place by a clamping bracket. after disconnecting the hoses and electrical connector, you loosen the big bolt on the clamp, and slide the ICV out.

but i agree about feeling better by removing everything and renewing it.

i would still put a gauge on there first. if you have a larger problem, you will only frustrate yourself by doing all of that work, and still not solving your problem

also, both the bosch hammer and the durametric have an ICV test

Agree with the vacuum gauge, and then a smoke test to find where the leak is...

http://forums.pelicanparts.com/uploa...1484310046.jpg

Is that a cigar jammed into a $5 Harbor Freight transfer pump? That. Is. Awesome.