Looking for feedback on the below product. Would simplify the engine compartment quite a bit, make adjusting the idle easier...

Click to view attachment


Does it replace the plenum?

Seem like it would attach to the throttle body, like most hi flow intakes. Not sure how it would fit to the verticle TBs?

Replaces the air box.

As long as your not buying it expecting 5hp...


It will make a cool engine noise..

Just dont expect a lot of power increase from it... Maybe a little..

Andrew

I built one of these for my 914 and it works great. I went to my local Menards store and purchased 2 - 2" PVC street ells, 3 - 1/2" hose barbs, 1 - 2" sewer pipe clamp, and ordered a K&N RU-1520 filter. The small end of the street ell just fits the throttle body and the larger end fits the 2 3/4" opening of the filter. You could make it with one street ell if you use a smaller filter or you have a different throttle body location.

You do get more noise from the free flow air filter, but I don't mind that and really like the result. They are also selling these on ebay if you want to avoid the hastle of putzing around with it yourself.

Obviously only fits the 1.7s only; the 2.0s with their vertical throttle bodies would need something else. The 1.8s would need to have the air flow meter between the filter and the pipe.

Looks like a very PVC pipe elbow. With a few holes and some brass plumbing fittings. I'm guessing you could be like Trekkor and visit Home Depot and make up something just as good for cheaper...

Doesn't look like there's any way to keep rain out of the filter. Not much of an issue if you have your rain tray, but if you don't, it could be a real problem!

--DD

Fewer square inches of filter media, bigger pores in the material. Allows more and larger dust particles into the engine. Requires maintenance(and the service kit!) makes a LOT more noise, enriches both the seller and thee guy selling you the rebuild parts. Still want one?

I've never liked the air filter on the 1.7L FI setup. I'm not convinced this is the best way to go but might try it in the future. I'd think different filters would have diff results as far as leting in crap particles (finer filter, etc). Then again, I don't know diddly about K&N filters. I'm not sure if I want to deliberatly make the car louder - it does a pretty good job of being loud on its own...

hmmmmm...so far pretty good info guys, thx.

-Pete

I made one for my 2.0. Use a 2 " elbo with a 3 inch on the other end and a piece of 3" PVC about 6-10 inches long. You may need a support bracket to keep it from sagging too much. It's easy to do. The 3 inch diameter gives more air than a 2". I put a rubber hose around the base of the intake and over the bottom of the PVC with a couple clamps to secure it. Use what ever KN conical filter fits a 3" tube. By removing the air box you now have a lot of space freed up under the hood.

Another way to do it is to get a flat round KN filter like one for a chevy engine and mount it.

For what it is worth, I bought the K & N unit from 9Xauto.com. It fits on my 1.8 perfectly and the rain tray still fits as well.(this pic is before I got the tray back on)

I bought the kit and now i can wheelie in 2nd with all the additional power

I want what he's smokin...

Actually I researched this quite thoroughly and found that the stock 914/1.7 filter is 57 inches filter area and the K&N I chose is 156 inches. Much more. The K&N filter is 97-98% efficient according to their website, but I don't know what the paper stock filter is.

Check out K&N facts on their website:
http://www.knfilters.com/filter_facts.htm#WORD

K&N filters aren't cheap, however. All the offroad CORR racers I know use them.

I love my oil bath filter.

I think it works.

b

are you sure about that? the stock paper element has fairly wide segments. just by the looks of it, if strectched out and cut to 1" high stripes, those should add up to much more than just 57" in length ...

Andy

According to a test done many years ago and written up in _Racecar Engineering_, paper, oiled gauze (K&N), and oiled foam (UNI, Pipercross, etc) filters are all 97-98% efficient at filtering dirt when new. They're also all 97% efficient at allowing airflow through them WHEN NEW.

The main difference is that paper filters clog up much more quickly than the oiled gauze/foam types, so they start to flow a lot less air a lot more quickly in use.

The key in the oiled types is the oil. With no oil, the gauze/foam types were all only about 30% efficient at catching the dirt (i.e, only slightly better than having no filter at all).

Basically, the paper filters work just as well as long as you keep changing them regularly. The oiled filters can be easily cleaned, and filter just as well as long as you keep them properly oiled.

Any power increase you'd see would be due to removing the airbox rather than changing the filter, and even then, it would only work if the airbox really was too restrictive. It CAN be, but isn't always.

Dropping an OEM type K&N filter into the OEM airbox will, effectively, do nothing.

And there in lies the rub... no one has ID'd a size filter to fit the 73 1.7 that will fit in the stock air filter housing.

"According to their website". Think they's say anything that might cause you not to buy? Other websites, ones not quite so K&N friendly, show actual test results vs. stock air filters, and they're not so kind. Take a little time and read this:

http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

I don't have a stock 1.7 paper air filter on hand, but your calculations seem a bit off. Measure the height times the width of the pleats to get the pleat area, count them on the outside, multiply that by 2, and multiply that by the area of the individual pleats to get the total area. So, if there are a hundred pleats, and each one is 2 square inches, and each pleat you counted is actually 2 panels, you have 400 square inches. For example, I have here a standard duty air filter from an 86 Vanagon. 3.25x1.50x140x2 = 1356 square inches of media. The 914 paper filter is shorter, and the pleats may be fewer in number and not as wide, but I'd guess it has FAR more than 57 inches.

As for off road racers, how often do they rebuild those engines?

I use something similar in terms of the actual element in my BMW 2002. Steve

"The main difference is that paper filters clog up much more quickly than the oiled gauze/foam types, so they start to flow a lot less air a lot more quickly in use. "

Lab tests contradict this statement. Bigtime. The Cap'n

http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

So $0.12 worth of oil to renew a foam type filter or $20 (estimated cost) for a paper one

Lies, damned lies, and statistics. The results I mentioned aren't online, and I doubt I have that back number of _Racecar Engineering anymore. The test did use the same ISO dirt test procedure, but came up with different results.

I note that some of those graphs are very misleading, and are the type to make Edward Tufte wince. If the scale on the top graph were 0-100%, not 96-100%, the difference between the top and bottom filter would be fairly difficult to see.

That said, those filtering efficiency numbers were very similar to the numbers quoted in the earlier results. They did NOT mention the "total dirt through the filter" numbers, which are much more dramatic, and basically show that using "filtering efficiency" as a percentage is not particularly useful. The difference between the best and worst filter on the "total dirt" is 0.4 grams v. 7.9 grams, meaning the best filter is roughly 20 times better at holding out dirt.. This is not at all well represented by the difference between 96% and 99% "filtering effeciency", which by itself suggests there's little difference between the best and worst.

Thanks for that pointer, Cap'n. Always good to have more data.

After reading all the valuable insight/advice/analysis/etc I'm more confused than ever. But, I've been confused most my life so I'm used to it by now...

Actually, the main difference is how they remove particles from the intake air.

A paper filter is a mechanical barrier. An oiled cotton or foam filter is a mechanical barrier, coupled with the advantage of electrostatically attracting the particles. I can't remember which is which, but say the dust and dirt is generally positively charged, and the oiled filter element is negatively charged, the filter will tend to pull dirt towards it.

I also look at the cost factor, as Bruce mentioned. I tend to drive cars a very long time. If I am servicing the air filter annually, or semi-annually and the filters are $16, and it costs a dollar worth of time and materials to service a reusable filter, it buys me 1/4 to 1/2 tank of gas every year, which is not much, but adds up. For example, I had the bug for 25 years, you can do the math.

Would you like it any better if they re-labeled the graph (something like "normalized stuff allowed through"), subtracted the numbers from 100%, and scaled the graph to 0-5%?

Numbers are numbers. There's a difference between 96% and 99%--especially when we're talking about cumulative results over time.

Still, the cone-type filter appears to be a viable option for people who can't find a 73 1.7 paper filter and don't want to deal with the (potential) mess of the oil bath one. Just don't expect another 10 HP and 10 MPG from it...

--DD