lets talk air cleaners

[danaspider]

Well, the 1800 manifold and new carb are on and working well. Amazing difference in performance.

Now I want to talk on Air cleaners. I see most folks have added "high performance" air cleanerts to their spiders. I am interested if anyone has considered the benifit of the smaller open air cleaner pulling air from the hot inside of the engine, vs the fresh air ducting to the air cleaner in the original 79 spider. Cool air is always a benifit. I have removed all of the emission stuff from the origina air pipes, so I am getting some nice fresh air to the engine. I am sure it is choking some compaired to the 360 degree pull of the performance cleaners.

Ideas? Seems to be a good discussion point. I do admit the original doesn't look as cool, but might work better for everyday driving?!?

[TJC]

I posted a very similar question on Mira just recently...
http://forum.mirafiori.com/mirafiorum/m ... msg=169459
...so I'm interested in what people have to say. I never liked the looks of the stock air cleaner, either, but I agree it probably provides the best trade-offs. Unfortunately, I never thought the shorter square "performance" air cleaners were that great. For one, there's the hot air issue, but more importantly I believe they are too short to provide a nice smooth airflow down the venturi. I was surfing K&N's website recently and found this really nice looking tall one that even comes with an aluminum velocity stack...
http://www.knfilters.com/search/product ... od=56-1020
...but this still doesn't solve the hot engine compartment issue (besides, I think this is too tall on my spider that has a no-bump hood and carb using a phenolic spacer).
Now this is sweeeeet....
http://www.knfilters.com/Racing/plenum.htm
...especially together with this....
http://www.knfilters.com/universal/apollo.htm
...but this is on the edge of ridiculousness, with my spider at least.

[So Cal Mark]

it's hard to have this discussion unless you can come up with flow figures for the stock air cleaner assy/filter compared to the aftermarket stuff. The K & N plenum looks great with the cold air intake set up. The 79 setup with cold air and a free flow filter in the housing might be best but it sure doesn't look very sexy

[danaspider]

Good points and ideas on both sides. Just wanting to hear if anyone has numbers or is it all sex appeal? Mark good point, but it might be like the ex wife, keep it wrapped up until at the beach. Seemed to ride better in the old sweats that the other stuff.

Will be interesting to see who has a real opinion on the matter. Or could build the original into the hood, so when open it looks better.

[dlbj]

I'm not sure if my thinking here is correct but consider this: The "performance" air filter with dimensions 1.75" high and 6.5"x4.5" has 38.5" of surface area. The cold air intake on my stock air filter housing for my '79 spider has a 2.5" opening meaning 4.9" of surface area or roughly 13% of the surface area of the "performance" filter (38.5 sq in vs. 4.9 sq in). The density of air on a cold day (30 c) at sea level is about .0138 kg/m cubed and the air in a heated engine compartment (230 c) under the same conditions is about .0085 kg/m cubed. Soooooo, I think that he logic should go something like the 40% gain in density doesn't overcome the 87% loss in surface area.

Having said that you should probably consider this, in a 34ADF setup (for instance, and because this is a popular carb upgrade) the surface area of the primary and secondary when fully opened is 2.6", oddly enough very close to the surface area of cold air intake on the stock air filter housing. But, the density inside the air filter housing should drop due to expansion when the dense air coming in goes to occupy the larger space that the stock air filter occupies.

All said, my opinion is that the performance air filter looks pretty neat and takes up less space than stock. I also think that the straight surface area comparison is probably the most compelling argument to support the performance air filter over the stock with the small cold air intake.

[stefhahn]

Not having calculated anything but tried out several so-called FreeFlow vs. stock/modified stock aifilter setups I must say, that:
- the K&N and comparable filters are far too loud on a long trip. First your passenger then you just go mad after several hundered miles of driving
- none of the freeflow airfilter did result in a performance gain that is a breakthrough
- the stock arifilter housing is far too restrictive for cold air on warm days (engine overheat problems)

So - with the 34ADF I did cut off the side of an original airfilter housing - just leaving the top and bottom - resulting in a nice (town) but not too loud (autobahn) tone and a sufficient amount of cold air flow. Ah - and it looks nearly stock (good for official inspections that we need to go though every other year).

I can make some pictures if you like.

ciao,
Stefan

[danaspider]

Stefan, very well stated. While I like the "sexy" ideas, I look at my Spider as a driver, so noise and such is very important. Especially as we have been know to be able to go crazy without the added nosie.

I am still thinking and playing with ideas. I would like to see the pictures of your modifications.

Thanks. By the way I am continuing to be impressed by the feel of the car with the new carb and intake. Am thinking about taking it to the emissions place and have it checked to see how bad I am to the environment vs the original. At least I can put the top down and be comfortable in the global warming.

[baltobernie]

On my 1973, I am planning on relocating my battery to the trunk, and the coolant bottle adjacent to the radiator. But if I leave the bottle on the firewall, I could modify this stock opening and route a formed hose (radiator?) to the stock air cleaner. These photos show the OEM rubber hose remnant from my air cleaner. Wouldn't take much to fab a flange, enlarge the opening a little, and rummage in a parts store for a US car or truck hose.

[mdrburchette]

You can run a stock air cleaner from an 1800 and have a snorkel on each side of the radiator.

[stefhahn]

Cars tell a lot about their owners.... Denise, your cars are lovely

[mdrburchette]

Thank you Stefhahn. That was a very nice compliment. I guess I better not show my other cars or your perception might change!

[So Cal Mark]

yes, keep the X under wraps

[stefhahn]

Yes Mark. But the one starting to make me wonder is big red....