Arrwin

Anyone use BMC Filters? I believe they are similiar to K&N Filters, which are usually not suggested here. Are these any better or should I just stick with OEM?

CAHRERA

Arrwin, My car came with the BMC filter. I would say it's pretty much identical to the K&N filter. I can't feel any HP gain like they mention. Too me it's all marketing fluff on HP gains with Air filters no matter what product it is BMC or K&N. just my .02

The nice thing about these filters (K&N or BMC) is that you can clean them and reuse them.

Rezal

HP gains with air filters matter a lot more in Turbocharged cars. Even that is limited unless you put in a corresponding free flow exhaust.

I used to own a 300ZX TT. For less than $2K, I could get a 'claimed' +96Hp (intake, exhaust, chip). Spending three times as much on a 993NA wouldn't even get you a third of that gain!

Arrwin

I read here that there may be a concern with oil seeping into the air intake(??) when using the cleaning solvent to clean the filter. True or not?

97Targa

I always use the (correect) filter oil sparingly. Wipe off any excess. Then let it sit out over night and check to make sure no oil collects at the low areas. Problems arise when to much oil is applied to the filter.
The filter has to be removed to clean it.
I think if you carefully folow the instructions you'll be ok.

vuugti

Yea, I have the BMC cone filter. Had I not had an intake to accomodate it, I'd use the stock one. I had a K&N, and never had any issues. I chose the BMC for something different. Each one is pretty much a ripoff, go with stock filter and a modded airbox if you can. These things are reusable but not very durable, at least the cone ones. The screens that hold the element intact are pretty flimsy. I have read the oil issues as well. But used correctly I think either one will work.

Cheers,
Andy

GabiOsz

I am fairly sure an oiled air filter damaged my MAF sensor, an expensive replacement.

kkim

Arrwin,

When I first got my car, I experimented with K&N, BMC and stock paper filters in the stock 993 airbox. I could not feel a significant difference, if any at all, when switching between the 3. I have, however, gone back to the stock paper filter due to the other 2 filter's poor seating in the stock airbox. I was never comfortable if I was getting a good seal between the filter edge and the box. There is no question in my mind that the stock filter seals that edge the best of the filters.

As far as oil problems on the MAF, I think those that over oil the filters tend to get this as the oil is sucked from the filter into the intake. If you follow the reoiling directions, as mentioned, this shouldn't be a problem. I've used K&N filters in one form or another in a lot of previous vehicles from dirt and street bikes to import cars. In those cases, I felt a difference in power. With the 993, it doesn't seem to do much as far as I can tell. I'd pass on it and look for other things to enhance your ride. Short shifter, perhaps?

mkol1248

I don't think that K&N or BMC filter gives you any horsepower increase. As the air moves through the engine, there are several potential bottlenecks: air filter, intake valve, exhaust valve, and exhaust system. In 993 NA engine, I think the intake valve is the dominant bottleneck. Improving airflow elsewhere, without addressing the dominant bottleneck, gives you pretty much nothing.

You might get a proof with your own dyno test. Put car into 2nd gear, get to near 2500 rpm, and press the gas pedal to the floor and accelerate past 6000 rpm. Record the sound of engine as it accelerates with your cellphone (voice memo). Put in the other air filter and repeat the acceleration, making second audio recording. Obviously, one needs to find a road with no traffic as the test can be distractive.

At home, upload the audio recordings from cellphone to computer and apply Fourier transform, which will extract the the engine frequencies from the audio background noise. Now you have two graphs that shows how engine rpm is increasing in time. Each graph basically is a power curve of your engine. Look at the 3000-6000 rpm part. If the BMC filter is better, its curve will be higher, and 6000 rpm will be reached sooner. My guess is that BMC curve is no better than stock filter curve.

To verify the whole method is sensitive enough, one can make recordings on a cold morning and a hot afternoon (everything else being equal, including air filter, tire pressure, weight of car, gas octane). The morning curve should be better.

There is some Windows software to do the transformation at
http://home.netpower.no/pberg/rpmanalyzer_en.html

Martin
1997 C4S

Arrwin

Kelly,

I would love to upgrade the SSK, but the install isn't as straighforward for the AWD cars as it is for the 2WDs.

Ray Calvo

Been using the BMC for awhile in my '95; no problems but no performance enhancements. Went to the BMC rather than the K&N as I heard the K&N had problems sealing properly in the air box.

kkim

Arrwin,

You are correct... from what I have read, the tunnel cover needs to be "modified" for the bottom of the shift lever to clear it, but nothing that a ball peen hammer and some aggression release wouldn't solve.

Other than that issue, I would think the install is even easier for C4 cars as I believe you don't have to do one of the steps that had to do with flipping the tunnel guide around.

To keep this on topic, what have you decided on the BMC filter?

95 C4 993

BMC Filter right here. No issues in the past 1.5 years.

Arrwin

I think I am going to stick with the OEM filter since the performance filters do not add any gains and cost at least 2x as much.

How much of a role does the air filter play in cooling the engine? Any?

kkim

I'd have to say none or very little, if any. It's main function is to... well, filter air.

If you are tracking your car, the SS idea keeps the shift lever closer to the steering wheel and shortens the shift stroke. Another mod I would suggest are the RS motor mounts. In combination w/ the SS kit, the car shifts better and also lets you feel what the rear end of the car is doing, instead of having that vague, rubbery feeling of the stock mounts.