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After reading posts here, I ordered the Schnell air intake hose and I plan on performing the Intake Air Box Modification thanks to Izzy (http://www.renntech.org/forums/index.php?showtopic=6422&hl=schnell). At the very least I'd like the benefit of better sound even if I can't feel a difference in power.

I also know many here have added aftermarket performance air filters, such as K&N, and I'd like to know what people think of them. Did you experience an increase in power, improved gas mileage, or any other appreciable benefits? Were any problems experienced with a new air filter?

I think squeezing out a few extra horses and better gas mileage would be great, but I am skeptical. Any comments would be greatly appreciated.....

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After reading posts here, I ordered the Schnell air intake hose and I plan on performing the Intake Air Box Modification thanks to Izzy (http://www.renntech.org/forums/index.php?showtopic=6422&hl=schnell). At the very least I'd like the benefit of better sound even if I can't feel a difference in power.

I also know many here have added aftermarket performance air filters, such as K&N, and I'd like to know what people think of them. Did you experience an increase in power, improved gas mileage, or any other appreciable benefits? Were any problems experienced with a new air filter?

I think squeezing out a few extra horses and better gas mileage would be great, but I am skeptical. Any comments would be greatly appreciated.....

The Fabspeed airbox mod wouild be a better bet. It removes the muffler inside the airbox and gives you better sound. No noticeable increase in power though (I know because I've fitted them to both my old 3.4 and current 3.6). I would also stay with the standard Porsche air filter. On a standard car, these are as good as K&N etc. if they are replaced regularly (paper filters clog up more quickly and their performance goes off noticeably). The upside is they cannot contaminate your MAF sensor as oiled filters can.

Ian W

P.S. The Fabspeed airbox mods sound superb on the 3.4 and less so on the 3.6. They also sound dire with the PSE as the sounds produced by each clash horribly. Sounds very good with Fabspeed mufflers though.

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After reading posts here, I ordered the Schnell air intake hose and I plan on performing the Intake Air Box Modification thanks to Izzy (http://www.renntech.org/forums/index.php?showtopic=6422&hl=schnell). At the very least I'd like the benefit of better sound even if I can't feel a difference in power.

I also know many here have added aftermarket performance air filters, such as K&N, and I'd like to know what people think of them. Did you experience an increase in power, improved gas mileage, or any other appreciable benefits? Were any problems experienced with a new air filter?

I think squeezing out a few extra horses and better gas mileage would be great, but I am skeptical. Any comments would be greatly appreciated.....

The Fabspeed airbox mod wouild be a better bet. It removes the muffler inside the airbox and gives you better sound. No noticeable increase in power though (I know because I've fitted them to both my old 3.4 and current 3.6). I would also stay with the standard Porsche air filter. On a standard car, these are as good as K&N etc. if they are replaced regularly (paper filters clog up more quickly and their performance goes off noticeably). The upside is they cannot contaminate your MAF sensor as oiled filters can.

Ian W

P.S. The Fabspeed airbox mods sound superb on the 3.4 and less so on the 3.6. They also sound dire with the PSE as the sounds produced by each clash horribly. Sounds very good with Fabspeed mufflers though.

I believe Izzy's air box modification does remove the muffler and thus creates a better sound similar to Fabspeed's setup.

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After reading posts here, I ordered the Schnell air intake hose and I plan on performing the Intake Air Box Modification thanks to Izzy (http://www.renntech.org/forums/index.php?showtopic=6422&hl=schnell). At the very least I'd like the benefit of better sound even if I can't feel a difference in power.

I also know many here have added aftermarket performance air filters, such as K&N, and I'd like to know what people think of them. Did you experience an increase in power, improved gas mileage, or any other appreciable benefits? Were any problems experienced with a new air filter?

I think squeezing out a few extra horses and better gas mileage would be great, but I am skeptical. Any comments would be greatly appreciated.....

Look at it this way, absent track time, 99.9% of the time the throttle plate, buttefly valve, is THE major restriction against airflow into the engine. That other 00.1% of the time, at WOT and engine RPM on the high end, the OEM filter represents at most about 5% airflow restriction. So, with improved aiflow you gain 5% airflow 00.1% of the time.

Someone needs to design an engine sound synthesizer synchronized with engine RPM/loading and become a millionaire.

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Basically, yeah, mostly grin-effect, car-sound-boy-thing IMO. Cheap thrills. The only thread you could hang on to is, K&N's claim of capturing better the dirt particles.

On the airbox, same thing, by itself mostly sound. If you want to get more air faster in the engine, mufflers are more important as the backpressure will restrict anything anyway.

The only other consideration is, with airbox less restricted and more open, the pressure in the airbox for the same volume of air would be lower. The throttle body will restrict it, but the reduction of area for a given pressure and volume result in increase velocity. With that comes the potential for a bit more air getting in to the chamber, and lower temp as air will pass through faster, leaving less heat transfer time from the engine to the air mass. I won't even try to describe that nightmare of a second order differential equation.

Very small gains in HP (K&N may claim some crazy number) if at all. But pretty much useless without higher flow mufflers.

One point of interest for us engineering geeks, what is the size of the intake throat before the airbox (area) compared with the throttle body diameter (area)? I will have to measure and calculate when I get home.

Being a compressible fluid, air will behave different than liquid, so we have to adjust the flow equations (Darcy's) for other factors, and a "smoother" aftermarket hose will have a lower loss coefficient than the stock.

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I use a BMC and it adds a better intake sound - I doubt it adds much if any HP by itself. Maybe a few more horses (10-20) if you also change the headers (Carrera) and tune the DME. Porsche uses BMC in all their race cars.

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I use a BMC and it adds a better intake sound - I doubt it adds much if any HP by itself. Maybe a few more horses (10-20) if you also change the headers (Carrera) and tune the DME. Porsche uses BMC in all their race cars.

Visually, I think the BMC and K&N look pretty similar; do you know how they are different? Did you notice any difference in gas mileage with the BMC filter? Of course, a better sound may be enough reason to buy it regardless of whether there is a hp/gas mileage improvement.

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The oiled gauze filter in my car kept popping the MAF check engine light. Pulled it and no more MAF related CEL. Oiled gauze also does not clog up as quick because it doesn't filter as well. It has much larger pores than the paper element, therefore it allows more material, including dirt, to pass through the filter and into the engine. The flow increase in the testing that I have seen is also negligible compared to a clean paper element. Yes, if you're racing the car and plan on regular rebuilds then you might experience some benefit. But remember, racers have also in the past used no filter whatsoever with the knowledge that they are rebuilding at the end of the race. Personally, I won't put one back in my car unless someone proves that it gives me a 50% increase in HP and Torque. :D

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Dave,

I have the Fabspeed cold air intake, airbox kit, headers, high performance cats and free flow mufflers on my 99 996 coupe (all Fabspeed). I have never dyno tested the car for actual gains but.....

I can tell you it kicks a stock 996 ***!!

The headers do not change the sound but add 10 to 12 hp.

The cats add about the same but make the car quite a bit louder ( I like it but some people would hate it.)

If you are concerned about sound maybe just go with the free flow mufflers, air box kit and chip. Makes a huge difference and has a really nice throaty sound.

I find the Fabspeed mufflers sound much more appealing than the Porsche factory sport exaust (which to me sounds like a bucket of bolts) :oops:

I'm running the stock filter. My mechanic (master Porsche mechanic for 19 years) told me there is no real benefit to using a K & N. I trust him and the car sounds awesome as is.

Hope this helps!!

Phillip

Edited by phillipj
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Although I have no data on a 996, in the past I tested a K&N against a Amsoil performance filter on the dyno. Car was a 1994 Toyota Supra making ~330 at the wheels. The K&N showed a 10 hp increase over the Amsoil in back to back testing. I also performed oil analysis to confirm that adequate filtration was occuring. The the contaminant levels were fine, and at 206,000 miles when the car was total it still ran like it was new and had great compression.

I never had issues with the MAF on that vehicle, but I understand the Denso MAFs are more tolerant of contamination than the Bosch units.

Edited by Ubermensch
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So, here's what I ended up doing: I removed the resonator and modified the airbox (thanks to Izzy's post), added the Schnell cold intake hose, cleaned the MAF using electrical solvent, and thoroughly cleaned the throttle body by removing it and using Gumout Carb cleaner (as explained by Loren on other threads). The car seems to be running much more smoothly now, idles beautifully with great throttle response and even power throughout.

Concerning filters: it is pretty clear that K&N filters improves air flow, improves sound, but doesn't filter as well as OEM paper filters, but does that really matter? I spoke with a service advisor at Newport Beach Porsche, and asked him about his thoughts on K&N filters. He actually recommended using it because of the increased air flow, but recommended washing it first and lightly oiling it to prevent problems with the MAF (they come over-oiled). Instead, I prefer Loren's recommendation of wrapping it in newspaper overnight to absorb the excess oil. I also asked if I should be worried about the extra dirt that the K&N filters allowed through (as compared with the OEM paper filter), and he said that since so many Porsche owners have been using it with no problems (beyond the oil screwing up the MAF), that he felt using the K&N filter wouldn't hurt the engine and recommended that I go for it.

I believe that K&N and BMC are pretty similar filters (high-flow and uses oil on cotton), but BMC was recommended by Loren because of its use by Porsche race cars, so I opted for the BMC over K&N. I found a place on Ebay that sells the BMC filter at the very reasonable price of $49.99 + $10.99 shipping (supposed to be $120 on the BMC website), so I just ordered it and I suspect that at the very least it will improve intake sound and may increase HP and gas mileage by a marginal amount. In case anyone was wondering, here where I bought the BMC filter:

http://www.luxwheelsandaccessories.com

1-888-438-4649

Thanks to everyone for their opinions; this thread has been very helpful........

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  • 2 weeks later...

Ok, it's been a little over a week since I installed the BMC filter. It came lightly oiled and it didn't affect my MAF at all. You can definitely sense that the sound of the engine is louder now, and, coupled with cleaning the throttle body and the MAF, the car does feel appreciably more powerful with much better throttle response.

If you have significant mileage on the car, I would definitely recommend cleaning the throttle body. That alone improved the car's responsiveness and smoothness of power

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  • 2 months later...

I also installed the Schnell Cold Air intake with the BMC filter, however I did not remove the internal muffler box and installed the pipe fitting as Izzy was suggesting. I have now noticed couple of times that the plastic cap that came with Schnell has come off. Responsiveness definitely improved.

Izzy, I have read was some concerns in the past about damaging the airbox if that hole was permanently sealed. Any comments on this?

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I have not had any problems with it, and the only add on to the mod was a small rubber gasket on the cap (outisde) part to get a better seal on the box. You can find the gasket at a local hardware or plumbing store, 75 cents.

I read somewhere in the Fabspeed site about the issue with airboxes and backfire, which according to what I read was a problem in the oil (air) cooled 911 but not a problem in the 996. That is why Fabspeed cold air kit removes the muffler and uses the screw holes for a sealing cap.

I have not had any issues with it. Also a consideration, the smaller area in the intake system is the square section of the airbox. The measured area is smaller than the throttle body.

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  • 1 month later...

UPDATE:

I installed the BMC filter four months ago. I immediately felt that the car was a bit louder, and coupled with cleaning the throttle body and MAF sensor, my C2 appeared to be more powerful and responsive.

Shortly thereafter, I did start to feel some hesitation, which started to get worse recently. I decided to clean the MAF sensor again, and I once again recoved the power and responsiveness I had gained earlier.

My conclusion is that even though I did not have a CEL come on, my MAF sensor was affected by the oil from the BMC filter and, as a precautionary measure, it would be wise to clean the MAF sensor after installing a BMC or K&N filter after driving with it for a period of time (whether hesistation is felt or not). My BMC filter was very lightly oiled, but I suspect reminants of the oil still got onto the sensor.

My C2 now drives very smoothly with even power throughtout the RPM range....I am very happy.

Edited by zegypt
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K&N first impressions.

I did not use the oiled filter that came with the kit to prevent possible issues with MAF ---> installed an AEM Dry filter instead, ~$50. About 500 miles since install - no CEL.

I did have some issues installing it, specifically there were some brackets and fasterners missing from the kit, nothing that Home Depot couldn't solve.

Change in engine noise? can't say since I had the FabSpeed kit insalled before. Sounds about the same maybe a bit louder. I also have the FabSpeed exhaust. All else is stock with the engine.

As for drivability/performance, I definitely noticed an increase in performance. Seems to spool up faster and at speed, increasing your speed (say 80 -->100) is quicker. Very nice feeling. Overall, I like the kit. As for rain issues. Haven't come across that (SoCal) yet. I am looking to solve that.

So far, i give it a :thumbup:

jorge

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