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Old 10-30-2000, 12:58 AM   #1
codemunky
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Post Installing cone filter directly on back of engine

Is there anything wrong w/ installing a cone air filter directly behind the engine (in place of that filter box)? I zip-tied the breather tubes. I'm thinking that this is ram-air like... I have a 2000 RS, (MAP, not MAF such as 99'). I am currently experimenting with this...just put one on.

Thanks for your help.
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Old 10-30-2000, 05:39 AM   #2
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I have had this for a few months now.

You will loose low end torque (noticibly) and you will gain a small amount of power up top. It will be VERY loud at anything over light throttle.

I am using one as a stand in until someone (cough cough....COBB) makes a dyno-proven 'real' intake.

Matt
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Old 10-30-2000, 06:53 AM   #3
ColinL
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You loose the low-end torque because the box atop the throttle body is a torque chamber-- it acts as a secondary intake plenum.

IMO it is not smart to remove it assuming your engine is naturally aspirated and has the stock rev limiter.
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Old 10-30-2000, 08:10 AM   #4
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I am using this system right now. I did two things differently though.

First I routed all the breathers to a Puralator breather filter, I can't imagine that it is a good idea just to plug them.

Second a used a very large filter and a short ramtube between the filter and the TB.

I think the larger filter helps with reserve air Like the air box did. And the Ramtube helps increase intake velocity by Bernouli's effect. I have about the same low-end possibly a very slight loss but there is a dramatic improvement in throttle response and topend power. It pulls to redline much stronger.
P.S.
The filter and Ramtube's internal volume is approximately equal to the "black box"

[This message has been edited by skidplatez (edited October 30, 2000).]
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Old 10-30-2000, 08:44 AM   #5
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definitly do not plug the crankcase vents. Thats a terrible idea, leaving them open to the air, or using a breather filter is a much better one.

A VERY short intake can make a nice improvement on a nasty convoluted system, but a good long smooth tube will be even better. I would try that intake from the guy in colorado, but replace the box with a u bend, and put the filter in the fender. That should make the best all around power of any intake.
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Old 10-30-2000, 08:50 AM   #6
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Sorry, yes, DONT plug the vents. I made a 'catch can' for mine and routed them there so they can vent.

Forgot to mention that.
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Old 10-30-2000, 09:06 AM   #7
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XT6Wagon-

That Might not be true I think that Larry tried that as one of his tests and although his test is strange (max speed at 6000feet) His current intake out performed that set-up and I think several others have too. The long smooth intake is definately not best for topend power (look at any N/A drag car) That style intake maybe very good for lowend and mid but because changes to the revband are so subjective we may never have a "Best" intake.
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Old 10-30-2000, 01:19 PM   #8
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XT6Wagon-

Are these observations based on a SHO or a 2.5rs?
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Old 10-30-2000, 04:29 PM   #9
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I've tried a cone filter directly on the t/b, and 3" stainless u-bend pipe going right down to the abs controller with the same cone filter on the end, and compared it against the std setup aswell as the standard plenum box with with better piping.

The cone I used is a unifilter ram pod with quite a large aluminum trumpet... the best design IMHO, K&N filters don't have a large trumpet/velocity stack.

If you want, you can check out what they look like at this web address: http://www.uniflow.com.au

Results?

ok (takes deep breath..) here we go:

Cone on throttle body = top end gain, not worth it for the bottom end losses. Our engines just don't rev. We need to use the torque.

Cone on 3" u-bend pipe = great gain in low-midrange, still not as good as standard intake setup for that low-end punch though. The top end above 5000rpm was better. It sounded wild, but I couldn't really care for that over performance.

Standard = much better to 3500rpm (useful) than the above two combinations. You can pull away easily in traffic, and low rev overtaking manouvres. Couldn't really tell an acceleration difference between the standard compared to u-bend and cone setup till 5000rpm. The standard setup is also a ****load smoother.

Standard plenum box with better piping = best I've found, although I tried lots of different combinations here using 2.5" PVC piping...

I ended up favouring a 45 degree connecting bend off the plenum joining up with a length of piping - just enough to get it close to the ABS controller. This is where the stock setup gets its air anyway.. (I know it's not the coolest source of air)

At the end of the pipe, I heated it with a heatgun and flanged it to the shape of a velocity stack by forcing it over a glass bottle. Then I smoothed the edges of the flange out with sandpaper so that the 1mm gauge pvc thinned out into almost nothing.

I have found this to be the best compromise over anything - has all the bottom end of the stock system, it has the smoothness, and it has a lot more top end, bettering the u-bend but not quite rivaling the pod on the throttle body.

In any case, I can vouch for the effectiveness of a velocity stack on the end of any induction pipe.

[This message has been edited by rx (edited October 30, 2000).]
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Old 10-30-2000, 04:40 PM   #10
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oh I nearly forgot, you can see pictures of the cone, and cone and u-bend setups here:
http://www.lime.net.au/adrian/motor.html

I havn't got pics of my current setup (flanged pvc piping) there yet, will advise when I do.

Has anyone tried a mini velocity stack inside the plenum box yet?
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Old 10-30-2000, 05:40 PM   #11
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Well I have done my experiments on a SHO, but intake design is universal, as the physics behind it are constant.

I've also had fun playing with other cars making intakes.

General rules
Larger diamiter=higher torque peak
Smaller diamiter=lower torque peak
Longer tube= lower torque peak
shorter tube= higher torque peak.
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Old 10-30-2000, 11:11 PM   #12
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rx,

Nice research. The intake you chose as best is very similar to the one I sell for under $100 bux of my website, www.ImprezaRS.com!



It uses 2.5" ID polished aluminum tubing from the intake plenum/air-box to the passenger side inner fender for plenty of cool air. This performs better than your 2.5" PVC did, because of the ID being only 2.0" for the PVC.

I live at 6,000 feet, so that is where I test it, and my top speed only climbs from 120mph stock to 123mph with the PVC tubing and a Stromung exhaust - the 2.5" aluminum intake with Stromung tops out at over 131mph at 5,850 rpm! Not bad

Larry
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Old 10-31-2000, 12:11 AM   #13
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Well in my personal testing, yes you buy a little (or more than a litte) with the short intake for top end power, its just that you can never get there due to the lack of midrange.

On my SHO at one point was basicly a filter the size of west texas clamped onto the MAF directly. From this was a very short 40-45 degree rubber elbow, which connected the MAF to the TB. Sure it was great from 5,500-6,500
where the stock POS intake cam, and exaust call it quits, but below 4K you had 0 power. I now have a smash bent 3" exaust pipe that puts the MAF, and a smaller filter in the fender. Top end is down a TINY bit, but I have some power under 4K and 4,500-6,000 is a BLAST.

If the 3" pipe is killing the high end in that very long pipe setup (it shouldn't) then 3.5" pipe is avalible. The big thing is ditching that airbox right before the TB. That just flat BLOWS CHUNKS for ultimite performance. Thats why I would replace it with a U bend, as this keeps the flow rate up, and turbulence down.
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Old 10-31-2000, 04:38 PM   #14
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thanks larry - yeah I've seen yours around this bulletin board before... sounds good.

what is the rubber attachment at entrance to the fender wall? Is that to shield the vibration on the pipe caused by engine movement?

Have you tried some sort of velocity stack at the end of the pipe? Wouldn't be too hard to fit a small one inside the fender.

As I said before I recommend this, it made *quite* a difference to just a straight pipe.

On with the R&D!
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Old 10-31-2000, 04:45 PM   #15
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rob - I think the key thing about that article was the 60mm length pipe had an all round improvement - up to 8 hp somewhere in the mid range, like 4500rpm, and something like 2-3hp more on average throughout the rev range.

I don't think there was much of a difference in the peak horsepower though.

Peak horsepower means sweet jack all if all the rev ranges around it are affected badly.

But hey, some hi-po n/a cars are setup with really short, individually tuned velocity stacks, and make A LOT of power. Big $$$ though.
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Old 10-31-2000, 04:54 PM   #16
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The rubber thing is a 2" to 3" PVC pipe coupler, which has an ID of 2.4" on one end, and 3.4" on the other end that goes into the inner fender. If a person were to install this, but cut the aluminum tubing shorter, I'm sure the coupler WOULD act as a velocity stack.

However, I cannot do the R&D on my car anymore, since I now have a turbo. I live at 6,000 feet and the 18% gain in N/A power that we can get with NA mods will only take us back to the 165hp that you guys at sea-level enjoy stock. The turbo was the easiest way for me to hit 200hp at this altitude...

I'll see if I can get one of the local guys with my intake on their MY00 to let me cut it up Maybe Will or JJCassaSubeDriver, Schizmatic or PunkRS, etc...

Larry www.ImprezaRS.com
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Old 11-01-2000, 12:15 AM   #17
rob
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Common misconception. A zero length intake pipe does not mean highest horsepower.

Autospeed did a dyno test where they changed only the length of pipe. A filter right on the TB did not result in the best power (in fact, the worst). The largest difference in power was between the the filter on the TB and one of 50-60 mm (I think) and it was around %6....if my memory serves me correctly (which it usually doesn't).

The only trouble is that the best way to figure this out the optimum length and diameter, is to do some dyno tuning which becomes a bit of a hastle for us.

-rob
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Old 11-01-2000, 07:21 AM   #18
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rob and RX-
Do you realize how small 50-60mm is?
Is that some kind of typo? That's only 2-3".
BTW three inches is the height of my velocity stack/ramtube.
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Old 11-01-2000, 03:58 PM   #19
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oops - 60cm.

cool, thanks for the info larry.
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