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Old 07-04-2009, 11:32 PM   #1 (permalink)
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Join Date: Feb 2008
Location: maine
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oldscoob - '87 subaru wagon gl/dr
90 day: 47.06 mpg (US)
Thanks: 21
Thanked 18 Times in 14 Posts
CAI venturi carb

I have another post here inquiring about math for a venturi, and well, there is no perfect answer.



this is made from remnants of a fuel injected version of the same model of subaru I am running. The hot MAF is removed.



the fuel injected version had quite an atomospheric rumbling bellow, and I did not forget. As this opening is nearly 3 inches, and the end of the pipe is 2.5 (the same size as the top of the carb opening) I REALLY emphasized holding it in tightly. It should be much quiter on 3 degree cams (no back wards air to bellow) and it has a larger opening than the maf that was in it.



the inside metal is softer than the outside clips you see, acting as a gasket on the ring of the tube, and above it is to be siliconed. It is very rigid. I swung it around and banged things.

As the venturi goes, it is simply 3 inch to 2.5 inch and it is a long run. I used the whole thing to reach the carb.

Next photos will show it in the car. I am awaiting a high grade 90 degree silicone turbo elbow to make the turn from carb to the venturi. The flex part will also be in photo, and that is a subaru oem part. and of course there is the charcoal canister, and a place for the suck in side of pcv that I will add on the "level straightaway". photos will show results soon enough

any ideas on what will happen? This is not a fuel injected car, there is no heat riser. it is wide open venturi from the get go...with a modern air filter not even subaru can extinct.
the lower half of this is already bolted to the car, exact fit of course, no hacks. ourside source of air all ducted OEM exceot for what you see here, and will see when it is done.


Last edited by bgd73; 07-04-2009 at 11:41 PM..
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Old 07-12-2009, 12:22 AM   #2 (permalink)
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Join Date: Feb 2008
Location: maine
Posts: 758

oldscoob - '87 subaru wagon gl/dr
90 day: 47.06 mpg (US)
Thanks: 21
Thanked 18 Times in 14 Posts
here is a shot of version 1 in the car. the fi box bolted right in.


below is the tricky part. I haven't even had a v8 that could take cold air without heat rise. the little sube is the same...and quite dramatic if itsn't right. the backside of thes little chrome filter is open to breather warmer neutral air, rather than cramming bugs butts from the front. It is just right.



last night was a fun trip, the car is sporty to drive. the body is as stiff as a brick, alot of serious welding lately. older tires thumped down the highway. t-rated really comes back at the body now. It is actually very quick. I can judge by 12 years of throttling this engine. smoother touring tread and this little boxer can see 120 mph. a 300 mile trip was in the mid 30s mpg to go along with this fun. the carb bellowed in the hills, and I could lug it down to 2500 rpm. The legend continues....without the jackasses that killed at it.

a serious tip if you do run carbs..the heat rise is not a performance killer, all carbs have to have it. most oe air plenums for carbs do not even go to the outside anywhere. I made this sube get some, the boxer and its location, with the spare tire needed some help. I may post yet another version, as I got the silicone turbo hose today (that was supposed to be where the chrome filter is). I may not even use it, the longer trip was a blast proving I got what I wanted.
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Old 07-14-2009, 04:11 PM   #3 (permalink)
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Join Date: Feb 2008
Location: maine
Posts: 758

oldscoob - '87 subaru wagon gl/dr
90 day: 47.06 mpg (US)
Thanks: 21
Thanked 18 Times in 14 Posts
here is a picture with text for seemingly a simple task. It is not a simple task, it is all mechanical at all times. (and fuel injection is for malfunctioning kids)


I could not go all cold flow. I could not go all warm. I could not create a thunderstorm of clashing temps....I could not hook up the pcv inlet side to the plenum (very serious oem error). the orange line also has a serious function, it is a fuel system vent...it was also part of the very serious oe error..the engine PCV (little blue cone) sucked on the orange vent, which has ethanoled maine fuel and other repulsive eye watering things... right into the engine as oem setup. I later learned the giant steel plenum for such a little carb was a cheapskate hack job by subaru, as it was originally made for 2 carburators, and forced to function by engineers for one. (subaru secret for you) Too much on the orange line, the canister plunger gently hovering open to vacuum just right.....never does..too little, and the fuel system is choking like a tin can with a one way vacuum source (loss of power in other words- and fuel pump death , carb gasket death, and engine eventually...).
Believe it or not..everything in this photo is trial and error to a perfect function.
I won't be forgetting what I trialed and errored. In one barrel normal mode it is mid to high 30s, city or not it doesn't matter...I like the sporty bellow and can't help but having fun by stepping out a little bit once and awhile, this drops it to 30. the highway of course is the 3 main boxer mythologically making vtec hondas as feministically babbled as ever...90mph is 3600 rpm and absolutely loving it for eternity.and a honda wont ever have 10 gears and 3000 pounds on 1781cc. (I despise the inline four and have facts to disprove its horrifying success.)
anyway, I did see some metro carbed as a favorite, feel free to learn from this post. the smaller engine is very sensitive.

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