What's the function of the Venturi Tube on a Tiptronic?
Can someone explain what the function of the Venturi Tube on a Tiptronic is? Is it sucking in air or pushing in air into the intake system? What does it do for the Tiptronic trans?
In my picture you can see that it connects into the intake system at 2 spots and both are after the MAF sensor. http://i58.tinypic.com/16b0plk.gif I tried Googling it several ways, but you know how Google has become. It only pays attention to Boxster and Tiptronic, so I get results for Boxsters for sale with a Tiptronic instead of the answer to the question I asked. Thanks! |
Good question! I replaced mine since it was old and brittle and kept breaking. (Sound familiar?) I hadn't realized it was only in the tip. I know it is part # 96611017000 and costs just over $100. I understand the venturi principle. I too would like to know what a hundred plus dollar plastic tube, that I had to replace, does in my car! :confused:
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I know that the front connector is the vacuum line for the brake booster. Not sure why the tips take that from the aft side of the engine. I forget what the other end connects to. (Drove a Del Sol today and no Boxsters in sight.)
http://986forum.com/forums/426619-post16.html |
dude. i googled 'boxster tiptronic vacuum' and this was the first thing that came up (refer to post #10):
air intake/vacuum line routing - Pelican Parts Technical BBS |
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sorry, i confused the two. a venturi in this context is usually associated with vacuum. this looks like a bypass around the throttlebody at idle, using an existing port on the manifold (the manifolds are the same piece reversed, so the brake booster port is available). at idle air is drawn from the intake tube into the manifold (throttlebody is closed and there is a vacuum in the manifold as a result). it moves past the y fitting and creates a vacuum. where does the third end of the venturi system connect to? probably to do with idle control and the torque converter, or maybe just to create additional vacuum for additional functions.
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ah - the third end goes to the brake booster. prolly just to give addnl vacuum to the brake booster because on a tip you stay on the brakes at idle whereas on a manual you would just release the clutch.
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This is interesting. See on this engine where there is a connection to the intake plenum and then runs down to the fuel rail? EDIT: Visual misinterpretation on that, it does not run down to the fuel rail.
http://data.motor-talk.de/data/galle...7014-14666.JPG This spot is capped off and the venturi tube uses that spot as a mounting point. Where it goes from there would be the brake booster? I'm not sure if this is a Boxster engine either as my air compressor is way more to the right. That last bolt on the intake plenum was not fun to get to. Lots of stuff in the way, not a clear shot like this picture shows. . |
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The overall function is that it is the brake booster vacuum line. On a manual transmission there is only an elbow fitting at the left front of the intake manifold (no. 23): http://986forum.com/forums/uploads01/231417229247.jpg On the Tiptronic there is only a blank cover in that position. The Venturi tube connects to the right rear intake manifold and additionally to the pre-throttle intake, then terminates at the front left to connect to the booster line. The effect is greater vacuum. http://986forum.com/forums/uploads01...1417228454.jpg |
so the venturi tube ties in to #12 and #14 here (why i don't have these on my car):
Intake Distributor |
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http://i58.tinypic.com/16b0plk.gif If this is for the brake booster, why did they do it this way on the Tiptronic cars? Do they require more vacuum? Why run all the way across the engine like they did? How does the engine compensate for the extra vacuum? http://i58.tinypic.com/2gw5r49.jpg . |
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aha, i see now. proportions seemed off to me and was trying to figure a way for that line to get all the way to the front of the engine.
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EDIT: Scratch this post.
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EDIT: Scratch this post.
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Pelican Technical Article: Replacing the Boxster Brake Booster and ABS Controller - 986 / 987
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Went out and disconnected the line to the brake booster. It works opposite of how I thought it does. The line to the brake booster pulls air from the booster, a massive amount of air. So the engine isn't losing air, it's getting air added to it.
So you have the venturi tube adding air and the AOS adding air after the MAF sensor, how does the ECU actually know the amount of air going into the engine? |
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There are some good "How it Works" diagrams and videos if you Google it. You got me curious about the whole venturi tube. Why just on automatics and what does it do.... It seems like it is common on German cars: VW, Audi, BMW, and in most applications the venturi is called a "suction jet pump". There is some good reading about it: How does the BMW E39 sucking jet pump (aka suction jet pump) work & how does it fail? - Bimmerfest - BMW Forums Post #4 in this thread addresses it: *DIY* - B5 1.8T Vacuum/Check Valve/SAI/PCV - Delete & Simplification |
Ok, yes that makes sense. So the venturi tube basically has zero affect on the air volume to the engine?
So do the O2 sensors sort out what the AOS does? The AOS adds air and gases, correct? Never thought about the SAI. From what I saw during the intake work, it looks to be pretty crucial to the operation of the engine and Tiptronic trans. Not sure how people delete that? |
The SAI is an emissions control device and only runs for a very short period at start up. Apparently this is only in North American cars and doesn't exist in ROW cars. It can be deleted by flashing the ECU but the file is different for tiptronic cars than for manual cars. It doesn't seem to affect the performance of the engine, only the emissions at startup.
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The venturi keeps air speed up during gear changes with the tip. Removing it will create a loss of performance between gear changes, especially between 4-5 gears.
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Whhoooo. A loss in performance. I think that is a no go for KRAM36. :D ;) :cheers:
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http://i58.tinypic.com/16c191c.jpg Move it to here? This would also allow me to use larger pipping and not worry about putting that connection into it. http://i60.tinypic.com/rvbpds.jpg |
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