Alfa Pages

[RBL]

I'm thinking of removing the breather pipes on my 1.7 8v and just running the oil filler breather pipe to a catch tank.

Who else has done this - are there any downsides?
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Porsche 550 spyder replica with Alfa Sprint 1.7 engine

[bobbber]

The crankcase is supposed to run under negative pressure (slight vacuum) - so you will be running it at normal (ish) air pressure. I'm not sure about the advantages/disadvantages of this.

If you have an injected car (I guess you don't!) - you need to block the oil vapour input tube hole to the intake elbow - otherwise there is unmonitored air entering the engine.

Bob
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Fiat Bravo 165 Sport

[RBL]

Thanks bob. I'll give it a try (It's not injected)
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Porsche 550 spyder replica with Alfa Sprint 1.7 engine

[Ben_nz]

I've run my car with the crankcase breather going through a filter to the atmosphere, or into a catch can, on two different track days.
My car didn't explode. Next to zero oil came out.

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"Now, all that is left to do ... is wait that something else brokens, to fix up again!"

[Eddie_W]

Hi Ben, your car is looking mint under the bonnet. Those trumpets must sound wicked when you get it on the gravy stroke.
Regards Eddie
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The pop star formerly known as Eddie W

[Ben_nz]

They sound wicked right from low rpm upward, and eliminate the need to watch the rev counter!
When the scrutineers saw my setup at the last Alfa club track day, they told me something I didn't understand:
That plastic breather junction thing that normally clips to the airbox has 7 pipes going to it. Two feed gases back into the air stream to be recirculated through the engine. One big one brings the hurricane from the oil filler tube. And four little ones come from the intake manifold below the throttles, I think.
The scrutineers told me to take these four little pipes off and seal up the holes, because the car would go better.
Why is this, and what do these pipes do
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"Now, all that is left to do ... is wait that something else brokens, to fix up again!"

[stedee]

they are vacuum pipes, on mine they are linked to the idle sensor and the fuel regulator so i presume they control the idle
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brum brum

[Eddie_W]

I'd say that they are there to create a negative crankcase pressure for the closed circuit breather system. Otherwise the spinning of the crank has a centrifugal compression effect on the air creating a pressure that would continually blow your filler cap off. That pressure also robs horsepower with the work the crank is doing to create that pressure and the work the piston is doing on the inlet stroke when it is trying to move downwards with atmospheric minus on top and atmospheric plus underneath. That's where the HP gains of dry sumping come from.
With you venting the crankcase to air through those filters the vacuum pipes become redundent but as soon as you revert to a closed system they are necessary.
Incidentally, the more rolled the lip on the trumpets, the more efficient as around 30 percent airflow is drawn from behind the lip . Also the trumpets help control standoff.
Regards Eddie
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The pop star formerly known as Eddie W

[knighty]

ben_nz - make sure you run some intake filters over those trumpets, yest they may look nice, but let me assure you that you will polish the cylinder bores in no time, and the rings will wear away at an alarming rate, and you will then start to burn a lot of oil and the engine will be knackered, get some good quality foam filters from someone like ITG or pipercross.........failing that some cotton-gauze jobbies from K&N wil be fine