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David Salama

I definitely have positive pressure at idle. My car failed it's leak down test, so I believe I have blow by around the piston rings. I have invented a check valve that I now use instead of the oil fill cap to prevent high crankcase pressure under boost. At idle, the check valve is opening (positive pressure). My car is running really strong, so I have no need for a rebuild yet. Hopefully, my bandaid of the check valve will work for a while. I am also curious what other 951s do at idle as well. Hopefully we'll see some posts.

David Floyd

Mine blows out at idle, brand new engine with about 30 mins of run time.

Alan C.

My BodyMotion of NJ engine sucked. Sorry, you were talking about positive things.

On that note my current engine with new everything including the right size rings does have a bit of positive pressure. Not sure about what it does at idle. I'll try to check in the next day and post.

Did see an interesting item in Summits latest catalogue. They have a small vacuum pump which could be adapted to our cars. The drag race guys have been doing this for quite awhile. It is supposed to help with sealing the rings.

Interesting idea.

Alan

tecart

thanks for replying, i guess the answer is yes their should be some positive air pressure coming out of the fill tube at idle, this has been the case on every car ive checked so far, i better tell the porsche mechanic who is doing some other mods on my car to stop looking for hidden gremlins that arent their, god i feel much better now, i mean how could he think rings or head gasket my car runs good and last time a headgasket blew on my car it wouldnt even idle above 700 rpm at all and blew white smoke when on the gas, anyhow im having him do a compression check just to be safe and ill report the numbers to all who care, that should be in 4 days or so, ps Mr. Floyd how is the car running? is it a screameer? hoe did you get over not having the motor for so long? did you have to threaten to get the job done? would you do it again based on the long wait for the motor?

David Floyd

[quote]Mr. Floyd how is the car running? is it a screameer? hoe did you get over not having the motor for so long? did you have to threaten to get the job done? would you do it again based on the long wait for the motor? <hr></blockquote>

It has about 75 miles (easy, no boost) on it so far, Tim wants me to run 2000 miles at 10 psi and then I can turn it up.

It was tough not having my car for sooooo long, but Tim did what he could to keep me happy.

Would I do it again? I will wait till I can turn up the boost to answer that question.

Edman951

On my 135m 951,i check it when it was cold on idle and i get vaccum suction
I forgot to check it when i got home to see if their is a difference on my car when it's hot.
I will check it out tomorow just for fun.

Edman951

When my car is @ running temp, i get a good vaccum suction.
And since my motor is stong, i question witch is better. Vaccum or presure out of the oil cap?
<img src="graemlins/wave.gif" border="0" alt="[byebye]" />

Russ Murphy

I'd have to say vacumn. At least then you don't have to smell "that smell".

David Floyd

So which way is correct ? <img src="confused.gif" border="0">

superjet.1

this is a good question!we know the pistons moving up and down in the bores create both positive pressure and negative in the crank case as they move up and down thus eliminating them selves.since one piston coming down creates pressure in the case and one going up creates vacuum they cancel each other out.the crank creates windage as it spins but has no effect on pressure since it only disturbes the air that is already there.soooo.. i think that poor ring seating(blow by) is probabley what causes some of your cars to have positive pressure at idle.

David Floyd

Ok, so when my new rings seat I should have vacuum at idle. Thanks superjet.1

Do the Guru Guy's have a MAP about ready to come my way ?

Rob

[quote] So which way is correct ? <hr></blockquote>

You should be running a slight vacuum. The top of the air oil separator has a hose that connects to the inlet boot of the turbo to provide this vacuum or alleviate any positive pressure buildup. I would have to say that if you have any pressure building up, either you are missing this connection or have some excessive blow-by that the (approx. 1/2" dia.) hose can't relieve.

Rob

Alan C.

So that's what that plugged fitting was for. Thanks again Bodymotion <img src="graemlins/nono.gif" border="0" alt="[nono]" />

Alan

David Floyd

[quote] either you are missing this connection or have some excessive blow-by that the (approx. 1/2" dia.) hose can't relieve <hr></blockquote>

This hose is connected, so my new rings are still not seated I suppose.