Thread: Zen and the art of B15 Performance

if you throw a turbo in the mix everything changes again, damn. I still haven't gotten to the point.

because the intake manifold is the lowest pressure point in the system air flows to it from the intake track, through the crankcase, to the intake manifold

It's only the lowest pressure point in vaccum (TB closed) right?

How does the crank case build pressure?

Originally Posted by ash

It's only the lowest pressure point in vaccum (TB closed) right?

How does the crank case build pressure?

it blows by the cylinder rings from the combustion chamber...... which is funny because at WOT blow by is higher (because cylinder pressure is higher, that whole pressure differential thing, yet again) but the damn intake stops sucking, WTF.

Originally Posted by Big J

it blows by the cylinder rings from the combustion chamber...... which is funny because at WOT blow by is higher (because cylinder pressure is higher, that whole pressure differential thing, yet again) but the damn intake stops sucking, WTF.

education

At that point the PCV system pressure is high enough that the the system vents into the intake manifold and tract (in a stock system), but since both the DSN and the PCV valve are restricted in design, they can only flow so much at WOT...........

part of the reason they are restricted is because the PCV system is a metered air leak (in a stock system). If the DSN wasn't restricted by design, the car would pull too much air at idle to idle. The main purpose of the PCV system is emissions related, performance isn't really a concern.

So at WOT you have to rely on the crankcase pressure rising above atmospheric for it to vent, because the intake isn't in vacuum anymore, and once it starts to vent due to positive pressure, the amount it can flow is restricted, so pressure comes up again. Low tension piston rings, like in the QR, like lower pressures in the crankcase.

we're still talking about a stock system, no turbo yet.

Originally Posted by ash

the vaccumm at WOT should be VERY VERY low. like 0-3 inches.

Originally Posted by ash

when the throttle opens the intake manifold goes from vacuum (sucking) to no vacuum (not sucking), so now for a pressure differential to exist, and flow to happen, the pressure in thecrankcase has to come up higher than the intake and intake tract.......... and this is a point of confusion.......... because......... when you identify compartments to identify pressure differentials and such, the largest container and easiest to overlook some times it the whole freaking atmosphere of the earth.

A boost gauge shows 0 as being atmospheric pressure, which is actually about 14.7 psi (on the absolute scale, which is another scale all together), but 0 according to a pressure gauge. Anything below 0 on a boost gauge is refered to as vacuum, anything above 0 as boost, because atmospheric pressure is the reference. So because the atmosphere is about 14.7 psi (at sea level), even an NA car is really running 14.7 psi.

a pressure differential only considers the difference in pressure between 2 compartments, so if one is at 30psi and the other is at 28psi, there is a differential of 2psi, if one is at 12psi and one at 10psi, there is a differential of 2 psi........ but that opens another can of worms I'll leave out for now, it's a big can of worms.

flow will occur between the 2 compartments until the pressure equalizes, when that happens flow stops (in this can of worms it does)

w/o a differential (or other motive) flow stops

bump for more

are you another djtorello with your advanced vehicle knowledge? lol j/k

bump

Big J for some reason you sound like my last semester classes LOOL, but so far i love the way you're describing everything specially how your using diferent laws of phisics without using the long hateful formulas they teach like bernoulli's principle, dude have you ever though of studying engineering or something? BTW you explain stuff way better than some college profesors i have giving me classes... keep posting!!

So....Big J. Or really anybody that can think like this awesome man.
Is this okay? The red cylinders are catch cans. I'm N/A.

totally forgot about this thread.

I'll have to wright some more

here is a good one for basic diagnostic of a engine that isn't runnin.... A motor needs 4 things to run: Air,Fuel,Compression,Ignition. Except a deisel because it uses compression as an ignition source... this little trick has made things easy for me a couple of times. And if you can't figure it out see what is working properly and eliminate that as the problem

Originally Posted by b1ynd

Big J for some reason you sound like my last semester classes LOOL, but so far i love the way you're describing everything specially how your using diferent laws of phisics without using the long hateful formulas they teach like bernoulli's principle, dude have you ever though of studying engineering or something? BTW you explain stuff way better than some college profesors i have giving me classes... keep posting!!

That's typical in many engineering departments...go to a physics department, they'll teach you the right way!

BTW Justin, great stuff here...keep it coming!!!

All things considered, I understand about 90% of this. In terms of thinking outside (or inside as it may be) I understand. I am not so mechanically inclined to fully understand the technical data contained within.

Your approach is fairly open, in which I mean that you can use this same approach to explain anything and everything you want. I have to say, this is the first time anyone has explained a motor to me without trying to explain the whole thing like the front of a puzzle box. You are explaining it as separate pieces of the same puzzle but showing me the picture first, than explaining how each piece fits with another. I am enjoying this thoroughly, my good chum.

this is all awesome info.