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Old 08-03-2008, 03:23 PM   #141
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Quote:
Originally Posted by rb26dett View Post
I'd go so far as to say that using both of the stockers is NOT enough either.
It may be impractical and unnecessary, but would it be feasible to monitor crank case pressure by tapping the VC for a vacuum line which would go to a second MAP sensor, like the one for barocor?

Your log would show exactly what pressures you're dealing with, possibly producing evidence which would determine if OE vent size and baffles are adequate
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Old 08-03-2008, 03:38 PM   #142
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Indeed it would be feasible and not too hard. Just hook a map sensor to a spare ADC input and log the values. You can do the conversion to pressure afterwards easily. I'm interested to see what you find out, but you have to thrash the crap out of the car to do a good test on this.
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Old 08-03-2008, 07:58 PM   #143
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Originally Posted by rb26dett View Post
You fail reading comprehension.

If velocity stays the same pressure stays the same. Movement alone (without change on rate of movement etc) does not generate pressure differences.

Your equation is only valid away from any walls of say an intake tube and also only to incompressible fluids. The air in your intake satisfies neither of those requirements.

You are right that there will be a pressure gradient leading into the compressor, however its contour would be something like the inverse square. If you applied a still body of air to that vacuum source you might be able to detect it. With a steady state equilibrium reached where the speed of the air moving in and the pressure differential across it (it's invalid to say that it is sucked in just the same as it is invalid to say that it is pushed in) that makes it move are matched then the pressure drop relative to the outside ambient air should be so close to zero that you'd have a hard time measuring it. If it's not, your intake sucks.

End rant :-)

Fred.
bernoulli applies for both compressible fluids and boundaries.

and last time i checked, the ambient air outside my intake pipe is not moving and the air inside it IS moving.

I bet my intake tube flows better than any miata with a filter on this site.
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Old 08-03-2008, 08:38 PM   #144
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I could get "moving" air between 10 psig and 11 psig, and have higher pressure. :-P

More to the heart of this conversation, you're not going to get *significantly* low pressure in the intake unless the system really is restrictive. A bad air cleaner might do a bit. Certainly an OEM intake has a significant pressure drop, though still not large.

Anyway, what I'm taking from all this is the OEM system is a good thing to shoot for, an upgraded PCV and catch can are what the descerning turbo enthusiast will be putting on his miata this season.

Mine are on order, and will be installed with catch can directly.
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Old 08-03-2008, 09:44 PM   #145
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ok fine, BRAINEACK, can you bring your magnehelic over and put it in my intake behind the filter??

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Old 08-03-2008, 11:12 PM   #146
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Um, bends are bad fer flow, m'kay?
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Old 08-04-2008, 03:25 AM   #147
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http://gallery.y8s.com/d/17058-2/DSC02751.JPG
Not only is your filter half the size of mine (flow area wise) your intake tube is also less than half at the intake end! ;-) (It's the same at the turbo though) Mine also has a "velocity stack" leading from the 6" into the 4" <<< (quotes required for Dr Evil style pronunciation)

I'm sorry for being less of a man than you y8s ;-) I'll just have to take consolation in the fact that I'm less of a man while not driving a Miata :-)

Fred. (living dangerously)
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Old 08-04-2008, 04:12 AM   #148
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"Living" he says. In England. Oxymoron.
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Old 08-04-2008, 10:40 AM   #149
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Quote:
Originally Posted by rb26dett View Post
Not only is your filter half the size of mine (flow area wise) your intake tube is also less than half at the intake end! ;-) (It's the same at the turbo though) Mine also has a "velocity stack" leading from the 6" into the 4" <<< (quotes required for Dr Evil style pronunciation)

I'm sorry for being less of a man than you y8s ;-) I'll just have to take consolation in the fact that I'm less of a man while not driving a Miata :-)

Fred. (living dangerously)
my velocity stack is built into the turbo. if I ran a different compressor housing, i'd be all over a velocity stack, but I'd probably put it in front of a filter to avoid obstructing the opening of the stack.

honestly, with a filter on there mucking it all up, it probably is sub optimal anyway.
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Old 08-04-2008, 10:53 AM   #150
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Quote:
Originally Posted by y8s View Post
ok fine, BRAINEACK, can you bring your magnehelic over and put it in my intake behind the filter??

yes i could. it's in my trunk.
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Old 08-04-2008, 11:49 AM   #151
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Quote:
Originally Posted by y8s View Post
my velocity stack is built into the turbo. if I ran a different compressor housing, i'd be all over a velocity stack, but I'd probably put it in front of a filter to avoid obstructing the opening of the stack.

honestly, with a filter on there mucking it all up, it probably is sub optimal anyway.
Let's be honest here, if there was a measurable pressure difference between your setup and mine at the same RWHP I would be extremely surprised.

All bullshit aside, a lot of the stuff we all do to our cars make so little difference that it just doesn't matter. Even when you assemble them all together the increase in HP isn't that much. The key thing is to not do anything badly :-)

I'm going to summarise all of Rob's PCV threads into an article at some point when I have more time. I'll link it here when I do.

Fred.
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Old 08-04-2008, 11:26 PM   #152
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A lot of times I'm willing to do the legwork myself, experiment, and do a writeup on my findings... but would somebody just make a drawing and tell me what to do. Whadda I hafta build to get the best of all worlds here?

Please spell it out and use small words.
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Old 08-05-2008, 09:50 AM   #153
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I believe the drawing below illustrates the general consensus on a crank case vent system adequate to manage boost blow by and still remain somewhat eco-friendly.
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Girly Catch Can Mounted-ccvent.jpg  
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Old 08-05-2008, 10:17 AM   #154
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www.autoshop101.com/forms/h63.pdf

Toyota and Braineack seem to disagree on PCV valve operation. I'm with Toyota on this and claim you shouldn't/don't need the check valve. I'll stick with that opinion until someone proves that their crank case is being pressurised by boost through a pcv sized hole when the exit hole is equally sized or larger. (note, not physically possible :-p)

You do the loveliest diagrams Rob! I'd note that the "breather" location needs to flow well and that the main issue seems to be that it doesn't and the crank case get's pressurised.

Fred.
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Old 08-05-2008, 10:34 AM   #155
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Default pvc catch can

And here's a diagram for a cheap catch can. This fixes some stuff wrong with mine. I don't have the pipe nipples penetrating into the can nor the divider, so some of the oil vapor actually makes it out of the filter I have stuck on the end (no it doesn't go to the turbo intake...yet). So that means if it did run to the intake, I'd have vapor condensing in the hose and possibly making it to the compressor. The divider wall and pipe nipples should for the vapor deeper into the can and provide more surfaces/opportunity for condensation. I prefer the divider over packing.
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Old 08-05-2008, 10:38 AM   #156
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Leave the internet. Go idle your car with a hose directly from the IM to the valve cover.

I'll be here waiting for your "discovery"


Quote:
Originally Posted by rb26dett View Post
Toyota and Braineack seem to disagree on PCV valve operation.

REALLY???!?!
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Old 08-05-2008, 10:48 AM   #157
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Originally Posted by Braineack View Post
Leave the internet. Go idle your car with a hose directly from the IM to the valve cover.

I'll be here waiting for your "discovery"
No discovery required. The throttle plates in stock config pass almost no air at all. The PWM idle control corrects idle level based on what the rpm actually is. Thus, if it's getting some air from the crank case it's going to close the PWM valve to match. Likewise, if it's getting some O2 free gas from there it's going to feed in sufficient air to keep the idle up. Given the diameter of the PCV orifices and the engines idle air requirement, I doubt you could keep it alive based only on the PCV "leak".
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Old 08-05-2008, 10:50 AM   #158
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Too slow with the edit there... or too fast.

Yes really. You stated that it is CLOSED at high vacuum. It is not closed, merely restricted. Restriced != Closed.

Smile, it'll do ya good :-)
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Old 08-05-2008, 11:17 AM   #159
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Quote:
Originally Posted by rb26dett View Post
It is not closed, merely restricted. Restriced != Closed.

oh give me a break, go suck on a pcv.


I was mearly letting Abe become aware of his potential unrestricted "leak" based on his drawing.
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Old 08-05-2008, 11:25 AM   #160
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I'd be curious to know the exact differences between the stock miata valve and the gtx, and why the stock unit is built the same. What compromise is made with the gtx valve being more resistant to boost?
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