Turbo and Vacuum Lines
02-15-2002, 01:27 AM
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Turbo and Vacuum Lines
Hey guys,
I was thinking about the auxilliary plumbing for the turbo (vacuum lines, fuel lines, bypass lines, etc) and was wondering:
how do factory turbo cars supply vacuum to the various subsystems?
Two things I know need vacuum are the brake booster and the heater assembly (it uses vacuum to move the direction valves).
Two that I'm not sure about are the EVAP cannister line and the PCV line. I know the EVAP will need a check valve (and the PCV is already a check valve), but will they still function?
Just wondering,
ac
I was thinking about the auxilliary plumbing for the turbo (vacuum lines, fuel lines, bypass lines, etc) and was wondering:
how do factory turbo cars supply vacuum to the various subsystems?
Two things I know need vacuum are the brake booster and the heater assembly (it uses vacuum to move the direction valves).
Two that I'm not sure about are the EVAP cannister line and the PCV line. I know the EVAP will need a check valve (and the PCV is already a check valve), but will they still function?
Just wondering,
ac
02-15-2002, 04:12 AM
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Most of them run vacuum straight off the manifold -- and don't give a rat's ass about boost.
Wanna know why?
How often do you use your brakes while mashing the throttle? Not very often eh? When you're not on the gas, you're not making boost and thus your brakes have vacuum to assist.
Same goes for the heater controls... You don't necessarily drive around in boost ALL the time. And while it's certainly possible for you to adjust the controls while boosting, at some point you'll slow down, the vacuum will pick up and the valve will move.
I dunno about the PCV valve and the EVAP system; quite honestly they're both being "overridden" anyway with the Haltech system
-Red-
Wanna know why?
How often do you use your brakes while mashing the throttle? Not very often eh? When you're not on the gas, you're not making boost and thus your brakes have vacuum to assist.
Same goes for the heater controls... You don't necessarily drive around in boost ALL the time. And while it's certainly possible for you to adjust the controls while boosting, at some point you'll slow down, the vacuum will pick up and the valve will move.
I dunno about the PCV valve and the EVAP system; quite honestly they're both being "overridden" anyway with the Haltech system
-Red-
02-15-2002, 04:28 AM
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Yeah, I figure a couple of $2 check valves should make sure the heater, evap, and brake (which already has a check valve, I think) don't see boost. I also think the brake booster has a "storage tank", so even if you have to "Oh-$hit!!!" brake, it should still have enough to help you out.
What I'm most concerned about is the PCV and breather lines. PCV should be fine as-is, it'll just have to wait until you slow down to vent. What has me baffled is the breather hose that attaches to the valve cover and goes before the throttle body. Without a check valve, you would pressurize the crankcase (not good), but at idle, I believe it's supposed to suck in a little bit of air (which the check valve would defeat).
another option is routing it to before the compressor, but then positive crankcase pressure will blow oil vapor into the inlet, which is not necessarily a bad thing, but it then has a tendancy to re-liquify in the intercooler (which sounds cool, but isn't).
Random, what did Alpine do with your vacuum / bypass hoses? I'll e-mail Onpol and ask him as well.
Factory turbo cars have to have a way to deal with this. I wonder if the WRX dealer would let me look under the hood . . .
ac
What I'm most concerned about is the PCV and breather lines. PCV should be fine as-is, it'll just have to wait until you slow down to vent. What has me baffled is the breather hose that attaches to the valve cover and goes before the throttle body. Without a check valve, you would pressurize the crankcase (not good), but at idle, I believe it's supposed to suck in a little bit of air (which the check valve would defeat).
another option is routing it to before the compressor, but then positive crankcase pressure will blow oil vapor into the inlet, which is not necessarily a bad thing, but it then has a tendancy to re-liquify in the intercooler (which sounds cool, but isn't).
Random, what did Alpine do with your vacuum / bypass hoses? I'll e-mail Onpol and ask him as well.
Factory turbo cars have to have a way to deal with this. I wonder if the WRX dealer would let me look under the hood . . .
ac
02-15-2002, 04:56 AM
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Vehicle: 2008 Toyota Prius 2006 Suzuki SV650S
QUOTE
Originally posted by Curtas:
What has me baffled is the breather hose that attaches to the valve cover and goes before the throttle body. Without a check valve, you would pressurize the crankcase (not good), but at idle, I believe it's supposed to suck in a little bit of air (which the check valve would defeat).
another option is routing it to before the compressor, but then positive crankcase pressure will blow oil vapor into the inlet, which is not necessarily a bad thing, but it then has a tendancy to re-liquify in the intercooler (which sounds cool, but isn't).
What has me baffled is the breather hose that attaches to the valve cover and goes before the throttle body. Without a check valve, you would pressurize the crankcase (not good), but at idle, I believe it's supposed to suck in a little bit of air (which the check valve would defeat).
another option is routing it to before the compressor, but then positive crankcase pressure will blow oil vapor into the inlet, which is not necessarily a bad thing, but it then has a tendancy to re-liquify in the intercooler (which sounds cool, but isn't).
The Alpine method was to route the crankcase breather UPSTREAM of the MAF. This mean that Oil Vapor kept horking up the MAF.
I now run the CrankCase breather to a small filter, and it vents/sucks air that way. The problem with this is I get Aspxhiated by Hydrocarbon (gas) stench after a full throttle run.
I am going to route it back to the intake, AFTER the MAF but before the Turbo. This will allow some degree of oil vapor to get sucked in by the turbo, but I do not think it will be a major problem. One possible method would be to include an "airbox" on that breather line, that would allow the air to slow down, and drop the oil prior to it being sucked into the compressor, however, I don't thing the design of said device is really necesary or even feasable.
In regards to brakes.
There is not a 1 way valve on the brake booster now, but it does have a small vacuum canister that 'stores' vacuum for when you need it. The biggest problem I have is a complete and total lack of vacuum execpt after an acceleration run when I close the throttle. At idle, there is little, if any vacuum. The turbo actually pushes the Idle Air Bypass tube open, and forces air into the Intake Manifold at idle, and while the turbo is still spooled up but the throttle closed. Hooking my Idle Bypass up to the intake, with a 1 way valve on it should hopefully solve the problem.
02-15-2002, 05:06 AM
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Cool, thanks for the reply. So, if I have this straight:
PCV Breather: no change
Valve Cover Breather: routed before the compressor, but after MAF
Brake Booster: no change
IAC bypass: no change (but probably should be routed pre-compressor, post-MAF)
I'm probably going to try and put check valves on all the vacuum lines, route the brether pre-compressor (probably where the recirc-BOV will hookup), and maybe even put the IAC pre-compressor.
I've seen some plans on RX7 sites for an oil-condenser and drip can. I may invest in one of those, and maybe even plumb the oil drip back to the turbo-oil return line. I'll have to think about it for a bit.
thanks again guys,
ac
PCV Breather: no change
Valve Cover Breather: routed before the compressor, but after MAF
Brake Booster: no change
IAC bypass: no change (but probably should be routed pre-compressor, post-MAF)
I'm probably going to try and put check valves on all the vacuum lines, route the brether pre-compressor (probably where the recirc-BOV will hookup), and maybe even put the IAC pre-compressor.
I've seen some plans on RX7 sites for an oil-condenser and drip can. I may invest in one of those, and maybe even plumb the oil drip back to the turbo-oil return line. I'll have to think about it for a bit.
thanks again guys,
ac