Can you vent blow off to atmoshere on supercharged car?
- Thread starter cathartic
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if your mass air sensor is the blow-through type up by the intake, you can blow off to the atmosphere...the idea is that you don't want the air to be metered and then blown off to the atmosphere. If it's the normal MAF down by the air box, then no, you'd want a bypass valve, which would reroute it though the system.
DirtyD916
Active Member
Actually go to the power adder section of this forum and there a man by the name ryansg. He has a 306 with an sc-trim and an hks ssq BOV. Its vented into the atmosphere and he has a regular MAF like anyone else. He says that he has no problems watso ever and that if his car ever tends to run rich it goes right back to normal once he gives it more gas.
TT91
Active Member
you can, but your not supposed to, I had mine vented for a while, never really noticed a tuning issue.
Michael Yount
Mustang Master
I think the issues are these -- if you have the pcv valve hooked up to the intake so that vacuum is pulling on the crankcase when the throttle is closed, you have to allow for that air to ENTER the crankcase from somewhere. On the factory set up, it comes into the crankcase from the throttle body - where it has already been metered - through the little hose that connects to the valve cover oil fill tube. Obviously, that line must be blocked under boost or you'll pressurize the crankcase. When you block it, you must provide some other path for make-up air to enter the engine when vacuum is pulling through the pcv valve. Most people simply vent the valve covers. And when they do, they now have allowed a source of unmetered air to enter the engine. At high vacuum, it comes INTO the crankcase through the breathers and gets pulled into the intake through the pcv valve. By the way, unmetered make up air is a fancy way of saying vacuum leak. How badly that messes up things I don't have a clue - seems like it gives some folks idle problems, and others don't notice it at all.
So, if you want to put breathers on to ventilate the crankcase better under boost, and you don't want unmetered air entering under high vacuum conditions - then you need to disable the pcv feature. With a vent on each valve cover, you can simply plug the pcv opening. Alternatively, some people just put a small K&N breather on the pcv line and vent it to atmosphere.
The challenges of that approach are that it's emissions illegal - not that that matters to a lot of folks - and over time breathers make a hell of a mess no matter where they're located. An oily mist will cover everything in sight.
I think if it were me, I'd route big lines (at least 1/2") from both the back of the manifold (pcv location) and one valve cover to a large catch can mounted down low in the compartment. And then I'd vent the catch can. That way, at least some of the oil would be trapped by the catch can. Any oil mist would be in the vicinity of the can, not all over the top of the engine. And there'd be no unmetered air entering the engine. Some people try to route the crankcase blow by into the suction side of the compressor. But be careful - if you're running a blow through maf then the oil in the blow by can and will eventually foul the hot film throwing off your maf readings.
So, if you want to put breathers on to ventilate the crankcase better under boost, and you don't want unmetered air entering under high vacuum conditions - then you need to disable the pcv feature. With a vent on each valve cover, you can simply plug the pcv opening. Alternatively, some people just put a small K&N breather on the pcv line and vent it to atmosphere.
The challenges of that approach are that it's emissions illegal - not that that matters to a lot of folks - and over time breathers make a hell of a mess no matter where they're located. An oily mist will cover everything in sight.
I think if it were me, I'd route big lines (at least 1/2") from both the back of the manifold (pcv location) and one valve cover to a large catch can mounted down low in the compartment. And then I'd vent the catch can. That way, at least some of the oil would be trapped by the catch can. Any oil mist would be in the vicinity of the can, not all over the top of the engine. And there'd be no unmetered air entering the engine. Some people try to route the crankcase blow by into the suction side of the compressor. But be careful - if you're running a blow through maf then the oil in the blow by can and will eventually foul the hot film throwing off your maf readings.
The problem is with most superchargers you mount your meter before the blower. The meter reads the air being drawn in. The computer adjusts for the extra amount of incomming air and adds more fuel. If the BOV vents that air to atmosphere then all that extra fuel that was added to go alone with that air has no where to go but be wasted causing a huge rick condition all of the sudden. Usually that air is vented back into the intake tract, abd still being used in the engine, just not in as big of a mass beacuse it is re-directed temporarily.
If you mount your meter after the blower, with your BOV before the meter, you certainly can vent to atmosphere. The BOV is venting the air before the meter has a chance to read it so it does not add the extra amounts of fuel.
Problem is, with your stardard pass side mount kits, you don't have room to mount the MAF after the head unit, and a BOV also.
If you mount your meter after the blower, with your BOV before the meter, you certainly can vent to atmosphere. The BOV is venting the air before the meter has a chance to read it so it does not add the extra amounts of fuel.
Problem is, with your stardard pass side mount kits, you don't have room to mount the MAF after the head unit, and a BOV also.
TT91
Active Member
Haven't really touched the car all summer. Rebuilt project TT, went with some slightly larger turbo's, completely rebuilt the system(will have pics soon). I've been kinda discouraged with my car. Wasted a lot of money building the stroker only to ruin everything.sirsureshot39 said:
sirsureshot39 How loud was it when it was vented? Why did you change it? I just want the noise. Turbo cars with blow offs sound sick. I have a HKS blowoff as well on my aftercooler and its currently bieng installed now as i type. However he is trying to figure out how to route the hose from blow off back into system. He is thinking of routing it right before blower. The guy i bought the aftercooler from was running it open atmoshere but he said he tightened it way down. What do you guys think?
P.S siresureshot email me some pics of your BOV routing if you can
P.S siresureshot email me some pics of your BOV routing if you can
88stangmangt
Active Member
s-trim with bov on dyno
This one sounded pretty cool i think it was a hks ssq bov. it was in the power adders forum
http://208.37.31.68/~ryan/ryan tuning day.mpg
This one sounded pretty cool i think it was a hks ssq bov. it was in the power adders forum
http://208.37.31.68/~ryan/ryan tuning day.mpg
88stangmangt
Active Member
88stangmangt
Active Member
dsoes anyone know who's car that is????? i would like to know what kinda BOV and how much boost he has i have the same s/c he does.............
DirtyD916
Active Member
88stangmangt
Active Member
what kinda blower? 14psi is brave if that is a production block....................i plan to run 10........ 12 being max.................
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