Blowoff valve

[F=MA]

Just for giggles, I put one of those cheapo blowoff valves from Ebay on the Mustang. I don't know how it's gonna work or what adjustments/range it has. I'm really only interested in it working on high vac during shifts and such, to smooth day to day driving.

Here's what I used, any insight appreciated:

http://cgi.ebay.ca/ws/eBayISAPI.dll?...Pr4_PcY_BIN_IT


F=MA

[speedytang]

I posted a couple of weeks ago about using one and it works great. I have it set to open at -20 vacuum and I also gained boost so my Bosch unit was not holding.

[F=MA]

I just tried this out, with the spring tension set pretty low, as the valve came from the factory. It makes the car easier to drive, as I don't have to time the crack throttle on the shift just right for it to be smooth. It still makes full boost so, I guess the job is done. It makes no more noise than before it was installed. I do wish I had a vac pump, to see where it actually cracks open but, seems to work so....

F=MA

[NMNOTCH]

I also gained boost so my Bosch unit was not holding.

I also had one of the bosch units fail a long time ago they seem to not be able to handle the heat.

The BOV should open at 3 to 5 inches of vaccuum on a mass air equiped car.

[speedytang]

If the BOV was set to open at 3-5" of vacuum a MAS car won't run because it would be pulling non-metered air into the system.

[F=MA]

My car is SD, so I don't care but, it appears to be opening around 20+ inches of vac. It's not opening at idle, when I'm pulling 17 or so. It bangs open lightning fast when the vac hits 25 on the overrun. Mine's not a Bosch unit but, it's gotta operate similarly.

F=MA

[speedytang]

With SD that is the same setting as a MAS because you would be sucking crap from under the hood into the intake since the BOV is not filtered. I dropped about 40 degrees from the intake air temperature.

[NMNOTCH]

If the BOV was set to open at 3-5" of vacuum a MAS car won't run because it would be pulling non-metered air into the system.

On any MAF car you run the discharged air from the blow off valve back to the inlet side of the blower keeping it a closed system and therefore keeping the air metered. Also the opposite is true undern vaccuum conditions where the air is pulled through the meter from the inlet side of the blower.

3 to 5 inches is a safe point because it allows boost pressure to be released almost instantaneously on decel which is the way it should be.

[F=MA]

How would it suck crap up anyway? It's on the intake side of the throttle plate and the only time it opens is when there's and outgoing pressure wave from the blower on it and high vacuum from the manifold supplied to the nipple.

F=MA

[speedytang]

If you have the BOV set at 3-5" the valve would always want to open with a weak spring and it would become a vacuum when the BOV opens. You don't need to return the air back on a MAF car and no negative effects at all of matter of fact my intake charge is 40 degrees cooler not recycling the hot air back around thru the blower again.
Since the BOV only need to open during boost and the throttled closed it only takes a second to release the damaging pressure and the EECIV never even notices.

[NMNOTCH]

If you have the BOV set at 3-5" the valve would always want to open with a weak spring and it would become a vacuum when the BOV opens. You don't need to return the air back on a MAF car and no negative effects at all of matter of fact my intake charge is 40 degrees cooler not recycling the hot air back around thru the blower again.
Since the BOV only need to open during boost and the throttled closed it only takes a second to release the damaging pressure and the EECIV never even notices.

You must run the air back to the inlet of the supercharger on any MAF application. Yes venting it to the atmosphere will keep AIT down but effects:

1. Meter reads incoming air before the supercharger on a pull through application, Venting this air at the discharge area at idle, part throttle, or decel conditions will cause a rich condition .

2. part throttle surging or stumbling

3. Idle issues where the iac motor cannot respond fast enough due to the ECU correction needed to make up for the rich condition.

There should be no issues with the valve opening at 3 to 5 inches of vaccumm. If it is opening under boost than it is either faulty or not the correct BOV for the application

[speedytang]

None of the problems as you state has happen to my car or the dozens of cars in my area. Of matter of fact the car had a couple those issues at random and have not had them since changing. My C&L meter does such a better job now and the car runs better. I think the return style bov was causing metering issues and now that does not happen.

[speadfreak]

I'm confused now. My car pulls way more vaccum than 3 - 5 at idle. Seems to me that this would leave the BOV open all the time at idle, allowing unmetered air to enter the throttle body or let air that had already been metered escape (not really sure which way it would go). I blew the discharge tube hose on my car yesterday. It created a small opening between the silicone hose and the supercharger outlet........the car would barely idle. I see no problem at all with setting the BOV to 20....that way the valve would stay shut during idle and blow off the pressurized air when shifting under boost. Under hard acceleration, the "rich condition" created by the air being blown off during shifting would hardly be noticeable. I would like to put a BOV on my car, just for the simple fact that between shifts I can hear the blower whine on my car, I'm pretty sure this is because of the throttle body being closed but the blower still pushing air from the motor not being wound down yet.

[NMNOTCH]

Attached is a blow off valve, most likely not the one you are using, however the principle is there. If you follow what I tell you than you will not have a problem. When you use a fuel injection system with a mass air meter there must be no air leaks from the meter to the throttle body. This is case closed, you must run the blown off air back into the inlet side of the blower, this is why they make the provisions to do so and tell you specifically to do as such in the instructions. You are not creating an air leak by letting the air return to the inlet, this is a closed system. By venting the BOV you are creating an air leak which is then unmetered air. I would do research on basic ford fuel injection and learn about the adaptive strategy and reference tables of the ford EEC IV before you doubt that there will be any drivability issues. I know the sound of the blowoff valve sounds "COOL" but if thats what you really must have I would look into a programmable engine management system that is MAP based so you can happily ditch the MAF and vent the BOV anywhere you want.

As for the 3-5 inches of vaccuum issue the reason why it is set here is so it will be keeping pressure off of the impeller at idle and part throttle, areas where the valve should be open and I highly doubt you see 20 inches in these areas. If you have any doubts feel free to contact Vortech Engineering and ask for Andy 805-247-0226.