[Mahonroy]

Hello, I had a question about blow off valves and forge diverter/dump valves... Ok, so, I understand that streight from the intercooler or turbocharger a tube will lead into the throttle body, and on this tube is where the blow off valve would be located, and from the vacume line comming off the intake manifold would connect streight to the blow off valve, so when the butterfly valve closes, there will now be a vacume inside the intake manifold, which will then trigger the blow off valve to open letting all of the pressurized air escape so your turbocharger doesn't sieze etc., but my question is this... the MAF sensor reads the air that is passing through, so it expects that the engine is going to burn it, so the computer is going to mix in the correct amount of fuel, but the problem is that when the blow off valve lets all of the air escape, the computer thinks that all the air is going to get burned, but instead the air isn't there so its going to be super rich. So, is this a problem? And also I heard that a Forge Diverter/Dump Valve is a mechanism that will solve this problem, but I don't understand how one of these devices work so just curious if someone could explain this to me, thanks! Any help is appreatiated

 

[2GTS]

Try looking for a recirculating blow of valve. I don't know how they work but that is what alot of people are using to solve the maf/rich mixture issue.

 

[Elantra2.001]

For most cars with a MAF, you need to run a recirculating BOV. Because of the location of the MAF sensor, the engine expects the engine to be stuffed with a certain amount of air so it adds fuel to compensate and when the air isnt there cause it gets vented, the engine can actually bog down or even shut off from too much fuel. One way to get around this though is to put the BOV in front of the MAF, but then you can have the opposite problem where depending on where your remote is attached, air could have passed the BOV and the MAF already but because of the venting, there may be more air in the engine than the ECM expects and you get a momentary lean condition. This usually isnt too harmful, but the best solution is to recirculate. You get most of the sound still anyway. Or you could convert to MAP.

 

[Mahonroy]

So how does a MAP sensor work anyways? Or to refrase the question; how is a MAP car different from a MAF car? Thanks for the replies!

 

[OdessitPashka]

MAF - mass air flow, reads how much air passes through it and send this info to the computer and computer adds just enough fuel!
MAP - manifold absolute pressure, measures pressure inside of your intake manifold, and sends reading to the ECU and ECU adds fuel. Our map sensors will only be good for 4.5 PSI of boost, but it shouldnt be too hard to change the voltage with a simple clamp and get a lot more out of it!!!


So how does recirculating BOV work?

Thanks

 

[Mahonroy]

I was trying to find information about these but couldn't find much. So, if a car is a MAP sensor car, the pressure is read from the intake manifold (is it hooked up to the PCV system or something?) so after the air is "in" the engine is when it knows how much is there, so if you have an atmospheric blow off valve and the air gets bypassed its ok because the air doesn't get read until after this point. Now for the MAF sensor, the MAF sensor goes before the turbo, so when the blow off valve gets triggered, the engine is already to mix in the amount of fuel for the air that is currently getting blown out into the atmosphere, causing a rich burn, which I guess can sometimes cause flames to shoot out the back of your exhaust pipe everytime you shift lol. So then I was trying to find information on recirculating blow off valves but I couldn't really find anything. I tried finding pictures of engine bays with a recirculating blow off valve installed on it so I could try and see how it was hooked up/how it works, but couldn't find any. I am just confused; so since the blow off valve isn't limiting the MAF signal or anything, this means that the air still needs to get burned, while the turbo isn't trying to press against pressurized air and sieze up, so somehow the air still is going into the intake manifold somehow, I don't know, I don't understand how it works...anyways, I found two clips, the first clip is this car driving around with no blow off valve, and you can hear the turbo siezing (sounds not too good!), and the second clip is the same exact car but with a recirculating blow off valve installed, here they are...
Turbo Siezing Clip:
http://www.wpi.edu/~jck15243/MOV00495.MPG
Recirculating Blow Off Valve Clip:
http://www.mazdamp3.com/members/505zoom/mov00533.mpg
So, I will go look and see if I can figure more about how the recirculating blow off valve works, thanks for the replies!

 

[OdessitPashka]

yea, it sounds like turbo is falling apart! well what i can tell you is that you wont be able to get enough fuel with stock FPR, so you will have to get a new one, and that FPR will be hooked up to the vacuum line. so when there will be no boost no fuel will be added, when you press your clutch, you loose boost, therefore you loose fuel goin into your engine.... so we should be fine wit our MAFs.

 

[Elantra2.001]

Our stock fuel systems are good for 300 whp. Its been tested in Korea. The problem is no one knows how to do it here. The reason you use a blow off valve is to stop the pressure wave from the turbo hitting the butterfly valve when its closed and working down the pipe again and hitting the spinning compressor blades. This can actually cause the turbo to spin backwards. Now there is still exhaust gass trying to spin it the right way and the torque can damage the turbo. Also the turbo now has to try and regain its previous momentum to create boost and that means that when you shift gears, there isnt the amount of boost there should be if the turbo had been able to continue spinning freely with a BOV. A MAF senso works by using a heated wire that is cooled by incoming air. The change in resistance caused by the cooling is what tells the ECM what amount of fuel to add. Its not quite that simple, but thats the basic idea. A MAP sensor is mounted on the manifold and reads how much pressure is present in the manifold greater than a perfect vacuume. So if you boost 10 PSI, the MAP actually sees 24.7 psi cause atmospheric pressure is 14.7. For a good example of MAF's and BOV's, look for pictures of DSM or Mitsu cars with aftermarket BOV's installed.

 

[OdessitPashka]

so, what shall people with MAFs do with their BOVs? just leave it the way it is?

 

[Elantra2.001]

If you dont want any engine bogging, then get a recirculating BOV. You will most like have issues if you do an atmospheric vent. I know some have managed it on DSM's but its not hard to do and it makes sense.

 

[Mahonroy]

Lol took me forever to find information on this thing, I tried calling it different names in the search fields and I got better results, here is all the information I could get at the moment, and some of it is still a little unclear:

First off, here are some different names for these devices:
Recirculating Valve
Diverter Valve
Compressor Bypass Valve

Here are some links to some information I found:
http://forums.vwvortex.com/zerothread?id=1200345&postid=13359804
http://wwwrsphysse.anu.edu.au/~amh110/Technical_pages/blow_off_valve.htm

And they refer to something as a "Fuel Dizzy"? I am assuming this would be the MAF sensor? Here is an image I made in photoshop...

So, the tube comming off the Recirculating Valve (being 3/4 inches in diameter I believe) would go down and connect to the tube inbetween the MAF sensor and the actual turbo? This is what I am under the impression of but I am not totally sure this makes much sence to me. What do you guys think and if you could explain some of these things to me that would be great! Thanks

 

[BlueGT]

Dizzy=distributor.

 

[OdessitPashka]

i read those links, but still confused....
is it really that big of a deal if we will be using regural BOV? wouldnt FPR be able to control fuel thats goin to the injectors when the pressure is dropped?

 

[Elantra2.001]

No OD, its not fast enough. The problem will range from a minor bog to the engine shutting off. You wont know until you try each application.

 

[OdessitPashka]

grrrr! that sux big time! so what shall people with MAFs do? put BOV before turbo and after MAFs?

 

[Elantra2.001]

If you have a MAF the best thing, IS A RECIRCULATING BOV! They arent hard to do. Just get a 1st gen DSM BOV and thats all there is to it.

 

[OdessitPashka]

I found out how it all gets done thanks anyways

 

[Mahonroy]

I found out how it all gets done thanks anyways

Lol can you share it with us then please? Because I don't understand how the recirculating BOV is supposed to be hooked up.

 

[OdessitPashka]

alright
u put your BOV anywhere between turbo and TB or intercooler and TB, connect one of the hoses to the pipe where BOV is route another hose all the way to a new bung which will be between MAFs and a turbo inlet.

 

[Mahonroy]

Dang I am confused... Ok so... lets say you have this tube which is going from your turbo streight into the throttle body. Now you take this tube, weld another tube to it so it comes off the side (smaller in diameter), and then you stick the BOV on the end of this. Now, from the intake manifold where the PCV system, vacume line hooks into it you splice a "T" connecter into the hose, and have one lead off into the BOV to make the BOV operate when there is a vacume present inside the intake manifold (e.g. the butterfly valve closed, because the gas peddle was lifted), now on the BOV there is a hole where the gas is vented when the valve is operating, and a metal tube comes off of this (3/4 inch in diameter), and this tube connects where? In between the MAF sensor and the turbo?