tici is right. no way will there be a suction on it. i think the positive pressure along with the vaccum line keep the valve open. once there is boost pressure in the intake manifold (when the throttle plates are completely open)... the pressure should be equal in the vaccum line and the pressure side piping. thus letting the spring in the valve hold the diaphram closed.

basically to answer your question.....the throttle body (at idle, and low throttle) keeps the pressure in the manifold negative....basically keeping the blown air from entering. thats why the bypass is there.....to relieve the pressure from the blower.

 

I just got my car running today, and have the bypass venting to the atmosphere. At idle there is a a$$load of air coming out of it. Just curious, other than noise reduction, what is the benefit of recirculating it back to the intake side of the charger?

BTW my MAF is on the pressure side after the bypass.

Thanks
Mike

 

Does anyone know where I can purchase Bosch part # 0 280 142 108? Anyone know if AutoZone can get this part?

Raymond

 

Well, there's really no "benefit" per se with recirculating it back in.....it's just that that's how the system (well, most anyway) is designed with the MAF being placed before the supercharger (not boosting through the MAF). If you're set up the way they were designed to be, the air that is entering the supercharger and being pressurized has already been metered and therefore needs to stay in the intake system. Best way to keep it in the intake system is just to recirculate it back via the bypass valve.


Here is a question for the rest of you, though, regarding the bypass valve venting to atmosphere and placement of it in the tubing system in relationship to the MAF.

I got my FMIC all piped in and the bypass valve is now venting to atmosphere and is placed BEFORE the MAF. So we're not venting metered air. Well, I fire up the car just yesterday and it runs like poop now. WOT is fine, but during cruising I'm getting nasty popping, loss of power, all that. I haven't had a chance to log it with DataMaster but will soon. Here's the thing though....the MAF and bypass valve are in the tubing that runs from the blower TO the FMIC. And the bypass valve is located about a foot away from the MAF in the piping.

What do you guys think is now causing all of these problems while cruising? Did I create a bunch of turbulence just before the MAF with the bypass valve there? Is that now causing the MAF readings to go haywire, or could it? I haven't changed the programming yet, its the same as it was with the regular S-Trim non-intercooled setup (with MAF not receiving boosted air). With the setup and programming how it was before, I would get some mild bucking during crusing, but nothing as bad as it is now. Any suggestions? Would it be best to move the MAF over to the FMIC->TB piping instead? Any helpful hints would be appreciated. Sorry for hijacking the thread, I'll probably make my own thread with this question later on anyway....

 

well let me be the first to ask you......

HOW DID YOU PUT A FMIC ON A VORTECH??!!!! Son, everyone has been asking how to mount a fmic on a vortech. did you re-clock the head unit? come on now.....show some pics!!!!!!

 

I've got a HKS SSV BOV. Previously had a recirculating ATI blow-off valve. The HKS is a poppet type Sequential Valve and is sealed so all high pressure air is @ the intake. It pops open when the manifold reduces in pressure (getting off the throttle). It runs good, but, I too am confused. It runs strong. I've been dumping air after the MAF (a sin???). MAF is located in compressor intake side. Don't really know what's happening here?

 

if your dumping air after the maf your car cannot run correctly. the PCM measures the amount of air using the maf. so it assumes that all the air passing through the maf is entering the engine. if your Bypass valve is dumping some of that air out then your car is at the very least running rich as hell.

others can give you more info on what will occur with this situation. but there it is in a nut shell.

i believe that the car should still run okay at WOT because the Bypass is closed so all measured air will be entering the motor.

BRYAN 94 Z28......WHERE ARE THOSE PICS?????

 

Alright alright....I went out and took some pics....

Here you go:

http://home.mchsi.com/~shortb2002/tubing.JPG
http://home.mchsi.com/~shortb2002/tubing1.JPG
http://home.mchsi.com/~shortb2002/tubing2.JPG
http://home.mchsi.com/~shortb2002/tubing3.JPG

You can see generally how I routed the piping up in the engine compartment. However, I still have the front bumper cover on (obviously), so you can't see the routing of the pipes at the actual FMIC.

Check out this page: http://www.jlturbo.com/fmic.htm

I used the same intercooler (OBX) and mounted it in the same manner they did. I just ran the piping differently.

You can also see that I did not re-clock the output from the S-Trim. I initially did try to do that, but the sway bar would have been in the way if I had rotated it to discharge at 6 o'clock....not to mention that the bracketing wouldn't allow me to do it. I wasn't willing to part with the sway bar, so we (friend who works for a pipe bending company) worked the mock-ups and he did some pre-bending....then we did some cutting and final fitting and he welded the pipes back together and there you see the finished product.

Also, I answered my own question from above just tonight. I put DataMaster on it, and with the blower operating, the MAF readings were ALL over the chart. I took the blower belt off, tried it again and the MAF readings were perfect. The bypass valve is creating too much turbulence right in front of the MAF. I am going to mount the MAF in the passengers' side pipe (after the intercooler) and extend the wiring harness to it and it should be fine (I hope ).

 

all of the pics ive seen where the maf was relocated, the valve was directly before the maf, and everyone says it works fine. i wonder why yours is having problems. maybe its just sensative. my car needed the maf messager from procharger to run right with the blower. no one else ive talked with has needed it with lower boost applications. kinda weird. hopefully you have found your problem.

thats cool you did it that way. on one of the posts talking about doing the FMIC with the vortech, i mentioned doing it your way but i thought it may not be possible to run the pipe between the radiator and the brake lines-n-stuff. glad to see that i can be done.

looks like you put a lot of time in though. also looks like you ditched the ac condensor....that probably made it easier huh?

jeremy

oh, show some pics of the front end. did you cut the black part, with the bow tie, out to let air in?

 

Why have you installed the MAF before the intercooler?
Is there a technical reason?
I can imagine that it well see the air move a little later than if it was closer to the TB.
...if it makes a difference...

 

What did you do about relocating the coolant overflow container, it look like you might just have a hose routed down to dump it under the car. I'm guessing you relocated the battery to the rear? I'm about to do the same thing to mine, intercooler is already mounted but I've got to finish assembling the engine and have the supercharger in place befor I can start mocking up the intercooler plumbing. I'm probly going to do it just like yours, I dont think there are any other options without adding an excessive amouont of tubing.

 

I mounted a blue recirculating overflow tank from Jegs underneath where the original overflow tank was. I'll take better pics of where it is located later on. I just used the screws that came with the tank and mounted it to the plastic wheel well molding. It worked out really well.

The battery is relocated to the rear. You can see the brass junction block I used to hook everything up. It was the only way I could get the room I needed to run the plumbing.

I had to move the radiator forward a bit to get that pipe to fit on the driver's side.

I'll get to the rest of your questions when I get home from work later on tonight. I'll try to take some more pics for you guys, too.

 

Take note though, in the pictures you can see that I had to move the radiator forward a bit to make clearance for that 3" pipe to fit in there. I simply drilled new holes in the radiator support top and moved it forward about 2" or so. (this did result in needing to clearance the hood some to get it to shut correctly) I did also take the condenser out, as you mentioned. The A/C didn't work anyway, so I gained a lot of space with that stuff out of there.

No, not yet. I'm going to try to keep the front cover as it is. I was thinking about fabbing up a couple of scoops to set in the foglight holes to direct the air to the FMIC.

 

*sigh* Looking back on it, I used a VERY weak reason to not put the MAF over on the TB side of the FMIC piping. I just didn't want to jack with the wiring and extend it over to that side. I didn't figure there was any advantage or disadvantage to putting the MAF before the intercooler, but maybe I'll get lucky and it'll get better readings up closer to the TB and iron out some of the bucking and stumbling on its own.

 

Back on topic.. breakmyfootoff hooked me up with his used BPV and it works like a charm. It purges lots off air at idle like it is supposed to. The problem with my old one was a poor seal in the valve/plunger. There was actually a vacuum leak past the seal to the atm. Now I'm venting to the atm and I <barely> got the new tube configuration to stay together w/out flaring on the ends (blowthrough MAF). The only other thing I had to do was open up the throttle blades a bit because the air it used to be getting at idle is now being purged.

Anyone using a high mileage Bosch BP might want to check its operation. Mine was ~8 years old with ~30K miles.

The car runs good with the new valve and MAF relocated. Some sound is noticeable through the valve as well as a distinct smell from the exiting air!