rx7tt95

I feel like sort of a *** for asking this but my brand new GReddy BOV doesn't seem to be doing it's job. I must qualify this however.

Engine is brand new, breaking it in currently. I have a big single turbo. I'm keeping boost to about 3kg/cm2 and revs below 4K rpm. I get surging when I let off the gas abruptly and the BOV is adjusted all the way out, ie. screw is about to fall out. Vacuum source is being taken from just behind the throttle body and vacuum line connects to the top port on the BOV, the bottom is left open as per GReddy's instructions.

My initial thought is that I must have the stiff spring in there and I need to swap it out for the standard spring...anyone else ever experience this?

My current thought is that it should still open when the engine returns to vacuum regardless and the spring determines how much boost it'll hold peak as in the standard may start to leak at say 15psi whereas the heavy duty will hold 40. Random numbers. I've pulled the BOV off and checked to see that the valve did move.

I've tried two different vacuum sources with the same result. Perhaps I need to reference the bottom port to a source before the throttle bodies? Thanks in advance.

mr_vaughn

iTrader: (1)

i had an issue with my type S because the Diaphram had a crack/split in it and it leaked and did not vent properly.
i have not see the type R diaphram.
So just pull that puppy apart and check the diaphram and that it is sealed correctly.
also do a vacume test on the BOV as per the FSM works sort of the same on the Greddy type S .

rx7tt95

It's brand spankin' new. GReddy says that it won't operate "normally" at anything less than 5psi and not to worry about it. Apparently it's just not enough pressure to open it regardless of whether it's the standard or firm spring.

MakoDHardie

If you're going real light on the throttle and not seeing any boost build at all, I wouldn't expect the bov to vent, especially with an R valve. I wouldn't worry too much if you're running a good turbo and not pushing anything. Compressor surge at vacuum or neutral levels of boost shouldn't be a problem. Once the engine is broken in, you will be able to drive the car differently and get everything to function the way it should. I'm assuming you have it welded on a flange to an intercooler pipe. In that case if you were really worried about it, you could always swap it out for a Type-S until your engine is broken in, but that would only give you minor action at positive boost levels. I think the same thing will happen with that valve because the spring is not the actuator of the valve- the vacuum chamber above it is. I'd break the motor in the rest of the way and start opening it up a little bit. You'll start getting some action out of that valve then.

lane_change

iTrader: (20)

Is the flange for the Type R and the Type S the same?

rx7tt95

I don't believe so...I think the R flange is larger. It's welded on the throttle body side of the IC plumbing. Switched to a different Type R BOV just to try, also brand new. Same thing initially, but now it seems to be opening at modest boost levels. The only variable being that I can now rev a bit higher. I'm going to swap them back tonight but first I'll take both apart and see if the springs are different. Mine takes quite a bit of effort to open using my thumbs.

Mako, yes, being light, but still producing positive boost, around 3kg/cm2 for now. Just passed 1500 miles so she's going on the dyno soon. I too believe that the valve should open when it sees vacuum, but it's still required to vent against spring pressure. The spring's tension is constant regardless of vacuum level so in order for it to open it must have enough vacuum/boost to push the valve open. At this point I really believe I have the heavier spring in there. I'll open them up and post some pics.

3isacharm

Is there a minimum amount of boost that should be run on the type R BOV? The reason I ask is because I was told a couple of weeks ago I was told that I shouldn't run the type R BOV with my BNR stage 3 twins because I won't be running enough boost (max boost of 18 - 19lbs). Instead this guy wants to trade me his super sequential and some cash for my typr R BOV. Any input would be appreciated!

rx7tt95

According to GReddy's site, the Type R should be used, generally speaking, with hp levels above 325hp. No real psi rating. I have heard the Type S can leak at higher boost levels. I compared the two type R valves. Mine most definitely has the stiff spring and the other has the standard. The standard BOV with small boost levles will blow off, the stiff spring will not allow bleed AT ALL. I'll try it when I'm running a bit more boost. Thing is, I don't plan on running 14psi+ with EVERY shift. I'd have to drive at WOT all the time with the stiff spring. So the standard spring it is!

3isacharm

Thanks for the info. I should hae around 400hp with the bnr's. It all depends on the condition of my twins when I take them off of my car. If there cracked to hell then I am going to just have to go with a single setup. I am torn between the T04B (60-1) or the gt35/40. Oh well decisions decisions