tial BOV not operating correctly

[EVOSTi]

my tial BOV hasnt worked properly since i got it so im after some thoughts.
when driving and i change gears, i hear obvious compressor surge as if the BOV is not opening. however if i have my head under the bonnet and give the car a flick of the throttle i can see that the BOV opens quickly and completely then closes slowly so it should work. the only time i actually 'hear' the BOV working when driving is when i have boost up around the 18psi mark.
so when i had the car on the dyno today i paid attention to the BOV on each run. at gear changes off boost or low boost, there is compressor surge. when the boost is wound up a bit, say 14psi, i hear loud compressor surge then a split second later i see the BOV open. does anyone have any ideas what could cause this?
my theory is that its not getting enough vacuum. the hose from the BOV is connected to a fitting on the manifold which has three hoses coming off that, one for MAP sensor, one for fuel reg and one for the BOV.
i just dont want to drill and tap a dedicated fitting into the mani if its not needed.

thoughts?

[jonra23]

Definitely sounds like vacuum port problem, how big is the fitting they are teed to?

regards
jon

[EVOSTi]

not sure on the exact size, but its the standard vacuum fitting on a 4age manifold, its not very big. having said that ive seen countless turbo 4a's with this setup and i havent heard of this problem. but then again its a damn huge BOV so perhaps i will need to tap a new fitting to the manifold, just a PITA cause ill have to remove it if i dont want fillings in the head

[Jorrs]

i had the same problem mate, easily solved though
create its own vacum source of the manifold.

drill in and run it through the welsh plug ! , will work like a charm !




hope that helps !

[EVOSTi]

so you had the same problem and a dedicated line fixed it? cheers for that, looks like i might be taking the manifold off in the near future

[Jorrs]

yeh exact same thing.. couldnt get enough vacum to the BOV from any other source.. as i have other applications running of T piece, so ran it into the other side of the manifold through the welsh plug and made it dedicated, u wont have any problems then !

[BigWorm]

I'm running my BOV signal line off the throttle body, mostly just because it's closer/neater. Any reason you can't do this?
As for tapping the welsh plugs, 4A manifolds don't have them (I'm 99.999999% sure of this, but I have been known to be wrong before. )

[BigWorm]

Although where you have it really shouldn't be the source of any problems.
Is the BOV adjustable? If it is it sounds like it's adjusted up too tight. If it's not, sounds like the spring may be too tight.

[Jorrs]

I'm running my BOV signal line off the throttle body, mostly just because it's closer/neater. Any reason you can't do this?
As for tapping the welsh plugs, 4A manifolds don't have them (I'm 99.999999% sure of this, but I have been known to be wrong before. )

ahhh ok yeh no idea hey, im a 3S man personally
just trying to help out with what i new about the same situation i had.

[oldcorollas]

it may not be a matter of "enough" vacuum... since pressure has nothing to do with area..

rather, the Tee piece is likely too small (it's internal openings) to remove the air at the rate required.... so a larger line means you remove more air (to the same level of vacuum) faster.

why not take the time to run each line (MAP, fuel pressure reg, and WBOV) off seperate fittings? and since WBOV just needs good fast vacuum signal, put it where the vacuum will be highest on closed throttle?

[Mos]

The black fitting for the map sensor and fuel pressure reg has a restrictor in it to smooth out the vac reading (i'm pretty sure). As your BOV needs to draw a large volume of air (as Stu has alluded to) this restrictor is giving you the problem.

I'd advise against giving the map sensor and fuel pressure reg their own dedicated ports if there's nothing wrong with the current setup. If the job of the restrictor is to smooth out the vac signal (I'm not 100% sure that's how it works), removing it could cause problems if the ECU (and FPR) are relying on it instead of electronics.

Any reason you can't T into the brake booster line? (and use a couple of fittings to make the line smaller).

Mos.

[oldcorollas]

ahh, thanks Mos, i didn't realise they had a restrictor in there..
but the WBOV should still have dedicated line no? (or at least Tee'd before the restrictor?)

[jonra23]

Make sure the restrictor is not between the vacuum point and the BOV Tee,place it further down the line.

Generaly recomend people dont use the Vaccum brake line for a vauum source, it is one vaccum line you want to maintain maximum integraty of.

regards
jon

[BigWorm]

As for tapping the welsh plugs, 4A manifolds don't have them (I'm 99.999999% sure of this, but I have been known to be wrong before. )

Ok, you can now believe without doubt the next 99999999 things I say, as I was wrong about the welsh plug.
Still, it wouldn't be the best place to run it from anyway, as it's at the other end of the manifold, and requires tapping. You can see in this pic where I ran mine from, with no probs whatsoever.

[EVOSTi]

ok so heres the update.

today when i had some spare time at work, i blocked of the line i was using (it was t'd with the boot guage) and tried something different.

first i was going to remove the yellow sensor as it isnt used and get a barbed fitting to fit and use that. i removed the fitting on a spare manifold i had at work and it had clear access to the inside of the manifold.
but instead what i did cause i didnt have much time was use the fitting on the manifold that the breather from the rocker cover goes to, which was blocked off. you can see what i mean in this pic:


heres a pic of the BOV so you get an idea:


and heres a pic of the stock vacuum fitting which has one for the MAP, one for the fuel rail which has the boost controller t'd to it and one for the boost guage which did have the BOV t'd to it:


so after i connected the BOV to the breather fitting i still have the same problem. can it still be that i havent got a good enough feed? the fitting is definetely big enough and is not blocked (i blew through it) but maybe inside the manifold the passage gets really small and tortured?