wantboost

iTrader: (2)

On my past setups I've always ran my blow off valve on the hot pipe pre-intercooler. It seems pointless to waste air the intercooler has cooled (plus added ricer bonus, they're louder lol) plus having the bov on the hot pipe insures that it does its job of preventing compressor surge.

I ran 14psi (at the intake manifold, unknown what pre intercooler pressure was) with a turbonetics raptor on the hot pipe with a very efficient PWR core (not eBay) so there wasn't enough pressure drop across the intercooler to cause issues with the valve opening under pressure (signal line came from the intake manifold, post throttle body as usual) and it worked flawlessly, no surge ever.

Now my new setup will be seeing pressures somewhere in the 20-25psi+ area, still hoping to use my Greddy type r on the hot pipe, pre intercooler.

My only concern is now that I'll be running pressure ratios that high, that pressure drop across the intercooler will cause issues. I run my pressure signal lines for everything from the intake plenum, so it would be 20-25psi at the plenum, not at the compressor outlet. I know even the best of cores have pressure drop but I don't know what sort of differential I'll be looking at as the setup isn't done yet.

Thoughts, opinions?

EDIT: Title meant to say blow off valve, all this talk of wastegates got me confused for a second lol

wantboost

iTrader: (2)

No one has am opinion or advice?
*sniffles

SiRCiviC94

My bros 750hp talon runs it where everyone else runs it. It shouldn't matter it's all a pressurized system

OneBadTurboCRV

Not to be mean BUT...

1.) You should know 3 hours isn't a long enough time to give people a chance to respond.
2.) You should have stuck with the wastegate story.... do you even realize how a BOV works?
3.) Pressure drop can be calculated and still doesn't have anything to do with where a BOV vacuum/boost reference has to be.
4.) Finally, you know 20-25 psi isn't even high enough to worry about even on a horrible intercooler.

Balor_Gr

The way i visuallize it is that the recirculation must start to take place to the area close to the throttle body.It would take maybe more time to put unwanted air out if you put it close to the compressor.I may be wrong.
On the other side i think there are turbos that have the bov on the compressor housing.Who knows.

wantboost

iTrader: (2)

Sorry Neva, I lost track of time

I know how a blow off valve works...

My concern in the pressure differential COULD POTENTIALLY cause valve lifting issues

Me and a buddy had a 20,000sq ft shop where we built nothing but 240s, modified/repaired FormulaD cars, etc,

I've cleared up a lot of compressor surge issues by moving the blow off valve to the hot pipe. Everyone says near the throttle body because that's where pressure builds up first... but a bov is not designed to save a throttle plate, we place them on the hot pipe because that prevents any pressure from ever reaching the turbo.

Just looking for opinions, I don't think I'll have issues with a Greddy type r with a stiff spring, unless I run the lower assist port. Here's a pic of what I'm talking about..



The fake type s came with a car, fluttered horribly and caused terrible surge with both springs in, hooked up the assist line to the pipe it was on and no more issues (that pipe mount by the way) but that was only at 14psi on a small turbo

You can also see the assist port on my real type r

Here are other valves I might use/test



Thoughts, other examples, etc?

4genaccordfreak

Hmm. From my experience, the placement of the BOV on the cold side was usually good enough, as long as you run something that is working correctly and has the efficiency to evacuate large volumes of air in a high-pressure application. Something like a Tial Q or a Greddy-R.

Since the throttle-plate is the blockoff point, all the built up air/pressure will have to revert back down the cold side, through the intercooler and vent at the hot side location if you want to run it that way.

Whereas on the cold-side (mid-way up like usual locations), it will efficiently evacuate all the air built up at the throttle plate and (since the turbo is still spinning and moving air) continue to ventilate all the air as long as the engine is in vac.

If you were having surge problems, I wonder if your previous BOV was efficient enough?

I do know that some high-pressure applications do benefit from running dual BOV's. One on the cold side, one on the intercooler itself or hotside pipe.

Either way, I don't think your surge issues are as bad as you think they are. If you have a proper working BOV, the surge-back should be minimal, even if you can hear a slight fluttering from the compressor. I would doubt it is even close to enough to do any damage.

vtechjunkie

iTrader: (2)

Putting my bov on the hot side is what started my surge issues. Switching up the ic setup, so I'm going a different route this time.

Charlie Moua

iTrader: (3)

there should not be anything that you need to "test" as for placement.
Your splitting hairs

Get a tail or turbosmart bov (50-52mm)
EVO/DSM guys love them, they work flawlessly, don't make annoying sounds & are proven... and for them 25psi is considered low boost.

wantboost

iTrader: (2)

I only had surge issues because the greddy knockoff that came with the car sucked and would stick. I had a back pack full of parts and tools in my carry on when I flew to Indiana to buy my s13

Among them was my turbonetics raptor. I got so tired of hearing the surge that I stopped at a random gassstation and swapped it out and adjusted the spring preload. Never had a surge issue.... ever