Jump to content
SAU Community

Blowoff Valve Question Help

GTRAAH

By GTRAAH,
in Engines & Forced Induction

 Share

Recommended Posts

paulr33 Grand Master

paulr33

Posted
Posted

nope. why would it?

all it does is recirculate excessive built up pressure when you close the throttle body to prevent compressor surge.

there is no perfomance gains to be had from having a given type of blow off valve or recirculation valve.

the aftermarket ones are usually ass and either make the car run like ass or make silly noises.

GTRAAH Experienced

GTRAAH

Posted
  • Author
Posted
nope. why would it?

all it does is recirculate excessive built up pressure when you close the throttle body to prevent compressor surge.

there is no perfomance gains to be had from having a given type of blow off valve or recirculation valve.

the aftermarket ones are usually ass and either make the car run like ass or make silly noises.

OK cool i just thought the aftermarket ones release more pressure then the normal ones becasue they can be bigger which means they clear out more of the pressure built up

paulr33 Grand Master

paulr33

Posted
Posted

no the standard ones are fine, please do not change them, aftermarket bov's are pointless and no gain

i suggest doing some reading of the upgrade threads to avoid wasting $ on pointless changes / upgrades etc

T04GTR Grand Master

T04GTR

Posted
Posted
^ No. Aftermarket ones seal on idle - which is BAD.

stock gtr ones are fully open at idle... wich is why they need to be plumbed back if using air flow meters.

i tryed two wanker hks ssq's, absolutly shit compared to stock. massive delay and nowhere near as much flow.

T04GTR Grand Master

T04GTR

Posted
Posted

in a perfect world the bocv would have such a light spring that its just enough to seat the valve and hold no more than 3 or 4 pound. dont forget its the boost pressure acting on the opposite side of the valve that seals it not the spring tension.

so in reality a proper poppet style bov with a rubberised seat (stock gtr) can never leak boost. ever. so long as the bov has got the same boost acting on its diaphram as it got in the pipe it sits in.

sh@un Grand Master

sh@un

Posted
Posted

Here's a handy one for a track car: If you run MAP-sensored load metering, you can get rid of the recirc' setup on OE GT-R and have them vent to atmosphere, and K&N happen to make some of those little 'breather filters' that have exactly the same ID circumference as the OD of the factory GT-R bov outlet ports :D (you'll need the filters so you don't suck crap into the engine while running in manifold vacuum)

Pro tip. Fully hektic PSSSCHTTTTTT!!!! noise, if you like that kinda thing...

Deano 1 Mentor

Deano 1

Posted
Posted (edited)

im 99% sure if u run pods u can here the stock BOV alot louder. but hey.... i dont no cause i got stock BOV and a stock Airbox. i cant hear anything, every now and than when driving next to a concrete wall on the freeway or somthing other than that, my engine bay looks factory, and my car is quite as...... till i cut her loose that is... than Kaki regu starts making some noise. haha

Edited by Deano 1
Don Dada Mentor

Don Dada

Posted
Posted
having them leak @ idle/low RPM eliminates compressor surge when using larger turbos.

same as the factory piping. It was all designed that way for a reason.

Doesn't comp surge occur when the turbo is making positive pressure in which case the stock bov will be closed anyway?

For what its worth i had a greddy recirculating valve which was shut on idle on my 25 and had no probs with idle,stalling when stopping etc etc.

jrm Veteran

jrm

Posted
Posted
im 99% sure if u run pods u can here the stock BOV alot louder. but hey.... i dont no cause i got stock BOV and a stock Airbox. i cant hear anything, every now and than when driving next to a concrete wall on the freeway or somthing other than that, my engine bay looks factory, and my car is quite as...... till i cut her loose that is... than Kaki regu starts making some noise. haha

There's a sorta 'baffle' thing in the stock airbox that you can remove that will make the stock BOV much louder if you remove it - if you like that sort of thing.

scotty nm35 Grand Master

scotty nm35

Posted
Posted

R31Nismoid is correct. Most stock blowoff valves have a small bypass hole about 5mm in diameter to stop the low throttle surge, I have blocked mine thinking it would be ok but there is the odd flutter when on boost at low revs and throttle opening.

(OO)SKYLINE(OO) Grand Master

(OO)SKYLINE(OO)

Posted
Posted

Stock GTR BOV can handle above 300kW's.

Aftermarket BOV's have no gain.

Only reason to change if you are running a ridiculously high amount of boost and the stock BOV cannot handle it any more.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
Doesn't comp surge occur when the turbo is making positive pressure in which case the stock bov will be closed anyway?

For what its worth i had a greddy recirculating valve which was shut on idle on my 25 and had no probs with idle,stalling when stopping etc etc.

Comp surge can occur anywhere on a compressor's map.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Erelyes
      Ceramic turbine damage to engine - what did yours do?

      By Erelyes · Posted

      Ha, well, it's been.... a bit of a journey. Things have taken much longer than I'd hoped. I'll probably put up a thread at some stage. Hopefully soon. The car's not done any kms since my update in June though, put it that way.
    • Dose Pipe Sutututu
      M35 Aftermarket Fuel Pump

      By Dose Pipe Sutututu · Posted

      Here's the chart for fuel pressure vs. current draw, assuming your base fuel pressure is 3 bar and you run like 0.5bar boost on WOT, you should only momentarily hit 9amps here and there. (Ignore my prev post, I cannot read a chart these days it seems)
    • GTSBoy
      RB25 Drama's

      By GTSBoy · Posted

      Those comp test results are not hideous. Whether they are accurate or not (ie, when that comp tester says 140 psi, is the real pressure120, 140 or 160?) is unknown to us. The state of the battery used to crank it over is unknown, etc etc. Many people around here would say that the absolute values and the spread are perfectly fine to just add boost and keep going. I personally would be happier with a narrower spread than that, but even the diff between 125 and 145 is not terrible. That one cylinder at 125 though, has probably copped some damage relative to the others. You should inspect the valves seeing as you've got it open. Do you know how to measure installed ring gaps? That, and an inspection of the rings themselves, is how you will determine whether they need to be replaced. If you're not good to do these things, take the block and the pistons and rings to a shop that is, and ask them for the go/no-go on them. Do the bores need a hone at all? If so, you might well be justified in getting some different pistons in order to get away from the ring supply problem. Whether you're happy to spend a lot more money right now, on more gear, rather than less money, but an amount that looks stupid given that you will only get a handful of rings in exchange for that money, is for you to decide.
    • iain_ST44GA
      M35 Aftermarket Fuel Pump

      By iain_ST44GA · Posted

      also possibly backed up to my filler and shat down it! 🤣
    • Julsmadrid
      RB25 Drama's

      By Julsmadrid · Posted

      Ok so i would love some advice here please, i purchased an R33 a few months back and its had a few mods done to the engine, its an RB25det running a Master ECU, 1200cc injectors, bigger turbo, oil cooler, oil filter relocation kit, Spool H-beam rods, acl/ross pistons. When i removed the motor from the vehicle (as its getting a respray) i thought i would compression test it and these are the following results. Cylinder 1-145psi, Cylinder 2-143psi, Cylinder 3-125psi, Cylinder 4-145psi, Cylinder 5-140psi, Cylinder 6-135psi this test was done with the motor on the ground and powering up the starter motor. I dropped the sump and found broken oil squirters on cylinder 3,5 and 6. I was told my rings are probably worn so i stripped the motor completely to get a new set of rings for it. The trouble is no one has these rings anywhere and they have to be custom made by Ross over in the states and will cost about $600+$200 delivery. My question is how can i tell if my rings are at fault and if they are still ok and is this price ok for a set of rings?
×
×
  • Create New...