How many people run without a BOV or Recirc? - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

carlreeve · 22nd August 2006, 06:44 PM

How many people run without a BOV or Recirc?
Any running issues, failures etc etc.

skyline69_uk · 22nd August 2006, 07:10 PM

Only the mugs

.

It's there for a reason, they appeared in the turbo racing world in the very early 70's to improve lap times and life of the turbos and there is no reason whatsoever to remove even today as they still do the same job. Some rally cars etc can do without them as can any car that has an open throttle shifter which isn't the GT-R.

This question is asked everywhere lol...

http://www.dsmtalk.com/forums/showthread.php?t=159821

R32 Combat · 22nd August 2006, 07:12 PM

Er, I don't use a BOV or re-circ. I use 2 overboost valves venting to atmosphere.

SteveN · 22nd August 2006, 09:11 PM

Quote:

Originally Posted by skyline69_uk

It's there for a reason

Purely noise suppresion reasons on 99% of standard cars fitted with em

IMO they not ANYWHERE near as vital as most people think.
But most people who know that still fit them in a "better safe than sorry" manor.

Can usually find a lot more people with proof its had no noticable effect than people who can prove running with one has helped them.

Lot of AFM equipped cars NEED them as airflow going backwards past the AFM messes the fueling up tho.

Performance reasons are generally laughable and despite a lot of searching, seems to have never been proven. Just tons of internet/book/tv rumour and myth, like "wastegate chatter" and other such bollocks.

Turbo reliablility reasons are genuine depending on boost level and turbo strength.

Some turbos are fine without one, I ran 30psi held boost for over 12k miles with no DV at all with no ill effects, hell, I ran agressive ALS at the same time just to make it worse, lol.
Did the same at 23psi on another car, and know countless people doing the same.

Theory has it that they do something, reality is what they do is far more often than not not even slightly noticable.

carlreeve · 22nd August 2006, 09:40 PM

The reason I ask is my car came with BOV's (not recirc ones) and all my recirc tubing has gone so no chance to retrofit to recirc.
BOV's mess up the AFM's but also leak and only hold boost to the spring rate of the BOV. Stronger springs can hold more boost but then BOV pressure release has increased also, same effect as not having a BOV at all?
Remove them and the leakage has gone, no more pressure relief but at a measily 1 bar does it really matter.

So do I invest in some new BOV's (as mine are past there best) or blank them off and run BOV-less.

Thats my choice but was wondering what the Skyline population has tried.

SteveN · 22nd August 2006, 10:23 PM

I doubt anyone in the UK skyline world has tried with none, its not the most daring scene ever!

I dunno how well the ceramic turbos will take it, but otherwise id have a go personally as never done me anything but good in the past.

But id never advise someone tho, as tried it on tons of cars, just never a GTR.

tyndago · 22nd August 2006, 11:32 PM

The Super Taikyu N1 race cars didn't have them. Not the 2 cars we have.

I am not that much of a fan of them. Most of my old experiences of them have been leaking under high boost. The leak does more damage by over spinning the turbo.

RoboPope · 22nd August 2006, 11:47 PM

it depends more on your ecu runs anything else, if you have a MAP sensor then who gives a shit but if you have metered air then you could over fuel and stall from time to time

pokey · 23rd August 2006, 08:30 AM

i've been "temporarily" running with blocked-off recircs for about a year now. had a bad one that wouldn't shut even at idle. figured blocking the outlet was a quick and easy fix till i got a replacement. haven't had any real problems.

SteveN · 23rd August 2006, 08:49 AM

Quote:

Originally Posted by tyndago

The Super Taikyu N1 race cars didn't have them. Not the 2 cars we have.

I am not that much of a fan of them. Most of my old experiences of them have been leaking under high boost. The leak does more damage by over spinning the turbo.

Careful mate, someone on the internet might call you a mug cause of stuff theyve heard but never tried

Glad someone else can back me up here, as id tried it many many maaaany times, but as ever on here, I expected the internet backlash, lol...

ExScoobyT · 23rd August 2006, 08:52 AM

BoVs do not rely on the spring pressure to hold them shut against boost, they have boost pressure applied to the rear of the diaphram via the actuation pipe. The spring is only there to define the opening point in relation to manifold vacuum and to hold them shut during spool when there is a delay between pressure on either side of diaphram......

Philip · 23rd August 2006, 09:36 AM

My car didn't have one over the past year, for what it's worth.

Phil

skyline69_uk · 23rd August 2006, 09:54 AM

Quote:

Originally Posted by SteveN

Careful mate, someone on the internet might call you a mug cause of stuff theyve heard but never tried

Glad someone else can back me up here, as id tried it many many maaaany times, but as ever on here, I expected the internet backlash, lol...

I'm only going by what half a dozen professional auto engineering books and a friend who spent 3 months with the Renault F1 team say but maybe they're all mistaken.

I know none of this from experience unfortunately just from what the text books and auto engineers say (I was going to be one but ended in computers instead (I'm the mug this time) and work with several people who did it at Uni etc).

I'm sure there are many situations when they are not needed or indeed cause more issues than they fix but I have never seen an AE textbook that ever stated those conditions - only pictures of the damage caused due to the lack of them Steve. The problem is surge causes other failures to happen first that mask the real cause and it appears like something else e.g. inbalance is the cause etc when the surge caused the metal on metal contact over time that in turn caused the inbalance. Only a professional test environment shows the real cause and AEs will look to see what caused the inbalance while everyone else just put it done to "wear" or a "dodgy turbo".

ExScoobyT · 23rd August 2006, 10:02 AM

Indeed - you will not achieve 160 000km durability without a dump valve. Does this concern the average GTR owner / tuner, probably not. It does not change the reason for the component being used!

SteveN · 23rd August 2006, 10:07 AM

Quote:

Originally Posted by skyline69_uk

I'm only going by what half a dozen professional auto engineering books and a friend who spent 3 months with the Renault F1 team say but maybe they're all mistaken.

Yeah, cause TURBOS are such a top subject on a modern F1 car

And for what its worth, when F1 cars were turbod in the 80s, did they run dumpvalves? Not on any ive seen, and I know someone who builds historic turbo F1 engines for a living...
Neither do any LeMans/GT cars ive seen actually...

Must be mugs

22nd August 2006, 06:44 PM	#1 (permalink)
carlreeve GTR Register Member Join Date: Mar 2004 Location: Derby Posts: 130	How many people run without a BOV or Recirc? How many people run without a BOV or Recirc? Any running issues, failures etc etc.

22nd August 2006, 07:10 PM	#2 (permalink)
skyline69_uk GTROC Member Join Date: Jan 2005 Location: NI Posts: 2,833	Only the mugs . It's there for a reason, they appeared in the turbo racing world in the very early 70's to improve lap times and life of the turbos and there is no reason whatsoever to remove even today as they still do the same job. Some rally cars etc can do without them as can any car that has an open throttle shifter which isn't the GT-R. This question is asked everywhere lol... http://www.dsmtalk.com/forums/showthread.php?t=159821 __________________ Do it right or don't do it at all. "You're a pack of a*holes!" - Jim Richards 1992. スカイライン６９　UK Last edited by skyline69_uk; 22nd August 2006 at 07:20 PM.*

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22nd August 2006, 07:12 PM	#3 (permalink)
R32 Combat New Users Join Date: Jan 2004 Location: Berkshire Posts: 4,357	Er, I don't use a BOV or re-circ. I use 2 overboost valves venting to atmosphere.

22nd August 2006, 09:40 PM	#5 (permalink)
carlreeve GTR Register Member Join Date: Mar 2004 Location: Derby Posts: 130	The reason I ask is my car came with BOV's (not recirc ones) and all my recirc tubing has gone so no chance to retrofit to recirc. BOV's mess up the AFM's but also leak and only hold boost to the spring rate of the BOV. Stronger springs can hold more boost but then BOV pressure release has increased also, same effect as not having a BOV at all? Remove them and the leakage has gone, no more pressure relief but at a measily 1 bar does it really matter. So do I invest in some new BOV's (as mine are past there best) or blank them off and run BOV-less. Thats my choice but was wondering what the Skyline population has tried.

22nd August 2006, 10:23 PM	#6 (permalink)
SteveN GTR Register Member Join Date: Aug 2002 Location: Just off the M5/A40 Posts: 7,209	I doubt anyone in the UK skyline world has tried with none, its not the most daring scene ever! I dunno how well the ceramic turbos will take it, but otherwise id have a go personally as never done me anything but good in the past. But id never advise someone tho, as tried it on tons of cars, just never a GTR.

22nd August 2006, 11:32 PM	#7 (permalink)
tyndago GTR Register Member Join Date: Oct 2002 Location: LBC , CA Posts: 2,400	The Super Taikyu N1 race cars didn't have them. Not the 2 cars we have. I am not that much of a fan of them. Most of my old experiences of them have been leaking under high boost. The leak does more damage by over spinning the turbo.

22nd August 2006, 11:47 PM	#8 (permalink)
RoboPope GTR Register Member Join Date: Sep 2001 Location: Berkshire / Oxfordshire Posts: 477	it depends more on your ecu runs anything else, if you have a MAP sensor then who gives a shit but if you have metered air then you could over fuel and stall from time to time

23rd August 2006, 08:30 AM	#9 (permalink)
pokey GTR Register Member Join Date: Sep 2003 Posts: 22	i've been "temporarily" running with blocked-off recircs for about a year now. had a bad one that wouldn't shut even at idle. figured blocking the outlet was a quick and easy fix till i got a replacement. haven't had any real problems.

23rd August 2006, 08:52 AM	#11 (permalink)
ExScoobyT GTR Register Member Join Date: Jan 2004 Location: `down sourfff Posts: 1,052	BoVs do not rely on the spring pressure to hold them shut against boost, they have boost pressure applied to the rear of the diaphram via the actuation pipe. The spring is only there to define the opening point in relation to manifold vacuum and to hold them shut during spool when there is a delay between pressure on either side of diaphram......

23rd August 2006, 09:36 AM	#12 (permalink)
Philip GTR Register Member Join Date: Jan 2002 Posts: 1,854	My car didn't have one over the past year, for what it's worth. Phil

23rd August 2006, 10:02 AM	#14 (permalink)
ExScoobyT GTR Register Member Join Date: Jan 2004 Location: `down sourfff Posts: 1,052	Indeed - you will not achieve 160 000km durability without a dump valve. Does this concern the average GTR owner / tuner, probably not. It does not change the reason for the component being used!