RBs with no bov?

[gawdzilla]

Anyone running this? Before I get flamed by everyone who claims the BOV is oh so critical to prevent air from shuffling back and killing your turbo, I'm considering deleting mine for response and b/c recirc is not an option.

Most rally/race cars dont have them, and from advice I have gotten from some engine builders, it really makes no difference in the longevity of the turbo. Anyone have experience running without one?

Has anyone ACTUALLY seen a turbo's life shortened by compressor surge? besides reading what all the bov manufacturer's webpages say of course...

[SeVa-S13]

The turbo on my first RB20 was pretty well shot; the original owner in japan had blocked off the recirc hose so I got surge like crazy and no audible BOV sound. I don't know if that's what caused it but that was my theory.

[rb240det]

When I upgrade my turbo to a larger one, I had some issues with my BOV opening. Being my daily driver, I had to drive it around for weeks in that condition. With less than 1K miles on the new turbo, it already had significant side to side shaft play, which had to coincide with the compressor surge it was experiencing due to the BOV not opening all the way (or at all sometimes). That's just my experience though....

[Darius]

This is just my reasoning since I do a lot of water hammer modeling which is basically surge but with water. If you have a mass of air moving in one direction and then close the valve at the end of the line, a shockwave is sent back through the piping back towards the compressor at a such a high rate of speed that in that short of piping, it's practically instantaneous. Once this wave hits the spinning compressor wheel, it puts a lot of force on it in the opposite direction. The wave then bounces back towards the throttle body and reflects off of it again. Repeat until friction dissipates the surge wave. That is why when you hear surge it kind of flutters. The wave is bouncing between your turbo and throttle body between each flutter sound.

The blowoff valve is designed to release pressure above a preset amount to allow the turbo to produce boost but blow-off excess pressure above that amount to protect the turbo and associated piping. When you're dealing with large diameter water force mains, a surge pressure of 320psi or greater is easily produced by closing a butterfly valve at the end. A surge relief valve is installed in this instance to protect the pumps and I would recommend you do the same with your motor. Recirc or not, run with a BOV to protect your turbo.

The reason I think some rally cars do not run them is because they can go through turbos like popcorn and don't have to worry about longevity. They are more concerned with extreme performance.

[krayton]

i killed my t3/t4 turbo cause of the no bov.

1.2bar killed my turbo. i still got some nice miles out of it though

but iirc a dual ball bearing turbo will last longer under that condition.

[Bluefire]

I've been running no BOV for quite some time now and my turbo seems fine. I'm sure it has some detrimental effect on the turbo, but I doubt I will see it anytime soon. If there is any major wear on my stock turbo I think the bigger culprit will be increased boost not compressor surge.

-Bluefire

[Joe]

no BOV will shorten the life of the turbo unless you have one thats specifically built for a high surge enviornment.

racecars use them but how often are they rebuilt? just because its on a racecar dosent mean its good for longevity. ill bet money no turbo on a rally car goes more than 2000 miles.

i used to scream at krayton about this, and i was right.

and a BOV will also give you better response. you are practcally stopping the turbo when you remove the BOV under a high throttle shift. that hurts your respool pretty significantly.

[nukeone]

Then answer me this, oh wise ones... the RB20DET in a Cefiro shipped from the factory without the BOV - did Nissan make a mistake?

[SeVa-S13]

Then answer me this, oh wise ones... the RB20DET in a Cefiro shipped from the factory without the BOV - did Nissan make a mistake?

Yes, and same with the CA.

BOV's become more and more important and boost levels rise, so it's not *as* detrimental on low boost; but who here wants to run stock boost?

[projeks13]

question... why wouldn't you want a bov....

[Kansei240sx]

Nissan did that on a few other cars as well, for luxury reasons to keep it quiet, and they'd put what is known as a POV, Pop off valve... .Non intercooled turbo 300zx's have pop off valves that are basically ways of keeping boost in check and keep the motor from over boosting...

For instance, you want to run 12 psi but the POV is maxed out at 10 psi, 2 pounds of pressure will be leaked out of that pop off valve so that the engine stays safe from being leaned out and the turbo from over boosting.

[xsvhp]

IMO, a bov is not needed unless you're running serious boost, above 18 psi. Most factory applications get by just fine with just a wastegate.

[Gold Digger]

Then answer me this, oh wise ones... the RB20DET in a Cefiro shipped from the factory without the BOV - did Nissan make a mistake?

Also the C33 Laurels. I have been told that those cars were not intended 16 years ago for what people use them for now, plus they were all automatics. Every single one of them. Really no need for a BOV in a semi luxury family sedan. Even though the C34 and C35 Laurel turbo RB's did have them. I don't know why though.

Nissan did that on a few other cars as well, for luxury reasons to keep it quiet, and they'd put what is known as a POV, Pop off valve... .Non intercooled turbo 300zx's have pop off valves that are basically ways of keeping boost in check and keep the motor from over boosting...

For instance, you want to run 12 psi but the POV is maxed out at 10 psi, 2 pounds of pressure will be leaked out of that pop off valve so that the engine stays safe from being leaned out and the turbo from over boosting.

And where would said pop off valve be located. If my car has one, I would like to know where so I can remove it. I plann on upping the boost on my C33 in the very near future, and I want to make sure I am not going to have any issues with this.