Running without a BOV

[MattL]

Curiosity has struck me again, and probably for the worst.

My mate is running hig CA18DET without the BOV and gets quite an impressive flutter... and whilst I know the side effects of doing this is additional strain on the turbo, what are the main pitfalls of it?
I only ask as I've always loved flutter but never understood what damaged is caused and why it's always said to be so unhealthy for the turbo.

Thoughts / Opinions on this would be great. Thanks

 

[Smutt]

Pitfalls....?

A mates R32 Gtr runs without a BOV (mid 11's), and when your cruising around in it on partial throttle you can keep the flutter going for ages (20 secs), like skipping a rock across a pond.
I know what you mean, it sounds pretty neat.

i've run without one for a while in the past and thought boost response was quicker between quick changes, goes against the ideal tho...?

i'd lilke to see some times on the drag strip with and without a BOV on the same night... interesting experiment......

 

[DIESTI]

fulli sick dosing!!!!!

no 100% sure if it damages anything but it would be a good experiment as above...

 

[MattL]

it's easy enough for me to test at the next track night, however when it comes to gear changes being that Im Auto I don't have too many issues with loss of boost so I maintain a fairly good pressure the whole way through the process.

I must admit, I love flutter, really really love it. But if there is potential for damage or causing too many issues, I'd not do it.

 

[Rockabilly]

Matt 20psi on a guage is 20psi that the motor isn't digesting yet. Slam the throttle body shut & that 20psi @ 6k becomes 50psi in a few seconds
before the T/B & the turbo comp wheel cops that pressure trying to stop the turbo, while the exhaust is still spining the exh wheel.
It's of no benefit to have no bov on an auto at the drags & a fucken no no on the street. Carpish ?
Cheers !

 

[bazeng]

Not good for the turbo mate..

I believe SSSVET lost his comp wheel due to no bov..
The nut on the comp wheel came free and killed the turbo..

You can get that flutter noise with a turbosmart type bov at low boost.

 

[MattL]

Not good for the turbo mate..

I believe SSSVET lost his comp wheel due to no bov..
The nut on the comp wheel came free and killed the turbo..

You can get that flutter noise with a turbosmart type bov at low boost.

afaik the turbosmart ones run an adjustable dial which allows you to adjust release pressure so you still dose at low boost. I did notice from the test I did earlier with the BOV disabled that it flutters more on the low end rather than under high load.
I'll probably get a turbosmart or keep it stock for a while.

 

[BMGTZ]

in the old days......before blow off valves. it was a pain in the arse putting hoses back on. taking your bov out is a great way to find all those loose clamps :blink:

 

[CLuTZ]

SSQV

 

[SIVART]

SSQV

they sound great, I would have another one of them

but I like the AVO plumb back as you can adjust it to flutter and use the venting at higher boost

 

[htgsr]

I haven't got a BOV simply cos the car didn't have one when i bought it an i haven't got around to putting one in, ive got a mate pushing 320ish kilowatts out of his Silvia and he has never run one an never had a problem either, in saying that i know of a few that have spun the nut off an destroyed themselves. As mentioned above the dousing sound is the intake side trying to stall while still be forced around by the exhaust side so it cant be good.

 

[D3bb4]

lack of BOV can sometimes generate enough pressure to hold the throttle open. Can get pretty hairy.

flutter = jarring the turbo. Would also partly subject it to bending forces, so would screw up the bearings faster.

Plumb-Back BOV is ideal. The compressed air helps re-spool the turbo.

Quicker between gear changes might be if you shift fast enough, there might not be anough time for the throttle to close completely, so the lines essentially remain pressurised the whole time. That said, if there's enough of a pressure difference to actuate the bov between changes, then there would be a significant pressure build in the pipes before the throttle, so when you re-open it, you're likely to get a pressure spike entering the motor.

I'd run one if wanting to keep the turbo and motor working for longer.

 

[milkandoj]

Ive got an evo 8MR bov and if i back off when its still building low boost it flutters a bit. If the spring inside the bov is hard it'll do it. But i definitely wouldn't want it when the cars on full boost. Ive got it all plumbed back but i can hear it.
Ive watched the boost gauge on a car without a bov and all the air hammering the turbo back an forward for a fair while, cant be good for wear. People inspect the in and out shaft play on a turbo, running no bov would make this much worse.

Leave the no bov, flutter to fully sick Nissan drivers i say.

 

[rob323]

Autospeed did some proper testing of all this if anyone is interested in the physics going on behind the flutter.

 

[turbovr4]

apparantly if your on high boost e.g 15psi and above then having no BOV can pssibly snap the turbo shaft on the tdo5h turbos.me personally have never had one and still have both my original tdo5h 14b turbos that come wirh my jap import vr4 motors,and driven for the last 15years with no problems.But i only run between 10psi and 14psi.I just never ran one because the original plumback was leaking on boost because it was stuffed.And i tried one of the first turbosmart ones years ago but i could never stop it leaking at idle.Got the shits with car nearly stalling.Now im just slack and didn't bother with another

 

[evopwr]

just get a v-port turbosmart valve and have best of both worlds. Flutter at 10psi (or whatever you adjust it to) and atmo venting at higher pressures.

 

[CLuTZ]

I've run a few cars without b.o.v's- never had an issue.

Considering alot of high HP cars (albeit race cars that get their turbos rebuilt/replaced frequently) don't run b.o.v's, then I wouldn't see them not running one on the off chance the impeller shaft would break and they'd be out of the competition?

O.T: turbovr4- wanna sell your ZR4? I'm serious....!

/o.t

 

[turbovr4]

I've run a few cars without b.o.v's- never had an issue.

Considering alot of high HP cars (albeit race cars that get their turbos rebuilt/replaced frequently) don't run b.o.v's, then I wouldn't see them not running one on the off chance the impeller shaft would break and they'd be out of the competition?

O.T: turbovr4- wanna sell your ZR4? I'm serious....!

/o.t

Sorry, wont be selling this car,always wanted a hatch back vr4 ever since i saw the first sedan vr4 when i was 20years old.took 20years to find one{as rough paint as this one is}

 

[JayRome]

... currently built a VT V6 TT with the GTR turbos, and with out a BOV the pressure physically moves the front turbine wheel forward on both turbos with enough back pressure when the throttle shuts, but when stand still there is no shaft play.......

 

[JAP63]

I dont reckon you would ever see a problem with turbine wear in the average life of an engine from this issue. Roller bearings are robust, especially when loaded radially. On stock boost youd never see an issue, at very high boost you might, but still, ive never seen an issue.

Most factory cars run a plum-back for noise requirements and also compressor response after a gear change, it makes no sense to slow impeller speed, hence the use of it.