Bov Ughhhh.... Please I Am Not A Wanker.....

[CEF11E]

OK.

First of all my need just so coensides with 1000 new forum posts about BOV's and I would like to add I am not after any sound or cool looking shiny metal thing to bolt to my intake. I need a solution...

I have a VG20DET Auto nissan and have recently put an RB25 turbo, 3" exhaust, highflow cat, Retuned ECU, Water/Methanol Injection kit, transmission cooler ect ect...

The car came WITHOUT a BOV from the factory and was fine without one untill I added my list of goodies...

Since adding the bigger turbo it seems to make a huge Whoosh coming off the accelerator as all the air goes through the custom airbox/pod. It also feels slower coming onto boost between gears.. The car is putting out 204RWKW and the tune is almost perfect so it has nothing to do with leaning out or anything silly like that. Sounds like a need to recirc some of that air...

I know what I am doing with mechanical/electrical stuff most of the time and I reprogrammed my EPROM myself, Fitted the turbo and all other bits myself and built my water meth kit myself so I am not a silly teenage dirtbag...

So... my questions are

Will a R32 or R33 standard BOV handle 14PSI? or should I get another aftermarket Recirc BOV.

My space is limited as there is about 12" inches between the turbo and the throttle body. Also I have a water/meth kit installed and I don't want the BOV to Recirc Methanol and Water thru my turbo so it will have to plumb in before the mist nozzle giving me a total of about 6" to work with.

Any advice would be greatly appreciated...

[Wink]

Yes the stock bov will handle 14PSI

[FATGTS-R]

If they fit in the space you have the factory GTR bovs would be a good choice.

[R31Nismoid]

It shouldnt be slower on boost after a gear change.

Its an auto. There should be little difference.

IMO the BOV has less of an effect as you are on the loud pedal the whole time, so no real loss of load. If you put an ATMO BOV on there you wouldnt even hear it go off between gear changes...

Hrm...

[CruiseLiner]

It shouldnt be slower on boost after a gear change.

Its an auto. There should be little difference.

IMO the BOV has less of an effect as you are on the loud pedal the whole time, so no real loss of load. If you put an ATMO BOV on there you wouldnt even hear it go off between gear changes...

Hrm...

very true, only goes off when backing off the throttle. worth protecting the turbo though considering the pressure on it when the air suddenly comes back out the air filter.

[TTT]

so I am not a silly teenage dirtbag...

it's true.. he's decent..

hahahaha

my under standing is that you are saying it feels slow to come on boost when you've come off the gas, not between gears.

yes the stock skyline bovs will handle 14 psi of boost.

but you might have problem mounting it.

You might want to consider a BOSCH bov.

they are plastic, good for about 15 psi and are sold from repco type places for about $45.

the reason I say this is because it is a universal fitting bov.. as in it doesn't have to be bolted in to place like the skyline ones do.

just reading through what you've done, you're a handy bugger aren't ya?

hahahaha

well done.

see what I mean by mounting..

skyline/vr4 bov

bosch bov

[CEF11E]

thanks guys,,,

much appreciated.

What happens is that I floor it from take off and it gets to 8000rpm and changes into second, the turbo goes WHOOSH and then starts spooling again.

What it seems like is the shaft speed is really high before the change and between 1st and 2nd it slows down as there is nowhere for the pressure to go. Once 2nd is engaged it lags and 1/2 a second later it builds boost again.

On the boost guage it never reads below 9~10 psi between changes.

BOV is a cheap bit on insurance anyway so i will get a standard rb25 BOV seeming as it is a rb25 turb,

Cheers guys.

[paulr33]

what you are seeing and experiencing is the fundamental reasons why the BOV was designed and setup to correct;

turbine shaft being flung back to a lower speed on gearchange

to reduce the stress placed on the compressor wheel during geachange

so yes fit a BOV and all should be well

[BezerkR32]

I agree with Nismoid, should not see any boost drop on gearshift in a automatic. BOV will help in back off situation, but somethings not right there., if anything you might see a spike on shift.

It shouldnt be slower on boost after a gear change.

Its an auto. There should be little difference.

IMO the BOV has less of an effect as you are on the loud pedal the whole time, so no real loss of load. If you put an ATMO BOV on there you wouldnt even hear it go off between gear changes...

Hrm...

[JCMarshall_Law]

From what you have described, yes a BOV will help. Although it is not quite what I expected on an auto.

Interesting problem you've got there, I started writing a technical response but found there were too many things I don't know about your situation. I'd need to talk to you to work out what is happening.

[someonestolecc]

You wanker...

Just kidding. Just use any nissan bov? silvia, skyline, whatever. I know exactly what you mean about the shitty feeling, happened first time I put my atmo on and had it screwed real tight (no bov effect).

You can do a pretty good setup with the right sized radiator hose for plumbing back. I'd just rip out the pipe and have welded on it a flange thingy, then measure of the distance and run down to repco/whatever to buy a radiator hose that fits the bill. Plumbacks galore!

Also isn't the methanol sprayed right before the intake plenum? if so you shouldn't get too much blow off coming back through the bov into the intake, just put some sort of filter on it!

PS great work on the figure - you're the man!!! When ya comin back to sydneY!?!

[TTT]

so foot is flat on floor, gear changes, foot still on floor.

I don't see how a bov will help this at all.

it doesn't go in to VACUUM at all (you said stays around 9psi) so how will the bov even open to circulate this?

although, maybe the stock skyline (R32 or R33 is same.. by part number even) which has that little bleed hole under it next to the bov piston will allow circulation during AUTO gearshift.

If you want to TEST, I can help you out on the weekend with stock bov on my car.

TT

[CEF11E]

Thanks TT and CC

but i am in Canberra now

I will be buying a stock BOV as it should really have one anyway.

If that dosen't fix the problem i will cross that bridge when I come to it.

I just increased my timing by +3 deg from 4000 to 4900 (change point into second when flooring it) and it has helped the situation but it dosen't hit like a hammer when going into 2nd.

As this may be useful information to others I will keep this updated when I have added the BOV.

[R31Nismoid]

The turbo should not be "whosing" when the car is upshifting... is your foot FLAT to the floor when this happens?

If so you have other problems as the TB should be wide open and not causing anything.

Installing a BOV wont fix the problem you are having unfortunately.

Time to visit a workshop or someone that knows a bit more

cheers

[TTT]

nismoid.. was that last statement supposed to say WON'T fix the problem?

CEFFIE - you moved to Canberra? why on earth would you do that?

what.. sydneys daily shootings is not good enough for ya?

hahaha

[Abo Bob]

Maybe what you have is something like reversion (I think it's called) or surging.

What I'm trying to say is perhaps the engine when it drops revs down on the change of gear is suddenly unable to ingest the large amount of air being shoved down it's throat creating a temporary partial blockage which forces some of the air backwards through the turbo.

Pure speculation based on incomplete knowledge.

Hey cef11e - are you going to/have you done a write up on the water methanol injection and subsequent tuning? Is that what you used my old fuel pump for? I'd love to hear the full in depth story.

[R31Nismoid]

nismoid.. was that last statement supposed to say WON'T fix the problem?

yep

edited

[CEF11E]

Maybe what you have is something like reversion (I think it's called) or surging.

What I'm trying to say is perhaps the engine when it drops revs down on the change of gear is suddenly unable to ingest the large amount of air being shoved down it's throat creating a temporary partial blockage which forces some of the air backwards through the turbo.

Pure speculation based on incomplete knowledge.

Hey cef11e - are you going to/have you done a write up on the water methanol injection and subsequent tuning? Is that what you used my old fuel pump for? I'd love to hear the full in depth story.

I used your old fuel pump as a pickup pump in my tank Abo bob. It's working a treat . I will do a writeup on the meth kit as soon as I get some concrete results and I have been running it for a few weeks.

I had to rewrite an eprom to suit after the meth kit was fitted as the AFR's were to rich running a mix of 50/50. Before fitting the meth kit I was making 154RWKW with 10psi and bugger all timing(as i had no intercooler and i didn't want to risk pinging) and after fitting it I am running 14psi with 10+ deg more timing and making 204RWKW. I am really supprised at the power level as it's a stock rb25 turbo. But the dyno operator said it was to do with the massively increased timing and higher octane.

BTW there is no sign of knock at all.

I am really pushing the envelope and may drop the timing back and reduce the boost a little in the colder weather as my AFM is reading 4.0V at WOT over 7000RPM... injector duty cycle is also getting into the mid 80's.

I am injecting using a 2.75US gallon hago oil burner nozzle @ 110psi. I am in the process of setting up an intake temp probe and some other bits. But I am really happy with the performance...

[CEF11E]

nismoid.. was that last statement supposed to say WON'T fix the problem?

CEFFIE - you moved to Canberra? why on earth would you do that?

what.. sydneys daily shootings is not good enough for ya?

hahaha

yep the only real thing canberra has going for it is 0deg winter nights and my cushy new job. + saving for a house

You got yourself a new ride i see nice one dude... looks really nice.

[TTT]

cheers.. write me an eprom.. ahahahhaha