EPA - running no blow off valve at all - is this legal?

[JAPCAB]

Hi All,

Unfortunately copped a canary, and the cops did me the favour of reporting me into EPA; letter in the mail to bring my car down to EPA in macleod so they could test my car.

I went down to macleod - I passed the noise test no problems - 85dB with stock cat and exhaust. I was running an atmo BOV and i removed this and blocked up the hole; at the moment i am running no blow off valve at all (not even a stock one, i have blocked up the hole for that too)

They have said that I need to fit the stock pressure relief system. I disagreed with them on that point - My argument to this is that I am not running any blow off valve at all and no gas is venting anywhere at the moment. As everyone knows their problem with an atmo BOV is that the gas that it vents is not plumbed back into the system; as you all know the stock BOV does plumb back into the system. Despite what i said to them they insisted that the stock blow off valve be fitted back to the car - i explained that my current setup of no blow off valve at all is not venting any gas anywhere and not causing any detriment to the environment.

Anyone else had any experience with this? Will I have to fit the stock blow off valve even though I am currently running no blow off valve and not externally venting any gasses where an atmo BOV would?

thanks guys

[adznight]

I didn't even know you could do that. Where is the presure build up going? Can't be good for the compresor wheels etc?

[|PRESA|]

I beleive the non-bov setup is undertaken by alot of VL turbos, the build up of pressure is chopped up by the compressor wheel giving it that deep du du du sound.

Sounds cool but isn't too cool on ur turbo!

[JAPCAB]

I didn't even know you could do that. Where is the presure build up going? Can't be good for the compresor wheels etc?

The pressure build up stays in your engine, yeah i heard no blow off valve isn't good for your turbo; it definately sucks the big one for gear change response, but besides the fact that it may not be good for your engine - no gas is getting vented so surely its legal? A lot of guys with massive coolers run no blow off at all; it helps them get that 'WOOP WOOP WOOP' noise from the cooler.

[adznight]

Yeah that woop woop sound is the air being chopped as it hit the compressor wheel. Nice what to get shaftwheel play I've been told

I think you'll find that modifications to pollution systems are no go full stop. They don't know that it lets out less gas and to be honest I don't think they'd care that fact is it's different to factory specifications and those specs have been ADR approved for import Your car could run on air and they wouldn't care if you didn't have the engineer's papers to prove it.

I would just do your self a favor and get a stock blow off valve. It's not worth the hassel is it?

[|PRESA|]

Performance wise, is there a difference between a bov which is plumbed back in the system or venting straight out to the atmosphere?

[sky^rkt]

i was thinkin to get a plumbak bov and put it in the stock location, when i went to the epa with myc ar they didnt say anything about my stock bov being blocked off, there are alot of discusions about it being bad for the turbo or not, idle is shit gear shanges suck etc etc. on mine when it blockedo ff or not, it was the same shit no difference at all so yeh it just depends i guess. anyways good luck with it, best bet would be to get your stock bov fitted

[JAPCAB]

Performance wise i would imagine no; however the stock BOV is only good for like 1.2 or 1.5 bar, so if you are running higher levels of boost then you would need to look at an upgrade bov, however there may be aftermarket models out there that are plumbed back and can handle higher levels of boost.

With regards to EPA i'll just borrow my mates stock BOV and roll on down there again.......oh yeah that and a new O2 sensor, they did a test on my o2 sensor and its cactus!

Performance wise, is there a difference between a bov which is plumbed back in the system or venting straight out to the atmosphere?

[R31Nismoid]

Performance wise, is there a difference between a bov which is plumbed back in the system or venting straight out to the atmosphere?

yes there is, plumbed BOV is far better for performance.

Having NO BOV on a car that came with a BOV... is simply...

(who siad it?) ILLEGAL

So you do need your stock one if thats how thec ar came factory.

You cant argue the point at all.

VL's are different as they didnt come with one from the factory.

[predator]

don't argue with the EPA guys..

just fix it..

[Guest decksla]

there has been MANY arguments on forums, mags, workshops, etc, about the performance value of a BOV. i personally dont have one and im running 26psi through a 4 banger. in my opinion, my car spools alot quicker without the BOV as there is still pressure in the pipes when it comes to spool up again. with the BOV, all pressure is released and so starts the task of building up boost from scratch.

i dont want to get too technical about it, or say that one is better than the other, but im more than happy to run my car without one.

ive seen alot of japanese car vids and im positve 3/4 of them dont run blow off valves, again dont ask me why, i may be wrong, but engine pics and in car sounds dont lie.

on another note, my FJ standard, came out with an atmo venting pop off valve (ala ET turbo) does that mean i COULD run an atmo BOV if i choose too?

in regards to EPA, youve had it sweet for now, keep them happy and get it done.

dEx

[Horus]

moral of the story: stealth is the key

[R31Nismoid]

how does a BOV slow the spool speed of your turbo?

thats the most ridiculous coment i've ever heard

[Guest decksla]

how does a BOV slow the spool speed of your turbo?

thats the most ridiculous coment i've ever heard

you drive, you hit 20psi, you clutch in, 20psi worth or pressure goes out of your BOV, you shift, you have 0psi of pressure in your intake, you accelarate, 20psi of pressure builds up, repeat process.

you drive, you hit 20psi, you clutch in, 20psi worth or pressure fights against your impellers, you shift, you may have still around 10psi of pressure in your intake (depending on your shift), you accelarate, 20psi of pressure builds up, repeat process.

it may sound dumb but ive had my car both with and without the bov and i can DEFINETALY feel the difference in spool up time.

everyone is entitled to their own opinion, but unless you can tell me youve done the same and felt no or worse spool up times, all you are doing is speculating.

[Guest decksla]

http://www.autospeed.com/cms/A_1457/article.html

from someone more qualified to comment. and a better explanation at what im trying to say.

[adznight]

Just read it and it's doesn't say all that much, yeah it explains what they do and I can understand what you mean when you say you loose preasure in the intake piping but it's not going to effect the turbo spool. You'll find its more reliant on RPM I think

[WazR32GTSt]

does this make sense to anyone else?:

well if you have no BOV then when the throttle body closes, the boosted air travels back through the intercooler and through the turbo with the flutter sound as mentioned above from the air being 'chopped up'.

Then, the air passes trhough the AFM, which is a wire that cools with the flow of air thus the amount of cooling determines the airflow. So the AFM detects the air coming back out of the intake system and thinks its sucking air in so adds enough fuel to compensate.

Result? the car blows a puff of black smoke as its just run real rich for a second...

thus its bad for environment and the EPA is right (again!)

OR, am i completely wrong? (wouldn't be the first time...)

[R31Nismoid]

you drive, you hit 20psi, you clutch in, 20psi worth or pressure fights against your impellers, you shift, you may have still around 10psi of pressure in your intake (depending on your shift), you accelarate, 20psi of pressure builds up, repeat process.

everyone is entitled to their own opinion, but unless you can tell me youve done the same and felt no or worse spool up times, all you are doing is speculating.

you drive, you hit 20psi, you clutch in, 20psi worth or pressure fights against your impellers... and thus the turbo is slowed right down due to the pressurised air going the wrong way... hence slowing the rate you'll achieve boost once you open the throttle.

in a race car its different due to a 100 reasons... but we are talking street here.

i've had manual/auto... no BOV, plumb-back etc.

in amny different turbo cars. Plumb-back is the way to go.

[Guest decksla]

R31, lets call it a truce and stick to the topic aye?

whats good for one bloke aint necessarily good for the other. i cant knock ya anyway, you drive a nissan.

[GTRgeoff]

Warren has it almost right in his explanation, but was probably confused by the Nizpro twaddle. The airflow effectively stops but doesn't flow backward (or not very much) as the compressor is still working to force the air, but there is cavitation causing the woofle noise. Any air that would go back out the AFM would be hot from compression and cavitation and would cause little cooling of the hot wire anemometer, and the mass momentum of the air coming in would still be fighting it as well. Nizpro may have some nice cars going around but Simon got that very very wrong and even changes his argument through the interview.

Why then do all turbo rally cars, that rely on throttle response, use a fast acting large bore BOV? I saw them at Bates workshop in ACT when I was whoring myself to them. Doesn't mean Nizpro can't do a mean car tune though from all indications, just don't understand the underlying thermodynamics, aerodynamics/fluid dynamics and dynamic response of the system.

There would be no significant reason I could see for No BOV being illegal, but a vented one would as the AFM sees flow that isn't entering the engine, but it is fuelling it anyway causing the black overich puff. I would ask for a written explanation and the legislation/guidelines from the EPA facility.

To clarify on the benefits of a good BOV, and I will concede to the expert opinion of anyone with more experience and qualifications in compressed airflow:

the BOV is designed to not only prevent back pressure in the turbine causing cavitation in the denser compressed air, thereby slowing the turbo faster, but to maintain the inertia of the airflow in the system. Without a BOV the airflow effectively stops when the throttle is closed, then needs to be accelerated again, and the turbo slows dramatically, also needing to be accelerated again. This energy comes from the exhaust gasses and so creates a momentarily higher back pressure. The result is sluggishness beyond the sum of the individual effects. This can easily be proven through mathematical representation of the system to those who understand.

I just changed to a nice atmo BOV plumbed for track (the orig is still on and can be returned to operational instantly) and found an improvement on gear changes. The wheels spin a bit longer changing into third, but then the changes only take about 0.4 of a second anyway. I simply don't like the noise on the road, and attention, but realise the benefits on the track.