BOVs?

[Rupewrecht]

thread split as requested!

[zappy65]

Does anyone know of any Techs/ Workshops that have any major knowledge on the BP/ BPT platforms, im talking tuning and mechanical knowledge of turbo setups etc?

[project.r.racing]

Yes my old room mate:-

Company: Cox Automotive Services / Redline Garage.
Contact Person: Dave Cox.
Location/Address: 3/5 Service Rd, Maroochydore 4558.
Contact Number: 07 5443 3507.

He did his apprentiship in the mid 90s at a Mazda dealer, knows all there is to know about Mazdas engines from that era. Know everything about my car! He has done multiple GTX and GTR set ups on TX3s and built a MX5 racecar with quads. Knows all there is regards turbo applications into motorsports, mainly drag and drift. If he cannot answer your questions, then no one can...

Ryan

[zappy65]

Ryan you are a god sent, thanks mate....ill give him a bell after Christmas...

[project.r.racing]

Originally Posted by zappy65

Ryan you are a god sent, thanks mate....ill give him a bell after Christmas...

No worries John, I'll let him know you'll be contacting him. Oh and btw - the pic of the engine bay in your GTX plans thread was his work...

[zappy65]

Mate that is awesome, after seeing that plumb back method, i want it...one question though, why did he weld it so the air flow from the BOV was facing toward the pod and not toward the turbo?

[project.r.racing]

Since the purpose of a BOV is to release pressure from building up and destroying a turbo. Having the plumbing venting back directly into the turbo would defeat the purpose I think. Plus it sounds awesome when the BOV goes off inside the airbox/filter. Much like a rally car. But ask Dave, because most likely I am totally wrong as usual.

[zappy65]

I thought the purpose of the plumb back was to send the extra air into the turbine to keep it spinning when under boost...?

[DavoAust]

i thought a plumb back was a legal way of releasing the extra pressure as atmospheric ones aren't legal. i guess if you plumbed it into the manifold you could possibly use it to keep the turbo spooling, although i doubt big sudden pressure increases would be good for the system long-term. Also would you want your turbo to suddenly spool for a sec every time you shifted before dying off?

[zappy65]

A plumb back is a legal way but it has its advantages....the whole point of plumb back is to keep the air circulating, it does have proven effects on FI cars, this is why im opting for this option, plus i want to be sleeper...the air that the BOV does put back is not necessarily strong...just enough to keep it spooling whiile you are below the torque range of the turbo...meaning the turbo will spool up quicker and stronger....

[Rupewrecht]

Originally Posted by zappy65

A plumb back is a legal way but it has its advantages....the whole point of plumb back is to keep the air circulating, it does have proven effects on FI cars, this is why im opting for this option, plus i want to be sleeper...the air that the BOV does put back is not necessarily strong...just enough to keep it spooling whiile you are below the torque range of the turbo...meaning the turbo will spool up quicker and stronger....

...do you have any proof to back this up?

The point of a plumb back is for emissions and noise purposes, not to keep the air circulating. There will be virtually no difference between the performance of an atmosphere venting BOV and a recirculating one

[project.r.racing]

^Agreed^

[zappy65]

Originally Posted by Rupewrecht

...do you have any proof to back this up?

The point of a plumb back is for emissions and noise purposes, not to keep the air circulating. There will be virtually no difference between the performance of an atmosphere venting BOV and a recirculating one

No, i dont have any evidence but word of mouth and unfortunately these days that aint very reliable...ahhahaha, this is what ive been told by other turbo enthusiasts...

[project.r.racing]

Originally Posted by zappy65

This is what ive been told by other turbo enthusiasts...

Ricers that drive S13s or R33s right? lol jk/z

The point a a BOV/PRV is to vent the compressed air out of the system. When a driver jumps of the go pedal, the throttle closes, cause the compressed air to find another way out. the only direction is back thru the turbo. Compressed air being pumped back into the turbo's blades causes them to become brittle and damage after a while. It's called compressor surge, it sounds awesome but kills turbos within 12-18 months. Blades break, go places the souldn't, you know the rest...

But as natural air goes thru a turbo, it gains oily, exhaust,fuel gasses and there for under EPA rules for environmentally friend emmisions, the compressed gases are vented back into the intake system, where they are sucked back into the turbo afterwards as per normal turbo operations.

All gases must go thru the cat convertor, so all gases and recycled back thru the system, etc.

normal air flow:-
airbox - turbo - ic - throttle - cylinders - turbo - cat - exhaust

vented air flow:-
airbox - turbo - ic - bov/prv - turbo (again) - ic (again) -throttle - cylinders - turbo - cat - exhaust

Did I make sense?

Ryan

[LordWorm]

Originally Posted by project.r.racing

Since the purpose of a BOV is to release pressure from building up and destroying a turbo. Having the plumbing venting back directly into the turbo would defeat the purpose I think. Plus it sounds awesome when the BOV goes off inside the airbox/filter. Much like a rally car. But ask Dave, because most likely I am totally wrong as usual.

you plumb back to before the turbo.... (i.e. you plumb back from the charge pipe, to the intake pipe before the compressor)

does the job well, but higher boost applications would obviously benefit from an atmo setup.

I don't really understand the "emmissions" side of it, the air isn't mixed with fuel at the point it is "blown off" - and a near instantanious return to vacuum conditions in the engine would cause any unburnt fuel in the manifold to be sucked through the engine as per normal.

I think its more a case of throwing fancy words at the legislation to make it carry more weight....but its primarilly a noise thing from what i can tell.

for a street car, i can't see why there would be any appreciable difference between a plumback and an atmo bov, all else being equal. However, there can be issues if you are running an atmo bov with a MAF sensor, as, depending on the location of the BOV, you can vent already metered air (this is an issue alot of the mazdaspeed protege guys in the states have)...it all comes down to placement of the bov at the end of the day, but most like to keep the stock location and so plumb back is the way they have to go unless they delete the MAF by going to a stand alone.

Of course, i could be wrong too.....but thats my understanding of it.

[zappy65]

Originally Posted by project.r.racing

Ricers that drive S13s or R33s right? lol jk/z



Ryan

They probably say the same things about Astina's....lol and no actually the person/s who fed me that was actually off this forum, i dont wish to casue fuss so i wont disclose furthur info....i understand how they work, i jst think its stupid, im with Lordworm, i think its all a whole heap of Cr@p and noise pollution...is the main reason behind it all...but without saying i do want it to be legal...and i dont care much about the WWWHHHOOOSSSHHH sound...+ im going to have a FMIC so anyone who knows what to look for will know..hahahaha DONT MESS WITH JOHNNY!!!

[bourbon]

can this please be talked about in another topic...back on track..this is a reccomendations thread not a general smack talk on BOV...

[Aaron]

Originally Posted by project.r.racing

Compressed air being pumped back into the turbo's blades causes them to become brittle and damage after a while. It's called compressor surge, it sounds awesome but kills turbos within 12-18 months. Blades break, go places the souldn't, you know the rest...

Not quite. Many early factory turbo cars didn't run BOVs and didn't have those failures. They are linked to boost pressure and driving style.

However once you start to fiddle with things it does become more of an issue. You can basically end up witha compressor stall situation where the intake (compressor) side of the turbo stops spinning, while the exhaust side still has "drive" from the exhaust gases. It's not unheard of to have the shaft snap under that condition.

However the biggest and worst part of having a lack of BOV is that you get a significant drop in performance on/after gear shifts as the compressor is being slowed or stalled whne the throttle is lifted and then needs to "spool" back up again to an efficient speed for the gas flow. This takes time and energy. With a BOV the compressor doesn't generally get that significant forced slow down so when the throttle is opened again (and BOV closed) it's pretty much immediately at the same boost generating capability as when the throttle was closed.

Anti-lag systems work off this same principle, except using a lot more smarts they essentially run the turbo as a gas turbine to maintain turbine speed whenever the wastegate or BOV would normally be reducing the speed of the turbo. There's all sorts of bypass and tricks involved but in simple terms the turbo is always kept at an optimum boost generating speed.

A.

[project.r.racing]

Originally Posted by Aaron

You can basically end up witha compressor stall situation where the intake (compressor) side of the turbo stops spinning, while the exhaust side still has "drive" from the exhaust gases. It's not unheard of to have the shaft snap under that condition.

However the biggest and worst part of having a lack of BOV is that you get a significant drop in performance on/after gear shifts as the compressor is being slowed or stalled whne the throttle is lifted and then needs to "spool" back up again to an efficient speed for the gas flow.

Well now I know, I was close, didn't realise about the proformance side of thing, but if you think about it, it make complete sense...

Ryan

[rodhog]

You want the truth

lets go back

way back

Original turob cars- they dind't have them.

Theyu had true BLOW off valves- Et - turob's Vl turobs' FJ20's had a nice mounted one 626 /capella turbo's

Most all throttle body injection and all only used the main valve as a pressure release.

All cars had some form of turbo surge on backing off.
It did not fail them.

In fact if you look at the most comon turbo failure, of then and back then?
Bearing oil seals. Now look at the most comon failure to day - of a turbo charger Bearing oil seals.
Nothing has changed.
It was in alot of cases lack of - water cooling.
Most comon fialure with the Vl's was it but notice how even the early mazda 626 and tx-5's didn't suffer it. depending on year they ran a water cooling section and added a oil cooler. Same goes for the toyota's and Rx-7's

Note the early Tx-5's beofre unleaded ran around 9psi boost. limited in the unleaded era to 6psi. Ford's cheap way of saving the motor. instead of chaning the timming in the dizzy.

Bpass valves arrived during the same time - As Noise emisson went up in 1988 - Note it was 1990 it was effective in Australia along with the rear 3rd main stop light.
You will note how all the Mazda 626's in 1987 had a rear 3rd top light along with 323's and I think Bg's etc
but the telstars did not - They were not sold in Europe - So they did not complie untill the law came here.
That year brought in tougher noise dampening, and emissions.

Now why is it they bypass it and then put it back in.
Factory cars have two reason one - for Airflow meters.

The other is Plain EPA.

There is a rule. for cars And you must obey it under all states etc blah blah blah. I went through this. QLD your right - I love your mod plate.
in NSW it's easy to get around but hard to get it approved. BLah blah
Vic - Your screwed - it's jsut plain expensive and pain full . The rest I have not dealt with.

Effectivley - One air has entered past the AIR FILTER - which must not contrain contamints - like oil - again a little law that is nothing really.
But once it past by the airfilter all that air must be consumed by the engine. OR out via the carbon canister eg filtration system.
Note how all oyur little solenoids have little proberly mitsubihis symboled filters ontop of the out let.
Once air enters it is considered dirty and must be expeled correctly.

This is why for- example PCV is run the way it is. some of you may remember a 187's in a only EH or even HQ with a 202 with just breathers.
in 1975/76 the first of the carrbon emisson laws came in to play here.
This is effectivley the same law that applies to the BOV.

Now you might say but it's only compressed air. That's right but your factory air intake is also a factory Recycle air intake.
So your not just compressing air.
but how come some cars come from EPA and are allowed I've seen 200sx's leave etc.
Simple the turbo is only compressing air.

but how come the BOv is still plumb can't it go open.
but when they do a drive by noise test, it pecks and it fails.


I hope that explains BOV's too you all.

Also just because I know in NSW it's going to get tighter. I'm in one of thme positions where I might be asked to sit on report again to try and defend owners. I tryed to get a mod plate system here but engineerrs here are well - trying not too. Some of you may or may of not heard but year the trail has ended and not too well either.

but The added bit is alot of you don't realise those nice fancy BODY Kit's Add noise to the driveby sound levels. especially on newer nicer cars as. I understand it effects post 93 models moslty.

So try and keep your body work tight and alot of the extra plasti underneath helps keep it quite alone with under bonnet dampening