Aftermarket BOV, performance or wank factor

[RB30-POWER]

Im going to add my 2c.

BOV are used on all late model cars for a couple of reasons.

First, having the BOV recirculate the air on throttle closings prevents the air from rushing back out the AFM and being measured twice which can cause overfuelling and bad emissions, where emmisions are a major part of todays tuning requirements

The second reason is that if you recirulate the air, it will stop the flutter and minimise noise. Imagine how many people would take their cars back and whinge to the manufacturer if it made strange noise on gear changes etc etc. All that noise is not something that is needed on a nice new performance vehicle.

As for it effecting turbolife, im not a big believer.

Once you close the throttle, the turbo looses it speed almost immediately with no exhaust gases pushing the turbine wheel. So even if the air flow coming back out throught the compressor blades did aid it in slowing down, its going to be stuff all in the scheme of things. Once the exhaust gas stops the turbine slows exremely rapidly.

[Roy]

Here is a challenge for you Roy, next time you have your ride in an appropriate place, try getting it sideways and mid slide just back off ever so slightly util the bov lifts - then see how long it takes to come back up again

We will have to agree to disagree:)

As for the experiment, lol i have tried it so many times, and like i said my car drives much better with a BOV. The 1st 6 months that i was running the TD06 i didnt have a BOV. Seat of the pants said it drove / performed worse:(

Now with the BOV and everything sorted, i know what works best with my car. Think about the last 3 corners at Phillip Island. 2nd gear open/balance throttle with wheelspin trying to get the car setup for the following fast two left handers. Coming onto the final turn at about 160km/h in 4th before hitting 5 at corner exit at 180km/h with susp fully loaded up in there is plenty of dancing on the throttle with the thing fully loaded up mid corner twitching sideways, the car has no problem in the response department. If i could convert to mpg some in car footage id be happy to post it up. Though i only have footage of Sandown ant Eastern Creek with the current setup

I have tried the no BOV, wound all the way in and wound all the way out...and my car (others may be different) loves the softest setting (and peak boost is exactly the same be it softest or hardest setting:))

LOL..yeh i love theory too, but in this case im comfortable there is theory and real life data supporting it...i need more convincing then some crazy drift jap guys:)

[Roy]

1/ I dont see how the volume of intercooler/pipework can be pressurised as quickly by a turbo spinning at near full speed, versus a slightly slower turbo with a nealy fully pressurised intake system - a BOV will dump ALL the inlet pressure almost instantly, vs reversion which takes time.

 

And have a real think about it, sit down and draw a cooler piping setup with BOV, throttle body and inlet plenum, think about what parts are open in differing states of throttle position and what are pressurised or vacuum, what are receiving airflow etc. Look at a few compressor maps for shaft rpm v boost and try to pull all the bits together and see what you think, not what someone has told you.

It could be as simple as the ppl you are talking about are using std turbos that offer lightning response anyway as they are so small they hit big rpm with very little exhaust airflow. Or a only a small turbo upgrade.

Go and drive a car with a big turbo, especially one that might have a slightly too big A/R exhaust housing and see if there is a difference. Different installations, in ine the difference could very well be negligible, in the other some tweaking of a BOV could have a different result:)

[lang]

if anyones interested theres an 12 page debate with a reasonably high technical level in some of the posts about running a bov vs not running one at all.

http://ausrotary.dntinternet.com/forums/vi...t=17113&start=0

interestingly enough riceracing who could be called the ausrotary equivalent of sydneykid has the opposite opnion, and has evidence of modified rotary running many km without a blow off valve and has experienced no ill effects on the turbo.

as for the aftermarket vs stock bov debate, id be suprised if you saw any difference performance wise between the two, unless your stock one is faulty.

[Cefiro_PWA]

if anyones interested theres an 12 page debate with a reasonably high technical level in some of the posts about running a bov vs not running one at all.

http://ausrotary.dntinternet.com/forums/vi...t=17113&start=0  

interestingly enough riceracing who could be called the ausrotary equivalent of sydneykid has the opposite opnion, and has evidence of modified rotary running many km without a blow off valve and has experienced no ill effects on the turbo.

as for the aftermarket vs stock bov debate, id be suprised if you saw any difference performance wise between the two, unless your stock one is faulty.

Mate, RICERACING ( peter ) has much more knowledge then anyone on these forums,and has a car that is 30 times faster and more upto date then Sydneykid will ever have..

nuff said.

[Roy]

I had a quick read of what he was saying, and he doesnt seem to consider the load on bearings:confused:

Will not having a BOV installed mean a dead turbo? Perhaps not. Will it increase the chances of a turbo failing? Yes. May still not happen, but you are increasing the chances as it does increase the loads on the bearing.

[Steve]

Go and drive a car with a big turbo, especially one that might have a slightly too big A/R exhaust housing and see if there is a difference.

Yeah, well I have only gone up to a 3037S on my 33, approx 321rwkw (0.87exhaust ar on decompressed (8.5:1) rb25), so medium sized (close to a TD06, depending on spec) - I did notice a huge amount of throttle lag - thats why I diced the bov. The D1 guy I am talking about uses a 2.2 stroked SR20 with T78, not really a small turbo as you suggested

And have a real think about it, sit down and draw a cooler piping setup with BOV, throttle body and inlet plenum, think about what parts are open in differing states of throttle position and what are pressurised or vacuum, what are receiving airflow etc. Look at a few compressor maps for shaft rpm v boost and try to pull all the bits together and see what you think, not what someone has told you.

Sorry Roy, but you lost me here, I find that sort of remark somewhat condescending - I tend to consider ALL ideas thoroughly and dont just accept the words of others as gospel. I do say though, I give weight to the words of someone based on their experience - alot of weight, as I believe experience is so much more valuable than words and theory.

I did think about it long and hard, especially as it flew in the face of what I believed at the time to be true, but I had a problem (throttle lag) and was given a solution by a PRO DRIVER and EXPERIENCED JAP PERFORMANCE MECHANIC AND WORKSHOP OWNER. What would you have done? ignored a well respected jap mechanic and pro driver with 15 years experience drivng and building performance cars? Well I didnt, I listened, asked questions and tried to understand - I gave it a try, because I had NOTHING to loose - and I found he was not talking shit based on what others had said - he based his ideas on tried principals that work for him. I have seen him solve problems on cars in minutes that others (here) had spend many hours on - respected, well know workshops - this guy KNOWS what he is talking about. Why would he suggest that I DOWNGRADE my setup?

I am not knocking your decision, its what works for your, and that is great - it points to the problem I had with removing my BOV in the first place - if they didnt work, why would so many people, respected performance houses etc use them? I do believe in Japan, it can be quite easily answered with one word - sponsorhip. Not saying that is the only reason, but it IS a possibility.

For others that find a performance enhancement great - I am not knocking that IN ANY WAY - all I was after was some quantifyable, accurate evidence. I only go by what I have tried, and what works for me. I wont change my idea for anything less - would you? I listen, consider, try then decide.

The whole point of my posts is that there are two different ways to reach the same goal, and not always only ONE right way.

If you are blocking the front then the fan slows down, because the air is bouncing back (reverse direction) and this creates drag on the spinning blades.

Cant see that, its not positive displacement, therefore it will not suck or push, to slow down it would need some sort of drag - equilibrium, less resistace, therefore more shaft speed

I just tested this theory on the wife's hair dryer - it speeds up, quite dramatically when you block the outlet

Perhaps this is one for myth busters

[elbee111]

The top draggers running huge boost would want to eliminate any loss in pressure (leaky BOV ?) and,therefore, decide to run without one.

These guys are running full throttle basically full time so why would you need one ?

For those of us on/off/on throttle, it seems to me that it would be best to keep that turbo spinning and have boost ready and available (not just latent pressure that would be spent it 0 secs flat and have to fire up the turbo again after it has been slowed down).

Back onto the original question, I am a convert to the aftermarket. Maybe the factory BOV was holding more pressure, slowing the turbo between gears, and not allowing the turbo to keep spinning freely while off boost between gears.

El Bee

[Cefiro_PWA]

The top draggers running huge boost would want to eliminate any loss in pressure (leaky BOV ?) and,therefore, decide to run without one.

These guys are running full throttle basically full time so why would you need one ?

For those of us on/off/on throttle, it seems to me that it would be best to keep that turbo spinning and have boost ready and available (not just latent pressure that would be spent it 0 secs flat and have to fire up the turbo again after it has been slowed down).

Back onto the original question, I am a convert to the aftermarket. Maybe the factory BOV was holding more pressure, slowing the turbo between gears, and not allowing the turbo to keep spinning freely while off boost between gears.

El Bee

Rice Racing aint no dragger's.

Running 2.1bar on pump fuel... call that dragger? :cooldance

[Cefiro_PWA]

http://www.members.optusnet.com.au/vu103/d...drag-combat.wmv

"NO BOV FOR YOU"

[elbee111]

Rice Racing aint no dragger's.

Running 2.1bar on pump fuel... call that dragger?  :cooldance

AND ??

[Cefiro_PWA]

AND ??

Which means he is a STREETER.

Street cars dont need to have BOV's. They do jack crap as most workshops have done and tested

[Steve]

lang, thanks for the link, some of that stuff is pure gold.

F1 cars running 4bar plus with no bov - love it

[elbee111]

Which means he is a STREETER.

Street cars dont need to have BOV's. They do jack crap as most workshops  have done and tested

Which one is the streeter. Me perhaps ? Or someone earlier. I don't know.

Anyway. Someone will have worked it out. If it is me then "so be it".

Enjoy

[elbee111]

OK. I've decided that cefiro_PWA has referred to me and I don't really care.

If this is the case then he/she is just a dickhead who reckons that he/she is top shit.

You could start a thread of your own bragging about your conquests or, stick with the original thread.

The tone of the original question does not tell me that he is as leet as you.

El Bee

[RB30-POWER]

haha, i give this thread about another 24hours.

it wouldn't be a BOV thread if things don't turn to shit

suprisingly it has been fairly civilized so far, compared to others, i've seen...

[Cefiro_PWA]

OK. I've decided that cefiro_PWA has referred to me and I don't really care.

If this is the case then he/she is just a dickhead who reckons that he/she is top shit.

You could start a thread of your own bragging about your conquests or, stick with the original thread.

The tone of the original question does not tell me that he is as leet as you.

El Bee

Im not l337

im just not ignorant, and i believe what people have researched physically and not read from internet forums ...( most of the times people just use theory )

[elbee111]

Cefira_PWA,

Sorry that I have shown that I am also not as l337 as you but..........

For the guys out there driving our cars on a daily basis, do you have anything to add ?

[elbee111]

haha, i give this thread about another 24hours.

it wouldn't be a BOV thread if things don't turn to shit

suprisingly it has been fairly civilized so far, compared to others, i've seen...

I would like to apologise if my posts stifle discussion on this matter in any way.

Please add anything that is likely to answer the original question etc.

El Bee

[lang]

Mate, RICERACING ( peter ) has much more knowledge then anyone on these forums,and has a car that is 30 times faster and more upto date then Sydneykid will ever have..

nuff said.

Mate, it was a quick way of saying he (riceracing) has alot of knowledge for those not familiar with him, dont interpret my comment as a direct comparison or some form of competition....