Steve

Beer Baron, his name is Bai, he was (until very recently) Signal Auto's D1 driver. He has his own workshop in Osaka.

another good article: http://autospeed.drive.com.au/cms/A_1457/article.html Simon Gishus of Nizpro the question is asked "What are some areas where people often make errors modifying their turbo car?" "The blow-off valve is designed as an emissions control device for OE manufacturers...The airflow meter is not all that smart and does not realise the air is going in the wrong direction; it therefore measures the air twice (once going into the engine and again going out in the wrong direction). The computer now tips in twice as much fuel as what's required, making it run rich - making it not pass emissions." Also goes on to say that he has "...tested one on a manual gearbox performance car run at Winton Raceway. I think it was running 1 minute 40s back then, but it would lose 2 seconds a lap putting the gobble-gobble valve on. When you look at data acquisition, what you find is - as you change gear - the blow-off valve dumps all the pressure built up through the intercooler and pipes. It then goes back to zero manifold vacuum when you get back on the throttle, you have to build all that boost back up."

Nice post Sydneykid, excellent food for thought! makes alot of sense. Just on a previous post, What you are very possibly seeing is a harmonic frequency, which occurs because of the strobe light, just as wheel spokes sometimes seem like they are travelling backwards when cars accellerate and decellerate.

Yes, that is what I am talking about, I agree completely with straight line rapid changing making very little difference. No probs, the guy drove for Signal, AFAIK it didnt have nos. Yes, that is exactly what I am talking about Bottom line, its individual choice. If it works for your its all good. As I posted once before, I went from stock to aftermarket (on GTSt) and found an improvement - I swore by these things - until I took a step in the opposite direction. PS, I though I would close with this quote (or two) from Peter (huge I know, but the guy writes so eloquently, I would love to meet this guy one day)

wearing a ball cap backwards would probably have a similar effect to beanie

vexed, this may sound strange, but try unplugging the hand controller - long shot, but it worked for me, after months of trying to figure out what the hell was causing a fluctuating idle.

lang, thanks for the link, some of that stuff is pure gold. F1 cars running 4bar plus with no bov - love it

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 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. 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

Theory is such a wonderful thing bit like statistics.... I dont agree with what you are saying, for two reasons. 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. 2/ Unlike you, I have experienced this myself, as have others I know. With the whole fan thing, speeding up, look what happens when a turbo crosses the surge limit, the wheel increases in speed, but no extra air is being pumped. Its amazing that a debate like BOV still attracts such conjecture and differing opinions Any of you guys who are into drag racing your street cars ready to take up the challenge of bov vs no bov - so its not a racing car or drag only car. It would be interesting, as I know of one guy who said he consistantly lost between 0.1 and 0.2 seconds without a bov. Woud be nice to compare. 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.

But who's attitude. I am not disagreeing with you, sometimes its the driver, sometimes its the cop. Not pointing the fingure at anyone here, but I do believe, more often than not, its the driver

yes, but that is a bit simplistic IMO How much does the turbo slow down? how long does it take to slow down or stop completely ( I doubt it does stop completely until the engine stops running) The turbo doesnt just stall as soon as you lift off the throttle, it takes a several seconds to wind down completely. Exhaust gasses will spin up a turbo very quickly, and provide more energy to spin the turbo than the boost pressure (if this wasnt the case, a turbo wouldnt work - or need a wastegate) - more pressure on the inlet side, means more exhaust gasses more quickly. Throttle LAG (time taken to build boost) is going to increase the larger the quantity of air needed to be pumped to pressurise the intercooler and pipework to full boost pressure - sometimes, with a bov, it seems like seconds (thats what it seemed like at the time - waiting, waiting, damn too long, better clutch it go get the damn thing back on tap). The quicker you get exhaust gasses moving at speed, the quicker you will have boost, the less air that needs to be compressed in the intercooler and inlet pipes, the quicker you will have boost. As someone else mentioned, if you stop the air flow around a fan, it increases in speed, perhaps due to the lack of resistance (bit like a vacuum cleaner getting blocked - no air being moved, speeds up), so reverting air through a turbine wont have the same effect as through a positive displacement pump.

Oh, and tonba, the wastegate is on the exhaust, or turbine side, it controls boost - has nothing to do with charge air directly.

did any of them say why not to use one? would be interesting. this does effect emissions - crank case gasses are mixed with the charge air from a turbo. Emissions requirements state that all crank case gasses are burned in the engine. Air reverting out of the compressor would contain these gasses and therefore a car without a bov would not comply. With a recirculating bov, the compressed air is just fed back into the turbo inlet, and therefore back into the engine. Any air going out the afm would increase the amount of fuel being dumped in by the ecu, it cant tell what direction it travels, only that it has passed.

ouch, seems a bit harsh

Did he have an SR in there before? (noting he is in the US, and the S14 came out with a 2.4L na engine)

AMARU, in your first link, it states: (2) Power to search An authorised officer may search a vehicle or combination for compliance purposes, if the officer believes on reasonable grounds that: (a) the vehicle or combination has been used, is being used, or is likely to be used, in the commission of an offence under an applicable road law or in the commission of a breach of an approved road transport compliance scheme... So, all they have to see is that the tyres are bald, or you have a box on suspect origins (not oem) mounted somewhere in the cabin - a bit of rust around a window, sounds a bit louder than oem, aftermarket wheels,etc to have reasonable grounds. An 'authorised officer' I think you will find includes police officers - they are within their powers to enforce the Road Transport Act. it actually states that he can search your car if he has reasonable grounds. Your post is misleading - if it stated they can only search your car if.... then you would be correct. I think you will find that most states are the same, they have allowances for search under different areas of the road traffic act AND criminal law. Shouldnt get them confused as meaning because they can search in a give scenario, its the only time they can search - may find yourself on the wrong end of the law.

what was wrong with the catch can? which inspection station?

sounds sweet - any reason you didnt go SR?

SA road traffic act gives the right for any inspector, or copper to demand a vehicle be made available for inspection at any time or any place. I checked this one, they can demand you allow them to inpsect the car in your garage if they wanted to. game over. Bottom line guys, if you are being reasonable, they will be reasonable (mostly), if you are being a dick, they will fark you. If you fark up, wear it on the chin like a man instead of trying to hide, it will only be worse for you in the long run. All these back room lawyers who spread little rumours about your rights - its so funny. I am not having a go at anyone here. Unless you are absolutely certain you have done nothing wrong, and your car is 100% legal (engineers report, permits etc for mods, tyres ok) then you are best off laying yourself at the mercy of the cops, being humble and showing manners - you never know, the cop might see someone who doesnt look like a gobby smart arse know all and go easy on you, after all would you feel ok about throwing the book at someone who seems like a decent sort of guy? or would you go easy on a clown who thinks he knows everything and just makes your job harder?

Perhaps this would be better on your state forum? rules change from state to state. Quick answers, to the best of my knowledge: are boost controllers illegal - see the local epa. They have a theory that changing the boost may change the emissions of the vehicle. You may have certain circumstances where they would be legal, but best check with epa to know for sure what your state legislation is. Ride height: If the cop fined you, and you had it inspected and it was fine, I would fight it in court, at least ring up the supervisor of the station and ask what options are open to you, as it wasnt illegal height.

depends on if the stock one is working ok or not. refer to elbee111's post refer to above This is what I have found, and what I was advised by a D1 driver amongst others - once again, refer to previous posts. Sydneykid, your turn

some one here believes it does make a difference to NVH. Emissions - once again, this is just theory - if no BOV, the compressed air reverts out of the turbo, and keeps going - back out to atmoshpere, this would have a similar effect to an atmo BOV. Turbo servicing: if it was the same turbo, but the servicing schedule changed once it was fitted to a car with BOV, then yes, good point. If its a different turbo, different story - how many cars do you run nowadays with the sierra turbos? didnt you seem to think that alot of the problem with the sierra turbos was the type of turbo, being old school bush bearing? Did you fit a bov to a cosworth and notice any improvement in the life of the turbo? The jap D1 driver I am talking about doesnt rebuild his turbo after every meet, certainly not 3 times in a weekend of driving - which, by your reasoning, would be the case - after all he uses a bush bearing T78 and runs 2 bar boost. He also uses no bov on his street car, which is in a pretty wild state of tune, and doesnt have dramas. I know others too, James Vahoumis, when he was running a T518Z with no bov on his drift car, never had to rebuild his turbo, and argueably he runs that alot harder than most people would run a road car. When he pulled the turbo off to upgrade, it was in perfect condition after many, many drift sessions and competitions where it spends most if its time on full boost, with lots of on/off throttle, more so than a circuit car would experience. If you are rebuilding your turbos every 2,000kms (track car) and D1 cars can make many meets without turbo failure problems - the point is mute. you could even say (using the comparison of different cars and different turbos, as you did above) that using NO bov is better than using one! Once you start pushing any limits, the longevity of parts is effected - the brighter it burns, the quicker it burns out. If longevity is the ultimate goal, then OEM is probably the best way to leave your car. If you want performance, it costs more than just the parts you fit. You must finish to finsih first, but you must have a performance advantage to finish first. Out of interest, what aftermarket bovs do you use? do they increase performance over stock parts - or just longevity?

Do you have a hand controller?

Think you may have the wrong end of the stick there. You are absolutely correct that if you stopped or put a brake on the turbine wheel while you were ON THE THROTTLE, it would cause a few issues. the bov debate refers to what happens when you are off the throttle, then back on. Here is a quote from another forum that explains it differently: and another like I said before, there are arguements for and against. I would love to see specifics of what controlled testing has been done - otherwise its just speculation as to what EXACTLY is happening. GTR-Ben, think you may be on the money - shift times would barely warrant any sort of bov - but its hard to say, dedicated drag cars dont always use intercoolers with turbos either.

Seems like a dumb idea to you, didnt really seem like a dumb idea to a jap guy I know who is a pro drifter (D1), qualified mechanic and owns his own mechanical workshop in Japan - he suggested it was the reason I was getting throttle lag, he doesnt run them for that reason - as alot of jap d1 drivers dont (yes some do). As for why manufacturers run them, PLEASE dont tell me that manufactures do things purely for performance - perhaps NVH and emissions have more of a job to play? To be objective in any comparison, you have to compare apples with apples, not turbo fitted to car type x to turbo fitted to car type y. Lastly, who the hell said air reverting is good for the turbo? If you read the comments above, they are talking about performance - not lack of it as in a stock car to do the shopping in, so lets keep things on track. As the title of the thread asks, is a BOV performance or wank factor??? note the use of the word 'performance' please, dont be so ready to come down on those that have a different opinion than yours, if you have any realistic evidence please present it, but lets try and keep it objective so that others can make up their own minds too.