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Discussion Starter · #1 ·
Hey guys,

Could you please inform me if the following is incorrect?

BOVs have advantages and disadvantages (I'm talking about vent to air BOVs). Advantage is that they release the pressurised air to atmosphere instead of back to intake pipe. This means that the turbine in the turbo spins longer and thus can spool up faster during gear changes..etc. Therefore reducing turbo lag. Disadvantage is that the car may run too rich. The air flow sensor still thinks the air is being recirculated back into the air intake pipe, but it's not. Thus there is a higher fuel to air ratio and thus the car runs to rich. You can then get flames coming outta your exhaust when gear changing. Also, there may be idling or stalling at low revs. This is because a vent to air BOV may leak boost...and this leakage may cause the car to stall or have idling problems. But if the BOV is good enough, then it should be air tight (like the HKS BOV I've heard??) when closed, thus acting like a standard plumback BOV thus meaning no/little idling or stalling problems?

Is this right guys? I just wanna learn more about the car that's all
Please correct me if I'm wrong. Cheers.

Also, which is the BEST BOV in your opinion? I wanna go for the HKS or BLITZ BOV - both vent to air
I heard that the HKS has better quality/technology (and it is a LOT heavier) than the BLITZ? That the HKS SQV is air tight when closed and will cause no/little stalling or idling problems?
 
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Discussion Starter · #2 ·
Yep I think what you said is right. http://www.ltregister.f9.co.uk/graphics/happy1.gif border|EQU| 0 align|EQU| absmiddle >

I guess it ultimately depends on how competent the mechanic who will be doing the installation of the BOV is.

Even a fine piece of machinery can get messed up if the mechanic is lousy. [img]http://www.ltregister.f9.co.uk/graphics/sad1.gif border|EQU| 0 align|EQU| absmiddle >
 
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Discussion Starter · #3 ·
Pretty much correct...I don't know if the advantages of fitting BOV outweigh the disadvantages, but personally I wouldn't fit one!! Sure if you get it fit by someone who knows what he is doing then it is no problem, but if it means that your car will run strangely and keep on stalling at low or high revs...then what is the point!!???
I have heard that recirculating BOVs don't have such problems. Maybe you should try one of these that don't release the air into the atmosphere.

Why exactly do you wanna fit one??? Is it just for the sound?? Are you sure that turbo lag is significantly reduced??
 
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Discussion Starter · #4 ·
The turbo lag should be worst with a vta valve!

The turbo has reduced lag with the air realeased by the recirculating valve,after braking and when you accelerate from lower revs.
The advantage,but I don't think that it's noticeable on a street slightly modified evo,is that when shifting at high rev,the air is realesed faster with a vta and as the turbo is already at high speed it doesn't need the extra air but just to get out the back pressure very fast.That's good if you fit it on a drag race 800bhp supra!

Probably some good vta valves as hks will have less stalling problems but it won't be a really nice set up as the car will not be smooth as before when changing gears,a recirculating one fitted with filter kit have a good sound and no problems!!!

The only nice effect of the vta is that sometimes you get flames!!!
 
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Discussion Starter · #5 ·
Isn't the secondary air system designed to reduce turbo lag anyway? In my opinion you are not going to gain a lot from fitting an aftermarket VTA BOV than say on a car that doesn't have the secondary air system (unless you are running a high power car as Maxi says).
Please discuss, I bow to Maxi's opinion on this as I am no expert.....

P.S. Has everybodies account been shagged?
 
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Discussion Starter · #6 ·
HH6. I've been told that the secondary air system is purely to get the emissions down and that it won't allow enough air into the exhaust to offer any significant anti lag. Apparently Porsche have been using the same idea on their tubo cars for about 10 years. Only repeating what I've been told and I'm not 100% sure about it.

Adrian
 
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Discussion Starter · #7 ·
In photos of the works evo's I think you'll find they use the standard Mitsubishi recirculating BOV - unless you want mega boost I would save the money for something more useful - cams/porting/fuel controller etc.
 
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Discussion Starter · #8 ·
If you fit a VTA BOV, you will slightly reduce the car's performance due to less air being given to the turbo. Now if you want a flame coming out of your exhaust from time to time, get a VTA BOV. If you dont care if your exhaust produces flames but just want the most performant car you can have for under GBP 30,000 than why would you get one??
I have a Forge recirculating dump valve made of alloy that will support 4 bars of pressure (!) cost GBP 140 (David Reid Motorsport www.drmotorsport.com or .co.uk GBP 120). Looks really nice and doesnt let pressure bleed off except when you lift off (OEM BOV lets pressure bleed off at lower revs) like it should. You can tell a very slight difference.
 
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Discussion Starter · #9 ·
HH, my account still seems to be OK. Looks like I might make senior member before you do again!
 
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Discussion Starter · #10 ·
Well according to the tech manual the secondary air system is designed to reduce lag but then you shouldn't believe everything you read.

Steve C,
Yep my account is shagged, I don't think I will bother making another one, doesn't seem much point, so everyone will be Member, Senior Member, whatever before me http://www.ltregister.f9.co.uk/graphics/sad1.gif border|EQU| 0 align|EQU| absmiddle >
There is a disadvantage of having an account with a lot of postings as people think you know a lot! (see the title of this thread)
 
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Discussion Starter · #11 ·
Yep HH6 My account is completly is shag-ed, looks like i'm a new member again!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Also looks liked my key board could be shag-ed too...................................................................................................................................................................................................................
 
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Discussion Starter · #12 ·
Get wotever BOV u want. VTA works very well, I got one no trouble with idle or fuelling WOTSOEVER and thats the end of it. the car is quicker through the gears. With a reciculating valve u are just dumping hot air back into the intake system which is not as good as a VTA.
cars with antilag also use VTA BOV's and the RS450 is proof of that, i have also seen photos of Tommi makinen's engine bay which clearly shows a VTA BOV dont argue with me just check the Jan/Feb 2000 issue of japanese performance if u dont believe me. IMHO u should not knock somthing till u have TRIED it and found it to be useless. I did and found the HKS VTA BOV to be nothing short of excellent. Remember it aslo depends on how the part is fitted, If fitted incorectly a VTA BOV can cause overfuelling and poor idle, but when fitted properly u wont get either.
 
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Discussion Starter · #13 ·
tommi has a different management system
this ecu needs re-circ type,dont take my word for it,read hks brochure
needs to be fitted correctly....???
is this something to do with the angle of the jubilee clips or what ?
 
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Discussion Starter · #14 ·
Cars with a mass air flow (MAF) meter before the turbo (such as Lancer Evos) ideally require a recirculating BOV to ensure the correct fuel mixture settings. Cars that are mapped using the MAP sensor values rather than those from the MAF can either use a VTA BOV or a recirc one, and will probably benefit (slightly) from a VTA valve due to reduced intake temps.

Most top of the range ECUs are mapped using MAP values. The MoTEC M48Pro ECU, for example, does not use values read from the MAF so can be used perfectly fine with a VTA valve. Doesn't the RS450 use a MoTEC ECU? If so, this is why it is fitted with a VTA BOV. The rally car will also be using a MoTEC/PECTEL or similar ECU, so will work with a VTA BOV. I did think, however, that the Anti Lag systems used on the current WRC did not work with BOVs, and therefore they were not fitted. I am not 100% sure though.

Simon
 
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Discussion Starter · #15 ·
There is no advantage at all to venting to atmosphere. The only thing you get is the pshhh sound. Any performance improvement gained by installing an aftermarket BOV comes from the valve being of higher quality (i.e. holds boost better and possibly responds more quickly) than the aftermarket valve. Therefore the best thing to do is to get an aftermarket valve that can be recirculated such as the Greddy Type S.
 
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Discussion Starter · #16 ·
Original Post:
There is no advantage at all to venting to atmosphere.
Not strictly true. As I am sure most people are aware, the cooler the air entering your engine, the denser the charge, and a denser charge |EQU| more power. When air is compressed by the turbocharger its temperature increases dramaticly. A recirc valve sends this warm air back into the induction system meaning a less dense charge, and hence less power, and possibly an increased chance of det. A VTA valve on the other hand dispenses this warm air to the atmosphere allowing the induction system to breathe in more cold air from outside of the engine.

Simon
 
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Discussion Starter · #17 ·
Wouldn't the air cool as the pressure drops when it is passes through the BOV (drops back to atmospheric pressure or less).
 
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Discussion Starter · #18 ·
Surely the short period while your dump valve activates can't result in much temperature rise. Won't any temperature gain from dumping internal be accademic as you are off throttle anyway?

More significant, I would think, would be the resultant loss of power from over fueling as the ECU tries to add a set volume of fuel to a diminished volume of air.
 
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Discussion Starter · #20 ·
having an externally vented bov is ok
the sudden increase in mixture isok as the excess fuel helps to cool the valves and piston
although the result can sometimes be a back fire or exhaust pop
i have a turbosmart type2(new version) bov and it works ok
 
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