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What Dump Valves or BOV's do people use?


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After sorting out the wastegate, with a 0.5bar spring from a Tial F38... I was wondering about blow off valves.

Again there's some cheaper ones and some expensive ones. But what does everyone run? I've had a look through a few build threads but these are slightly overlooked in detail.

Any suggestions welcome and video's/sound tests will be even better! (even if it's not a VR6T)

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Sorry mate, didn't know it had put 2 up :S was it the exact same thread??

I've had a look on the forge website now, and suppose I don't need one as big as yours, but this twin piston one seems ok and suitable for cars with an air flow meter.

http://www.forgemotorsport.co.uk/content.asp?inc=product&cat=0006&product=FMDV004

What are your thoughts?

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I have one of these on my R32

http://www.forgemotorsport.co.uk/images/products/FMDVSUPR.jpg

Forge supersize

Yeah that's a good size valve for V6 turbos if you're using a MAF :-)

I've got one of those going spare if a certain person wants to buy it ;-) LOL!

Because I don't run a MAF, I'm using a Tial 50mm BOV at the moment- http://www.gt3turbo.com/Merchant/product.php?productid=210&cat=350&page=1 which is a very splendid thing indeed! As it flows a huge amount, it gives a much more refined and deeper sound than what you get from little under-sized valves that psssshhhhht all over the place. It also only vents when it needs to aswell and I get absolutely zero compressor surge (that cha cha cha woofing noise some people love so much).

In a nut shell, fit the biggest valve your wallet and application will allow ;-)

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so how many notes do you want for the supersize then kev?

the reason i asked about that other one was because i wasn't sure if 25mm would be quick enough to release the pressured air quickly.

i'd want the supersize to vent to atmosphere so will it need anything on outlet side or just leave it as it is?

can you buy silicone t pieces to fit these then, the only t pieces i see split to 25mm

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Was thinking £50 with some 50mm ally tube and silicon bits thrown in? It's only sitting there unused, so if you can put it to good use :-)

The 25mm one you linked to is a bit small for a VRT and if you're going with OE management, you can't vent to atmosphere anyway, you would need to vent all the waste boost back into the intake (post MAF, pre turbo).

Well, you can dump to the air but your fuelling will go way too rich on gearchanges and coming back onto the throttle.... you'll have the fume police breathing down your neck!

If you're going standalone, you can run a BOV to atmosphere.

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I'll have that off you then kev. can't do it just yet because i'm on my phone but if you can send me your paypal address i'll sort it later for you. i'll send money as gift.

as for the routing i was going to run standard ecu for a while. so if i have to i'll run it that way.

can running rich when coming off the throttle damage anything or just dump fuel through the exhaust? i know it might sound saft but could it help cool the exhaust valves or wouldn't it make a difference?

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I'll have that off you then kev. can't do it just yet because i'm on my phone but if you can send me your paypal address i'll sort it later for you. i'll send money as gift.

as for the routing i was going to run standard ecu for a while. so if i have to i'll run it that way.

can running rich when coming off the throttle damage anything or just dump fuel through the exhaust? i know it might sound saft but could it help cool the exhaust valves or wouldn't it make a difference?

No worries chap....

My first turbo engine was a bog standard lump with spacer, BEGI fuel riser and uprated pump. Totally standard management and injectors etc.

On that engine I ran a BOV and on gear changes, the AFR dropped to 9:1 with a nice cloud of black smoke out the back. You don't get flames from fuel THAT rich. What you get is bore wash, which dilutes the oil down and can accelerate bore wear. Petrol engines make best power between 12 - 13.5:1. Anything richer than 10:1 is borderline bore wash. Try and keep your fueling around 14 on cruise and 12 in boost.

On standalones you can adjust the gearchange fuelling (known as "Tip out") and really back it off, but there is always a momentary delay in injectors closing and the Lambda responding, so sometimes it's only an 'apparent' richness. But if you're going for a chip tune this will be sorted for you, but you MUST recirc the waste boost mate :-)

Using excess fuel to cool the valves is an excuse I see the American tuners who favour over-rich boost fuelling use all the time. Put bluntly, if the motor is built to handle the EGTS it's likely to see, then you don't need to run silly boost fuelling lower than 12:1

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