Hi Guyz, I would like to read some thoughts about where to put these blow off valves. I am getting the four rubber hoses changed to s/steel ones, and because the blow off valves look good I want them under the bonnet. They are a bit crap under the bumper any way. Which set of pipes do you all think would be better the inside or the outside set? Which would be louder and which ones lost a member about 40 bhp???.

I thought all blow off valves are a downgrade on a Z anyway?

Maybe I'm wrong...

 

All Z's have Recirc valves so Guff-Off valves are a waste of time & money which is why somebody probably lost 40 horses out of an install!

 

 

Tim

;-)

 

Andy, checked with a few z guys and other z websites, it seems they favour using the outside pipes for big jap blow off valves, report no loss of power, if anything a more responsive turbo, which is as it should be.

However it seems your normal kind of dump valves used on the z and fitted to inside pipes have not worked very well, guy i bought my car off had his kit supplied by SE-Nissan and he lost power for certain, hope this helps, Smithy

Can anyone supply and fit two large mid-range speakers under the bonnet that are wired to amps in the boot.. The amps are then wired to a Laptop that is wired into the ECU. The laptop detects gear changes and sends a sampled wave file of a tshhhhshhh noise via the Amps fitted in the boot.

Costs about the same and has a similar performance gain?

I'll get my coat.

 

Glen

Senna,

What kind of stupid idea is that?!!

 

As you approach the person you are trying to impress, put a pinch of pepper up your nose and sneeze loudly out the window.

Far cheaper and no performance hit, although loss of control can be an issue.

 

Dont know about you guys but when I push it over 5000 rpm and change gear I can hear my rec valves, but only with my windoes open or roof off.

 

Is there some thing wrong there?

 

senna,

Like the Idea of the laptop.

Can it also have a wire to the horn so it will say

"Move out of the F*%king way"

when pressed.

Getting slightly back on topic there seem to be two questions :

 

1) Performance. Properly fitted dump valves will not affect performance when the engine is under load - they're not doing anything at that point. However, I've heard reports about unstable idle etc which could be associated with the dump valves.

 

2) Location-wise, my belief is it's marginal but general thinking seems to be that as close to the throttle body is the best place.

 

This is logical because the air flow from the turbos will continue in the correct direction when the dump valves are open and are releasing. If the dump valves are close to the turbos then the high pressure in the hoses which AFTER the dump valves will have to be released by backwards flow (i.e. air flowing back along the pipes to the dump valves). When the dump valve then closes, flow has to start in the right direction again.

 

The difference would be in the throttle response immediately after the gear change. Personally, I can't see it being noticeable but the theory works !

 

Dave

 

Nissan didn't equip the twins with recircs just for fun...there's a well thought theory behind it.

 

Anyway..here's a very good writeup about BOV's (copied from tt.net)

---------------------------------------

The Great Blow Off Valve Debate:

First of all to understand the functionality and benefits of a blow off valve you have to have a complete understanding of how a turbocharger works. If you don't understand the basic mechanics of a turbocharger you can forget about trying to understand the benefits of a blow off valve. If you do understand the mechanics of a turbocharger, read on...

 

An Explanation of Compressor Surge:

 

The turbine in a turbocharger in its ideal mode is spinning at a very high rate and therefore generating lots of pressurized air that is fed into the OPEN (wide open throttle) intake manifold which translates into more power, but what happens when you take your foot off the gas when shifting between gears? The turbine in the turbo is still spinning at a high rate but now you've taken your foot off the gas and the intake manifold is CLOSED. Now the turbine spinning at a high rate and is trying to push out all this compressed air but since the manifold is closed, that compressed air has nowhere to go. What happens next is that the turbine slows down because of this pressure build-up between the compressor and the intake manifold. Since the pressurized air can't go forward into the engine it heads the wrong way back towards the turbo where it slows the turbine down (compressor surge). After you shift gears and you step on the gas again you want to have the turbine spinning fast so that its producing boost but since you took your foot off the gas and caused compressor surge, it slowed down, so you have to wait for the turbine to "spool up" (spin fast) again. This delay waiting for turbines to spool up is what causes some of the performance degradation that were trying to avoid.

 

The Blow off Valve:

 

What if we could figure out a way of eliminating compressor surge? Then the turbine in our turbo would have a much easier time keeping its speed up and we wouldn't get the lag in power waiting for the turbine to spool up between shifts. Enter the Blow off valve. At that moment in time between shifts when compressor surge is slowing the turbine down we'll just poke a hole in the tube running between the turbo and the intake manifold and let all that air leak out somewhere. The turbine can keep spinning fast & we'll have lots of boost when we step on the gas again. We'll also want to plug up that hole we made because we have a purpose for that pressurized air now, where as when we let off the gas we did not. The blow off valve is a gizmo that's constantly opening and closing giving you that cool sneeze sound when it "pokes" that hole in the intake manifold tube to keep the turbine spinning fast. We've eliminated compressor surge but we did confuse the engine just a bit since the ECU already told the injectors to issue fuel to be used for the air that we've now thrown out. Other than that sounds like a good idea right? so what if were running a bit rich for a moment, no big deal. Before you place your order read on...

 

The Re-circulating Valve... a better idea:

 

How about instead of poking a hole in the turbo to intake manifold tube and just letting the air leak out wherever it wants to, we could direct that pressurized air somewhere else where we could hold on to it until we need it again? The intake side of the compressor housing (between the intercooler and the turbo) would be a good place wouldn't it? that way we wouldn't slow the turbine down and we would have that pressurized air that would have otherwise been thrown out, ready in a really good place when we need it. On top of that eve got still got the correct air/fuel ratio going since we're not throwing and air out, just moving it from one place to another within the intake system. Instead of having to suck in air for the turbo to pressurize, we've got some pressurized air with the correct fuel amount already waiting. Now we've got all the benefits of a blow off valve and then some. That's a re-circulating valve. Let's all order re-circulating valves then and skip the blow off valves completely. They're probably gonna cost a bit more than the blow off valves since they work a little better right? Now the big surprise... Re-circulating valves were engineered into the design of your 90+ twin turbo z on the drawing board... you've already got them...

 

In conclusion: You could always disconnect your stock re-circulating valves (which you have to do to install blow off valves) and spend 500-600 bucks for blow off valves and what will you get? better performance? No, basically you do get the cool sneeze sound though you aren't going to be any faster than you were before (but you might sound like you are). If by chance you are running boost levels that exceed the airflow capacity of the re-circulating valves (~600+ hp?) then you've probably spent enough money and have enough experience and knowledge to know where the benefit reverses. For the rest of you who weren't in the know, I hope I've helped you save some time and money...

 

 

NEVER BUY SE-NISSAN'S OWN DUMP VALVE KITS!! They make the car run like an absolute sack of crap!! I had them fitted to mine a few months back. Turned out to be a pair of 'Forge Motorsport' group A dump valves which you can buy for £80 each - and they charged me £400!!!! I got a refund and bought some HKS Blow-Off valves. I spoke to Jonathon at Grasshopper (where I got them from)- he said put them where the stock ones are. I put them there and they are great!! I get virtually no lag now at all.

BOW in a Z are USELESS until you reach the 700 (SEVEN HUNDRED) HP range.

Before that...well...it's YOUR money, right.

People told me that they are producing a LOT more HP....but miserably failed to produce any Dyno Sheets.....too bad...

 

A long time ago...I posted a JOKE about making chip with a speaker....to produce a digitalized sound (because...it's the ONLY thing it will produce)...with the sound of a single turbo / twin turbo / or even chose your best car noise....I SHOULD have done that....because the Japaneses are NOW marketing such a thing....hell you can even put one in a NA (or even in a truck in fact)...

 

Damm, I missed a market....

 

Zee you

 

Henri

CheerZ Eric,

 

I was looking for that last night but got bored and buggered off home! I posted that a couple of months back when this came up. Correction, I read it on TT.net and then copied it as Eric has done.

 

Come on guyZ, like Henri says, they're useless until you hit high power gains. I try to research mods as much as poss. before deciding to buy them and then put them on my car(when I get it back!) so as not to get ripped off anymore than I already have in the past!

 

BOV's might sound cool, but as other peeps have stated "your money!", might aswell set light to it in my opinion than waste on BOV's.

 

 

Tim

;-)

 

Thanks guyz for all your helpfull comments, the bov's were bought about 3 years ago and I am very happy with the noise they make. I just wanted to hear from (the experts) which set of turbo pipes to mount them on, thats all. Thanks anyway.

One point about re-circ valves:-

 

When I plugged mine after fitting Blitz BOVs (on the outer pipe - first question answered ) I noticed that the air is re-circulated back to just after the MAS! What good does this do??? The air is going to flow in the direction it can escape easiest - ie the outside world!!!

 

Anyone any views on this???

 

CheerZ,

 

Andy

The differences between the conventional BOV and Re-circ. are discussed in the post that Eric has put up!

 

To be honest with you, I don't see much point in putting BOV's back into a system which already has Re-circs which do a better job anyway?!??!?!?!?

 

If you like the sound of a "hisssss!" so much, why not take up steam trains or something. Anyway, I have my own opinion on BOV's and loud hissing noises! I was driving along quite happily down a high street when I saw this escort RS Turbo come flying up behind me with some young lad in. He kept hanging back and then accelerating right up my arse and I couldn't help notice this really loud hissing sound. I thought there was something wrong with his car and then realised that he'd got BOV's.

 

Well he carried on doing this right down the length of the high street and all the way down the dual carriageway. Hangin back and then accelerating right up my arse so that I could hear his hissing sid RS. One word to describe this guy, well two actually...LEO WANKER! I just thought to myself, how f**king sad can you get?

 

 

Tim

;-)

 

Alternatively, staple a snake to the underside of your accelerator pedal. Obviously making sure the head can't get your ankle... Lots of hiss, no performance reduction!

 

And for that Outside Hiss noise, to let everyone else hear, staple or No More Nails some more snakes along the underside of the car (avoid the jacking points otherwise you'll have to replace the snakes after squishing).

Apparently the blow off valves work really well in conjunction with the RAM-AIR intake mod, octane booster, a superchip and go faster stripes...

 

8)

 

------------------

 

Henri,

 

Some one Stole your Idea mate :

http://www.takakaira.com/

 

NA BOV - ROFL

 

Z ya

Nico 91TT

i disagree about the 700bhp thing lehiiir or whatever..

 

at the end of the day, they still work way below that power figure, (i know cause mine go SWOOSSHHH) and i only have 696 bhp lol